WO2011078259A1 - Flexible circuit board and structure of bend section of flexible circuit board - Google Patents
Flexible circuit board and structure of bend section of flexible circuit board Download PDFInfo
- Publication number
- WO2011078259A1 WO2011078259A1 PCT/JP2010/073198 JP2010073198W WO2011078259A1 WO 2011078259 A1 WO2011078259 A1 WO 2011078259A1 JP 2010073198 W JP2010073198 W JP 2010073198W WO 2011078259 A1 WO2011078259 A1 WO 2011078259A1
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- WO
- WIPO (PCT)
- Prior art keywords
- circuit board
- flexible circuit
- metal foil
- wiring
- foil
- Prior art date
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Images
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/09—Use of materials for the conductive, e.g. metallic pattern
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L79/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen or carbon only, not provided for in groups C08L61/00 - C08L77/00
- C08L79/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
- C08L79/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C9/00—Alloys based on copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/0277—Bendability or stretchability details
- H05K1/028—Bending or folding regions of flexible printed circuits
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/03—Use of materials for the substrate
- H05K1/0393—Flexible materials
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/03—Conductive materials
- H05K2201/0332—Structure of the conductor
- H05K2201/0335—Layered conductors or foils
- H05K2201/0355—Metal foils
Definitions
- the present invention relates to a flexible circuit board that is used with a bent portion in any one of them, and a bent portion structure of the flexible circuit board. More specifically, the invention has durability against bending and is flexible. The present invention relates to an excellent flexible circuit board and a bent portion structure of the flexible circuit board.
- a flexible circuit board (flexible printed circuit board) having a resin layer and a wiring made of metal foil can be used by being bent, a movable part in a hard disk, a hinge part of a mobile phone, Widely used in various electronic and electrical devices such as sliding slides, printer heads, optical pickups, and notebook PCs.
- the flexible circuit board can be folded and stored in a limited space or used in various movements of electronic devices. Corresponding flexibility is required. Therefore, it is necessary to improve the mechanical characteristics such as the strength of the flexible circuit board so that it can cope with the bending with a smaller radius of curvature at the bent portion and the operation in which the bending is frequently repeated. It has become.
- the flexible circuit board (see Patent Document 1) wired so as to be inclined with respect to the rotation axis, or in the rotation direction of the hinge portion.
- a method has been proposed in which a spiral portion formed by spiraling one or more turns is formed and the change in the diameter of the spiral portion due to the opening / closing operation is reduced to reduce damage by increasing the number of turns (see Patent Document 2). .
- any of these methods restricts the design of the flexible circuit board.
- the strength (I) of the (200) plane determined by X-ray diffraction (X-ray diffraction in the thickness direction of the copper foil) of the rolled copper foil was determined by X-ray diffraction of fine powder copper (200 ) It has been reported that when I / I 0 > 20 with respect to the surface strength (I 0 ), the film has excellent flexibility (see Patent Documents 3 and 4). That is, the flexibility of the copper foil improves as the cube orientation, which is the recrystallized texture of copper, develops. Therefore, a flexible circuit board in which the degree of development of the cube texture is defined by the parameter (I / I 0 ) A copper foil suitable as a wiring material is known.
- a rolled copper alloy foil containing elements such as Fe, Ni, Al, Ag, etc. in a concentration in the range of solid solution in copper, and obtained by annealing and recrystallization under predetermined conditions is shear along the sliding surface. It has been reported that the deformation is facilitated and the flexibility is excellent (see Patent Document 5).
- a copper foil containing impurities such as oxygen and silver may be used for a flexible circuit board that requires a high bending property, and its purity is about 99% to 99.9% by mass. Copper foil. In the present invention, purity is expressed as mass concentration unless otherwise specified. Further, at the test level, there are examples in which tough pitch copper having a purity of about 99.5% and oxygen-free copper containing no oxide, which are widely used as cable conductors, are used (see Patent Documents 3 and 4). Impurities of tough pitch copper include several hundred ppm of oxygen (mostly included as copper oxide), silver, iron, sulfur, phosphorus, and the like.
- Oxygen-free copper is usually copper having a purity of about 99.96 to 99.995%, and has been greatly reduced in oxygen to 10 ppm or less.
- Patent Documents 3 and 4 described above it is reported that the bending fatigue characteristics of a copper foil made of oxygen-free copper is superior to that of a tough pitch copper foil and depends on the presence or absence of copper oxide.
- impurities such as silver, phosphorus, and sulfur.
- the present inventors have no restrictions on the design of the flexible circuit board, and the flexible circuit board has durability against repeated bending and bending with a small radius of curvature.
- the present inventors found that a substrate was obtained and completed the present invention.
- an object of the present invention is to provide a flexible circuit board having excellent durability, and in particular, repeated bending with a small radius of curvature, such as a hinge part or a slide sliding part of a mobile phone or a small electronic device. It is to provide a flexible circuit board that exhibits durability even under severe use conditions such as, and has excellent flexibility.
- Another object of the present invention is to provide durability and resistance to harsh conditions such as hinge portions or slide sliding portions of mobile phones, small electronic devices, etc., particularly in repeated bending portions having a small curvature radius.
- An object of the present invention is to provide an excellent flexible circuit board bent portion structure.
- a flexible circuit board including a resin layer and a wiring formed from a metal foil, and having a bent portion at least at one place of the wiring,
- the metal foil is made of a metal having a face-centered cubic structure, and the basic crystal axis ⁇ 100> of the unit cell of the face-centered cubic structure is 2 in the thickness direction of the metal foil and a certain direction existing in the foil surface.
- the preferential orientation regions having an azimuth difference of 10 ° or less occupy 50% or more in area ratio, and the normal direction with respect to the cross section P of the wiring cut from the ridge line in the bent portion in the thickness direction of the metal foil
- a flexible circuit board, wherein the breaking elongation of the metal foil is 3.5% or more and 20% or less.
- the metal foil is a copper foil having a purity of 99.999% by mass or more.
- a bent portion structure of a flexible circuit board that includes a resin layer and a wiring formed from a metal foil, and is used with a bent portion in at least one portion of the wiring,
- the metal foil is made of a metal having a face-centered cubic structure, and the basic crystal axis ⁇ 100> of the unit cell of the face-centered cubic structure is 2 in the thickness direction of the metal foil and a certain direction existing in the foil surface.
- the preferential orientation region having an azimuth difference of 10 ° or less occupies 50% or more in area ratio Bending part structure of flexible circuit board, wherein elongation at break of metal foil is 3.5% or more and 20% or less.
- the metal foil constituting the wiring at the bent portion when the flexible circuit board is bent hardly causes metal fatigue and has excellent durability against stress and strain. Therefore, it is possible to provide a flexible circuit board having excellent flexibility with sufficient strength to withstand repeated bending and bending with a small radius of curvature without any restrictions on the design of the flexible circuit board. This makes it possible to realize highly durable electronic devices such as thin mobile phones, thin displays, hard disks, printers, and DVD devices.
- FIG. 1 is a diagram illustrating a relationship between a crystal zone axis in a cubic crystal structure and a plane obtained by rotating around the crystal zone axis.
- FIG. 2 is a stereo triangle of (100) standard projection.
- FIG. 3 is an explanatory cross-sectional view showing a state in which the flexible circuit board is bent.
- FIG. 4 is an explanatory plan view showing the relationship between the wiring in the flexible circuit board and the crystal axis of the metal foil, (a) and (b) show the flexible circuit board according to the present invention, and (c) ) And (d) show a prior art flexible circuit board.
- FIG. 5 is a perspective explanatory view of a single-sided copper-clad laminate.
- FIG. 5 is a perspective explanatory view of a single-sided copper-clad laminate.
- FIG. 6 is an explanatory plan view showing a state in which a test flexible circuit board is obtained from a single-sided copper-clad laminate in the embodiment of the present invention.
- FIG. 7 is an explanatory diagram of an MIT flex test apparatus.
- FIG. 8A is an explanatory view of an IPC bending test apparatus, and
- FIG. 8B is an X-X ′ sectional view of a test flexible circuit board used in the IPC bending test.
- the wiring provided in the flexible circuit board of the present invention is formed of a metal foil made of a metal having a face-centered cubic crystal structure.
- a metal having a face-centered cubic crystal structure for example, copper, aluminum, nickel, silver, rhodium, palladium, platinum, gold and the like are known. Copper, aluminum, and nickel are preferable because of their utility as copper, and copper foils that are mainly used as wiring for flexible circuit boards are the most common.
- the present invention provides a flexible circuit board excellent in bending durability and flexibility, and in particular, provides a flexible circuit board having excellent fatigue characteristics in a high strain region where the radius of curvature is 2 mm or less.
- one of i) the metal foil is highly oriented and ii) the elongation at break in the principal stress direction of the metal foil is large at the bent portion.
- it does not become a flexible circuit board that is resistant to fatigue failure during high bending as in the present invention. That is, by satisfying both i) and ii) at the same time, a flexible circuit board that is resistant to fatigue failure during high bending can be obtained.
- the basic crystal axis ⁇ 100> of the unit cell of the face-centered cubic structure is respectively in relation to two orthogonal axes of the thickness direction of the metal foil and a certain direction existing in the foil surface.
- the preferred orientation region within an orientation difference of 10 ° or more occupies 50% or more in area ratio
- the elongation at break of the metal foil in the normal direction relative to the cross section P of the wiring cut in the thickness direction of the metal foil from the ridgeline at the bent portion Needs to be 3.5% or more and 20% or less.
- the metal foil is a polycrystalline body as found in general electrolytic foils and rolled foils, a high breaking elongation can be obtained, but a flexible circuit having high fatigue characteristics against the high strain fatigue required in the present invention. It is not a substrate.
- a flexible circuit board having the characteristics required by the present invention cannot be obtained.
- the breaking elongation of the metal foil in the flexible circuit board which requires particularly high bending characteristics, is an important factor. This is the first time revealed.
- the metal foil may be a rolled foil or an electrolytic foil, but is preferably a rolled foil in order to obtain high orientation.
- a metal foil having a highly oriented cubic texture with ⁇ 100> main orientations in the rolling direction and the normal direction of the foil surface is produced by devising rolling conditions and heat treatment conditions. can do.
- the feature of the mechanical characteristics of the metal foil having a strong cubic orientation is not limited to the use of the flexible circuit board, and is that the elongation at break is anisotropic.
- the elongation at break takes a very small value when pulled in the ⁇ 100> direction.
- the basic crystal axis ⁇ 100> of the unit cell of the face-centered cubic structure is the thickness direction of the metal foil (the normal direction of the foil surface) and one direction existing in the foil surface (one of which is the rolling direction).
- the breaking elongation in the principal stress direction at the bent portion does not reach 3.5%.
- the term “elongation at break” used herein refers to a specimen having a width of 5 to 15 mm, which is sufficiently larger than the thickness of the metal foil, and is 10 to the length. This refers to the elongation to break when a tensile test is performed at a strain rate of% / min.
- the elongation after breaking of the metal foil is determined by the measurement method shown in the following examples, and the value after the flexible circuit board is obtained by laminating with the resin layer.
- the recrystallized texture has a ⁇ 100> orientation in the rolling direction, that is, the longitudinal direction of the metal foil.
- the longitudinal direction of the circuit and the longitudinal direction of the copper foil coincide with each other from the viewpoint of increasing the yield. Therefore, in the normal usage mode in which the longitudinal direction of the circuit is bent, the main stress direction coincides with the ⁇ 100> direction, so that the conventional rolled copper foil cannot obtain high fatigue characteristics against repeated bending.
- the present invention aims to increase the purity of the metal foil used.
- a copper foil intentionally or inevitably contains impurities such as oxygen and silver is used. This is for the purpose of facilitating shear deformation along the slip surface and suppressing an increase in electrical resistance, as described in Patent Document 5, for example.
- these impurity elements reduce the stacking fault energy.
- the present inventors paid attention to this point. That is, when the stacking fault energy is decreased, dislocations are easily expanded and cross slipping is unlikely to occur, and particularly when stretched in the ⁇ 100> direction, elongation is difficult to occur.
- a metal foil preferably a copper foil having a predetermined preferred orientation as described below and preferably having a purity of 99.999% or more is used, whereby the ⁇ 100> direction is used.
- the elongation at break can be increased to 3.5% or more, and as a result, the fatigue characteristics are increased when repeated strain is applied in a high strain region.
- the higher purity of the metal foil is desirable, it is most preferable to use 99.999% to 99.9999% from the viewpoint of manufacturing cost.
- an oxygen-free copper foil having a low oxygen concentration has a face-centered cubic shape depending on rolling and heat treatment conditions in a narrow condition, as shown in the following examples.
- the three-dimensional crystal orientation of the metal foil is defined with respect to the sample coordinate system of the metal foil constituting the circuit, and the degree of integration of the texture is in the following range. That is, a region in which one of the basic crystal axes ⁇ 100> of the face-centered cubic structure, for example, the [001] axis is within 10 ° in orientation difference with respect to the thickness direction of the metal foil (the normal direction of the foil surface) is an area.
- the foil plane which has a preferential orientation that accounts for 50% or more, preferably 75% or more, more preferably 98% or more, and is in a direction parallel to the surface of the metal foil
- another basic crystal An axis having a preferential orientation such that a region within 10 ° from the [100] axis occupies an azimuth difference accounts for 50% or more, desirably 85% or more, and more desirably 99% or more is used.
- it is sufficient that at least the bent portion has the above-mentioned texture integration degree, but preferably all the metal foils laminated on the resin layer have the above-mentioned integration degree.
- a so-called single crystal-like metal foil is preferable without being restricted in wiring design.
- the metal foil used in the present invention has a main orientation of ⁇ 100> in the thickness direction of the metal foil, It can be said that the foil plane has a main orientation of ⁇ 100>.
- indices that indicate the priority of texture orientation that is, the degree of orientation or accumulation
- An index based on simple data can be used.
- the metal foil is a copper foil
- the intensity (I) from (002) perpendicular to the above-mentioned zone axis determined by X-ray diffraction here, according to a general notation method in X-ray diffraction, (200) plane
- the wiring having a predetermined pattern is formed from a copper foil having I / I 0 ⁇ 25 with respect to the strength (I 0 ) of the (200) plane obtained by X-ray diffraction of fine powder copper.
- the I / I 0 is preferably in the range of 33 to 150, more preferably in the range of 50 to 150.
- the parameter I / I 0 represents the degree of orientation of the zone axes of (100) and (110), that is, the common axis [001], and is an objective index indicating the degree of development of the cube texture. is there.
- the metal foil is a rolled copper foil, it is strongly processed at a rolling rate of a certain level or higher, and then recrystallized by applying heat, so that the rolled foil surface is rolled into the (001) main orientation and foil plane.
- a recrystallized cube orientation with the direction as the (100) principal orientation develops.
- the bending fatigue life of the copper foil is improved as the cubic orientation, which is the recrystallized texture of copper, develops.
- a recrystallized texture of the copper foil may be obtained.
- the intermediate annealing conditions and the cold rolling process rate are targeted.
- a rolled copper foil having a large texture of crystal grains and I / I 0 ⁇ 25 can be obtained.
- the copper foil is subjected to heating conditions such that a temperature of 300 to 360 ° C. is loaded for an accumulated time of 5 minutes or more.
- a recrystallized texture of copper foil may be obtained.
- the texture can be specified using the area ratio of the preferentially oriented region that falls within 10 ° with respect to the main orientation of the texture. That is, as to what crystal orientation the predetermined surface of the metal foil has, for example, X-ray diffraction method such as EBSP (Electron Back Scattering Pattern) method, ECP (Electron Channeling Pattern) method or X-ray method such as micro Laue method It can be confirmed by a line diffraction method or the like.
- EBSP Electro Back Scattering Pattern
- ECP Electrode
- X-ray method such as micro Laue method
- the EBSP method analyzes a crystal from a diffraction image called a pseudo Kikuchi line that is diffracted from each crystal plane generated when a focused electron beam is irradiated on the surface of a sample to be measured.
- This is a method of measuring the crystal orientation distribution of the measurement object from the position information of the above, and it is possible to analyze the crystal orientation of the texture in the microscopic region as compared with the X-ray diffraction method.
- An orientation mapping image can be obtained by highlighting the distribution of regions (crystal grains) having substantially the same plane orientation. It is also possible to define the orientation including the orientation plane having an orientation within a predetermined angle with respect to a specific plane orientation, and to extract the existence ratio of each plane orientation by the area ratio. In the EBSP method, in order to obtain an area ratio of a region within a specific angle from a specific orientation, in order to obtain an area ratio at least in a region larger than the circuit bent region in the flexible circuit board of the present invention.
- the difference in structure between the present invention and the inventions described in Patent Documents 3 and 4 is that the orientation definition of the inventions of these Patent Documents is only the normal direction of the foil measured by X-ray.
- the present invention is defined in three dimensions.
- the main strain, the main stress direction that is, the ⁇ 100> integration degree in the foil surface, particularly when bent is important.
- the size of recrystallized grains, that is, crystal grains having a cubic orientation is preferably 25 ⁇ m or more on average.
- the metal foil forming the flexible circuit board is preferably a rolled copper foil having a thickness of 5 to 18 ⁇ m, preferably a thickness of 9 to 12 ⁇ m. It is preferable to use a rolled copper foil.
- the rolled copper foil is thicker than 18 ⁇ m, it becomes difficult to obtain a flexible circuit board having excellent fatigue characteristics in a high strain region where the radius of curvature is 2 mm or less.
- the thickness is less than 5 ⁇ m, handling in laminating the metal foil and the resin layer is difficult, and it is difficult to form a homogeneous flexible circuit board.
- the present invention provides a second method for improving the breaking elongation of a face-centered cubic metal foil close to a highly oriented single crystal.
- the wiring configuration of the flexible circuit board is devised so that the ⁇ 100> direction having a small elongation at break does not become the principal stress direction.
- a metal foil having a highly oriented cubic texture having a ⁇ 100> main orientation in both the rolling direction and the foil surface normal direction is produced. can do.
- the direction of cutting the circuit as wiring is shifted by a predetermined angle from the rolling direction, that is, the ⁇ 100> direction, and the circuit is pulled diagonally, so that flexibility is large in elongation at break in the main stress direction when bent.
- a circuit board can be obtained.
- the cross section P needs to have a main orientation on any plane included in the range of (20 1 0) to (1 20 0) with [001] as the zone axis.
- the relationship between the zone axis and the plane orientation is shown in FIG. (20 1 0) and (1 20 0) have a relationship with [001] as a common axis, that is, a zone axis, from (100) to (110) with [001] as the axis [from (100) (010)] in the plane of rotation. That is, when this is shown on the reverse pole figure with respect to the normal direction of the cross section P, the surfaces of (001), (20 1 0), and (110) are as shown in FIG.
- the metal of the metal foil in the present invention has a face-centered cubic structure.
- the crystal axes of the unit cell are [100], [010], and [001].
- ⁇ 100> preferred orientation in the thickness direction of the metal foil (the direction perpendicular to the surface of the metal foil).
- this axis is expressed as [001], that is, the foil plane orientation is (001), but it is equivalent even if these axes are interchanged due to the symmetry of the face-centered cubic structure, and these are of course included in the present invention. It is.
- the main orientation in the foil plane is in the main strain direction of the bent portion, that is, in the normal direction of the cross section of the wiring cut from the ridge line in the bent portion in the thickness direction (with respect to the perpendicular to the wiring cross section P), It is necessary to have an angle of 2.9 ° to 87.1 ° [(20 1 0) to (1 20 0)], preferably 5.7 ° to 84.3 ° [(10 1 0) ⁇ (1 10 0)], more preferably 11.4 ° to 78.6 ° [(510) to (150)], and more preferably 26.6 ° to 63.4 ° [(210) to It is desirable that the angle is (120)], most preferably 30 ° or 60 ° [(40 23 0) or (23 40 0)].
- [] represents the plane orientation of the cross section P corresponding to each angle. From the symmetry of the crystal, it can also be described that the normal to the wiring cross section P has an angle of 2.9 to 45 ° with the basic crystal axis ⁇ 100> in the metal foil plane.
- the cross section P of the wiring when it is cut in the thickness direction from the ridgeline at the bent portion is, for example, as shown in FIG. 3, when the flexible circuit board is bent in a U shape, a ridgeline L is formed on the outside thereof.
- the ridge line L is an apex formed when the cross section of the flexible circuit board is viewed along the bending direction (thick arrow in FIG. 3) in a state where the flexible circuit board is bent. It is a connected line.
- the case where the ridgeline L moves a flexible circuit board, such as sliding bending mentioned later, for example is also included.
- 3 shows a state in which the resin layer 1 is on the outside and the wiring 2 is bent inward (the side on which a circle having a radius of curvature is inscribed is inward), but the wiring 2 is bent outward. Of course, it may be.
- the metal foil when subjected to a forced displacement with a certain curvature, is mainly subjected to tensile or compressive stress.
- Which part of the flexible circuit board that is bent is subjected to tension or compression depends on the configuration of the metal foil and the resin, but is bent from the neutral axis (or neutral surface) of tension and compression.
- the outermost part which is the outermost part, is severe due to the destruction of the metal, and the tensile stress in the normal direction of the cross section of the wiring when cut in the thickness direction from the ridgeline at the bent part becomes the main stress. That is, the main stress direction of the wiring in the bent portion is the direction indicated by the arrow 21 in FIG. 3, and is typically the normal direction to the wiring cross section P cut from the ridge line of the bent portion in the thickness direction of the metal foil. And the direction perpendicular to the [001] axis oriented in the thickness direction of the metal foil.
- the stress strain characteristic when the metal foil is simply pulled in the main stress direction indicated by the arrow 21 in FIG. 3 is an important characteristic.
- the metal foil having a face-centered cubic crystal structure is bent so that a ridge line perpendicular to the [100] axis is formed.
- the cross section of the wiring cut in the thickness direction of the flexible circuit board from the ridge line at the bent portion becomes the (100) plane, but the cross section P of the wiring when cut in the thickness direction from the ridge line at the bent portion is As shown in FIG.
- the cross section P of the wiring when it is cut in the thickness direction from the ridgeline at the bent portion is preferentially oriented with a main orientation in a specific orientation between (20 1 0) and (1 20 0). Therefore, the reason why the elongation at break is improved is that when a tensile stress is applied in the normal direction of the cross section P, that is, the principal stress direction, the metal having a face-centered cubic structure has eight ⁇ 111 ⁇ , Since the main slip surface having the largest Schmid factor is four, the shear slip is good and local work hardening is less likely to occur.
- the longitudinal direction of the metal foil corresponds to the rolling direction, and as shown in FIGS.
- the most desirable orientation is 30 ° or 60 ° with respect to the main strain direction of the bent portion, that is, the normal direction of the cross section of the wiring when cut from the ridge line in the bent portion in the thickness direction. This is because the direction of stress coincides with the stable orientation of tension.
- at least the cross section P of the wiring when cut in the thickness direction from the ridgeline at the bent portion is between (20 1 0) and (1 20 0) with [001] as the crystal axis. It suffices to have the preferential orientation with the main orientation in the specific orientation.
- the second policy in the present invention is that the metal foil has a face-centered cubic structure, the thickness direction of the metal foil has a main orientation of ⁇ 100>, and the foil surface of the metal foil has ⁇ 100>. And the normal direction of the cross section P of the wiring when cut in the thickness direction from the ridge line at the bent portion is the main direction in a specific direction between (20 1 0) and (1 20 0). A wiring that has a preferential orientation is provided.
- the normal direction of the cross section P is preferably preferentially oriented with a main orientation in a specific orientation between (10 1 0) and (1 10 0), and more preferably (510 ) To (110) having a main orientation in a specific orientation, and more preferably having a main orientation in a specific orientation between (210) and (110).
- the preferred orientation is centered in the vicinity of (40 23 ⁇ ⁇ 0).
- the main direction of the cross section P of the wiring when cut in the thickness direction from the ridge line at can be described as a specific direction between (1 20 0) and (110), preferably (120) to (110) It can also be described that it is preferable to preferentially align with a main direction in a specific direction between them, and most preferably to preferentially align with a main direction in the vicinity of (23 40 0).
- the thickness direction of the metal foil has a main orientation of ⁇ 100>
- the foil surface of the metal foil has a main orientation of ⁇ 100>
- the wiring when cut from the ridgeline at the bent portion in the thickness direction The fact that the cross section P has a main orientation in a specific orientation between (20 1 0) and (1 20 0) is reversed on the stereo triangle of the (100) standard projection shown in FIG.
- the cross-sectional orientation of the wiring when cut in the thickness direction from the ridgeline at the bent portion is either on a line segment connected by a point representing (20 1 0) and a point representing (110)
- the flexible circuit board in the second measure is formed by forming a wiring from a 3 (2) axis-oriented material in which the thickness direction of the metal foil is the [001] axis, and cutting the ridge line at the bent portion in the thickness direction.
- the cross-sectional normal of the wiring at that time has an angle in the range of 2.9 ° to 87.1 ° with the [100] axis in the foil plane.
- the breaking elongation of the metal foil in the principal stress direction at the bent portion can be 3.5% or more, and the repeated strain such that the curvature radius is 2 mm or less, Alternatively, metal fatigue is less likely to occur due to stress, and a flexible circuit board with high flexibility can be obtained. Further, in the present invention, a flexible circuit board excellent in metal fatigue characteristics and bendability can be obtained more reliably by combining the first policy and the second policy described above, and the main stress direction can be obtained.
- the breaking elongation of the metal foil can be 3.5% or more, preferably 4% or more, more preferably 9% or more.
- the basic crystal axis ⁇ 100> of the unit cell of the face-centered cubic structure is in the thickness direction of the metal foil (the normal direction of the foil surface) and in one direction (in the direction of the foil surface)
- Rolling that can be taken within the scope of the present invention, in which the preferential orientation region with an orientation difference of 10 ° or less is 50% in area ratio and the thickness is 18 ⁇ m with respect to two orthogonal axes (one is the rolling direction)
- the upper limit of the foil can be defined as 20% or less, but the basic crystal axis ⁇ 100> of the copper unit cell is two orthogonal directions of the thickness direction of the copper foil and one direction existing in the foil plane.
- the preferential orientation regions each having an orientation difference within 10 ° with respect to the axis occupy 95% or more in area ratio and the thickness is 12 ⁇ m or less
- the upper limit of elongation at break is 15% or less. .
- the type of resin forming the resin layer is not particularly limited, and examples thereof include those used in ordinary flexible circuit boards, such as polyimide and polyamide. , Polyester, liquid crystal polymer, polyphenylene sulfide, polyether ether ketone and the like. Of these, polyimide and liquid crystal polymer are preferred because they exhibit good flexibility when used as a circuit board and are excellent in heat resistance.
- the thickness of the resin layer can be appropriately set in accordance with the use, shape, etc. of the flexible circuit board, but is preferably in the range of 5 to 75 ⁇ m from the viewpoint of flexibility, and in the range of 9 to 50 ⁇ m. Is more preferable, and the range of 10 to 30 ⁇ m is most preferable. If the thickness of the resin layer is less than 5 ⁇ m, the insulation reliability may decrease. On the other hand, if it exceeds 75 ⁇ m, the thickness of the entire circuit board may be too thick when mounted on a small device, etc. A decline in sex is also possible.
- a cover material made of a coverlay film or the like may be used on a wiring formed from a metal foil.
- a polyimide having a tensile elastic modulus at 25 ° C. of 4 to 6 GPa and a thickness of 14 to 17 ⁇ m is used as a resin layer, and a thermosetting resin having a thickness of 8 to 17 ⁇ m is used.
- a cover layer film having a cover layer film having a tensile elastic modulus of 2 to 4 GPa of the entire adhesive layer and the polyimide layer, and a cover material having two layers of an adhesive layer and a polyimide layer having a thickness of 7 to 13 ⁇ m A polyimide having a tensile elastic modulus at 25 ° C. of 6 to 8 GPa and a thickness of 12 to 15 ⁇ m is used as a resin layer, an adhesive layer made of a thermosetting resin having a thickness of 8 to 17 ⁇ m, and a polyimide layer having a thickness of 7 to 13 ⁇ m.
- a cover lay film having a tensile elastic modulus of 2 to 4 GPa for the entire adhesive layer and polyimide layer is used as a cover material.
- the metal foil may be thermally laminated by applying or interposing a thermoplastic polyimide to the polyimide film (so-called laminating). Law).
- a thermoplastic polyimide film used in the laminating method include “Kapton” (Toray DuPont Co., Ltd.), “Apical” (Kanebuchi Chemical Industry Co., Ltd.), “Upilex” (Ube Industries Co., Ltd.), and the like.
- a thermoplastic polyimide resin exhibiting thermoplasticity is preferably interposed.
- a polyimide precursor solution also referred to as a polyamic acid solution
- a polyamic acid solution may be applied to the metal foil, and then dried and cured to obtain a laminate (so-called “so-called”). Cast method).
- the resin layer may be formed by laminating a plurality of resins.
- two or more kinds of polyimides having different linear expansion coefficients may be laminated, and in that case, heat resistance and flexibility are ensured.
- the tensile elastic modulus of the resin layer is preferably 4 to 10 GPa, preferably 5 to 8 GPa, including the case of being composed of a single polyimide and the case of being composed of a plurality of polyimides.
- the linear expansion coefficient of the resin layer is preferably in the range of 10 to 30 ppm / ° C.
- the linear expansion coefficient of the entire resin layer may be in this range.
- a low linear expansion polyimide layer having a linear expansion coefficient of 25 ppm / ° C. or less, preferably 5 to 20 ppm / ° C., and a linear expansion coefficient of 26 ppm / ° C. or more, preferably 30 to It is a resin layer comprising a high linear expansion polyimide layer at 80 ppm / ° C., and can be adjusted to 10 to 30 ppm / ° C.
- the low linear expansion polyimide layer is the main resin layer of the resin layer, and the high linear expansion polyimide layer is preferably provided so as to be in contact with the metal foil.
- the linear expansion coefficient was determined by using a polyimide whose imidization reaction was sufficiently completed as a sample, raising the temperature to 250 ° C. using a thermomechanical analyzer (TMA), cooling at a rate of 10 ° C./min, and 240 to 100 ° C. It can obtain
- TMA thermomechanical analyzer
- the flexible circuit board according to the present invention includes a resin layer and a wiring formed from a metal foil, and is used with a bent portion in one of them.
- it is widely used in various electronic and electrical devices such as movable parts in hard disks, hinges and slides of mobile phones, printer heads, optical pickups, movable parts of notebook PCs, etc., and the circuit board itself Is bent, twisted, or deformed according to the operation of the mounted device, and a bent portion is formed in either of them.
- the flexible circuit board of the present invention since the flexible circuit board of the present invention has a bent portion structure with excellent bending durability, it is frequently bent with repeated operations such as sliding bending, bending bending, hinge bending, and sliding bending.
- the radius of curvature is 0.38 to 2.0 mm in bending behavior, 1.25 to 2.0 mm in sliding bending, and 3. 0 to 5.0 mm, suitable for severe use conditions such as 0.3 to 2.0 mm for slide bending, and for slide applications where bending performance is severe with a narrow gap of 0.3 to 1 mm Especially effective.
- a rolled metal exhibiting a cubic texture in which the [001] axis is finally oriented in the normal direction to the foil surface (perpendicular to the surface of the metal foil) Obtain a composite in which the foil and the resin layer are bonded to each other with the foil surface of the metal foil, and design the principal stress direction of the bending, that is, the normal direction of the cross section of the wiring when cutting from the ridgeline at the bent portion in the thickness direction.
- the foil may have a purity of 99.999% or higher, or iii) the methods i) and ii) may be adopted at the same time.
- the metal foil does not necessarily have to exhibit a cubic texture from the beginning, and the cubic texture may be formed by heat treatment.
- a manufacturing process of a flexible circuit board, specifically a resin A cubic texture may be formed by heat treatment in the layer formation process. That is, by heat treatment, one of the basic crystal axes ⁇ 100> of the unit cell is given priority in the thickness direction of the metal foil so that the area within 10 ° from the ⁇ 100> axis occupies an area ratio of 50% or more.
- another one of the basic crystal axes ⁇ 100> is preferentially oriented in the horizontal direction with respect to the surface of the metal foil so that the area within 10 ° from the ⁇ 100> axis occupies an area ratio of 50% or more.
- the recrystallized texture of the rolled copper foil usually has a rolling plane orientation of ⁇ 100 ⁇ and a rolling direction of ⁇ 100>. Therefore, the (001) main direction is formed as the rolling surface direction.
- the elongation at break can be secured to 3.5% or more regardless of the orientation of the circuit formed and wired, and the flexible application range is wide. Circuit board can be formed.
- the width, shape, pattern, etc. of the wiring are not particularly limited, and may be appropriately designed according to the use of the flexible circuit board, the mounted electronic device, etc. Even if the second measure is adopted, it is necessary to dare to wire in an oblique direction with respect to the rotation axis of the hinge portion, for example, in order to reduce the bending stress on the wiring. Therefore, wiring along the direction orthogonal to the ridgeline in the bent portion, that is, wiring with the minimum necessary minimum distance is possible.
- FIGS. 4A and 4B show a flexible circuit board used for, for example, a hinge part of a cellular phone, which is an example having a resin layer 1, a wiring 2 formed from a metal foil, and a connector terminal 3. is there.
- FIG. 4A and 4B show the position of the ridge line L in the bent portion near the center, and this ridge line L is (with respect to the [100] axis direction of the metal foil forming the wiring 2 ( 90 + ⁇ ) °.
- FIG. 4A is an example in which the wiring is formed obliquely in the vicinity of the ridge line L in the middle of the connector terminals 3 at both ends.
- FIG. Wiring is also possible.
- the slide sliding bend in which the ridge line L in the bent portion moves as in a slide type mobile phone may be the direction of the thick arrow).
- the flexible circuit board in this invention is equipped with the wiring which consists of metal foil in at least one surface of a resin layer, you may make it equip both surfaces of a resin layer with metal foil as needed.
- the metal foil constituting the wiring in the bent portion when the flexible circuit board is bent is highly oriented and has a large elongation at break in the main stress and main strain directions.
- the metal foil even when repeated bending with a small bending radius and high bending is performed, local stress concentration caused by crystal anisotropy hardly occurs and dislocation accumulation hardly occurs. Due to these effects, metal fatigue is less likely to occur, it has excellent durability against stress and strain, and there is no restriction on the design of the flexible circuit board, and even against repeated bending and bending with a small radius of curvature. It is possible to provide a flexible circuit board that has sufficient strength and can be bent.
- Copper foil A and copper foil H are commercially available rolled copper foils
- copper foil B is a commercially available electrolytic copper foil produced in a copper sulfate bath. These are all copper foils that are commercially available as high-bending products, and the purity is 99.9%, which is high as a commercial product.
- Copper foils C to G are processed by the present inventors, and are obtained by casting and solidifying a copper material having a predetermined purity in a graphite mold and rolling it to a predetermined thickness. The thickness of the casting ingot is 10 mm, and after dropping to 1 mm by cold rolling, for copper foil C, copper foil D, and copper foil E, after carrying out intermediate annealing at 300 ° C.
- Process condition A the copper foil F was cold-rolled to 9 micrometers (process condition B), without performing intermediate annealing. Further, the copper foil G was subjected to an intermediate annealing temperature of 800 ° C. and cold-rolled to 9 ⁇ m (process condition C).
- Example 1 The polyamic acid solution a prepared above is applied to seven types of copper foils from copper foil A to copper foil G, dried (after curing, a 2 ⁇ m-thick thermoplastic polyimide film is formed), and then polyamic acid b is applied thereon. And dried (after forming a low thermal expansion coefficient polyimide with a film thickness of 9 ⁇ m), and further coated with polyamic acid a and dried (after curing, formed with a polyimide film with a film thickness of 2 ⁇ m), 300 ⁇ A polyimide layer having a three-layer structure was formed through a heating condition in which a temperature of 360 ° C. was loaded for 5 minutes or more in the integration time.
- the copper foil was cut out to a rectangular size of 250 mm in length along the rolling direction (MD direction) and 150 mm in the direction perpendicular to the rolling direction (TD direction), as shown in FIG.
- the tensile elastic modulus of the entire resin layer was 7.5 GPa.
- the single-sided copper clad laminate 4 obtained above is subjected to mechanical and chemical polishing using colloidal silica on the rolled surface 2a of each copper foil 2 from the copper foil A to the copper foil G.
- the azimuth analysis was performed with an EBSP apparatus.
- the apparatuses used were FE-SEM (S-4100) manufactured by Hitachi, Ltd., EBSP apparatus manufactured by TSL, and software (OIM Analysis 5.2).
- the measurement area was an area of approximately 800 ⁇ m ⁇ 1600 ⁇ m, and the measurement acceleration voltage was 20 kV and the measurement step interval was 4 ⁇ m.
- the evaluation of the orientation was shown by the ratio of the measurement points where ⁇ 100> is within 10 ° with respect to the thickness direction of the foil and the rolling direction of the foil to the total measurement points. The number of measurements was made on five different samples of each variety and rounded to the nearest whole number. Further, using the obtained data, the crystal grain size was evaluated by setting the crystal grain boundaries to those having an orientation difference of 15 ° or more between adjacent crystal grains, and the average grain size was determined for the polycrystal. The results are shown in Table 1.
- These copper foils were composed of grains having a cubic orientation in a field of 800 ⁇ 1600 ⁇ m, and crystal grains having different orientations of 5 ⁇ m or less were dispersed in an island shape inside. Since the area ratio of the island-like structure is as small as 2% or less, the recrystallized grains having a cubic orientation are integrated with the same orientation, and the size of the recrystallized grains is the same as the foil thickness in the thickness direction. 9 ⁇ m, and 800 ⁇ m or more in the foil surface. In addition, the recrystallized grains having a cubic orientation of the copper foil F and the copper foil G are not high in area ratio, and therefore exist independently of each other, and the average grain sizes in the foil surface are 25 ⁇ m and 20 ⁇ m, respectively. It was. On the other hand, the electrolytic copper foil B was a polycrystal having an average particle diameter of 1 ⁇ m, and almost no orientation was observed.
- a predetermined mask is put on the copper foil 2 side of the single-sided copper clad laminate 4 obtained above, and etching is performed using an iron chloride / copper chloride solution, as shown in FIG.
- the angle between the wiring direction H and the MD direction is 0 °
- the wiring direction H (H direction) of the linear wiring 2 having a line width (l) of 150 ⁇ m is parallel to the MD direction ( ⁇ 100> axis).
- the wiring pattern was formed so that the space width (s) was 250 ⁇ m.
- MIT flex test was performed according to JIS C5016 using the test flexible circuit board obtained above.
- a schematic diagram of the test is shown in FIG.
- the equipment is manufactured by Toyo Seiki Seisakusho (STROGRAPH-R1), one end of the test flexible circuit board 5 in the longitudinal direction is fixed to the holding jig of the bending test apparatus, and the other end is fixed with a weight.
- the wire 2 on the circuit board 5 is cut off from conduction while being rotated to 135 ⁇ 5 degrees alternately left and right at a vibration speed of 150 times / min. was determined as the number of flexing.
- the main stress applied to the copper circuit is obtained because the ridge line formed in the bent portion is bent so as to be orthogonal to the wiring direction H of the wiring 2 of the test flexible circuit board 5.
- the main strain is a tensile stress or tensile strain parallel to the rolling direction.
- the bending fatigue life depends on the degree of integration of the cube texture, but the copper foil C, the copper foil D, and the copper foil E, which are produced by the same processing method and have substantially the same degree of orientation. It has been found that the bending fatigue life varies greatly.
- a tensile test was performed in parallel with the main stress of bending, the main strain direction, that is, the rolling direction.
- the resin layer was dissolved from the single-sided copper clad laminate 4 before etching, and a tensile test was conducted on the copper foil alone. In the process of dissolving the polyimide, it was confirmed that there was no change in the structure of the copper foil.
- the tensile test uses a sample cut to a length of 150 mm in the rolling direction (MD direction) of the copper foil and a width of 10 mm in the direction perpendicular to the rolling direction in the foil plane, and the distance between the gauge points is 100 mm in the length direction.
- the elongation at break is correlated with the bending fatigue life, not the strength at break.
- copper foil B is large in both strength and elongation at break, this reflects that it is a fine polycrystalline body of crystal grains.
- the fatigue life was inferior.
- the copper foil C with a purity of 99.99% and the copper foil D with a purity of 99.999%, which have the same degree of cube texture accumulation were compared, the fatigue characteristics of the copper foil D with respect to bending were greatly improved.
- the oxygen concentration of these two copper foils is the same, and the amount of copper oxide inside is also small and equal, so it is not due to the difference due to copper oxide but due to the difference in elongation at break due to different purity. .
- the basic crystal axis ⁇ 100> exists in the thickness direction of the metal foil and in the foil plane.
- the main orientation is such that the preferential orientation region with an azimuth difference of 10 ° or less occupies 50% or more with respect to two orthogonal axes with a certain direction, and the ridge line at the bent portion It was found that the breaking elongation of the metal foil in the normal direction relative to the cross section P of the wiring cut in the thickness direction of the metal foil was required to be 3.5% or more.
- the purity is extremely high at 99.999% or more, and by developing the cube orientation, the elongation at break is improved, and the fatigue life against repeated bending in which principal stress and principal strain are applied in that direction. It has been found to be a long flexible circuit board.
- Example 2 for a single-sided copper-clad laminate using copper foil A and copper foil E produced by the same method as in Example 1, as shown in FIG. 6, the wiring of linear wiring 2 having a line width (l) of 150 ⁇ m
- the wiring pattern was formed such that the direction H (H direction) had an angle of 30 ° and 45 ° with respect to the MD direction ([100] axis) and the space width (s) was 250 ⁇ m.
- the test having a width of 150 mm in the longitudinal direction along the wiring direction H of the circuit board and a width of 15 mm in the direction orthogonal to the wiring direction H.
- a flexible circuit board 5 was obtained.
- FIG. 6 shows an example in which the angle formed by the wiring direction H of the test flexible circuit board 5 and the MD direction is cut out at an angle of 45 °.
- the test flex circuit board 5 obtained above was repeatedly subjected to bending fatigue tests under the same conditions as in Example 1. Also, the resin layer is melted from the single-sided copper clad laminate 4 before etching so that the angle formed by the wiring direction H and the MD direction of the flexible circuit board 5 for testing is the same, and the longitudinal direction is rolled.
- a tensile test was performed in the same manner as in Example 1 using a sample of 150 mm ⁇ 10 mm cut so as to have an angle of 30 ° and 45 ° with respect to the direction. That is, the principal stress and principal strain direction in the fatigue test of the copper foil coincide with the tensile direction of the tensile test, and both the copper foil A and the copper foil E have a highly developed cubic texture. In the tensile test, the same crystal orientation is subjected to principal strain and principal stress. Table 2 shows the results of the fatigue test and the tensile test.
- Example 2 From the results of Example 2 above, when the copper foil was highly oriented between the fatigue life of the flexible circuit board against repeated bending of high strain and the breaking elongation of the copper foil constituting the wiring, It was found that there was a high correlation. As seen in Example 1, the polycrystalline body provides higher strength and ductility, but is not effective in high bending applications. Therefore, the relationship between the fatigue life and the elongation at break under conditions that have a highly integrated texture is that the slip system plays an important role, not just copper, but the same slip system. Even a face-centered cubic orientation metal holds, and if the metals have different stacking fault energies, it is expected that the elongation at break can be increased and the fatigue life can be expected to be increased.
- Example 3 The polyamic acid solution a prepared by the same method as in Synthesis Example 1 is applied to a rolled copper foil H having a purity of 99.9 mass% and a thickness of 12 ⁇ m and dried (after curing, a 2 ⁇ m-thick thermoplastic polyimide is formed) ), And polyamic acid b is applied and dried (forms a low thermal expansion coefficient polyimide having a film thickness of 8 ⁇ m after curing), and further polyamic acid a is applied and dried (film thickness after curing). 2 ⁇ m thermoplastic polyimide is formed), as shown in conditions a to d below, the polyimide layer (resin layer) is subjected to heating conditions such that the maximum temperature of 180 to 240 ° C. is added for 10 minutes in the total time. Formed.
- a polyimide layer (resin) having a thickness of 250 ⁇ m along the rolling direction (MD direction) of the copper foil and a rectangular size of 150 mm width in a direction orthogonal to the rolling direction (TD direction) and having a thickness of 12 ⁇ m.
- a predetermined mask is placed on the copper foil side of the single-sided copper-clad laminate 4 obtained above, etching is performed using an iron chloride / copper chloride solution, and a straight line having a line width of 150 ⁇ m and a space width of 250 ⁇ m is based on the IPC standard.
- a low-speed IPC test wiring 2 having a shape-like wiring was formed.
- the maximum temperature of the heating conditions in forming the polyimide layer is set to four levels of 180 ° C. (condition a), 200 ° C. (condition b), 220 ° C. (condition c), and 240 ° C. (condition d).
- the wiring direction (H direction) of the linear wiring 2 is 0 °, 2 °, 2.9 °, 5.7 °, 9.5 °, 11.4 ° with respect to the rolling direction (MD direction). 14 °, 18.4 °, 25 °, 26.6 °, 30 °, 40 °, 45 °, 55 °, 60 °, 63.4 °, 78.6 °, 80 °, 82.9 °, Wiring patterns were formed so as to have angles of 22 levels of 87.1 °, 88 °, and 90 °, respectively.
- the cover material 7 (Arisawa Seisakusho CVK-0515KA: thickness 12.5 ⁇ m) was laminated on the surface of each wiring pattern side using an epoxy adhesive.
- the thickness of the adhesive layer 6 made of an adhesive was 15 ⁇ m in a portion without a copper foil circuit, and 6 ⁇ m in a portion where a copper foil circuit was present. And it cut out so that it might become 15 cm in a length direction along a wiring direction (H direction), and 8 mm in the direction orthogonal to a wiring direction, and the flexible circuit board for a test for setting it as an IPC test sample was obtained.
- a tensile test was performed as follows.
- the resin layer is dissolved from the single-sided copper-clad laminate 4 before etching so that the angle relationship between the wiring direction H and the MD direction of the test flexible circuit board 5 is the same 22 level, and the copper foil is dissolved.
- a rectangular sample having a length of 150 mm and a width of 10 mm, which was cut out so that the longitudinal direction had the above-described 22 level angle with respect to the rolling direction, was prepared. At this time, it was confirmed that there was no change in the structure of the copper foil in the process of dissolving the polyimide.
- the distance between gauge points in the length direction is 100 mm
- the tensile speed is 10 mm / min. Measured with
- a single-sided copper-clad laminate produced under the heat treatment conditions of conditions a to d is 0 °, 2.9 °, 30 °, 63.4 with respect to the rolling direction.
- a total of 20 samples without wiring patterns cut out at 5 angles of 7 ° and 78.6 ° were produced.
- a simulated heat treatment was applied under the same conditions as the circuit formation etching, and a cover material was further laminated under the same conditions.
- these effects on the copper foil structure are minor, and it has been found that the copper foil structure is determined by the heat treatment conditions of conditions a to d at the time of polyimide formation.
- the number of points where the unit cell axis ⁇ 001> is within 10 ° is counted in the thickness direction and the rolling direction of the copper foil, and the ratio to the total number of points is calculated.
- the average value was obtained.
- the results are shown in Table 3.
- the variation between samples under the same heating condition is 1% or less, and it can be said that the same heat treatment condition has the integration degree shown in Table 3 over the entire surface of the copper foil. It was found that the higher the maximum heat treatment temperature and the greater the thermal history, the more recrystallization progressed and the higher the degree of integration of the cubic recrystallization texture.
- the IPC test is a test simulating slide bending, which is one of the bending forms used for mobile phones and the like, as shown in the schematic diagram of FIG.
- the IPC test is a test in which a bent portion is provided with a determined gap length 8 as shown in FIG. 8, one side is fixed by a fixing portion 9, and the slide operating portion 10 on the opposite side is repeatedly reciprocated as shown in the drawing. . Therefore, the substrate is repeatedly bent in a region corresponding to the stroke amount of the reciprocating portion.
- the test was conducted by repeatedly sliding the polyimide layer (resin layer) 1 with the cap length being 1 mm, that is, the bending radius being 0.5 mm and the stroke being 38 mm.
- the circuit breakage life was defined as the number of strokes at which the electrical resistance of the circuit reached twice the initial value.
- the test was conducted on a total of 88 levels in which wiring patterns having 22 levels of angles were formed under the four heat treatment conditions of the above conditions a to d. At each test level, four test pieces were measured, and the average number of strokes at which the circuit was broken was obtained.
- the copper foil after the circuit breaking life when the cross section of the copper foil cut in the thickness direction so as to be orthogonal to the sliding direction is observed with a scanning electron microscope, there is a difference in degree, but the resin layer side and the cover material side It was observed that cracks occurred on the surfaces of the copper foils, and that many cracks were introduced on the surface of the copper foil on the resin layer side, which is outside the bent portion.
- Table 4 shows the average value of circuit break life at each level and the elongation at break in the tensile test.
- the surface index is also shown only in the case of the low index direction of the cross section P of the wiring when the circuit is cut in the length direction (wiring direction), that is, the ridgeline at the bent portion in the thickness direction. .
- the fracture life (fatigue life) in the IPC test is the angle between the circuit length direction (H direction) and the rolling direction (MD direction), that is, the normal direction of the cross section of the wiring when cutting from the ridge line at the bent portion in the thickness direction. And [100] were found to depend greatly on the angle.
- This orientation dependency is manifested under conditions b, c, and d.
- the higher the degree of integration of the cube orientation the greater the fatigue life against repeated bending and the greater the orientation dependency.
- the ⁇ 001> main direction is such that the area where the copper [001] is within an orientation difference of 10 ° occupies an area ratio of 50% or more in the evaluation by the EBSP method with respect to the thickness direction of the metal foil.
- the orientation is preferentially oriented in the thickness direction of the metal foil, and the region within 10 ° of the orientation difference from the [100] axis of copper occupies an area ratio of 50% or more as evaluated by the EBSP method. It was confirmed that the main azimuth was expressed when preferentially oriented in the metal foil plane. In particular, when the thickness direction and the rolling direction show the area ratios of 75% or more and 85% or more, respectively, and the condition c has a high degree of integration of cube orientation, the fatigue life is large and the orientation dependency is also high.
- the effect becomes large, and in the condition d in which the thickness direction and the rolling direction show an area ratio of 98% or more and 99% or more, respectively, and the accumulation degree of the cube orientation is extremely high, the fatigue life is further increased and the orientation dependency is increased. It turns out that the effect is great.
- the normal direction of the wiring cross section P when cutting in the thickness direction from the ridgeline at the bent portion is the ⁇ 100> main orientation of the copper foil.
- the fatigue life of the circuit against bending is higher when it deviates from the above.
- the effect was observed with respect to the main strain direction of the bent portion, that is, with respect to the cross-sectional normal direction of the wiring when cutting from the ridge line in the bent portion in the thickness direction. This was the case with an angle of 9 ° to 87.1 °.
- the cross section P of the wiring when cut in the thickness direction from the ridgeline at the bent portion passes from (20 1 0) to (110) with [001] as the zone axis, and (1 20 0 ).
- the effect is large at 11.4 ° to 78.6 ° with respect to the main strain direction of the bent portion, that is, with respect to the normal direction of the cross section of the wiring when cut from the ridge line in the bent portion in the thickness direction. It was the case with an angle.
- the cross section P of the wiring when it is cut in the thickness direction from the ridgeline at the bent portion ranges from (510) to (110) to (150) with [001] as the zone axis.
- the bending characteristic further has an angle of 26.6 ° to 63.4 ° with respect to the main strain direction of the bent portion, that is, with respect to the normal direction of the cross section of the wiring when cut from the ridge line in the bent portion in the thickness direction. In the case of 30 ° and 60 °, the best results were obtained.
- the cross section P is in the range from (210) to (110) to (120) with [001] as the zone axis, and the most excellent is (40 23 0) and ( 23 40 0) Near.
- the basic crystal axis ⁇ 100> of the unit cell having a face-centered cubic structure has two orthogonal axes of the thickness direction of the metal foil and a certain direction existing in the foil surface.
- the main orientation is such that the preferential orientation regions having an orientation difference of 10 ° or less each occupy 50% or more in area ratio
- the wiring cut from the ridge line in the bent portion in the thickness direction of the metal foil It was found that when the breaking elongation of the metal foil in the normal direction relative to the cross section P is 3.5% or more, the metal foil has good bending fatigue characteristics with respect to bending that generates principal stress and principal strain in the direction.
- the area ratio of the ⁇ 100> preferentially oriented region was 49% or less, even if the elongation at break in that direction showed a value of 3.5% or more, good bending fatigue characteristics were not obtained.
- Example 4 A heat treatment (preliminary heat treatment) for 30 minutes was applied to copper foil C having a purity of 99.99% at five levels of 180 ° C. to 400 ° C. in an Ar stream, and the polyamic acid solution a was applied in the same manner as in Example 1. , Dried (after forming a 2 ⁇ m-thick thermoplastic polyimide film after curing), coated with polyamic acid b and dried (after curing, formed a 9 ⁇ m-thick low thermal expansion polyimide), and further The polyamic acid a is applied and dried (forms a thermoplastic polyimide with a film thickness of 2 ⁇ m after curing), and is heated to a temperature of 300 to 360 ° C.
- a polyimide layer was formed.
- the copper foil was cut out to a rectangular size of 250 mm in length along the rolling direction (MD direction) and 150 mm in the direction perpendicular to the rolling direction (TD direction), as shown in FIG.
- colloidal silica was used on the rolled surface 2a of the copper foil 2, mechanically and chemically polished, and then subjected to orientation analysis using an EBSP apparatus.
- the apparatuses used were FE-SEM (S-4100) manufactured by Hitachi, Ltd., EBSP apparatus manufactured by TSL, and software (OIM Analysis 5.2).
- the measurement area was an area of approximately 800 ⁇ m ⁇ 1600 ⁇ m, and the measurement acceleration voltage was 20 kV and the measurement step interval was 4 ⁇ m.
- the evaluation of the orientation was shown by the ratio of the measurement points where ⁇ 100> is within 10 ° with respect to the thickness direction of the foil and the rolling direction of the foil to the total measurement points.
- the number of measurements was performed on five different samples of each variety, and the percentages after the second decimal place were rounded off. Further, using the obtained data, the crystal grain size was evaluated by setting the crystal grain boundaries to those having an orientation difference of 15 ° or more between adjacent crystal grains, and the average grain size was determined for the polycrystal. The results are shown in Table 5.
- each of the copper foils C had a cubic texture, and both the copper foil surface orientation and the rolling direction had a main orientation of ⁇ 001 ⁇ ⁇ 100>.
- the rolled copper foil was recrystallized by pre-heat treatment and heat at the time of curing of the polyimide, and a recrystallized texture was formed.
- the higher the preliminary heat treatment temperature the greater the degree of orientation of ⁇ 001 ⁇ ⁇ 100>.
- the orientation other than the ⁇ 100> orientation was confirmed by the EBSP apparatus in the same manner as described above.
- the recrystallized residual orientation having an orientation of ⁇ 212> with respect to the rolling direction and an equivalent circle diameter of 5 ⁇ m or less was island-like. Was dispersed.
- a predetermined mask is put on the copper foil 2 side of the single-sided copper clad laminate 4 obtained above, and etching is performed using an iron chloride / copper chloride solution, as shown in FIG.
- the angle between the wiring direction H and the MD direction is 0 °
- the wiring direction H (H direction) of the linear wiring 2 having a line width (l) of 150 ⁇ m is parallel to the MD direction ( ⁇ 100> axis).
- the wiring pattern was formed so that the space width (s) was 250 ⁇ m.
- MIT flex test was performed according to JIS C5016 using the test flexible circuit board obtained above.
- a schematic diagram of the test is shown in FIG.
- the equipment is manufactured by Toyo Seiki Seisakusho (STROGRAPH-R1), one end of the test flexible circuit board 5 in the longitudinal direction is fixed to the holding jig of the bending test apparatus, and the other end is fixed with a weight.
- the wire 2 on the circuit board 5 is cut off from conduction while being rotated to 135 ⁇ 5 degrees alternately left and right at a vibration speed of 150 times / min. was determined as the number of flexing.
- the main stress applied to the copper circuit is obtained because the ridge line formed in the bent portion is bent so as to be orthogonal to the wiring direction H of the wiring 2 of the test flexible circuit board 5.
- the main strain is a tensile stress or tensile strain parallel to the rolling direction.
- a tensile test was performed in parallel with the main stress of bending, the main strain direction, that is, the rolling direction.
- the resin layer was dissolved from the single-sided copper clad laminate 4 before etching, and a tensile test was conducted on the copper foil alone. In the process of dissolving the polyimide, it was confirmed that there was no change in the structure of the copper foil.
- the tensile test uses a sample cut to a length of 150 mm in the rolling direction (MD direction) of the copper foil and a width of 10 mm in the vertical direction in the foil plane, the distance between the gauge points is 100 mm, and the tensile speed is 10 mm / min in the length direction. . Measured with For the measurement, seven samples were prepared for each preliminary heat treatment temperature of the copper foil, and the breaking stress (breaking strength) and the average value of breaking elongation obtained by measuring these were shown in Table 5.
- the elongation at break increased as the integration degree increased in the region where the ⁇ 100> integration degree (%) was 98.0% or more and 99.8% or less.
- the elongation at break was small in the copper foil from which the island-like structure disappeared. This is presumed to be related to the slip surface. From the above, it was confirmed that the elongation at break and the bending fatigue life have a strong correlation. That is, a texture with a ⁇ 100> accumulation degree (%) of 98.0% or more and 99.8% or less is highly developed, and the flexural fatigue life is increased when the elongation at break is 3.5% or more. I understand.
- the flexible circuit board according to the present invention can be widely used in various electronic and electrical devices.
- the circuit board itself is bent, twisted, or deformed according to the operation of the mounted device. , Suitable for use with a bent portion in either.
- the flexible circuit board of the present invention has a bent portion structure with excellent bending durability, it is frequently bent with repeated operations such as sliding bending, bending bending, hinge bending, and sliding bending.
- it is suitable for the case where a bent portion is required in which the radius of curvature is required to be extremely small in order to cope with downsizing of the equipment to be mounted. Therefore, it can be suitably used for various electronic devices such as thin mobile phones, thin displays, hard disks, printers, and DVD devices that require durability.
- Resin layer 2 Wiring (metal foil) 2a: Rolled surface 2b: Side surface 3: Connector terminal 4: Single-sided copper clad laminate 5: Test flexible circuit board 6: Adhesive layer 7: Cover material 8: Gap length 9: Fixing part 10: Slide operating part 21: Method of section P Line direction L: Ridge line P: Cross section of wiring when cut in the thickness direction from the ridge line at the bent portion
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Abstract
Disclosed is a flexible circuit board which has a bend section subjected to repeated bending and straightening with a small radius of curvature under severe conditions and which yet has durability and excellent flexibility. Specifically, the flexible circuit board is provided with a resin layer and wiring formed of metal foil and has a bend section in at least one portion of the wiring, wherein the metal foil is made of a metal having a face-centered cubic structure, wherein the preferred orientation region, in which the fundamental crystal axis <100> of each unit lattice of the face-centered cubic structure is within 10˚ of perpendicular to the thickness direction of the metal foil and to a direction along the surface of the foil, occupies an area of 50% or more of the area of the board, and wherein the breaking elongation of the metal foil in a direction tangent to a cross-section (P) of the wiring taken along a plane extending from the ridge line of the bend section in the thickness direction of the metal foil is 3.5% or more and 20% or less.
Description
この発明は、いずれかに屈曲部を有して使用される可撓性回路基板、及び可撓性回路基板の屈曲部構造に関し、詳しくは、屈曲に対して耐久性を備え、かつ、屈曲性に優れた可撓性回路基板、及び可撓性回路基板の屈曲部構造に関する。
TECHNICAL FIELD The present invention relates to a flexible circuit board that is used with a bent portion in any one of them, and a bent portion structure of the flexible circuit board. More specifically, the invention has durability against bending and is flexible. The present invention relates to an excellent flexible circuit board and a bent portion structure of the flexible circuit board.
樹脂層と金属箔からなる配線とを有してなる可撓性回路基板（フレキシブルプリント基板）は、折り曲げて使用することが可能であることから、ハードディスク内の可動部、携帯電話のヒンジ部やスライド摺動部、プリンターのヘッド部、光ピックアップ部、ノートＰＣの可動部などをはじめ、各種電子・電気機器で幅広く使用されている。そして、近時では、特にこれらの機器の小型化、薄型化、高機能化等に伴い、限られたスペースに可撓性回路基板を小さく折り畳んで収納したり、電子機器等の様々な動きに対応した屈曲性が求められている。そのため、屈曲部における曲率半径がより小さくなるような折り曲げや、折り曲げが頻繁に繰り返されるような動作にも対応できるように、可撓性回路基板の更なる強度等の機械的特性の向上が必要になっている。
Since a flexible circuit board (flexible printed circuit board) having a resin layer and a wiring made of metal foil can be used by being bent, a movable part in a hard disk, a hinge part of a mobile phone, Widely used in various electronic and electrical devices such as sliding slides, printer heads, optical pickups, and notebook PCs. In recent years, especially with the downsizing, thinning, and high functionality of these devices, the flexible circuit board can be folded and stored in a limited space or used in various movements of electronic devices. Corresponding flexibility is required. Therefore, it is necessary to improve the mechanical characteristics such as the strength of the flexible circuit board so that it can cope with the bending with a smaller radius of curvature at the bent portion and the operation in which the bending is frequently repeated. It has become.
一般に、折り曲げの繰り返しや曲率半径の小さい屈曲に対して強度が劣る等で不良要因となるのは樹脂層よりむしろ配線の方であり、これらに耐えられなくなると配線の一部に割れや破断が生じ、回路基板として利用できなくなってしまう。そこで、例えばヒンジ部における配線に対する曲げ応力を小さくするために、回動軸に対して斜めになるように配線された可撓性回路基板（特許文献１参照）や、ヒンジ部の回動方向に１巻き以上螺旋させた螺旋部を形成し、この巻き数を多くすることで開閉動作による螺旋部の直径の変化を小さくして損傷を少なくする方法（特許文献２参照）などが提案されている。しかしながら、これらの方法では、いずれも可撓性回路基板の設計が制約されてしまう。
In general, it is the wiring rather than the resin layer that causes failure due to repeated bending and bending with a small radius of curvature. As a result, it cannot be used as a circuit board. Therefore, for example, in order to reduce the bending stress on the wiring in the hinge portion, the flexible circuit board (see Patent Document 1) wired so as to be inclined with respect to the rotation axis, or in the rotation direction of the hinge portion. A method has been proposed in which a spiral portion formed by spiraling one or more turns is formed and the change in the diameter of the spiral portion due to the opening / closing operation is reduced to reduce damage by increasing the number of turns (see Patent Document 2). . However, any of these methods restricts the design of the flexible circuit board.
一方では、圧延銅箔の圧延面のＸ線回折（銅箔の厚み方向のＸ線回折）で求めた（２００）面の強度（Ｉ）が、微粉末銅のＸ線回折で求めた（２００）面の強度（Ｉ0）に対してＩ／Ｉ0＞２０である場合に屈曲性に優れることが報告されている（特許文献３及び４参照）。すなわち、銅の再結晶集合組織である立方体方位が発達するほど銅箔の屈曲性が向上するため、立方体集合組織の発達度を上記パラメータ（Ｉ／Ｉ0）で規定した、可撓性回路基板の配線材料として好適な銅箔が知られている。また、Ｆｅ、Ｎｉ、Ａｌ、Ａｇ等の元素を銅に固溶する範囲の濃度で含有し、所定の条件で焼鈍して再結晶化して得た圧延銅合金箔が、すべり面に沿ったせん断変形を容易にして、屈曲性に優れることが報告されている（特許文献５参照）。
On the other hand, the strength (I) of the (200) plane determined by X-ray diffraction (X-ray diffraction in the thickness direction of the copper foil) of the rolled copper foil was determined by X-ray diffraction of fine powder copper (200 ) It has been reported that when I / I 0 > 20 with respect to the surface strength (I 0 ), the film has excellent flexibility (see Patent Documents 3 and 4). That is, the flexibility of the copper foil improves as the cube orientation, which is the recrystallized texture of copper, develops. Therefore, a flexible circuit board in which the degree of development of the cube texture is defined by the parameter (I / I 0 ) A copper foil suitable as a wiring material is known. In addition, a rolled copper alloy foil containing elements such as Fe, Ni, Al, Ag, etc. in a concentration in the range of solid solution in copper, and obtained by annealing and recrystallization under predetermined conditions is shear along the sliding surface. It has been reported that the deformation is facilitated and the flexibility is excellent (see Patent Document 5).
また、高屈曲特性が要求される可撓性回路基板には、酸素や銀などの不純物を含有させた銅箔が使用されることがあり、純度にすると９９％～９９．９質量％程度の銅箔である。本発明では、断らない限り純度は、質量濃度で表記する。また、試験レベルでは、広くケーブルの導体として使われている純度９９．５％程度のタフピッチ銅や酸化物を含まない無酸素銅が用いられている例がある（特許文献３、４参照）。タフピッチ銅の不純物は、数百ｐｐｍの酸素（多くは酸化銅として含む）、銀、鉄、硫黄、リン等が含まれる。無酸素銅は、通常純度９９．９６～９９．９９５％程度までの銅であって、１０ｐｐｍ以下まで大幅に酸素を減じた銅である。上述した特許文献３、４では、無酸素銅で製造した銅箔の屈曲疲労特性が、タフピッチ銅箔より優れ、酸化銅の含有の有無によるものと報告されている。なお、これらの銅の純度を更に高める場合は、銀、リン、硫黄等の不純物を除去する必要がある。
In addition, a copper foil containing impurities such as oxygen and silver may be used for a flexible circuit board that requires a high bending property, and its purity is about 99% to 99.9% by mass. Copper foil. In the present invention, purity is expressed as mass concentration unless otherwise specified. Further, at the test level, there are examples in which tough pitch copper having a purity of about 99.5% and oxygen-free copper containing no oxide, which are widely used as cable conductors, are used (see Patent Documents 3 and 4). Impurities of tough pitch copper include several hundred ppm of oxygen (mostly included as copper oxide), silver, iron, sulfur, phosphorus, and the like. Oxygen-free copper is usually copper having a purity of about 99.96 to 99.995%, and has been greatly reduced in oxygen to 10 ppm or less. In Patent Documents 3 and 4 described above, it is reported that the bending fatigue characteristics of a copper foil made of oxygen-free copper is superior to that of a tough pitch copper foil and depends on the presence or absence of copper oxide. In addition, when further improving the purity of these copper, it is necessary to remove impurities, such as silver, phosphorus, and sulfur.
このような状況のもと、本発明者等は、可撓性回路基板の設計に制約が生じず、折り曲げの繰り返しや曲率半径の小さな屈曲に対しても耐久性を備えた可撓性回路基板を得るために鋭意検討した結果、高度に配向し、かつその破断伸びが大きな面心立方晶系の結晶構造を有する金属箔を用いることで、屈曲耐久性や屈曲性に優れた可撓性回路基板が得られることを見出し、本発明を完成した。
Under such circumstances, the present inventors have no restrictions on the design of the flexible circuit board, and the flexible circuit board has durability against repeated bending and bending with a small radius of curvature. As a result of diligent studies to obtain a flexible circuit that is highly oriented and has excellent bending durability and flexibility by using a metal foil having a face-centered cubic crystal structure with a large elongation at break. The inventors found that a substrate was obtained and completed the present invention.
したがって、本発明の目的は、耐久性に優れた可撓性回路基板を提供することにあり、特に、携帯電話や小型電子機器等のヒンジ部又はスライド摺動部など、曲率半径の小さな繰り返し屈曲を伴うような過酷な使用条件に対しても耐久性を示し、屈曲性に優れた可撓性回路基板を提供することにある。
Accordingly, an object of the present invention is to provide a flexible circuit board having excellent durability, and in particular, repeated bending with a small radius of curvature, such as a hinge part or a slide sliding part of a mobile phone or a small electronic device. It is to provide a flexible circuit board that exhibits durability even under severe use conditions such as, and has excellent flexibility.
また、本発明の別の目的は、携帯電話や小型電子機器等のヒンジ部又はスライド摺動部など、特に曲率半径の小さな繰り返し屈曲部における過酷な条件に対して耐久性を備え、屈曲性に優れた可撓性回路基板の屈曲部構造を提供することにある。
In addition, another object of the present invention is to provide durability and resistance to harsh conditions such as hinge portions or slide sliding portions of mobile phones, small electronic devices, etc., particularly in repeated bending portions having a small curvature radius. An object of the present invention is to provide an excellent flexible circuit board bent portion structure.
本発明は、上記従来技術の問題を解決するために鋭意検討した結果、以下の構成を要旨とする。
（１）樹脂層と金属箔から形成された配線とを備え、配線の少なくとも一箇所に屈曲部を有して使用される可撓性回路基板であって、
金属箔は、面心立方構造を有する金属からなると共に、面心立方構造の単位格子の基本結晶軸＜１００＞が、金属箔の厚さ方向と箔面内に存在するある一方向との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で５０％以上を占め、かつ屈曲部における稜線から金属箔の厚み方向に切った配線の断面Ｐに対する法線方向の金属箔の破断伸びが３．５％以上、２０％以下であることを特徴とする可撓性回路基板。
（２）金属箔が、純度９９．９９９質量％以上の銅箔からなる（１）項に記載の可撓性回路基板。
（３）金属箔が銅箔であり、箔面法線方向から見たときの結晶粒径が２５μｍ以上である（１）又は（２）項に記載の可撓性回路基板。
（４）金属箔の厚みが５μｍ以上、１８μｍ以下である（１）～（３）項のいずれかに記載の可撓性回路基板。
（５）配線の断面Ｐが、［００１］を晶帯軸として（１００）から（１１０）への回転方向における（20 １ ０）から（１ 20 ０）の範囲に含まれたいずれかの面に主方位をなす（１）～（４）項のいずれかに記載の可撓性回路基板。
（６）配線の断面Ｐが、（１００）標準投影図のステレオ三角形において（20 １ ０）を表す点と（１１０）を表す点とで結ばれた線分上にあるいずれかの面である（５）項に記載の可撓性回路基板。
（７）屈曲部における稜線に対して直交する方向に沿って配線が形成されている（１）～（６）項のいずれかに記載の可撓性回路基板。
（８）樹脂層がポリイミドからなる（１）～（７）項のいずれかに記載の可撓性回路基板。
（９）摺動屈曲、折り曲げ屈曲、ヒンジ屈曲及びスライド屈曲からなる群から選ばれたいずれかの繰り返し動作を伴う屈曲部が形成されるように使用される（１）～（８）項のいずれかに記載の可撓性回路基板。
（１０）上記（１）～（９）項のいずれかに記載の可撓性回路基板を搭載した電子機器。
（１１）樹脂層と金属箔から形成された配線とを備え、配線の少なくとも一箇所に屈曲部を有して使用される可撓性回路基板の屈曲部構造であって、
金属箔は、面心立方構造を有する金属からなると共に、面心立方構造の単位格子の基本結晶軸＜１００＞が、金属箔の厚さ方向と箔面内に存在するある一方向との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で５０％以上を占め、かつ、屈曲部における稜線から金属箔の厚み方向に切った配線の断面Ｐに対する法線方向の金属箔の破断伸びが３．５％以上、２０％以下であることを特徴とする可撓性回路基板の屈曲部構造。 The present invention is summarized as follows as a result of intensive studies to solve the above-described problems of the prior art.
(1) A flexible circuit board including a resin layer and a wiring formed from a metal foil, and having a bent portion at least at one place of the wiring,
The metal foil is made of a metal having a face-centered cubic structure, and the basic crystal axis <100> of the unit cell of the face-centered cubic structure is 2 in the thickness direction of the metal foil and a certain direction existing in the foil surface. With respect to two orthogonal axes, the preferential orientation regions having an azimuth difference of 10 ° or less occupy 50% or more in area ratio, and the normal direction with respect to the cross section P of the wiring cut from the ridge line in the bent portion in the thickness direction of the metal foil A flexible circuit board, wherein the breaking elongation of the metal foil is 3.5% or more and 20% or less.
(2) The flexible circuit board according to (1), wherein the metal foil is a copper foil having a purity of 99.999% by mass or more.
(3) The flexible circuit board according to (1) or (2), wherein the metal foil is a copper foil, and the crystal grain size when viewed from the normal direction of the foil surface is 25 μm or more.
(4) The flexible circuit board according to any one of (1) to (3), wherein the thickness of the metal foil is 5 μm or more and 18 μm or less.
(5) Any plane in which the cross section P of the wiring is included in the range of (20 1 0) to (1 20 0) in the rotation direction from (100) to (110) with [001] as the zone axis The flexible circuit board according to any one of (1) to (4), wherein
(6) The cross section P of the wiring is any surface on the line segment connected by the point representing (20 1 0) and the point representing (110) in the stereo triangle of the (100) standard projection view. (5) The flexible circuit board according to item (5).
(7) The flexible circuit board according to any one of (1) to (6), wherein a wiring is formed along a direction orthogonal to the ridge line in the bent portion.
(8) The flexible circuit board according to any one of (1) to (7), wherein the resin layer is made of polyimide.
(9) Any one of items (1) to (8) used so as to form a bent portion with any repetitive motion selected from the group consisting of sliding bending, bending bending, hinge bending, and sliding bending A flexible circuit board according toclaim 1.
(10) An electronic device on which the flexible circuit board according to any one of (1) to (9) is mounted.
(11) A bent portion structure of a flexible circuit board that includes a resin layer and a wiring formed from a metal foil, and is used with a bent portion in at least one portion of the wiring,
The metal foil is made of a metal having a face-centered cubic structure, and the basic crystal axis <100> of the unit cell of the face-centered cubic structure is 2 in the thickness direction of the metal foil and a certain direction existing in the foil surface. The normal orientation direction with respect to the cross section P of the wiring cut in the thickness direction of the metal foil from the ridgeline in the bent portion with respect to the two orthogonal axes, the preferential orientation region having an azimuth difference of 10 ° or less occupies 50% or more in area ratio Bending part structure of flexible circuit board, wherein elongation at break of metal foil is 3.5% or more and 20% or less.
（１）樹脂層と金属箔から形成された配線とを備え、配線の少なくとも一箇所に屈曲部を有して使用される可撓性回路基板であって、
金属箔は、面心立方構造を有する金属からなると共に、面心立方構造の単位格子の基本結晶軸＜１００＞が、金属箔の厚さ方向と箔面内に存在するある一方向との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で５０％以上を占め、かつ屈曲部における稜線から金属箔の厚み方向に切った配線の断面Ｐに対する法線方向の金属箔の破断伸びが３．５％以上、２０％以下であることを特徴とする可撓性回路基板。
（２）金属箔が、純度９９．９９９質量％以上の銅箔からなる（１）項に記載の可撓性回路基板。
（３）金属箔が銅箔であり、箔面法線方向から見たときの結晶粒径が２５μｍ以上である（１）又は（２）項に記載の可撓性回路基板。
（４）金属箔の厚みが５μｍ以上、１８μｍ以下である（１）～（３）項のいずれかに記載の可撓性回路基板。
（５）配線の断面Ｐが、［００１］を晶帯軸として（１００）から（１１０）への回転方向における（20 １ ０）から（１ 20 ０）の範囲に含まれたいずれかの面に主方位をなす（１）～（４）項のいずれかに記載の可撓性回路基板。
（６）配線の断面Ｐが、（１００）標準投影図のステレオ三角形において（20 １ ０）を表す点と（１１０）を表す点とで結ばれた線分上にあるいずれかの面である（５）項に記載の可撓性回路基板。
（７）屈曲部における稜線に対して直交する方向に沿って配線が形成されている（１）～（６）項のいずれかに記載の可撓性回路基板。
（８）樹脂層がポリイミドからなる（１）～（７）項のいずれかに記載の可撓性回路基板。
（９）摺動屈曲、折り曲げ屈曲、ヒンジ屈曲及びスライド屈曲からなる群から選ばれたいずれかの繰り返し動作を伴う屈曲部が形成されるように使用される（１）～（８）項のいずれかに記載の可撓性回路基板。
（１０）上記（１）～（９）項のいずれかに記載の可撓性回路基板を搭載した電子機器。
（１１）樹脂層と金属箔から形成された配線とを備え、配線の少なくとも一箇所に屈曲部を有して使用される可撓性回路基板の屈曲部構造であって、
金属箔は、面心立方構造を有する金属からなると共に、面心立方構造の単位格子の基本結晶軸＜１００＞が、金属箔の厚さ方向と箔面内に存在するある一方向との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で５０％以上を占め、かつ、屈曲部における稜線から金属箔の厚み方向に切った配線の断面Ｐに対する法線方向の金属箔の破断伸びが３．５％以上、２０％以下であることを特徴とする可撓性回路基板の屈曲部構造。 The present invention is summarized as follows as a result of intensive studies to solve the above-described problems of the prior art.
(1) A flexible circuit board including a resin layer and a wiring formed from a metal foil, and having a bent portion at least at one place of the wiring,
The metal foil is made of a metal having a face-centered cubic structure, and the basic crystal axis <100> of the unit cell of the face-centered cubic structure is 2 in the thickness direction of the metal foil and a certain direction existing in the foil surface. With respect to two orthogonal axes, the preferential orientation regions having an azimuth difference of 10 ° or less occupy 50% or more in area ratio, and the normal direction with respect to the cross section P of the wiring cut from the ridge line in the bent portion in the thickness direction of the metal foil A flexible circuit board, wherein the breaking elongation of the metal foil is 3.5% or more and 20% or less.
(2) The flexible circuit board according to (1), wherein the metal foil is a copper foil having a purity of 99.999% by mass or more.
(3) The flexible circuit board according to (1) or (2), wherein the metal foil is a copper foil, and the crystal grain size when viewed from the normal direction of the foil surface is 25 μm or more.
(4) The flexible circuit board according to any one of (1) to (3), wherein the thickness of the metal foil is 5 μm or more and 18 μm or less.
(5) Any plane in which the cross section P of the wiring is included in the range of (20 1 0) to (1 20 0) in the rotation direction from (100) to (110) with [001] as the zone axis The flexible circuit board according to any one of (1) to (4), wherein
(6) The cross section P of the wiring is any surface on the line segment connected by the point representing (20 1 0) and the point representing (110) in the stereo triangle of the (100) standard projection view. (5) The flexible circuit board according to item (5).
(7) The flexible circuit board according to any one of (1) to (6), wherein a wiring is formed along a direction orthogonal to the ridge line in the bent portion.
(8) The flexible circuit board according to any one of (1) to (7), wherein the resin layer is made of polyimide.
(9) Any one of items (1) to (8) used so as to form a bent portion with any repetitive motion selected from the group consisting of sliding bending, bending bending, hinge bending, and sliding bending A flexible circuit board according to
(10) An electronic device on which the flexible circuit board according to any one of (1) to (9) is mounted.
(11) A bent portion structure of a flexible circuit board that includes a resin layer and a wiring formed from a metal foil, and is used with a bent portion in at least one portion of the wiring,
The metal foil is made of a metal having a face-centered cubic structure, and the basic crystal axis <100> of the unit cell of the face-centered cubic structure is 2 in the thickness direction of the metal foil and a certain direction existing in the foil surface. The normal orientation direction with respect to the cross section P of the wiring cut in the thickness direction of the metal foil from the ridgeline in the bent portion with respect to the two orthogonal axes, the preferential orientation region having an azimuth difference of 10 ° or less occupies 50% or more in area ratio Bending part structure of flexible circuit board, wherein elongation at break of metal foil is 3.5% or more and 20% or less.
本発明によれば、可撓性回路基板を屈曲させた際の屈曲部において配線を構成する金属箔が、金属疲労が生じ難く、応力及び歪みに対して優れた耐久性を有する。そのため、可撓性回路基板の設計に制約が生じず、折り曲げの繰り返しや曲率半径の小さな屈曲に対しても耐え得る強度を備えて、屈曲性に優れた可撓性回路基板を提供することができ、薄型携帯電話、薄型ディスプレー、ハードディスク、プリンター、ＤＶＤ装置等をはじめ、耐久性の高い電子機器が実現可能になる。
According to the present invention, the metal foil constituting the wiring at the bent portion when the flexible circuit board is bent hardly causes metal fatigue and has excellent durability against stress and strain. Therefore, it is possible to provide a flexible circuit board having excellent flexibility with sufficient strength to withstand repeated bending and bending with a small radius of curvature without any restrictions on the design of the flexible circuit board. This makes it possible to realize highly durable electronic devices such as thin mobile phones, thin displays, hard disks, printers, and DVD devices.
本発明の可撓性回路基板が備える配線は、面心立方晶系の結晶構造を有する金属からなる金属箔によって形成される。面心立方晶系の結晶構造を有する金属としては、例えば、銅、アルミニウム、ニッケル、銀、ロジウム、パラジウム、白金、金などが知られており、これらはいずれであってもよいが、金属箔としての利用性から銅、アルミニウム及びニッケルが好適であり、なかでも、可撓性回路基板の配線として主に使用される銅箔が最も一般的である。
The wiring provided in the flexible circuit board of the present invention is formed of a metal foil made of a metal having a face-centered cubic crystal structure. As the metal having a face-centered cubic crystal structure, for example, copper, aluminum, nickel, silver, rhodium, palladium, platinum, gold and the like are known. Copper, aluminum, and nickel are preferable because of their utility as copper, and copper foils that are mainly used as wiring for flexible circuit boards are the most common.
本発明は、屈曲耐久性や屈曲性に優れた可撓性回路基板を提供し、特に曲率半径が２ｍｍ以下であるような高歪み領域で優れた疲労特性を有する可撓性回路基板を提供するものである。この目的を達成するために、本発明では、ｉ）金属箔が高度に配向していること、及び、ii）屈曲部において金属箔の主応力方向の破断伸びが大きいこと、のいずれか一方がかけても本発明のような高屈曲時の疲労破壊に強い可撓性回路基板とはならない。即ち、i）とii）との両方を同時に満足することで、高屈曲時の疲労破壊に強い可撓性回路基板が得られるものである。具体的には、ｉ）面心立方構造の単位格子の基本結晶軸＜１００＞が、金属箔の厚さ方向と箔面内に存在するある一方向との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で５０％以上を占め、かつ、ii）屈曲部における稜線から金属箔の厚み方向に切った配線の断面Ｐに対する法線方向の金属箔の破断伸びが３．５％以上、２０％以下である必要がある。
The present invention provides a flexible circuit board excellent in bending durability and flexibility, and in particular, provides a flexible circuit board having excellent fatigue characteristics in a high strain region where the radius of curvature is 2 mm or less. Is. In order to achieve this object, in the present invention, one of i) the metal foil is highly oriented and ii) the elongation at break in the principal stress direction of the metal foil is large at the bent portion. However, it does not become a flexible circuit board that is resistant to fatigue failure during high bending as in the present invention. That is, by satisfying both i) and ii) at the same time, a flexible circuit board that is resistant to fatigue failure during high bending can be obtained. Specifically, i) the basic crystal axis <100> of the unit cell of the face-centered cubic structure is respectively in relation to two orthogonal axes of the thickness direction of the metal foil and a certain direction existing in the foil surface. The preferred orientation region within an orientation difference of 10 ° or more occupies 50% or more in area ratio, and ii) the elongation at break of the metal foil in the normal direction relative to the cross section P of the wiring cut in the thickness direction of the metal foil from the ridgeline at the bent portion Needs to be 3.5% or more and 20% or less.
金属箔が一般的な電解箔や圧延箔で見られるような多結晶体である場合、高い破断伸びが得られるが、本発明で求める高歪み疲労に対して、疲労特性の高い可撓性回路基板とはならない。一方、集合組織が発達し、配向度が大きくなっても破断伸びが小さい場合は、同様に本発明が求める特性を有する可撓性回路基板は得られない。
When the metal foil is a polycrystalline body as found in general electrolytic foils and rolled foils, a high breaking elongation can be obtained, but a flexible circuit having high fatigue characteristics against the high strain fatigue required in the present invention. It is not a substrate. On the other hand, when the texture is developed and the elongation at break is small even when the degree of orientation is large, a flexible circuit board having the characteristics required by the present invention cannot be obtained.
本発明は、集合組織が発達し、配向度が大きい金属箔であることを条件に、特に高い屈曲特性を求められる可撓性回路基板内の金属箔の破断伸びが重要な因子であることを初めて明らかにしたものである。
In the present invention, on the condition that the texture is developed and the metal foil has a large degree of orientation, the breaking elongation of the metal foil in the flexible circuit board, which requires particularly high bending characteristics, is an important factor. This is the first time revealed.
金属箔は、圧延箔又は電解箔のいずれであってもよいが、高い配向性を得る上で、好ましくは圧延箔であるのがよい。面心立方金属の場合、圧延条件と熱処理条件を工夫することにより、圧延方向と箔面法線方向とにそれぞれ＜１００＞主方位を有する高度に配向した立方体集合組織を有した金属箔を製造することができる。
The metal foil may be a rolled foil or an electrolytic foil, but is preferably a rolled foil in order to obtain high orientation. In the case of face-centered cubic metal, a metal foil having a highly oriented cubic texture with <100> main orientations in the rolling direction and the normal direction of the foil surface is produced by devising rolling conditions and heat treatment conditions. can do.
可撓性回路基板の用途に限らず、強い立方体方位を有する金属箔の機械特性の特徴は、破断伸びに異方性があることである。破断伸びは、＜１００＞方向への引張りを行った時、非常に小さな値を取る。一般的に、配向度が増すほど、また、金属箔の厚さが小さくなるほど、＜１００＞方向に引張試験を行った時の破断伸びは小さくなる。面心立方構造の単位格子の基本結晶軸＜１００＞が、金属箔の厚さ方向（箔面法線方向）と箔面内に存在するある一方向（そのひとつが圧延方向である）との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で９５％以上を占め、かつ、厚みが１８μｍ以下の一般的な圧延銅箔の場合（以下、便宜上「従来圧延銅箔」と言う）、屈曲部における主応力方向への破断伸びは３．５％には達しない。ここでいう破断伸びとは、金属箔の厚さよりも幅を十分に大きく取った典型的には幅５～１５ｍｍの範囲内でいずれかの幅の試験片を使用し、長さに対して１０％／minの歪み速さで引張り試験を行った時の破断に至るまでの伸びをいう。本発明では、以下の実施例に示した測定方法により金属箔の破断伸びを求め、樹脂層と積層させて可撓性回路基板を得た後の値を言うものとする。
The feature of the mechanical characteristics of the metal foil having a strong cubic orientation is not limited to the use of the flexible circuit board, and is that the elongation at break is anisotropic. The elongation at break takes a very small value when pulled in the <100> direction. In general, the greater the degree of orientation and the smaller the thickness of the metal foil, the smaller the elongation at break when a tensile test is performed in the <100> direction. The basic crystal axis <100> of the unit cell of the face-centered cubic structure is the thickness direction of the metal foil (the normal direction of the foil surface) and one direction existing in the foil surface (one of which is the rolling direction). In the case of a general rolled copper foil having a surface area ratio of 95% or more and a thickness of 18 μm or less with respect to two orthogonal axes, each of which has an orientation difference of 10 ° or less (hereinafter referred to as “conventional rolling” for convenience) It is referred to as “copper foil”), and the breaking elongation in the principal stress direction at the bent portion does not reach 3.5%. The term “elongation at break” used herein refers to a specimen having a width of 5 to 15 mm, which is sufficiently larger than the thickness of the metal foil, and is 10 to the length. This refers to the elongation to break when a tensile test is performed at a strain rate of% / min. In the present invention, the elongation after breaking of the metal foil is determined by the measurement method shown in the following examples, and the value after the flexible circuit board is obtained by laminating with the resin layer.
圧延銅箔の場合、再結晶集合組織は圧延方向、すなわち金属箔の長手方向が＜１００＞方位になる。通常の可撓性回路基板では、基板を抜き出す時、歩留まりを高める点から、回路の長手方向と銅箔の長手方向は一致するように取る。したがって、回路の長手方向を折り曲げる通常の利用形態においては、主応力方向が＜１００＞方向と一致することから、従来圧延銅箔では、繰り返し屈曲に対して高い疲労特性は得られない。
In the case of rolled copper foil, the recrystallized texture has a <100> orientation in the rolling direction, that is, the longitudinal direction of the metal foil. In a normal flexible circuit board, when the board is extracted, the longitudinal direction of the circuit and the longitudinal direction of the copper foil coincide with each other from the viewpoint of increasing the yield. Therefore, in the normal usage mode in which the longitudinal direction of the circuit is bent, the main stress direction coincides with the <100> direction, so that the conventional rolled copper foil cannot obtain high fatigue characteristics against repeated bending.
このような方位関係で利用する可撓性回路基板の疲労特性を向上させる方法として、本発明では、使用する金属箔の高純度化を図るようにする。これまでに知られている高屈曲用途に用いられる可撓性回路基板では、酸素や銀などの不純物が意図的、あるいは不可避的に含有した銅箔が使用されている。これは、例えば特許文献５にあるように、すべり面に沿ったせん断変形を容易にしたり、電気抵抗の増加を抑制する目的がある。しかしながら、これらの不純物元素は積層欠陥エネルギーを低下させる。本発明者等はこの点に着目した。すなわち、積層欠陥エネルギーが低下すると転位が拡張し易くなり、交差すべりが起こり難く、特に＜１００＞方向に引張った時、伸びが出にくくなる。
As a method for improving the fatigue characteristics of the flexible circuit board used in such an orientation relationship, the present invention aims to increase the purity of the metal foil used. In a flexible circuit board used for high bending applications known so far, a copper foil intentionally or inevitably contains impurities such as oxygen and silver is used. This is for the purpose of facilitating shear deformation along the slip surface and suppressing an increase in electrical resistance, as described in Patent Document 5, for example. However, these impurity elements reduce the stacking fault energy. The present inventors paid attention to this point. That is, when the stacking fault energy is decreased, dislocations are easily expanded and cross slipping is unlikely to occur, and particularly when stretched in the <100> direction, elongation is difficult to occur.
そこで、本発明では、以下で説明するような所定の優先配向性を示すと共に、好ましくは純度が９９．９９９％以上の金属箔（好適には銅箔）を使用することで、＜１００＞方向の破断伸びを３．５％以上と大きくすることができ、結果として、高歪み領域で繰り返し歪みを加えた時の疲労特性を高めるようにする。金属箔の純度は高い方が望ましいが、製造コストの点から、９９．９９９％、ないし９９．９９９９％のものを使用するのが最も好適である。また、純度が９９．９９９％よりも低い銅箔であっても、酸素濃度が低い無酸素銅箔では、下記実施例に示されるように、狭い条件ながら圧延と熱処理条件によっては、面心立方構造の基本結晶軸＜１００＞のひとつ、例えば［００１］軸が、金属箔の厚さ方向（箔面法線方向）に対して方位差で１０°以内にある領域が９８％以上、９９．８％以下である場合、破断伸びが３．５％以上になる領域が存在し、耐屈曲疲労性が良好になる。この理由について現時点では定かではないが、熱処理によって所定の集合組織が得られた無酸素銅箔では、適度な大きさ、体積率で分散する圧延方向に対して＜２１２＞方位に対する再結晶残留組織の存在によって＜１００＞方向の破断伸びを大きくするものと推察する。
Therefore, in the present invention, a metal foil (preferably a copper foil) having a predetermined preferred orientation as described below and preferably having a purity of 99.999% or more is used, whereby the <100> direction is used. The elongation at break can be increased to 3.5% or more, and as a result, the fatigue characteristics are increased when repeated strain is applied in a high strain region. Although the higher purity of the metal foil is desirable, it is most preferable to use 99.999% to 99.9999% from the viewpoint of manufacturing cost. Further, even if the copper foil has a purity lower than 99.999%, an oxygen-free copper foil having a low oxygen concentration has a face-centered cubic shape depending on rolling and heat treatment conditions in a narrow condition, as shown in the following examples. 98% or more of a region in which one of the basic crystal axes <100> of the structure, for example, the [001] axis is within 10 ° in orientation difference with respect to the thickness direction of the metal foil (the normal direction of the foil surface); When it is 8% or less, there is a region where the elongation at break is 3.5% or more, and the bending fatigue resistance is improved. Although it is not clear at this time about this reason, in the oxygen-free copper foil in which a predetermined texture is obtained by heat treatment, a recrystallized residual structure with respect to the <212> orientation with respect to the rolling direction dispersed at an appropriate size and volume ratio It is assumed that the elongation at break in the <100> direction is increased by the presence of.
本発明の可撓性回路基板では、その回路を構成する金属箔の試料座標系に対して、金属箔の三次元結晶方位が規定され、その集合組織の集積度は、下記の範囲である。すなわち、面心立方構造の基本結晶軸＜１００＞のひとつ、例えば［００１］軸が、金属箔の厚さ方向（箔面法線方向）に対して方位差で１０°以内にある領域が面積比で５０％以上、望ましくは７５％以上、更に望ましくは９８％以上を占めるような優先配向を呈し、かつ、金属箔の表面に対して水平な方向である箔面内において、別の基本結晶軸、例えば［１００］軸から方位差で１０°以内にある領域が面積比で５０％以上、望ましくは８５％以上、更に望ましくは９９％以上を占めるような優先配向を呈するものを使用する。本発明では、少なくとも屈曲部において、上記のような集合組織の集積度を有していればよいが、好適には樹脂層に積層される金属箔の全てが上記のような集積度を有した、いわゆる単結晶ライクの金属箔であれば、配線設計において制約を受けることがなく好ましい。なお、優先配向の中心にある結晶方位を集合組織の主方位と呼ぶことから、本発明で使用する金属箔は、金属箔の厚さ方向が＜１００＞の主方位を有すると共に、金属箔の箔面内が＜１００＞の主方位を有すると言うことができる。
In the flexible circuit board of the present invention, the three-dimensional crystal orientation of the metal foil is defined with respect to the sample coordinate system of the metal foil constituting the circuit, and the degree of integration of the texture is in the following range. That is, a region in which one of the basic crystal axes <100> of the face-centered cubic structure, for example, the [001] axis is within 10 ° in orientation difference with respect to the thickness direction of the metal foil (the normal direction of the foil surface) is an area. In the foil plane, which has a preferential orientation that accounts for 50% or more, preferably 75% or more, more preferably 98% or more, and is in a direction parallel to the surface of the metal foil, another basic crystal An axis having a preferential orientation such that a region within 10 ° from the [100] axis occupies an azimuth difference accounts for 50% or more, desirably 85% or more, and more desirably 99% or more is used. In the present invention, it is sufficient that at least the bent portion has the above-mentioned texture integration degree, but preferably all the metal foils laminated on the resin layer have the above-mentioned integration degree. A so-called single crystal-like metal foil is preferable without being restricted in wiring design. Since the crystal orientation at the center of the preferential orientation is called the main orientation of the texture, the metal foil used in the present invention has a main orientation of <100> in the thickness direction of the metal foil, It can be said that the foil plane has a main orientation of <100>.
集合組織の優先配向の優先度、すなわち配向度又は集積度を表す指標は幾つかあり、Ｘ線回折強度、及び電子線回折で得られる局所的な三次元方位データの統計データを用いた客観的なデータに基づいた指標を用いることができる。
There are several indices that indicate the priority of texture orientation, that is, the degree of orientation or accumulation, and it is objective to use X-ray diffraction intensity and statistical data of local three-dimensional orientation data obtained by electron diffraction. An index based on simple data can be used.
例えば金属箔が銅箔の場合、Ｘ線回折で求めた上記晶帯軸と垂直な（００２）からの強度（Ｉ）（ここでは、Ｘ線回折における一般的な表記方法に従い（２００）面の強度としている）が、微粉末銅のＸ線回折で求めた（２００）面の強度（Ｉ0）に対してＩ／Ｉ0≧２５である銅箔から所定のパターンを有する配線を形成するがよく、好ましくはＩ／Ｉ0が３３～１５０の範囲、より好ましくは５０～１５０の範囲であるのがよい。ここで、パラメータＩ／Ｉ0は（１００）と（１１０）の晶帯軸、すなわち共通軸［００１］の配向度を表すものであり、立方体集合組織の発達度を表す客観的な一指標である。そして、金属箔が圧延銅箔の場合、これを一定以上の圧延率で強加工をおこなって、その後、熱を加えて再結晶させると、圧延箔面を（００１）主方位、箔面内圧延方向を（１００）主方位とする再結晶立方体方位が発達する。銅の再結晶集合組織である立方体方位が発達するほど、銅箔の屈曲疲労寿命が向上する。本発明の可撓性回路基板では、Ｉ／Ｉ0が２５より小さいと配線の屈曲疲労寿命の向上が十分に望めず、Ｉ／Ｉ0が３３以上であれば屈曲疲労寿命の向上が顕著になる。なお、銅箔の厚み方向のＸ線回折とは、銅箔の表面（圧延銅箔の場合は圧延面）における配向性を確認するものであり、（２００）面の強度（Ｉ）はＸ線回折で求めた（２００）面の強度積分値を示す。また、強度（Ｉ0）は、微粉末銅（関東化学社製銅粉末試薬Ｉ級、３２５メッシュ）の（２００）面の強度積分値を示す。
For example, when the metal foil is a copper foil, the intensity (I) from (002) perpendicular to the above-mentioned zone axis determined by X-ray diffraction (here, according to a general notation method in X-ray diffraction, (200) plane The wiring having a predetermined pattern is formed from a copper foil having I / I 0 ≧ 25 with respect to the strength (I 0 ) of the (200) plane obtained by X-ray diffraction of fine powder copper. The I / I 0 is preferably in the range of 33 to 150, more preferably in the range of 50 to 150. Here, the parameter I / I 0 represents the degree of orientation of the zone axes of (100) and (110), that is, the common axis [001], and is an objective index indicating the degree of development of the cube texture. is there. When the metal foil is a rolled copper foil, it is strongly processed at a rolling rate of a certain level or higher, and then recrystallized by applying heat, so that the rolled foil surface is rolled into the (001) main orientation and foil plane. A recrystallized cube orientation with the direction as the (100) principal orientation develops. The bending fatigue life of the copper foil is improved as the cubic orientation, which is the recrystallized texture of copper, develops. In the flexible circuit board of the present invention, if I / I 0 is less than 25, it is not possible to sufficiently improve the bending fatigue life of the wiring. If I / I 0 is 33 or more, the bending fatigue life is remarkably improved. Become. The X-ray diffraction in the thickness direction of the copper foil confirms the orientation on the surface of the copper foil (rolled surface in the case of a rolled copper foil), and the strength (I) of the (200) plane is X-ray. The integrated intensity value of the (200) plane obtained by diffraction is shown. The intensity (I 0) shows a fine powder of copper (manufactured by Kanto Chemical Co., Inc. copper powder reagent I grade, 325 mesh) in an intensity integral value of the (200) plane.
Ｉ／Ｉ0を２５以上にするためには、銅箔の再結晶集合組織が得られるようにすればよく、この手段については特に制限はないが、中間焼鈍条件や冷間圧延加工率を対象とする金属箔の種類や不純物濃度に応じて最適化することによって、結晶粒が大きな集合組織であって、かつＩ／Ｉ0≧２５の圧延銅箔を得ることができる。また、例えば樹脂層と圧延銅箔とを積層させて銅張り積層板を得た後、銅箔に３００～３６０℃の温度が積算時間で５分以上負荷されるような加熱条件を経ることにより、銅箔の再結晶集合組織を得るようにしてもよい。
In order to increase the I / I 0 to 25 or more, a recrystallized texture of the copper foil may be obtained. There is no particular limitation on this means, but the intermediate annealing conditions and the cold rolling process rate are targeted. By optimizing according to the type of metal foil and the impurity concentration, a rolled copper foil having a large texture of crystal grains and I / I 0 ≧ 25 can be obtained. In addition, for example, after a resin layer and a rolled copper foil are laminated to obtain a copper-clad laminate, the copper foil is subjected to heating conditions such that a temperature of 300 to 360 ° C. is loaded for an accumulated time of 5 minutes or more. A recrystallized texture of copper foil may be obtained.
また、集合組織を３次元的な集積度で規定するために、集合組織の主方位に対して１０°以内に入る優先配向領域の面積率を用いて特定することもできる。すなわち、金属箔の所定の面がどのような結晶方位を有するかについては、例えばＥＢＳＰ（Electron Back Scattering Pattern）法、ＥＣＰ（Electron Channeling Pattern）法等の電子線回折法やマイクロラウエ法等のＸ線回折法等により確認することができる。なかでも、ＥＢＳＰ法は、測定対象である試料表面に収束電子ビームを照射した際に発生する個々の結晶面から回折される擬菊池線と呼ばれる回折像から結晶を解析し、方位データと測定点の位置情報から測定対象の結晶方位分布を測定する方法であり、Ｘ線回折法よりもミクロな領域の集合組織の結晶方位を解析することができる。例えば、個々の微小領域でその結晶方位を特定し、それらをつなぎあわせてマッピングすることができ、各マッピング点間の面方位の傾角（方位差）が一定値以下のものを同色で塗り分け、ほぼ同一の面方位を有する領域（結晶粒）の分布を浮かび上がらせることにより方位マッピング像を得ることができる。また、特定の面方位に対して所定の角度以内の方位を有する方位面を含めてその方位であると規定し、各面方位の存在割合を面積率で抽出することもできる。ＥＢＳＰ法では、ある特定の方位から、特定の角度以内にある領域の面積率を出すためには、少なくとも本発明の可撓性回路基板における回路屈曲領域より大きな領域で、面積率を出すために十分な点数になるように細かく電子線を走査して、その平均的な情報を得る必要があるが、本発明で対象とする金属箔では、対象とする回路の大きさから考えて、０．００５ｍｍ2以上の領域において、平均的な面積率を出すために１０００点以上測定すればよい。
Further, in order to define the texture with a three-dimensional degree of integration, the texture can be specified using the area ratio of the preferentially oriented region that falls within 10 ° with respect to the main orientation of the texture. That is, as to what crystal orientation the predetermined surface of the metal foil has, for example, X-ray diffraction method such as EBSP (Electron Back Scattering Pattern) method, ECP (Electron Channeling Pattern) method or X-ray method such as micro Laue method It can be confirmed by a line diffraction method or the like. In particular, the EBSP method analyzes a crystal from a diffraction image called a pseudo Kikuchi line that is diffracted from each crystal plane generated when a focused electron beam is irradiated on the surface of a sample to be measured. This is a method of measuring the crystal orientation distribution of the measurement object from the position information of the above, and it is possible to analyze the crystal orientation of the texture in the microscopic region as compared with the X-ray diffraction method. For example, it is possible to specify the crystal orientation in each minute region, connect them and map them, and separate the ones whose tilt angle (azimuth difference) between each mapping point is below a certain value with the same color, An orientation mapping image can be obtained by highlighting the distribution of regions (crystal grains) having substantially the same plane orientation. It is also possible to define the orientation including the orientation plane having an orientation within a predetermined angle with respect to a specific plane orientation, and to extract the existence ratio of each plane orientation by the area ratio. In the EBSP method, in order to obtain an area ratio of a region within a specific angle from a specific orientation, in order to obtain an area ratio at least in a region larger than the circuit bent region in the flexible circuit board of the present invention. It is necessary to scan the electron beam finely so as to obtain a sufficient number of points to obtain the average information. However, in the metal foil targeted by the present invention, in view of the size of the target circuit, 0. In an area of 005 mm 2 or more, 1000 points or more may be measured in order to obtain an average area ratio.
ところで、本発明と特許文献３及び４に記載の発明での組織上の違いは、これらの特許文献の発明の方位規定は、Ｘ線で測定した箔法線方向のみの規定であるのに対して、本発明は３次元で規定している点である。屈曲に対して高い疲労特性を得るためには、特に屈曲させた時の主歪み、主応力方向、即ち箔面内の＜１００＞集積度が重要である。また、本発明では、再結晶粒、即ち立方体方位を有する結晶粒の大きさは、平均値で２５μｍ以上であることが望ましい。
By the way, the difference in structure between the present invention and the inventions described in Patent Documents 3 and 4 is that the orientation definition of the inventions of these Patent Documents is only the normal direction of the foil measured by X-ray. Thus, the present invention is defined in three dimensions. In order to obtain high fatigue characteristics with respect to bending, the main strain, the main stress direction, that is, the <100> integration degree in the foil surface, particularly when bent is important. In the present invention, the size of recrystallized grains, that is, crystal grains having a cubic orientation, is preferably 25 μm or more on average.
また、本発明において、特に高屈曲性を求める場合には、可撓性回路基板を形成する金属箔は、厚さ５～１８μｍの圧延銅箔を用いるのが良く、好ましくは厚さ９～１２μｍの圧延銅箔を用いるのが良い。圧延銅箔が１８μｍより厚くなると、曲率半径が２ｍｍ以下であるような高歪み領域で優れた疲労特性を有する可撓性回路基板を得るのが難しくなる。また、厚さが５μｍより薄くなると、金属箔と樹脂層とを積層させる上でのハンドリングが困難であり、均質な可撓性回路基板を形成することが困難である。
In the present invention, particularly when high flexibility is required, the metal foil forming the flexible circuit board is preferably a rolled copper foil having a thickness of 5 to 18 μm, preferably a thickness of 9 to 12 μm. It is preferable to use a rolled copper foil. When the rolled copper foil is thicker than 18 μm, it becomes difficult to obtain a flexible circuit board having excellent fatigue characteristics in a high strain region where the radius of curvature is 2 mm or less. On the other hand, when the thickness is less than 5 μm, handling in laminating the metal foil and the resin layer is difficult, and it is difficult to form a homogeneous flexible circuit board.
以上で述べた可撓性回路基板の疲労特性を向上させる第一の方策とは別に、本発明では、高度に配向した単結晶に近い面心立方金属箔の破断伸びを向上させるための第二の方策として、破断伸びの小さい＜１００＞方向が主応力方向にならないように、可撓性回路基板の配線構成を工夫することがあり、具体的には下記の方法が挙げられる。
Apart from the first measure for improving the fatigue characteristics of the flexible circuit board described above, the present invention provides a second method for improving the breaking elongation of a face-centered cubic metal foil close to a highly oriented single crystal. As a measure of the above, there is a case where the wiring configuration of the flexible circuit board is devised so that the <100> direction having a small elongation at break does not become the principal stress direction.
第一の方策で述べたように、圧延及び再結晶条件を工夫することによって、圧延方向と箔面法線方向ともに＜１００＞主方位を有する高度に配向した立方体集合組織を有する金属箔を製造することができる。その上で、配線として回路を切る方向を圧延方向、即ち＜１００＞方向から所定の角度でずらして斜めに回路を抜くことで、屈曲させた際の主応力方向に破断伸びが大きな可撓性回路基板を得ることができる。このような方法により、屈曲部における稜線から金属箔の厚み方向に切った配線の断面Ｐに対する法線方向（屈曲部における主応力方向）の金属箔の破断伸びが３．５％以上となるようにするためには、上記断面Ｐが、［００１］を晶帯軸として（20 １ ０）から（１ 20 ０）の範囲に含まれたいずれかの面に主方位をなしている必要がある。ここで、晶帯軸と面方位の関係を図１に示す。（20 １ ０）と（１ 20 ０）は、［００１］を共通軸、すなわち晶帯軸とした関係にあり、［００１］を軸とした（１００）から（１１０）へ〔（１００）から（０１０）へ〕の回転面内にある。すなわち、これを断面Ｐの法線方位に対する逆極点図上に示すと、（００１）、（20 １ ０）、（１１０）の各面は、図２に示すようになる。対称性から、逆極点図上では、（１ 20 ０）は（20 １ ０）と同じ位置に表される。本発明における金属箔の金属は面心立方構造である。その単位格子の結晶軸は、［１００］、［０１０］、［００１］であるが、本発明では、金属箔の厚さ方向（金属箔の表面に対して垂直方向）に＜１００＞優先方位がある場合、この軸を［００１］、すなわち箔面方位を（００１）として表記するが、面心立方構造の対称性からこれらの軸を入れ替えても等価であり、勿論これらは本発明に含まれる。
As described in the first policy, by devising the rolling and recrystallization conditions, a metal foil having a highly oriented cubic texture having a <100> main orientation in both the rolling direction and the foil surface normal direction is produced. can do. In addition, the direction of cutting the circuit as wiring is shifted by a predetermined angle from the rolling direction, that is, the <100> direction, and the circuit is pulled diagonally, so that flexibility is large in elongation at break in the main stress direction when bent. A circuit board can be obtained. By such a method, the breaking elongation of the metal foil in the normal direction (main stress direction in the bent portion) with respect to the cross section P of the wiring cut from the ridge line in the bent portion in the thickness direction of the metal foil is 3.5% or more. In order to achieve this, the cross section P needs to have a main orientation on any plane included in the range of (20 1 0) to (1 20 0) with [001] as the zone axis. . Here, the relationship between the zone axis and the plane orientation is shown in FIG. (20 1 0) and (1 20 0) have a relationship with [001] as a common axis, that is, a zone axis, from (100) to (110) with [001] as the axis [from (100) (010)] in the plane of rotation. That is, when this is shown on the reverse pole figure with respect to the normal direction of the cross section P, the surfaces of (001), (20 1 0), and (110) are as shown in FIG. Due to symmetry, (1 20 0) is represented at the same position as (20 1 0) on the inverse pole figure. The metal of the metal foil in the present invention has a face-centered cubic structure. The crystal axes of the unit cell are [100], [010], and [001]. In the present invention, <100> preferred orientation in the thickness direction of the metal foil (the direction perpendicular to the surface of the metal foil). In this case, this axis is expressed as [001], that is, the foil plane orientation is (001), but it is equivalent even if these axes are interchanged due to the symmetry of the face-centered cubic structure, and these are of course included in the present invention. It is.
そして、箔面内の主方位が、屈曲部の主歪み方向、すなわち屈曲部における稜線から厚み方向に切った際の配線の断面法線方向に対して（配線断面Ｐに対する垂線に対して）、２．９°～８７．１°〔(20 １ ０)～(１ 20 ０)〕の角度を有することが必要であり、好ましくは５．７°～８４．３°〔(10 １ ０)～(１ 10 ０)〕の角度、より好ましくは１１．４°～７８．６°〔(５１０)～(１５０)〕の角度、更に好ましくは２６．６°～６３．４°〔(２１０)～(１２０)〕の角度、最も好適には３０°又は６０°〔(40 23 ０)、又は(23 40 ０)〕であることが望ましい。ここで、〔 〕内は、それぞれの角度に対応する断面Ｐの面方位を表す。なお、結晶の対称性から、配線断面Ｐに対する法線が、金属箔面内の基本結晶軸＜１００＞と２．９～４５°の角度を有すると記述することもできる。
And, the main orientation in the foil plane is in the main strain direction of the bent portion, that is, in the normal direction of the cross section of the wiring cut from the ridge line in the bent portion in the thickness direction (with respect to the perpendicular to the wiring cross section P), It is necessary to have an angle of 2.9 ° to 87.1 ° [(20 1 0) to (1 20 0)], preferably 5.7 ° to 84.3 ° [(10 1 0) ~ (1 10 0)], more preferably 11.4 ° to 78.6 ° [(510) to (150)], and more preferably 26.6 ° to 63.4 ° [(210) to It is desirable that the angle is (120)], most preferably 30 ° or 60 ° [(40 23 0) or (23 40 0)]. Here, [] represents the plane orientation of the cross section P corresponding to each angle. From the symmetry of the crystal, it can also be described that the normal to the wiring cross section P has an angle of 2.9 to 45 ° with the basic crystal axis <100> in the metal foil plane.
ここで、屈曲部における稜線から厚み方向に切った際の配線の断面Ｐとは、例えば図３に示すように、可撓性回路基板をＵ字状に屈曲させるとその外側に稜線Ｌが形成されるが、この稜線Ｌから可撓性回路基板の厚み方向ｄに切った際に得られる断面のうち配線部分のものを言う。また、稜線Ｌとは、可撓性回路基板を屈曲させた状態で、その折り曲げ方向（図３中の太矢印）に沿って可撓性回路基板の断面を見た場合に形成される頂点を結んだ線である。なお、例えば後述する摺動屈曲など、稜線Ｌが可撓性回路基板を移動するような場合も含まれる。また、図３では、樹脂層１が外側であり、配線２が内側に屈曲された状態を表すが（曲率半径を有する円が内接する側を内側とする）、配線２が外側になる折り曲げ方であってもよいことは勿論である。
Here, the cross section P of the wiring when it is cut in the thickness direction from the ridgeline at the bent portion is, for example, as shown in FIG. 3, when the flexible circuit board is bent in a U shape, a ridgeline L is formed on the outside thereof. However, it refers to the wiring portion of the cross section obtained when the ridge line L is cut in the thickness direction d of the flexible circuit board. The ridge line L is an apex formed when the cross section of the flexible circuit board is viewed along the bending direction (thick arrow in FIG. 3) in a state where the flexible circuit board is bent. It is a connected line. In addition, the case where the ridgeline L moves a flexible circuit board, such as sliding bending mentioned later, for example, is also included. 3 shows a state in which the resin layer 1 is on the outside and the wiring 2 is bent inward (the side on which a circle having a radius of curvature is inscribed is inward), but the wiring 2 is bent outward. Of course, it may be.
様々な用途において、ある曲率の強制変位を受けるとき、金属箔は、主として引張、又は圧縮の応力を受ける。屈曲を受けた可撓性回路基板の中で、どの部分が引張又は圧縮を受けるかは、金属箔と樹脂の構成にもよるが、引張と圧縮の中立軸（あるいは中立面）より屈曲の外側である、最も遠い部分が金属の破壊で過酷であることが一般的であり、屈曲部における稜線から厚み方向に切った際の配線の断面法線方向への引張応力が主応力となる。すなわち、屈曲部における配線の主応力方向は、図３中に矢印２１で示した方向であり、典型的には、屈曲部の稜線から金属箔の厚み方向に切った配線断面Ｐに対する法線方向と等しく、金属箔の厚み方向に配向した［００１］軸と垂直に交わる方向である。
In various applications, when subjected to a forced displacement with a certain curvature, the metal foil is mainly subjected to tensile or compressive stress. Which part of the flexible circuit board that is bent is subjected to tension or compression depends on the configuration of the metal foil and the resin, but is bent from the neutral axis (or neutral surface) of tension and compression. It is common that the outermost part, which is the outermost part, is severe due to the destruction of the metal, and the tensile stress in the normal direction of the cross section of the wiring when cut in the thickness direction from the ridgeline at the bent part becomes the main stress. That is, the main stress direction of the wiring in the bent portion is the direction indicated by the arrow 21 in FIG. 3, and is typically the normal direction to the wiring cross section P cut from the ridge line of the bent portion in the thickness direction of the metal foil. And the direction perpendicular to the [001] axis oriented in the thickness direction of the metal foil.
可撓性回路基板内の金属箔の機械特性を考える時、図３中の矢印２１で示した主応力方向に金属箔を単純引張したときの応力歪み特性が重要な特性となる。ここで、図４（ｃ）及び（ｄ）の例に示すように、仮に面心立方系の結晶構造を有する金属箔の［１００］軸に対して直交する稜線が形成されるように屈曲させた場合、屈曲部での稜線から可撓性回路基板の厚み方向に切った配線の断面は（１００）面になるが、屈曲部における稜線から厚み方向に切った際の配線の断面Ｐが、図１に示すように、［００１］を晶帯軸として（１００）から（０１０）までの回転方向における（20 １ ０）から（１ 20 ０）の範囲（図中の両矢印）に含まれたいずれかの面に主方位をなしていれば、破断伸びを向上させることができる。なお、図１では（20 １ ０）から（１ 20 ０）の範囲を示したが、面心立方系の結晶構造ではこの範囲に含まれる面と等価な面が存在する。そのため、配線の断面が（20 １ ０）から（１ 20 ０）の範囲に含まれる面と符号の異なる等価な面については本発明に含まれる。
When considering the mechanical characteristics of the metal foil in the flexible circuit board, the stress strain characteristic when the metal foil is simply pulled in the main stress direction indicated by the arrow 21 in FIG. 3 is an important characteristic. Here, as shown in the examples of FIGS. 4C and 4D, the metal foil having a face-centered cubic crystal structure is bent so that a ridge line perpendicular to the [100] axis is formed. In this case, the cross section of the wiring cut in the thickness direction of the flexible circuit board from the ridge line at the bent portion becomes the (100) plane, but the cross section P of the wiring when cut in the thickness direction from the ridge line at the bent portion is As shown in FIG. 1, it is included in the range (20 1 0) to (1 20 0) in the rotation direction from (100) to (010) (double arrow in the figure) with [001] as the zone axis. If any of the surfaces has a main orientation, the elongation at break can be improved. In FIG. 1, the range from (20 1 0) to (1 20 0) is shown, but the face-centered cubic crystal structure has a plane equivalent to the plane included in this range. Therefore, an equivalent surface having a sign different from that of the surface in which the cross section of the wiring is in the range of (20 （1 0) to (1 20 0) is included in the present invention.
第二の方策において、屈曲部における稜線から厚み方向に切った際の配線の断面Ｐが、（20 １ ０）から（１ 20 ０）の間の特定方位に主方位を有して優先配向していることで、破断伸びが向上する理由は、断面Ｐの法線方向、すなわち主応力方向に引張応力を引加した時、面心立方構造を有する金属では、すべり面である８つの｛１１１｝のなかでも、シュミット因子が最も大きな主すべり面が４面となることから、せん断滑りが良好になり、局所的な加工硬化が起こり難くなるためである。通常の圧延銅箔では、金属箔の長手方向が圧延方向に相当し、図４（ｃ）や（ｄ）に示すように、その主方位＜１００＞に沿って回路を形成するのが通常である。例えば、特許文献５の実施例は、図４（ｄ）の形態に相当する。このように、屈曲部における稜線から厚み方向に切った際の配線の断面方位を（１００）にすると、屈曲させた際、８つのすべり面のシュミット因子が等価となって８つのすべり系が同時に働き、局所的に転位が蓄積し易くなる。このような従来技術との差異により、第二の方策を採用した可撓性回路基板の耐屈曲特性は、回路の長手方向で折り曲げる通常の利用形態に比べて優れる。
In the second policy, the cross section P of the wiring when it is cut in the thickness direction from the ridgeline at the bent portion is preferentially oriented with a main orientation in a specific orientation between (20 1 0) and (1 20 0). Therefore, the reason why the elongation at break is improved is that when a tensile stress is applied in the normal direction of the cross section P, that is, the principal stress direction, the metal having a face-centered cubic structure has eight {111 }, Since the main slip surface having the largest Schmid factor is four, the shear slip is good and local work hardening is less likely to occur. In normal rolled copper foil, the longitudinal direction of the metal foil corresponds to the rolling direction, and as shown in FIGS. 4C and 4D, it is normal to form a circuit along the main direction <100>. is there. For example, the Example of patent document 5 is equivalent to the form of FIG.4 (d). Thus, when the cross-sectional orientation of the wiring when cutting in the thickness direction from the ridgeline at the bent portion is (100), the eight Schmitt factors of the eight slip planes become equivalent when bent, and the eight slip systems become simultaneous. Dislocations tend to accumulate locally. Due to such a difference from the prior art, the bending resistance of the flexible circuit board adopting the second measure is superior to that of a normal usage mode in which the flexible circuit board is bent in the longitudinal direction of the circuit.
可撓性回路基板における断面Ｐに関し、最も望ましい方位は、屈曲部の主歪み方向、すなわち屈曲部における稜線から厚み方向に切った際の配線の断面法線方向に対して３０°又は６０°であるが、これは応力方向が、引張の安定方位と一致するためである。以上の機構を考えた時、少なくとも、屈曲部における稜線から厚み方向に切った際の配線の断面Ｐが、［００１］を晶帯軸として、（20 １ ０）から（１ 20 ０）の間の特定方位に主方位を有して優先配向を有していれば良い。
Regarding the cross section P in the flexible circuit board, the most desirable orientation is 30 ° or 60 ° with respect to the main strain direction of the bent portion, that is, the normal direction of the cross section of the wiring when cut from the ridge line in the bent portion in the thickness direction. This is because the direction of stress coincides with the stable orientation of tension. When considering the above mechanism, at least the cross section P of the wiring when cut in the thickness direction from the ridgeline at the bent portion is between (20 1 0) and (1 20 0) with [001] as the crystal axis. It suffices to have the preferential orientation with the main orientation in the specific orientation.
すなわち、本発明における第二の方策は、金属箔が面心立方構造を有して、金属箔の厚さ方向が＜１００＞の主方位を有すると共に、金属箔の箔面内が＜１００＞の主方位を有し、かつ、屈曲部における稜線から厚み方向に切った際の配線の断面Ｐの法線方向が（20 １ ０）から（１ 20 ０）の間の特定方位に主方位を有して優先配向するような配線を備えるようにする。この際、断面Ｐの法線方向は、好ましくは（10 １ ０）から（１ 10 ０）の間の特定方位に主方位を有して優先配向しているのが良く、より好ましくは（５１０）から（１１０）の間の特定方位に主方位を有して優先配向しており、更に好ましくは（２１０）から（１１０）の間の特定の方位に主方位を有して優先配向しており、最も好適には（40 23 ０）近傍に中心方位を持って優先配向しているのが良い。箔面が（００１）を主方位として優先配向している金属箔の場合、例えば箔面内の［００１］と［１００］とは等価であって、本発明における可撓性回路基板の屈曲部における稜線から厚み方向に切った際の配線の断面Ｐの主方位は、（１ 20 ０）から（１１０）の間の特定方位と記述することも出来、好ましくは（１２０）から（１１０）の間の特定の方位に主方位を有して優先配向し、最も好適には（23 40 ０）近傍に主方位を持って優先配向しているのが良いと記述することもできる。
That is, the second policy in the present invention is that the metal foil has a face-centered cubic structure, the thickness direction of the metal foil has a main orientation of <100>, and the foil surface of the metal foil has <100>. And the normal direction of the cross section P of the wiring when cut in the thickness direction from the ridge line at the bent portion is the main direction in a specific direction between (20 1 0) and (1 20 0). A wiring that has a preferential orientation is provided. At this time, the normal direction of the cross section P is preferably preferentially oriented with a main orientation in a specific orientation between (10 1 0) and (1 10 0), and more preferably (510 ) To (110) having a main orientation in a specific orientation, and more preferably having a main orientation in a specific orientation between (210) and (110). Most preferably, the preferred orientation is centered in the vicinity of (40 23 近 傍 0). In the case of a metal foil whose foil surface is preferentially oriented with (001) as the main orientation, for example, [001] and [100] in the foil surface are equivalent, and the bent portion of the flexible circuit board in the present invention The main direction of the cross section P of the wiring when cut in the thickness direction from the ridge line at can be described as a specific direction between (1 20 0) and (110), preferably (120) to (110) It can also be described that it is preferable to preferentially align with a main direction in a specific direction between them, and most preferably to preferentially align with a main direction in the vicinity of (23 40 0).
また、金属箔の厚さ方向が＜１００＞の主方位を有すると共に、金属箔の箔面内が＜１００＞の主方位を有し、かつ屈曲部における稜線から厚み方向に切った際の配線の断面Ｐが、（20 １ ０）から（1 20 ０）の間の特定方位に主方位を有するということは、図２に示す（１００）標準投影図のステレオ三角形（stereo triangle）上で逆極点表示したとき、屈曲部における稜線から厚み方向に切った際の配線の断面方位が、（20 １ ０）を表す点と（１１０）を表す点とで結ばれた線分上にあるいずれかの面であると言うこともできる。更に、第二の方策における可撓性回路基板は、金属箔の厚み方向が［００１］軸である３（２）軸配向した材料から配線を形成し、屈曲部における稜線から厚み方向に切った際の配線の断面法線が、箔面内における［１００］軸との間に２．９°から８７．１°の範囲の角度を有するものと言うこともできる。
In addition, the thickness direction of the metal foil has a main orientation of <100>, the foil surface of the metal foil has a main orientation of <100>, and the wiring when cut from the ridgeline at the bent portion in the thickness direction The fact that the cross section P has a main orientation in a specific orientation between (20 1 0) and (1 20 0) is reversed on the stereo triangle of the (100) standard projection shown in FIG. When a pole is displayed, the cross-sectional orientation of the wiring when cut in the thickness direction from the ridgeline at the bent portion is either on a line segment connected by a point representing (20 1 0) and a point representing (110) It can also be said that Furthermore, the flexible circuit board in the second measure is formed by forming a wiring from a 3 (2) axis-oriented material in which the thickness direction of the metal foil is the [001] axis, and cutting the ridge line at the bent portion in the thickness direction. It can also be said that the cross-sectional normal of the wiring at that time has an angle in the range of 2.9 ° to 87.1 ° with the [100] axis in the foil plane.
そして、このような第二の方策によれば、屈曲部における主応力方向の金属箔の破断伸びを３．５％以上にすることができ、曲率半径が２ｍｍ以下であるような繰り返しの歪み、もしくは応力に対しても金属疲労が起こり難くなり、屈曲性の高い可撓性回路基板が得られる。また、本発明では、上述した第一の方策とこの第二の方策を組み合わせることで、金属疲労特性及び屈曲性に優れた可撓性回路基板をより確実に得ることができ、主応力方向の金属箔の破断伸びが３．５％以上、好ましくは４％以上、より好ましくは９％以上にすることができる。なお、破断伸びの上限については、面心立方構造の単位格子の基本結晶軸＜１００＞が、金属箔の厚さ方向（箔面法線方向）と箔面内に存在するある一方向（そのひとつが圧延方向である）との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で５０％、かつ、厚みが１８μｍである、本発明の範囲で取り得る圧延箔の上限として、２０％以下と規定することができるが、銅の単位格子の基本結晶軸＜１００＞が、銅箔の厚さ方向と箔面内に存在するある一方向との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で９５％以上を占め、かつ、厚みが１２μｍ以下であるより好ましい形態をとる場合、破断伸びの上限は１５％以下である。
And according to such a second measure, the breaking elongation of the metal foil in the principal stress direction at the bent portion can be 3.5% or more, and the repeated strain such that the curvature radius is 2 mm or less, Alternatively, metal fatigue is less likely to occur due to stress, and a flexible circuit board with high flexibility can be obtained. Further, in the present invention, a flexible circuit board excellent in metal fatigue characteristics and bendability can be obtained more reliably by combining the first policy and the second policy described above, and the main stress direction can be obtained. The breaking elongation of the metal foil can be 3.5% or more, preferably 4% or more, more preferably 9% or more. As for the upper limit of the elongation at break, the basic crystal axis <100> of the unit cell of the face-centered cubic structure is in the thickness direction of the metal foil (the normal direction of the foil surface) and in one direction (in the direction of the foil surface) Rolling that can be taken within the scope of the present invention, in which the preferential orientation region with an orientation difference of 10 ° or less is 50% in area ratio and the thickness is 18 μm with respect to two orthogonal axes (one is the rolling direction) The upper limit of the foil can be defined as 20% or less, but the basic crystal axis <100> of the copper unit cell is two orthogonal directions of the thickness direction of the copper foil and one direction existing in the foil plane. In the case where the preferential orientation regions each having an orientation difference within 10 ° with respect to the axis occupy 95% or more in area ratio and the thickness is 12 μm or less, the upper limit of elongation at break is 15% or less. .
本発明における可撓性回路基板の樹脂層については、樹脂層を形成する樹脂の種類は特に制限されず、通常の可撓性回路基板で使用されるものを挙げることができ、例えばポリイミド、ポリアミド、ポリエステル、液晶ポリマー、ポリフェニレンサルファイド、ポリエーテルエーテルケトン等を例示することができる。なかでも、回路基板とした場合に良好な可撓性を示し、かつ、耐熱性にも優れることから、ポリイミドや液晶ポリマーが好適である。
With respect to the resin layer of the flexible circuit board in the present invention, the type of resin forming the resin layer is not particularly limited, and examples thereof include those used in ordinary flexible circuit boards, such as polyimide and polyamide. , Polyester, liquid crystal polymer, polyphenylene sulfide, polyether ether ketone and the like. Of these, polyimide and liquid crystal polymer are preferred because they exhibit good flexibility when used as a circuit board and are excellent in heat resistance.
樹脂層の厚さは、可撓性回路基板の用途、形状等に応じて適宜設定することができるが、可撓性の観点から５～７５μｍの範囲であるのが好ましく、９～５０μｍの範囲がより好ましく、１０～３０μｍの範囲が最も好ましい。樹脂層の厚さが５μｍに満たないと、絶縁信頼性が低下するおそれがあり、反対に７５μｍを超えると小型機器等へ搭載する場合に回路基板全体の厚みが厚くなり過ぎるおそれがあり、屈曲性の低下も考えられる。
The thickness of the resin layer can be appropriately set in accordance with the use, shape, etc. of the flexible circuit board, but is preferably in the range of 5 to 75 μm from the viewpoint of flexibility, and in the range of 9 to 50 μm. Is more preferable, and the range of 10 to 30 μm is most preferable. If the thickness of the resin layer is less than 5 μm, the insulation reliability may decrease. On the other hand, if it exceeds 75 μm, the thickness of the entire circuit board may be too thick when mounted on a small device, etc. A decline in sex is also possible.
また、可撓性回路基板を携帯電話のスライド摺動部等に適用する際には、金属箔から形成された配線上にカバーレイフィルム等からなるカバー材を貼り合わせて使用することがあるが、その場合には、配線に掛かる応力のバランスを考慮してカバー材と樹脂層の構成を設計するのが良い。本発明者らの知見によれば、例えば、２５℃における引張弾性率が４～６ＧＰａであると共に厚みが１４～１７μｍの範囲のポリイミドを樹脂層とし、厚さ８～１７μｍの熱硬化性樹脂からなる接着層と厚さ７～１３μｍのポリイミド層との２層を有して、かつ、接着層とポリイミド層全体の引張弾性率が２～４ＧＰａのカバーレイフィルムをカバー材とする構成例や、２５℃における引張弾性率が６～８ＧＰａであると共に厚みが１２～１５μｍの範囲のポリイミドを樹脂層とし、厚さ８～１７μｍの熱硬化性樹脂からなる接着層と厚さ７～１３μｍのポリイミド層との２層を有して、かつ、接着層とポリイミド層全体の引張弾性率が２～４ＧＰａのカバーレイフィルムをカバー材とする構成例などが挙げられる。
In addition, when a flexible circuit board is applied to a slide sliding portion of a mobile phone, a cover material made of a coverlay film or the like may be used on a wiring formed from a metal foil. In that case, it is preferable to design the structure of the cover material and the resin layer in consideration of the balance of stress applied to the wiring. According to the knowledge of the present inventors, for example, a polyimide having a tensile elastic modulus at 25 ° C. of 4 to 6 GPa and a thickness of 14 to 17 μm is used as a resin layer, and a thermosetting resin having a thickness of 8 to 17 μm is used. And a cover layer film having a cover layer film having a tensile elastic modulus of 2 to 4 GPa of the entire adhesive layer and the polyimide layer, and a cover material having two layers of an adhesive layer and a polyimide layer having a thickness of 7 to 13 μm, A polyimide having a tensile elastic modulus at 25 ° C. of 6 to 8 GPa and a thickness of 12 to 15 μm is used as a resin layer, an adhesive layer made of a thermosetting resin having a thickness of 8 to 17 μm, and a polyimide layer having a thickness of 7 to 13 μm. And a cover lay film having a tensile elastic modulus of 2 to 4 GPa for the entire adhesive layer and polyimide layer is used as a cover material.
樹脂層と金属箔とを積層させる手段については、例えば樹脂層がポリイミドからなる場合、ポリイミドフィルムに熱可塑性のポリイミドを塗布し又は介在させて金属箔を熱ラミネートするようにしてもよい（所謂ラミネート法）。ラミネート法で用いられるポリイミドフィルムとしては、例えば、”カプトン”（東レ・デュポン株式会社）、”アピカル”（鐘淵化学工業株式会社）、”ユーピレックス”（宇部興産株式会社）等が例示できる。ポリイミドフィルムと金属箔とを加熱圧着する際には、熱可塑性を示す熱可塑性ポリイミド樹脂を介在させるのがよい。また、樹脂層の厚みや折り曲げ特性等を制御しやすい観点から、金属箔にポリイミド前駆体溶液（ポリアミド酸溶液ともいう）を塗布した後、乾燥・硬化させて積層体を得てもよい（所謂キャスト法）。
Regarding the means for laminating the resin layer and the metal foil, for example, when the resin layer is made of polyimide, the metal foil may be thermally laminated by applying or interposing a thermoplastic polyimide to the polyimide film (so-called laminating). Law). Examples of the polyimide film used in the laminating method include “Kapton” (Toray DuPont Co., Ltd.), “Apical” (Kanebuchi Chemical Industry Co., Ltd.), “Upilex” (Ube Industries Co., Ltd.), and the like. When the polyimide film and the metal foil are heat-bonded, a thermoplastic polyimide resin exhibiting thermoplasticity is preferably interposed. In addition, from the viewpoint of easy control of the thickness and bending characteristics of the resin layer, a polyimide precursor solution (also referred to as a polyamic acid solution) may be applied to the metal foil, and then dried and cured to obtain a laminate (so-called “so-called”). Cast method).
樹脂層は、複数の樹脂を積層させて形成してもよく、例えば線膨張係数等の異なる２種類以上のポリイミドを積層させるようにしてもよいが、その際には耐熱性や屈曲性を担保する観点から、エポキシ樹脂等を接着剤として使用することなく、樹脂層のすべてが実質的にポリイミドから形成されるようにするのが望ましい。単独のポリイミドからなる場合及び複数のポリイミドからなる場合を含めて、樹脂層の引張弾性率は４～１０ＧＰａとなるようにするのが良く、好ましくは５～８ＧＰａとなるようにするのが良い。
The resin layer may be formed by laminating a plurality of resins. For example, two or more kinds of polyimides having different linear expansion coefficients may be laminated, and in that case, heat resistance and flexibility are ensured. In view of the above, it is desirable that substantially all of the resin layer is formed of polyimide without using an epoxy resin or the like as an adhesive. The tensile elastic modulus of the resin layer is preferably 4 to 10 GPa, preferably 5 to 8 GPa, including the case of being composed of a single polyimide and the case of being composed of a plurality of polyimides.
本発明の可撓性回路基板では、樹脂層の線膨張係数が１０～３０ｐｐｍ／℃の範囲となるようにするのが好ましい。樹脂層が複数の樹脂からなる場合には、樹脂層全体の線膨張係数がこの範囲になるようにすればよい。このような条件を満たすためには、例えば、線膨張係数が２５ｐｐｍ／℃以下、好ましくは５～２０ｐｐｍ／℃の低線膨張性ポリイミド層と、線膨張係数が２６ｐｐｍ／℃以上、好ましくは３０～８０ｐｐｍ／℃の高線膨張性ポリイミド層とからなる樹脂層であって、これらの厚み比を調整することによって１０～３０ｐｐｍ／℃のものとすることができる。好ましい低線膨張性ポリイミド層と高線膨張性ポリイミド層の厚みの比は７０：３０～９５：５の範囲である。また、低線膨張性ポリイミド層は、樹脂層の主たる樹脂層となり、高線膨張性ポリイミド層は金属箔と接するように設けることが好ましい。なお、線膨張係数は、イミド化反応が十分に終了したポリイミドを試料とし、サーモメカニカルアナライザー（ＴＭＡ）を用いて２５０℃に昇温後、１０℃／分の速度で冷却し、２４０～１００℃の範囲における平均の線膨張係数から求めることができる。
In the flexible circuit board of the present invention, the linear expansion coefficient of the resin layer is preferably in the range of 10 to 30 ppm / ° C. When the resin layer is made of a plurality of resins, the linear expansion coefficient of the entire resin layer may be in this range. In order to satisfy such conditions, for example, a low linear expansion polyimide layer having a linear expansion coefficient of 25 ppm / ° C. or less, preferably 5 to 20 ppm / ° C., and a linear expansion coefficient of 26 ppm / ° C. or more, preferably 30 to It is a resin layer comprising a high linear expansion polyimide layer at 80 ppm / ° C., and can be adjusted to 10 to 30 ppm / ° C. by adjusting the thickness ratio thereof. A preferred ratio of the thickness of the low linear expansion polyimide layer to the high linear expansion polyimide layer is in the range of 70:30 to 95: 5. The low linear expansion polyimide layer is the main resin layer of the resin layer, and the high linear expansion polyimide layer is preferably provided so as to be in contact with the metal foil. The linear expansion coefficient was determined by using a polyimide whose imidization reaction was sufficiently completed as a sample, raising the temperature to 250 ° C. using a thermomechanical analyzer (TMA), cooling at a rate of 10 ° C./min, and 240 to 100 ° C. It can obtain | require from the average linear expansion coefficient in the range.
また、本発明における可撓性回路基板は、樹脂層と金属箔から形成された配線とを備え、いずれかに屈曲部を有して使用されるものである。すなわち、ハードディスク内の可動部、携帯電話のヒンジ部やスライド摺動部、プリンターのヘッド部、光ピックアップ部、ノートＰＣの可動部などをはじめ各種電子・電気機器等で幅広く使用され、回路基板自体が折り曲げられたり、ねじ曲げられたり、或いは搭載された機器の動作に応じて変形したりして、いずれかに屈曲部が形成されるものである。特に、本発明の可撓性回路基板は屈曲耐久性に優れた屈曲部構造を有することから、摺動屈曲、折り曲げ屈曲、ヒンジ屈曲、スライド屈曲等の繰り返し動作を伴い頻繁に折り曲げられたりする場合や、或いは搭載される機器の小型化に対応すべく、曲率半径が折り曲げ挙動で０．３８～２．０ｍｍであり、摺動屈曲で１．２５～２．０ｍｍであり、ヒンジ屈曲で３．０～５．０ｍｍであり、スライド屈曲で０．３～２．０ｍｍであるような厳しい使用条件の場合に好適であり、０．３～１ｍｍの狭いギャップで屈曲性能の要求が厳しいスライド用途において特に効果を発揮する。
The flexible circuit board according to the present invention includes a resin layer and a wiring formed from a metal foil, and is used with a bent portion in one of them. In other words, it is widely used in various electronic and electrical devices such as movable parts in hard disks, hinges and slides of mobile phones, printer heads, optical pickups, movable parts of notebook PCs, etc., and the circuit board itself Is bent, twisted, or deformed according to the operation of the mounted device, and a bent portion is formed in either of them. In particular, since the flexible circuit board of the present invention has a bent portion structure with excellent bending durability, it is frequently bent with repeated operations such as sliding bending, bending bending, hinge bending, and sliding bending. In addition, in order to cope with the downsizing of the equipment to be mounted, the radius of curvature is 0.38 to 2.0 mm in bending behavior, 1.25 to 2.0 mm in sliding bending, and 3. 0 to 5.0 mm, suitable for severe use conditions such as 0.3 to 2.0 mm for slide bending, and for slide applications where bending performance is severe with a narrow gap of 0.3 to 1 mm Especially effective.
本発明における可撓性回路基板の製造方法については、そのひとつとして、ｉ）［００１］軸が最終的に箔面法線（金属箔の表面に対する垂線）に配向する立方体集合組織を呈する圧延金属箔と樹脂層とが金属箔の箔面で貼り合わされた複合体を得て、設計上の屈曲の主応力方向、即ち屈曲部における稜線から厚み方向に切った際の配線の断面法線方向を、金属箔面内の［１００］主方位に対して２．９°～８７．１°の角度を有して屈曲部の稜線が形成されるように配線するか、ii）配線を構成する金属箔を純度９９．９９９％以上とするか、又は、iii）これらi）とii）の方法を同時に採用するようにすれば良い。
Regarding the method for producing a flexible circuit board according to the present invention, as one of them, i) a rolled metal exhibiting a cubic texture in which the [001] axis is finally oriented in the normal direction to the foil surface (perpendicular to the surface of the metal foil) Obtain a composite in which the foil and the resin layer are bonded to each other with the foil surface of the metal foil, and design the principal stress direction of the bending, that is, the normal direction of the cross section of the wiring when cutting from the ridgeline at the bent portion in the thickness direction. , Wiring to form a ridge line of the bent portion at an angle of 2.9 ° to 87.1 ° with respect to the [100] main direction in the metal foil plane, or ii) metal constituting the wiring The foil may have a purity of 99.999% or higher, or iii) the methods i) and ii) may be adopted at the same time.
この際、金属箔は、必ずしも始めから立方体集合組織を呈している必要がなく、熱処理によって立方体集合組織が形成するようにしてもよく、例えば可撓性回路基板の製造過程、具体的には樹脂層の形成過程で熱処理されて、立方体集合組織が形成するようにしてもよい。すなわち、熱処理することで、＜１００＞軸から方位差１０°以内の領域が面積比５０％以上を占めるように、単位格子の基本結晶軸＜１００＞のひとつを金属箔の厚さ方向に優先配向させると共に、＜１００＞軸から方位差１０°以内の領域が面積比５０％以上を占めるように、基本結晶軸＜１００＞の別のひとつを金属箔の表面に対して水平方向に優先配向させるようにすればよい。圧延銅箔の再結晶集合組織は、通常、圧延面方位が｛１００｝であり、圧延方向が＜１００＞である。したがって、圧延面方位として（００１）主方位が形成される。また、純度９９．９９９％以上の金属箔を使用する場合、いずれの方位で回路を形成して配線しても破断伸びは３．５％以上を確保でき、設計上の適用範囲が広い可撓性回路基板を形成できる。
At this time, the metal foil does not necessarily have to exhibit a cubic texture from the beginning, and the cubic texture may be formed by heat treatment. For example, a manufacturing process of a flexible circuit board, specifically a resin A cubic texture may be formed by heat treatment in the layer formation process. That is, by heat treatment, one of the basic crystal axes <100> of the unit cell is given priority in the thickness direction of the metal foil so that the area within 10 ° from the <100> axis occupies an area ratio of 50% or more. In addition to the orientation, another one of the basic crystal axes <100> is preferentially oriented in the horizontal direction with respect to the surface of the metal foil so that the area within 10 ° from the <100> axis occupies an area ratio of 50% or more. You can make it. The recrystallized texture of the rolled copper foil usually has a rolling plane orientation of {100} and a rolling direction of <100>. Therefore, the (001) main direction is formed as the rolling surface direction. In addition, when using a metal foil with a purity of 99.999% or more, the elongation at break can be secured to 3.5% or more regardless of the orientation of the circuit formed and wired, and the flexible application range is wide. Circuit board can be formed.
第二の方策を採用する場合について、より詳しくは、図３に示すように、例えば可撓性回路基板をＵ字状に屈曲させると、その外側（曲率半径を有した内接円が形成される方とは反対側）に稜線Ｌが形成されるが、この稜線Ｌが、配線を形成する金属箔の［１００］軸と直交した状態からα＝２．９～８７．１（°）の範囲で傾きを有するようにすればよい。このような状態の例を図４の（ａ）及び（ｂ）に示す。ちなみに、図４の（ｃ）及び（ｄ）は［１００］軸に対し稜線が直交した状態（α＝０）である。ここで、αが２．９°未満であると屈曲性において明確な効果が確認されない。α＝１１．４～７８．６（°）であれば屈曲部構造の屈曲耐久性がより一層向上する。なお、本発明においては、上記α＝２．９°の場合に稜線から厚みｄ方向に切った際の配線の断面Ｐは（20 １ ０）面に相当し、α＝４５の場合には断面Ｐが（１１０）面に相当し、α＝８７．１の場合には断面Ｐが（１ 20 ０）面に相当する。また、面心立方構造においては、［１００］と［０１０］は等価であるから、図４（ａ）及び（ｂ）に示すような［１００］の箔面内直交軸と稜線のなす角αの角度範囲は、［１００］と断面Ｐ法線のなす角度範囲、及び［１００］と稜線のなす角度範囲と一致する。
More specifically, in the case of adopting the second measure, as shown in FIG. 3, for example, when a flexible circuit board is bent in a U shape, an outer circle (an inscribed circle having a radius of curvature) is formed. A ridge line L is formed on the opposite side of the metal foil, and the ridge line L is α = 2.9 to 87.1 (°) from a state perpendicular to the [100] axis of the metal foil forming the wiring. What is necessary is just to make it have inclination in a range. An example of such a state is shown in FIGS. Incidentally, (c) and (d) of FIG. 4 are states (α = 0) in which the ridge line is orthogonal to the [100] axis. Here, when α is less than 2.9 °, a clear effect on flexibility is not confirmed. When α = 11.4 to 78.6 (°), the bending durability of the bent portion structure is further improved. In the present invention, when α = 2.9 °, the cross section P of the wiring when cut from the ridge line in the thickness d direction corresponds to the (20 1 0) plane, and when α = 45, the cross section P corresponds to the (110) plane, and when α = 87.1, the cross section P corresponds to the (1 20 0) plane. In addition, in the face-centered cubic structure, [100] and [010] are equivalent, and therefore, the angle α formed between the orthogonal axis in the foil plane of [100] and the ridge line as shown in FIGS. 4 (a) and 4 (b). Is the same as the angle range formed by [100] and the cross-section P normal line, and the angle range formed by [100] and the ridge line.
また、配線の幅、形状、パターン等については特に制限はなく、可撓性回路基板の用途、搭載される電子機器等に応じて適宜設計すればよいが、本発明の屈曲部構造は屈曲耐久性に優れることから、第二の方策を採用する場合であっても、例えば配線に対する曲げ応力を小さくするためにヒンジ部の回動軸に対して斜め方向に配線するようなことをあえてする必要がなく、屈曲部における稜線に対して直交する方向に沿った配線、すなわち必要最小限の最短距離での配線が可能である。図４（ａ）及び（ｂ）は、例えば携帯電話のヒンジ部等に使用される可撓性回路基板を示し、樹脂層１と金属箔から形成した配線２とコネクタ端子３とを有する例である。図４（ａ）及び（ｂ）のいずれも、中央付近に屈曲部における稜線Ｌの位置を示しており、この稜線Ｌは、配線２を形成する金属箔の［１００］軸方向に対して（９０＋α）°の角度を有する。ここで、図４（ａ）は、両端のコネクタ端子３の途中、稜線Ｌ付近で配線が斜めに形成された例であるが、図４（ｂ）のようにコネクタ端子３間を最短距離で配線することも可能である。なお、折り畳み式携帯電話等のように、屈曲部における稜線Ｌの位置が固定される場合のほか、スライド式携帯電話等のように屈曲部における稜線Ｌが移動するようなスライド摺動屈曲（図４(ｂ)に記した太線矢印方向）であってもよい。なお、本発明における可撓性回路基板は、樹脂層の少なくとも片面に金属箔からなる配線を備えるが、必要に応じて樹脂層の両面に金属箔を備えるようにしてもよい。
In addition, the width, shape, pattern, etc. of the wiring are not particularly limited, and may be appropriately designed according to the use of the flexible circuit board, the mounted electronic device, etc. Even if the second measure is adopted, it is necessary to dare to wire in an oblique direction with respect to the rotation axis of the hinge portion, for example, in order to reduce the bending stress on the wiring. Therefore, wiring along the direction orthogonal to the ridgeline in the bent portion, that is, wiring with the minimum necessary minimum distance is possible. FIGS. 4A and 4B show a flexible circuit board used for, for example, a hinge part of a cellular phone, which is an example having a resin layer 1, a wiring 2 formed from a metal foil, and a connector terminal 3. is there. 4A and 4B show the position of the ridge line L in the bent portion near the center, and this ridge line L is (with respect to the [100] axis direction of the metal foil forming the wiring 2 ( 90 + α) °. Here, FIG. 4A is an example in which the wiring is formed obliquely in the vicinity of the ridge line L in the middle of the connector terminals 3 at both ends. However, as shown in FIG. Wiring is also possible. In addition to the case where the position of the ridge line L in the bent portion is fixed as in a folding mobile phone, the slide sliding bend in which the ridge line L in the bent portion moves as in a slide type mobile phone (see FIG. 4 (b) may be the direction of the thick arrow). In addition, although the flexible circuit board in this invention is equipped with the wiring which consists of metal foil in at least one surface of a resin layer, you may make it equip both surfaces of a resin layer with metal foil as needed.
以上、説明してきたように、可撓性回路基板を屈曲させた際の屈曲部において配線を構成する金属箔が、高度に配向していると共に、主応力及び主歪み方向への破断伸びが大きな金属箔を構成させることによって、屈曲半径の小さな高屈曲の繰り返し曲げを行ったときでも、結晶の異方性に起因する局所的な応力集中が起こり難く、また、転位集積が起こり難くなるといった２つの効果により、金属疲労が生じ難く、応力及び歪みに対して優れた耐久性を有し、可撓性回路基板の設計に制約が生じず、折り曲げの繰り返しや曲率半径の小さな屈曲に対しても耐え得る強度を備えて、屈曲性に優れた可撓性回路基板を提供することができる。
As described above, the metal foil constituting the wiring in the bent portion when the flexible circuit board is bent is highly oriented and has a large elongation at break in the main stress and main strain directions. By configuring the metal foil, even when repeated bending with a small bending radius and high bending is performed, local stress concentration caused by crystal anisotropy hardly occurs and dislocation accumulation hardly occurs. Due to these effects, metal fatigue is less likely to occur, it has excellent durability against stress and strain, and there is no restriction on the design of the flexible circuit board, and even against repeated bending and bending with a small radius of curvature. It is possible to provide a flexible circuit board that has sufficient strength and can be bent.
以下、実施例及び比較例に基づき、本発明をより具体的に説明する。なお、実施例等で用いた銅箔の種類、及びポリアミド酸溶液の合成は次のとおりである。
Hereinafter, based on an Example and a comparative example, this invention is demonstrated more concretely. In addition, the kind of copper foil used by the Example etc. and the synthesis | combination of a polyamic-acid solution are as follows.
［銅箔Ａ］
市販圧延銅箔、純度９９．９％、厚さ９μｍ。
［銅箔Ｂ］
市販電解銅箔、純度９９．９％、厚さ９μｍ。
［銅箔Ｃ］
無酸素銅箔、純度９９．９９％、厚さ９μｍ、プロセス条件Ａ。
不純物（mass ppm） 酸素：2、銀：18、リン：2.1、硫黄：4、鉄：1.5
［銅箔Ｄ］
精製銅箔、純度９９．９９９％、厚さ９μｍ、プロセス条件Ａ。
不純物（mass ppm） 酸素：2、銀：5、リン：0.01、硫黄：0.01、鉄0.002
［銅箔Ｅ］
精製銅箔、純度９９．９９９９％、厚さ９μｍ、プロセス条件Ａ。
不純物（mass ppm） 酸素：＜1、銀：0.18、リン：＜0.005、硫黄：＜0.005、鉄：0.002
［銅箔Ｆ］
精製銅箔、純度９９．９９９９％、厚さ９μｍ、プロセス条件Ｂ。
不純物（mass ppm） 酸素：＜1、銀：0.18、リン：＜0.005、硫黄：＜0.005、鉄：0.002
［銅箔Ｇ］
精製銅箔、純度９９．９９９９％、厚さ９μｍ、プロセス条件Ｃ。
不純物（mass ppm） 酸素：＜1、銀：0.18、リン：＜0.005、硫黄：＜0.005、鉄：0.002
［銅箔Ｈ］
市販圧延銅箔、純度９９．９％、厚さ１２μｍ。 [Copper foil A]
Commercial rolled copper foil, purity 99.9%, thickness 9 μm.
[Copper foil B]
Commercially available electrolytic copper foil, purity 99.9%, thickness 9 μm.
[Copper foil C]
Oxygen-free copper foil, purity 99.99%, thickness 9 μm, process condition A.
Impurities (mass ppm) Oxygen: 2, Silver: 18, Phosphorus: 2.1, Sulfur: 4, Iron: 1.5
[Copper foil D]
Purified copper foil, purity 99.999%, thickness 9 μm, process condition A.
Impurities (mass ppm) Oxygen: 2, Silver: 5, Phosphorus: 0.01, Sulfur: 0.01, Iron 0.002
[Copper foil E]
Purified copper foil, purity 99.9999%, thickness 9 μm, process condition A.
Impurities (mass ppm) Oxygen: <1, Silver: 0.18, Phosphorus: <0.005, Sulfur: <0.005, Iron: 0.002
[Copper foil F]
Purified copper foil, purity 99.9999%, thickness 9 μm, process condition B.
Impurities (mass ppm) Oxygen: <1, Silver: 0.18, Phosphorus: <0.005, Sulfur: <0.005, Iron: 0.002
[Copper foil G]
Purified copper foil, purity 99.9999%, thickness 9 μm, process condition C.
Impurities (mass ppm) Oxygen: <1, Silver: 0.18, Phosphorus: <0.005, Sulfur: <0.005, Iron: 0.002
[Copper foil H]
Commercial rolled copper foil, purity 99.9%, thickness 12 μm.
市販圧延銅箔、純度９９．９％、厚さ９μｍ。
［銅箔Ｂ］
市販電解銅箔、純度９９．９％、厚さ９μｍ。
［銅箔Ｃ］
無酸素銅箔、純度９９．９９％、厚さ９μｍ、プロセス条件Ａ。
不純物（mass ppm） 酸素：2、銀：18、リン：2.1、硫黄：4、鉄：1.5
［銅箔Ｄ］
精製銅箔、純度９９．９９９％、厚さ９μｍ、プロセス条件Ａ。
不純物（mass ppm） 酸素：2、銀：5、リン：0.01、硫黄：0.01、鉄0.002
［銅箔Ｅ］
精製銅箔、純度９９．９９９９％、厚さ９μｍ、プロセス条件Ａ。
不純物（mass ppm） 酸素：＜1、銀：0.18、リン：＜0.005、硫黄：＜0.005、鉄：0.002
［銅箔Ｆ］
精製銅箔、純度９９．９９９９％、厚さ９μｍ、プロセス条件Ｂ。
不純物（mass ppm） 酸素：＜1、銀：0.18、リン：＜0.005、硫黄：＜0.005、鉄：0.002
［銅箔Ｇ］
精製銅箔、純度９９．９９９９％、厚さ９μｍ、プロセス条件Ｃ。
不純物（mass ppm） 酸素：＜1、銀：0.18、リン：＜0.005、硫黄：＜0.005、鉄：0.002
［銅箔Ｈ］
市販圧延銅箔、純度９９．９％、厚さ１２μｍ。 [Copper foil A]
Commercial rolled copper foil, purity 99.9%, thickness 9 μm.
[Copper foil B]
Commercially available electrolytic copper foil, purity 99.9%, thickness 9 μm.
[Copper foil C]
Oxygen-free copper foil, purity 99.99%, thickness 9 μm, process condition A.
Impurities (mass ppm) Oxygen: 2, Silver: 18, Phosphorus: 2.1, Sulfur: 4, Iron: 1.5
[Copper foil D]
Purified copper foil, purity 99.999%, thickness 9 μm, process condition A.
Impurities (mass ppm) Oxygen: 2, Silver: 5, Phosphorus: 0.01, Sulfur: 0.01, Iron 0.002
[Copper foil E]
Purified copper foil, purity 99.9999%, thickness 9 μm, process condition A.
Impurities (mass ppm) Oxygen: <1, Silver: 0.18, Phosphorus: <0.005, Sulfur: <0.005, Iron: 0.002
[Copper foil F]
Purified copper foil, purity 99.9999%, thickness 9 μm, process condition B.
Impurities (mass ppm) Oxygen: <1, Silver: 0.18, Phosphorus: <0.005, Sulfur: <0.005, Iron: 0.002
[Copper foil G]
Purified copper foil, purity 99.9999%, thickness 9 μm, process condition C.
Impurities (mass ppm) Oxygen: <1, Silver: 0.18, Phosphorus: <0.005, Sulfur: <0.005, Iron: 0.002
[Copper foil H]
Commercial rolled copper foil, purity 99.9%, thickness 12 μm.
［銅箔の製造方法］
銅箔Ａと銅箔Ｈは、市販の圧延銅箔であり、銅箔Ｂは硫酸銅浴で製造した市販の電解銅箔である。これらはいずれも高屈曲用途品として市販されている銅箔であり、純度は９９．９％と市販品としては高いものである。銅箔Ｃ～銅箔Ｇは本発明者らが加工したものであり、所定の純度の銅素材を黒鉛鋳型内で鋳造凝固し、圧延加工して所定の厚さにしたものである。鋳造インゴットの厚さは１０ｍｍであり、冷間圧延で１ｍｍまで落とした後、銅箔Ｃ、銅箔Ｄ、及び銅箔Ｅについては、３００℃、３０分の中間焼鈍を実施した後、９μｍまで冷間圧延を実施した（プロセス条件Ａ）。また、銅箔Ｆは中間焼鈍を行わないで、９μｍまで冷間圧延を実施した（プロセス条件Ｂ）ものである。更に、銅箔Ｇは、中間焼鈍温度を８００℃で行い、９μｍまで冷間圧延を実施した（プロセス条件Ｃ）。 [Manufacturing method of copper foil]
Copper foil A and copper foil H are commercially available rolled copper foils, and copper foil B is a commercially available electrolytic copper foil produced in a copper sulfate bath. These are all copper foils that are commercially available as high-bending products, and the purity is 99.9%, which is high as a commercial product. Copper foils C to G are processed by the present inventors, and are obtained by casting and solidifying a copper material having a predetermined purity in a graphite mold and rolling it to a predetermined thickness. The thickness of the casting ingot is 10 mm, and after dropping to 1 mm by cold rolling, for copper foil C, copper foil D, and copper foil E, after carrying out intermediate annealing at 300 ° C. for 30 minutes, up to 9 μm Cold rolling was performed (process condition A). Moreover, the copper foil F was cold-rolled to 9 micrometers (process condition B), without performing intermediate annealing. Further, the copper foil G was subjected to an intermediate annealing temperature of 800 ° C. and cold-rolled to 9 μm (process condition C).
銅箔Ａと銅箔Ｈは、市販の圧延銅箔であり、銅箔Ｂは硫酸銅浴で製造した市販の電解銅箔である。これらはいずれも高屈曲用途品として市販されている銅箔であり、純度は９９．９％と市販品としては高いものである。銅箔Ｃ～銅箔Ｇは本発明者らが加工したものであり、所定の純度の銅素材を黒鉛鋳型内で鋳造凝固し、圧延加工して所定の厚さにしたものである。鋳造インゴットの厚さは１０ｍｍであり、冷間圧延で１ｍｍまで落とした後、銅箔Ｃ、銅箔Ｄ、及び銅箔Ｅについては、３００℃、３０分の中間焼鈍を実施した後、９μｍまで冷間圧延を実施した（プロセス条件Ａ）。また、銅箔Ｆは中間焼鈍を行わないで、９μｍまで冷間圧延を実施した（プロセス条件Ｂ）ものである。更に、銅箔Ｇは、中間焼鈍温度を８００℃で行い、９μｍまで冷間圧延を実施した（プロセス条件Ｃ）。 [Manufacturing method of copper foil]
Copper foil A and copper foil H are commercially available rolled copper foils, and copper foil B is a commercially available electrolytic copper foil produced in a copper sulfate bath. These are all copper foils that are commercially available as high-bending products, and the purity is 99.9%, which is high as a commercial product. Copper foils C to G are processed by the present inventors, and are obtained by casting and solidifying a copper material having a predetermined purity in a graphite mold and rolling it to a predetermined thickness. The thickness of the casting ingot is 10 mm, and after dropping to 1 mm by cold rolling, for copper foil C, copper foil D, and copper foil E, after carrying out intermediate annealing at 300 ° C. for 30 minutes, up to 9 μm Cold rolling was performed (process condition A). Moreover, the copper foil F was cold-rolled to 9 micrometers (process condition B), without performing intermediate annealing. Further, the copper foil G was subjected to an intermediate annealing temperature of 800 ° C. and cold-rolled to 9 μm (process condition C).
［ポリアミド酸溶液の合成］
（合成例１）
熱電対及び攪拌機を備えると共に窒素導入が可能な反応容器に、N,N－ジメチルアセトアミドを入れた。この反応容器に2,2-ビス[4-(4-アミノフェノキシ)フェニル]プロパン(ＢＡＰＰ)を容器中で撹拌しながら溶解させた。次に、ピロメリット酸二無水物（ＰＭＤＡ）を加えた。モノマーの投入総量が１５ｗｔ％となるように投入した。その後、３時間撹拌を続け、ポリアミド酸ａの樹脂溶液を得た。このポリアミド酸ａの樹脂溶液の溶液粘度は３,０００cpsであった。 [Synthesis of polyamic acid solution]
(Synthesis Example 1)
N, N-dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) was dissolved in the reaction vessel with stirring. Next, pyromellitic dianhydride (PMDA) was added. The total amount of monomers charged was 15 wt%. Thereafter, stirring was continued for 3 hours to obtain a resin solution of polyamic acid a. The solution viscosity of this polyamic acid a resin solution was 3,000 cps.
（合成例１）
熱電対及び攪拌機を備えると共に窒素導入が可能な反応容器に、N,N－ジメチルアセトアミドを入れた。この反応容器に2,2-ビス[4-(4-アミノフェノキシ)フェニル]プロパン(ＢＡＰＰ)を容器中で撹拌しながら溶解させた。次に、ピロメリット酸二無水物（ＰＭＤＡ）を加えた。モノマーの投入総量が１５ｗｔ％となるように投入した。その後、３時間撹拌を続け、ポリアミド酸ａの樹脂溶液を得た。このポリアミド酸ａの樹脂溶液の溶液粘度は３,０００cpsであった。 [Synthesis of polyamic acid solution]
(Synthesis Example 1)
N, N-dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) was dissolved in the reaction vessel with stirring. Next, pyromellitic dianhydride (PMDA) was added. The total amount of monomers charged was 15 wt%. Thereafter, stirring was continued for 3 hours to obtain a resin solution of polyamic acid a. The solution viscosity of this polyamic acid a resin solution was 3,000 cps.
（合成例２）
熱電対及び攪拌機を備えると共に窒素導入が可能な反応容器に、N,N－ジメチルアセトアミドを入れた。この反応容器に2,2'－ジメチル－4,4'－ジアミノビフェニル(ｍ－ＴＢ)を投入した。次に3,3',4,4'－ビフェニルテトラカルボン酸二無水物（ＢＰＤＡ）及びピロメリット酸二無水物（ＰＭＤＡ）を加えた。モノマーの投入総量が１５ｗｔ％で、各酸無水物のモル比率（ＢＰＤＡ：ＰＭＤＡ）が２０：８０となるように投入した。その後、３時間撹拌を続け、ポリアミド酸ｂの樹脂溶液を得た。このポリアミド酸ｂの樹脂溶液の溶液粘度は２０,０００cpsであった。 (Synthesis Example 2)
N, N-dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2,2′-Dimethyl-4,4′-diaminobiphenyl (m-TB) was charged into the reaction vessel. Next, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) were added. The total amount of monomers charged was 15 wt%, and the molar ratio of each acid anhydride (BPDA: PMDA) was 20:80. Thereafter, stirring was continued for 3 hours to obtain a resin solution of polyamic acid b. The solution viscosity of this polyamic acid b resin solution was 20,000 cps.
熱電対及び攪拌機を備えると共に窒素導入が可能な反応容器に、N,N－ジメチルアセトアミドを入れた。この反応容器に2,2'－ジメチル－4,4'－ジアミノビフェニル(ｍ－ＴＢ)を投入した。次に3,3',4,4'－ビフェニルテトラカルボン酸二無水物（ＢＰＤＡ）及びピロメリット酸二無水物（ＰＭＤＡ）を加えた。モノマーの投入総量が１５ｗｔ％で、各酸無水物のモル比率（ＢＰＤＡ：ＰＭＤＡ）が２０：８０となるように投入した。その後、３時間撹拌を続け、ポリアミド酸ｂの樹脂溶液を得た。このポリアミド酸ｂの樹脂溶液の溶液粘度は２０,０００cpsであった。 (Synthesis Example 2)
N, N-dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2,2′-Dimethyl-4,4′-diaminobiphenyl (m-TB) was charged into the reaction vessel. Next, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) were added. The total amount of monomers charged was 15 wt%, and the molar ratio of each acid anhydride (BPDA: PMDA) was 20:80. Thereafter, stirring was continued for 3 hours to obtain a resin solution of polyamic acid b. The solution viscosity of this polyamic acid b resin solution was 20,000 cps.
［実施例１］
銅箔Ａから銅箔Ｇまでの７種類の銅箔に上記で準備したポリアミド酸溶液aを塗布し、乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、そのうえにポリアミド酸ｂを塗布し、乾燥させ（硬化後は膜厚9μmの低熱熱膨張性ポリイミドを形成）、更にその上にポリアミド酸aを塗布し乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、３００～３６０℃の温度が積算時間で５分以上負荷されるような加熱条件を経て３層構造からなるポリイミド層を形成した。次いで、銅箔の圧延方向（MD方向）に沿って長さ２５０ｍｍ、圧延方向に対して直交する方向（TD方向）に幅１５０ｍｍの長方形サイズとなるように切り出し、図５に示すように、厚さ１３μｍのポリイミド層（樹脂層）１と厚さ９μｍの銅箔２とを有した片面銅張積層板４を得た。そのときの樹脂層全体の引張弾性率は７．５ＧＰａであった。 [Example 1]
The polyamic acid solution a prepared above is applied to seven types of copper foils from copper foil A to copper foil G, dried (after curing, a 2 μm-thick thermoplastic polyimide film is formed), and then polyamic acid b is applied thereon. And dried (after forming a low thermal expansion coefficient polyimide with a film thickness of 9 μm), and further coated with polyamic acid a and dried (after curing, formed with a polyimide film with a film thickness of 2 μm), 300 ~ A polyimide layer having a three-layer structure was formed through a heating condition in which a temperature of 360 ° C. was loaded for 5 minutes or more in the integration time. Next, the copper foil was cut out to a rectangular size of 250 mm in length along the rolling direction (MD direction) and 150 mm in the direction perpendicular to the rolling direction (TD direction), as shown in FIG. A single-sided copper cladlaminate 4 having a 13 μm thick polyimide layer (resin layer) 1 and a 9 μm thick copper foil 2 was obtained. At that time, the tensile elastic modulus of the entire resin layer was 7.5 GPa.
銅箔Ａから銅箔Ｇまでの７種類の銅箔に上記で準備したポリアミド酸溶液aを塗布し、乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、そのうえにポリアミド酸ｂを塗布し、乾燥させ（硬化後は膜厚9μmの低熱熱膨張性ポリイミドを形成）、更にその上にポリアミド酸aを塗布し乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、３００～３６０℃の温度が積算時間で５分以上負荷されるような加熱条件を経て３層構造からなるポリイミド層を形成した。次いで、銅箔の圧延方向（MD方向）に沿って長さ２５０ｍｍ、圧延方向に対して直交する方向（TD方向）に幅１５０ｍｍの長方形サイズとなるように切り出し、図５に示すように、厚さ１３μｍのポリイミド層（樹脂層）１と厚さ９μｍの銅箔２とを有した片面銅張積層板４を得た。そのときの樹脂層全体の引張弾性率は７．５ＧＰａであった。 [Example 1]
The polyamic acid solution a prepared above is applied to seven types of copper foils from copper foil A to copper foil G, dried (after curing, a 2 μm-thick thermoplastic polyimide film is formed), and then polyamic acid b is applied thereon. And dried (after forming a low thermal expansion coefficient polyimide with a film thickness of 9 μm), and further coated with polyamic acid a and dried (after curing, formed with a polyimide film with a film thickness of 2 μm), 300 ~ A polyimide layer having a three-layer structure was formed through a heating condition in which a temperature of 360 ° C. was loaded for 5 minutes or more in the integration time. Next, the copper foil was cut out to a rectangular size of 250 mm in length along the rolling direction (MD direction) and 150 mm in the direction perpendicular to the rolling direction (TD direction), as shown in FIG. A single-sided copper clad
上記で得られた片面銅張積層板４について、銅箔Ａから銅箔Ｇまでのそれぞれの銅箔２の圧延面2aに対してコロイダルシリカを使用し、機械的、化学的研磨を行なった後、ＥＢＳＰ装置にて方位解析を行った。使用した装置は、日立製作所製ＦＥ－ＳＥＭ（S-4100）、ＴＳＬ社製のＥＢＳＰ装置、及びソフトウエア（OIM Analysis 5.2）である。測定領域はおよそ８００μｍ×１６００μｍの領域であり、測定時加速電圧２０ｋＶ、測定ステップ間隔４μｍとした。配向性の評価は、箔の厚さ方向、及び箔の圧延方向に対して＜１００＞が１０°以内に入っている測定点の全体の測定点に対する割合で示した。測定数は各品種個体の異なる５つの試料について実施し、百分率の小数点以下を四捨五入した。また、得られたデータを用いて、隣り合う結晶粒の方位差が１５°以上であるものを結晶粒界として結晶粒径の評価を行ない、多結晶体については平均粒径を求めた。結果を表１に示す。
After the single-sided copper clad laminate 4 obtained above is subjected to mechanical and chemical polishing using colloidal silica on the rolled surface 2a of each copper foil 2 from the copper foil A to the copper foil G. The azimuth analysis was performed with an EBSP apparatus. The apparatuses used were FE-SEM (S-4100) manufactured by Hitachi, Ltd., EBSP apparatus manufactured by TSL, and software (OIM Analysis 5.2). The measurement area was an area of approximately 800 μm × 1600 μm, and the measurement acceleration voltage was 20 kV and the measurement step interval was 4 μm. The evaluation of the orientation was shown by the ratio of the measurement points where <100> is within 10 ° with respect to the thickness direction of the foil and the rolling direction of the foil to the total measurement points. The number of measurements was made on five different samples of each variety and rounded to the nearest whole number. Further, using the obtained data, the crystal grain size was evaluated by setting the crystal grain boundaries to those having an orientation difference of 15 ° or more between adjacent crystal grains, and the average grain size was determined for the polycrystal. The results are shown in Table 1.
銅箔Ｂを除く圧延銅箔はいずれも立方体集合組織を形成しており、銅箔面方位、圧延方向ともに｛００１｝＜１００＞の主方位を有していることが分った。これは、圧延加工された銅箔が、ポリイミドの硬化の際の熱によって再結晶し、再結晶集合組織が形成されたためである。ただし、その程度は品種によって異なり、銅箔Ａ、Ｃ、Ｄ、及びＥの立方体方位に対する配向性が極めて高かった。立方体方位の配向度は、純度が９９．９％以上の銅箔ではその純度によらず、銅箔の加工方法に対する依存性が大きかった。これらの銅箔は、８００×１６００μｍの視野において、視野全体が立方体方位を有する粒で構成され、その内部に方位の異なる５μｍ以下の結晶粒が島状に分散した組織になっていた。島状組織の面積率は２％以下と小さいため、立方体方位を有する再結晶粒は、同じ方位を有して一体化しており、再結晶粒の大きさは、厚さ方向に箔厚と同じ９μｍであり、箔面内に８００μｍ以上である。また、銅箔Ｆ、銅箔Ｇの立方体方位を有する再結晶粒は、面積率が高くないため、互いに独立して存在しており、箔面内の平均粒径は、それぞれ２５μｍ、２０μｍであった。一方、電解銅箔Ｂは平均粒径1μｍの多結晶体であり、殆ど配向性は認められなかった。
It was found that all the rolled copper foils excluding the copper foil B had a cubic texture, and both the copper foil surface orientation and the rolling direction had {001} <100> main orientations. This is because the rolled copper foil was recrystallized by heat at the time of curing of the polyimide, and a recrystallized texture was formed. However, the degree varied depending on the type, and the orientation of the copper foils A, C, D, and E with respect to the cube orientation was extremely high. The degree of orientation of the cube orientation was highly dependent on the copper foil processing method regardless of the purity of the copper foil having a purity of 99.9% or more. These copper foils were composed of grains having a cubic orientation in a field of 800 × 1600 μm, and crystal grains having different orientations of 5 μm or less were dispersed in an island shape inside. Since the area ratio of the island-like structure is as small as 2% or less, the recrystallized grains having a cubic orientation are integrated with the same orientation, and the size of the recrystallized grains is the same as the foil thickness in the thickness direction. 9 μm, and 800 μm or more in the foil surface. In addition, the recrystallized grains having a cubic orientation of the copper foil F and the copper foil G are not high in area ratio, and therefore exist independently of each other, and the average grain sizes in the foil surface are 25 μm and 20 μm, respectively. It was. On the other hand, the electrolytic copper foil B was a polycrystal having an average particle diameter of 1 μm, and almost no orientation was observed.
次に、上記で得られた片面銅張積層板４の銅箔２側に所定のマスクを被せ、塩化鉄／塩化銅系溶液を用いてエッチングを行い、図６に示したように（但し、配線方向ＨとＭＤ方向とのなす角は０°である）、線幅（ｌ）が１５０μｍの直線状の配線２の配線方向Ｈ（Ｈ方向）が、ＭＤ方向（＜１００＞軸）に平行になるように、かつ、スペース幅（ｓ）が２５０μｍとなるように配線パターンを形成した。そして、後述する耐屈曲試験用のサンプルを兼ねるように、JIS 6471に準じて、回路基板の配線方向Ｈに沿って長手方向に１５０ｍｍ、配線方向Ｈに直交する方向に幅１５ｍｍを有した試験用可撓性回路基板５を得た。
Next, a predetermined mask is put on the copper foil 2 side of the single-sided copper clad laminate 4 obtained above, and etching is performed using an iron chloride / copper chloride solution, as shown in FIG. The angle between the wiring direction H and the MD direction is 0 °), and the wiring direction H (H direction) of the linear wiring 2 having a line width (l) of 150 μm is parallel to the MD direction (<100> axis). The wiring pattern was formed so that the space width (s) was 250 μm. And in order to serve as a sample for bending resistance test to be described later, in accordance with JIS 6471, for test having 150 mm in the longitudinal direction along the wiring direction H of the circuit board and 15 mm in the direction orthogonal to the wiring direction H A flexible circuit board 5 was obtained.
上記で得られた試験用可撓性回路基板を用い、JIS C5016に準じてＭＩＴ屈曲試験を行った。試験の模式図を図７に示す。装置は東洋精機製作所製（STROGRAPH-R1）を使用し、試験用可撓性回路基板５の長手方向の一端を屈曲試験装置のくわえ治具に固定し、他端をおもりで固定して、くわえ部を中心として、振動速度１５０回／分の条件で左右に交互に１３５±５度ずつ回転させながら、曲率半径０．８ｍｍとなるように屈曲させ、回路基板５の配線２の導通が遮断されるまでの回数を屈曲回数として求めた。
MIT flex test was performed according to JIS C5016 using the test flexible circuit board obtained above. A schematic diagram of the test is shown in FIG. The equipment is manufactured by Toyo Seiki Seisakusho (STROGRAPH-R1), one end of the test flexible circuit board 5 in the longitudinal direction is fixed to the holding jig of the bending test apparatus, and the other end is fixed with a weight. The wire 2 on the circuit board 5 is cut off from conduction while being rotated to 135 ± 5 degrees alternately left and right at a vibration speed of 150 times / min. Was determined as the number of flexing.
この試験条件において、屈曲部に形成される稜線が試験用可撓性回路基板５の配線２の配線方向Ｈに対して直交するよう屈曲を受けることかから、銅回路に印加される主応力、主歪みは、圧延方向に平行な引張応力、引張歪みとなる。屈曲試験後に銅箔の厚さ方向から回路を観察すると屈曲部の稜線付近で圧延方向とほぼ垂直にクラックが入り、破線したことが確認された。屈曲寿命の結果を表１に示す。表１の屈曲寿命は、銅箔の種類ごとにそれぞれ５つ用意した試験用可撓性回路基板の結果の平均である。
Under this test condition, the main stress applied to the copper circuit is obtained because the ridge line formed in the bent portion is bent so as to be orthogonal to the wiring direction H of the wiring 2 of the test flexible circuit board 5. The main strain is a tensile stress or tensile strain parallel to the rolling direction. When the circuit was observed from the thickness direction of the copper foil after the bending test, it was confirmed that a crack occurred in the vicinity of the ridgeline of the bent portion, almost perpendicular to the rolling direction, and a broken line. The results of the bending life are shown in Table 1. The flex life in Table 1 is an average of the results of the test flexible circuit boards prepared for each type of copper foil.
表１に示した結果から、屈曲疲労寿命は、立方体集合組織の集積度に依存するが、同じ加工方法で作製し、配向度もほぼ同等である銅箔Ｃ、銅箔Ｄ、銅箔Ｅの屈曲疲労寿命は大きく異なることが分った。
From the results shown in Table 1, the bending fatigue life depends on the degree of integration of the cube texture, but the copper foil C, the copper foil D, and the copper foil E, which are produced by the same processing method and have substantially the same degree of orientation. It has been found that the bending fatigue life varies greatly.
次に、屈曲寿命の支配因子を調べるために、屈曲の主応力、主歪み方向、すなわち圧延方向と平行に引張試験を行った。銅箔単体の特性を調べるために、エッチングする前の片面銅張積層板４から樹脂層を溶解して、銅箔単体での引張試験を行った。ポリイミドを溶解する過程で、銅箔の組織に変化がないことを確認した。
Next, in order to investigate the governing factor of the bending life, a tensile test was performed in parallel with the main stress of bending, the main strain direction, that is, the rolling direction. In order to investigate the characteristics of the copper foil alone, the resin layer was dissolved from the single-sided copper clad laminate 4 before etching, and a tensile test was conducted on the copper foil alone. In the process of dissolving the polyimide, it was confirmed that there was no change in the structure of the copper foil.
引張試験は、銅箔の圧延方向（ＭＤ方向）に長さ１５０ｍｍ、箔面内においてこの圧延方向と直交する方向に幅１０ｍｍに切り出した試料を使用し、長さ方向に標点間距離１００ｍｍ、引張速さ１０ｍｍ／ｍｉｎ．で測定した。測定には銅箔の種類ごとにそれぞれ試料を７本用意し、これらを測定して求めた破断応力（破断強度）、及び破断伸びの平均値を表１に示した。
The tensile test uses a sample cut to a length of 150 mm in the rolling direction (MD direction) of the copper foil and a width of 10 mm in the direction perpendicular to the rolling direction in the foil plane, and the distance between the gauge points is 100 mm in the length direction. Tensile speed 10 mm / min. Measured with For the measurement, seven samples were prepared for each type of copper foil, and the breaking stress (breaking strength) obtained by measuring these samples and the average value of breaking elongation are shown in Table 1.
その結果、集合組織が発達した銅箔では、破断強度ではなく、破断伸びが屈曲疲労寿命に相関があることが分かった。また、銅箔Ｂは、強度、破断伸びが共に大きいが、これは、結晶粒の微細な多結晶体であることを反映している。しかしながら、銅箔Ｂは集合組織が発達していないため、疲労寿命は劣る結果であった。また、立方体集合組織の集積度が同等である純度９９．９９％の銅箔Ｃと純度９９．９９９％の銅箔Ｄを比較すると、銅箔Ｄの屈曲に対する疲労特性が大きく優れる結果となった。この２つの銅箔の酸素濃度は同じであり、内部の酸化銅の分散量も小さく、同等であったことから、酸化銅による差ではなく、純度が異なることによる破断伸びの差によるものである。
As a result, it was found that in the copper foil having a developed texture, the elongation at break is correlated with the bending fatigue life, not the strength at break. Moreover, although copper foil B is large in both strength and elongation at break, this reflects that it is a fine polycrystalline body of crystal grains. However, since the copper foil B did not develop a texture, the fatigue life was inferior. Further, when the copper foil C with a purity of 99.99% and the copper foil D with a purity of 99.999%, which have the same degree of cube texture accumulation, were compared, the fatigue characteristics of the copper foil D with respect to bending were greatly improved. . The oxygen concentration of these two copper foils is the same, and the amount of copper oxide inside is also small and equal, so it is not due to the difference due to copper oxide but due to the difference in elongation at break due to different purity. .
以上、実施例１に示した結果より、一般的な高屈曲用銅箔よりも良好な特性を得るためには、基本結晶軸＜１００＞が、金属箔の厚さ方向と箔面内に存在するある一方向との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で５０％以上を占めるように、主方位を有しており、かつ、屈曲部における稜線から金属箔の厚み方向に切った配線の断面Ｐに対する法線方向の金属箔の破断伸びが３．５％以上であることが必要であることが分かった。また、９９．９９９％以上と極めて純度が高く、かつ立方体方位を発達させることにより、破断伸びが向上し、その方向に主応力、主歪みが印加されるような繰り返し屈曲に対して疲労寿命の長い可撓性回路基板になることが分った。
As described above, from the results shown in Example 1, in order to obtain better characteristics than a general high bending copper foil, the basic crystal axis <100> exists in the thickness direction of the metal foil and in the foil plane. The main orientation is such that the preferential orientation region with an azimuth difference of 10 ° or less occupies 50% or more with respect to two orthogonal axes with a certain direction, and the ridge line at the bent portion It was found that the breaking elongation of the metal foil in the normal direction relative to the cross section P of the wiring cut in the thickness direction of the metal foil was required to be 3.5% or more. Also, the purity is extremely high at 99.999% or more, and by developing the cube orientation, the elongation at break is improved, and the fatigue life against repeated bending in which principal stress and principal strain are applied in that direction. It has been found to be a long flexible circuit board.
［実施例２］
次に、実施例１と同じ方法で作製した銅箔Ａと銅箔Ｅを用いた片面銅張積層板について、図６に示すように、線幅（ｌ）１５０μｍの直線状の配線２の配線方向Ｈ（Ｈ方向）がＭＤ方向（［１００］軸）に対して３０°及び４５°の角度を有するようにし、かつ、スペース幅（ｓ）２５０μｍで配線パターンを形成した。そして、後述する耐屈曲試験用のサンプルを兼ねるように、JIS 6471に準じて、回路基板の配線方向Ｈに沿って長手方向に１５０ｍｍ、配線方向Ｈに直交する方向に幅１５ｍｍを有した試験用可撓性回路基板５を得た。図６は、試験用可撓性回路基板５の配線方向ＨとＭＤ方向とのなす角を４５°の角度で切り出した時の例である。 [Example 2]
Next, for a single-sided copper-clad laminate using copper foil A and copper foil E produced by the same method as in Example 1, as shown in FIG. 6, the wiring oflinear wiring 2 having a line width (l) of 150 μm The wiring pattern was formed such that the direction H (H direction) had an angle of 30 ° and 45 ° with respect to the MD direction ([100] axis) and the space width (s) was 250 μm. And in order to serve as a sample for bending resistance test to be described later, in accordance with JIS 6471, for the test having a width of 150 mm in the longitudinal direction along the wiring direction H of the circuit board and a width of 15 mm in the direction orthogonal to the wiring direction H. A flexible circuit board 5 was obtained. FIG. 6 shows an example in which the angle formed by the wiring direction H of the test flexible circuit board 5 and the MD direction is cut out at an angle of 45 °.
次に、実施例１と同じ方法で作製した銅箔Ａと銅箔Ｅを用いた片面銅張積層板について、図６に示すように、線幅（ｌ）１５０μｍの直線状の配線２の配線方向Ｈ（Ｈ方向）がＭＤ方向（［１００］軸）に対して３０°及び４５°の角度を有するようにし、かつ、スペース幅（ｓ）２５０μｍで配線パターンを形成した。そして、後述する耐屈曲試験用のサンプルを兼ねるように、JIS 6471に準じて、回路基板の配線方向Ｈに沿って長手方向に１５０ｍｍ、配線方向Ｈに直交する方向に幅１５ｍｍを有した試験用可撓性回路基板５を得た。図６は、試験用可撓性回路基板５の配線方向ＨとＭＤ方向とのなす角を４５°の角度で切り出した時の例である。 [Example 2]
Next, for a single-sided copper-clad laminate using copper foil A and copper foil E produced by the same method as in Example 1, as shown in FIG. 6, the wiring of
上記で得られた試験用可撓性回路基板５について、実施例１と同じ条件で繰り返し屈曲の疲労試験を実施した。また、試験用可撓性回路基板５の配線方向ＨとＭＤ方向とのなす角が同じになるように、エッチングする前の片面銅張積層板４から樹脂層を溶解して、長手方向が圧延方向に対して３０°及び４５°の角度を有するように切り出した１５０ｍｍ×１０ｍｍの試料を用いて、実施例１と同様に引張試験を行った。すなわち、銅箔の疲労試験における主応力、主歪み方向は、引張試験の引張方向と一致し、銅箔Ａと銅箔Ｅは、ともに高度に立方体集合組織が発達しているため、疲労試験と引張試験において、同じ結晶方位に主歪みと主応力を受ける。疲労試験、引張試験の結果を表２に示す。
The test flex circuit board 5 obtained above was repeatedly subjected to bending fatigue tests under the same conditions as in Example 1. Also, the resin layer is melted from the single-sided copper clad laminate 4 before etching so that the angle formed by the wiring direction H and the MD direction of the flexible circuit board 5 for testing is the same, and the longitudinal direction is rolled. A tensile test was performed in the same manner as in Example 1 using a sample of 150 mm × 10 mm cut so as to have an angle of 30 ° and 45 ° with respect to the direction. That is, the principal stress and principal strain direction in the fatigue test of the copper foil coincide with the tensile direction of the tensile test, and both the copper foil A and the copper foil E have a highly developed cubic texture. In the tensile test, the same crystal orientation is subjected to principal strain and principal stress. Table 2 shows the results of the fatigue test and the tensile test.
表２に示した試験結果から、主応力、主歪み方向を＜１００＞方位から外すことで、高い疲労特性を得ることができる。これらの方位では破断伸びも＜１００＞方位よりも著しく大きくなり、特に３０°の場合、破断伸びと共に疲労寿命も長くなる。
From the test results shown in Table 2, high fatigue characteristics can be obtained by removing the principal stress and principal strain directions from the <100> orientation. In these orientations, the elongation at break is significantly larger than that in the <100> orientation. In particular, in the case of 30 °, the fatigue life is increased along with the elongation at break.
以上の実施例２の結果から、高い歪みの繰り返し屈曲に対する可撓性回路基板の疲労寿命と配線を構成する銅箔の破断伸びとの間には、銅箔が高度に配向していた場合、高い相関があることが分かった。実施例１で見られたように、多結晶体では、より高い強度と延性が得られるが、高屈曲用途では有効ではない。しかがって、このような疲労寿命と高度に集積した集合組織を有する条件での破断伸びとの関係は、すべり系が重要な役割を担っており、銅に限らず、同じすべり系を有する面心立方方位金属でも成り立つものであり、積層欠陥エネルギーの異なる金属であれば、破断伸びもより大きくとれることが見込まれ、疲労寿命も大きくなることが期待できる。
From the results of Example 2 above, when the copper foil was highly oriented between the fatigue life of the flexible circuit board against repeated bending of high strain and the breaking elongation of the copper foil constituting the wiring, It was found that there was a high correlation. As seen in Example 1, the polycrystalline body provides higher strength and ductility, but is not effective in high bending applications. Therefore, the relationship between the fatigue life and the elongation at break under conditions that have a highly integrated texture is that the slip system plays an important role, not just copper, but the same slip system. Even a face-centered cubic orientation metal holds, and if the metals have different stacking fault energies, it is expected that the elongation at break can be increased and the fatigue life can be expected to be increased.
［実施例３］
純度９９．９mass％であり、厚さ１２μｍの圧延銅箔Ｈに、合成例１と同じ方法で準備したポリアミド酸溶液ａを塗布して乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、その上にポリアミド酸ｂを塗布して乾燥させ（硬化後は膜厚8μmの低熱熱膨張性ポリイミドを形成）、更にその上にポリアミド酸aを塗布して乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、下記条件ａ～ｄに示したように、最高温度１８０～２４０℃の温度が積算時間で１０分付加されるような加熱条件を経てポリイミド層（樹脂層）を形成した。 [Example 3]
The polyamic acid solution a prepared by the same method as in Synthesis Example 1 is applied to a rolled copper foil H having a purity of 99.9 mass% and a thickness of 12 μm and dried (after curing, a 2 μm-thick thermoplastic polyimide is formed) ), And polyamic acid b is applied and dried (forms a low thermal expansion coefficient polyimide having a film thickness of 8 μm after curing), and further polyamic acid a is applied and dried (film thickness after curing). 2 μm thermoplastic polyimide is formed), as shown in conditions a to d below, the polyimide layer (resin layer) is subjected to heating conditions such that the maximum temperature of 180 to 240 ° C. is added for 10 minutes in the total time. Formed.
純度９９．９mass％であり、厚さ１２μｍの圧延銅箔Ｈに、合成例１と同じ方法で準備したポリアミド酸溶液ａを塗布して乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、その上にポリアミド酸ｂを塗布して乾燥させ（硬化後は膜厚8μmの低熱熱膨張性ポリイミドを形成）、更にその上にポリアミド酸aを塗布して乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、下記条件ａ～ｄに示したように、最高温度１８０～２４０℃の温度が積算時間で１０分付加されるような加熱条件を経てポリイミド層（樹脂層）を形成した。 [Example 3]
The polyamic acid solution a prepared by the same method as in Synthesis Example 1 is applied to a rolled copper foil H having a purity of 99.9 mass% and a thickness of 12 μm and dried (after curing, a 2 μm-thick thermoplastic polyimide is formed) ), And polyamic acid b is applied and dried (forms a low thermal expansion coefficient polyimide having a film thickness of 8 μm after curing), and further polyamic acid a is applied and dried (film thickness after curing). 2 μm thermoplastic polyimide is formed), as shown in conditions a to d below, the polyimide layer (resin layer) is subjected to heating conditions such that the maximum temperature of 180 to 240 ° C. is added for 10 minutes in the total time. Formed.
次いで、銅箔の圧延方向（MD方向）に沿って長さ２５０ｍｍ、圧延方向に対して直交する方向（TD方向）に幅１５０ｍｍの長方形サイズとなるように切り出し、厚さ１２μｍのポリイミド層（樹脂層）１と厚さ１２μｍの銅箔２とを有した実施例３に係る片面銅張積層板４を得た。
Next, a polyimide layer (resin) having a thickness of 250 μm along the rolling direction (MD direction) of the copper foil and a rectangular size of 150 mm width in a direction orthogonal to the rolling direction (TD direction) and having a thickness of 12 μm. A single-sided copper-clad laminate 4 according to Example 3 having a layer 1 and a copper foil 2 having a thickness of 12 μm was obtained.
上記で得られた片面銅張積層板４の銅箔側に所定のマスクを被せ、塩化鉄／塩化銅系溶液を用いてエッチングを行い、ＩＰＣ規格に基づき、線幅１５０μｍ及びスペース幅２５０μｍの直線状の配線を有した低速ＩＰＣ試験用配線２を形成した。この製造過程において、ポリイミド層の形成の際の加熱条件の最高温度を１８０℃（条件ａ）、２００℃（条件ｂ）、２２０℃（条件ｃ）、及び２４０℃（条件ｄ）の４水準とし、また、直線状の配線２の配線方向（Ｈ方向）が圧延方向（ＭＤ方向）に対して０°、２°、２．９°、５．７°、９．５°、１１．４°、１４°、１８．４°、２５°、２６．６°、３０°、４０°、４５°、５５°、６０°、６３．４°、７８．６°、８０°、８２．９°、８７．１°、８８°、及び９０°の２２水準の角度を有するように、それぞれ配線パターンを形成した。
A predetermined mask is placed on the copper foil side of the single-sided copper-clad laminate 4 obtained above, etching is performed using an iron chloride / copper chloride solution, and a straight line having a line width of 150 μm and a space width of 250 μm is based on the IPC standard. A low-speed IPC test wiring 2 having a shape-like wiring was formed. In this manufacturing process, the maximum temperature of the heating conditions in forming the polyimide layer is set to four levels of 180 ° C. (condition a), 200 ° C. (condition b), 220 ° C. (condition c), and 240 ° C. (condition d). Moreover, the wiring direction (H direction) of the linear wiring 2 is 0 °, 2 °, 2.9 °, 5.7 °, 9.5 °, 11.4 ° with respect to the rolling direction (MD direction). 14 °, 18.4 °, 25 °, 26.6 °, 30 °, 40 °, 45 °, 55 °, 60 °, 63.4 °, 78.6 °, 80 °, 82.9 °, Wiring patterns were formed so as to have angles of 22 levels of 87.1 °, 88 °, and 90 °, respectively.
次いで、図８（ｂ）に示したように、それぞれの配線パターン側の面に、エポキシ系接着剤を用いてカバー材７（有沢製作所製 CVK-0515KA：厚さ12.5μｍ）を積層した。接着剤からなる接着層６の厚さは、銅箔回路のない部分では１５μｍであり、銅箔回路が存在する部分では６μｍであった。そして、配線方向（Ｈ方向）に沿って長手方向に１５ｃｍ、配線方向に直交する方向に幅８ｍｍとなるように切り出して、ＩＰＣ試験サンプルとするための試験用可撓性回路基板を得た。
Next, as shown in FIG. 8B, the cover material 7 (Arisawa Seisakusho CVK-0515KA: thickness 12.5 μm) was laminated on the surface of each wiring pattern side using an epoxy adhesive. The thickness of the adhesive layer 6 made of an adhesive was 15 μm in a portion without a copper foil circuit, and 6 μm in a portion where a copper foil circuit was present. And it cut out so that it might become 15 cm in a length direction along a wiring direction (H direction), and 8 mm in the direction orthogonal to a wiring direction, and the flexible circuit board for a test for setting it as an IPC test sample was obtained.
一方で、銅箔単体の特性を調べるために、次のようにして引張試験を行った。上記試験用可撓性回路基板５の配線方向ＨとＭＤ方向とのなす角の関係が同じ２２水準になるように、エッチングする前の片面銅張積層板４から樹脂層を溶解して銅箔単体とし、長手方向が圧延方向に対して上記２２水準の角度を有するように切り出した長さ１５０ｍｍ×幅１０ｍｍの矩形の試料を用意した。この際、ポリイミドを溶解する過程で、銅箔の組織に変化がないことを確認した。引張試験は、長さ方向に標点間距離１００ｍｍ、引張速さ１０ｍｍ／ｍｉｎ．で測定した。
On the other hand, in order to investigate the characteristics of the copper foil alone, a tensile test was performed as follows. The resin layer is dissolved from the single-sided copper-clad laminate 4 before etching so that the angle relationship between the wiring direction H and the MD direction of the test flexible circuit board 5 is the same 22 level, and the copper foil is dissolved. A rectangular sample having a length of 150 mm and a width of 10 mm, which was cut out so that the longitudinal direction had the above-described 22 level angle with respect to the rolling direction, was prepared. At this time, it was confirmed that there was no change in the structure of the copper foil in the process of dissolving the polyimide. In the tensile test, the distance between gauge points in the length direction is 100 mm, and the tensile speed is 10 mm / min. Measured with
また、ＥＢＳＰによる組織解析を行なうための試料として、条件ａ～ｄの熱処理条件で作製した片面銅張積層板について、圧延方向に対して、０°、２．９°、３０°、６３．４°、及び７８．６°の５つの角度で切り出した配線パターンの無い試料、合計２０枚を作製した。ＩＰＣ試験サンプルと熱履歴を揃えるために、回路形成エッチングと同じ条件で模擬的な熱処理を加え、更に同じ条件でカバー材を積層した。ただし、銅箔組織に対するこれらの影響は軽微であり、ポリイミド形成時の条件ａ～ｄの熱処理条件によって、銅箔組織が決まることが後に判明している。
In addition, as a sample for performing a structure analysis by EBSP, a single-sided copper-clad laminate produced under the heat treatment conditions of conditions a to d is 0 °, 2.9 °, 30 °, 63.4 with respect to the rolling direction. A total of 20 samples without wiring patterns cut out at 5 angles of 7 ° and 78.6 ° were produced. In order to align the thermal history with the IPC test sample, a simulated heat treatment was applied under the same conditions as the circuit formation etching, and a cover material was further laminated under the same conditions. However, these effects on the copper foil structure are minor, and it has been found that the copper foil structure is determined by the heat treatment conditions of conditions a to d at the time of polyimide formation.
そして、上記のとおりＥＢＳＰ測定用に作製した４水準の熱処理条件、及び５水準の角度条件を有する２０枚の銅箔Ｈを基板厚さ方向に研磨し、研磨前の箔面と水平な面を有するようにして、銅箔Ｈの箔面を露出させた。更にコロイダルシリカを用いて仕上げ研磨して、銅箔Ｈの組織をＥＢＳＰで評価した。測定領域は０．８ｍｍ×１．６ｍｍであり、測定間隔は４μｍとした。すなわち、１領域の測定点数は８００００点である。その結果、条件ａから条件ｄの熱処理条件で熱処理した試料はいずれも立方体集合組織を形成しており、銅箔面方位、圧延方向に｛001｝＜100＞の主方位を有していることがわかった。そして、得られた結果を基に、銅箔の厚さ方向と圧延方向に対し、単位格子軸＜００１＞が１０°以内になっている点の数をカウントし、全体の点数に対する割合を計算し、平均値を求めた。その結果を表３に示す。同じ加熱条件における試料間のばらつきは１％以下であり、同じ熱処理条件では、銅箔全面にわたって表３に示した集積度を有しているといえる。最高熱処理温度が高く、熱履歴が大きいほど再結晶が進行し、立方体再結晶集合組織の集積度は高くなっていることが分った。また、箔面内の方位解析を行なった結果、圧延方向に対して０°、２．９°、３０°、６３．４°、及び７８．６°の５つ角度で切り出した試料の切り出し方向の主方位は、［１００］、［20 １ ０］、［40 23 ０］、［１２０］、［１５０］を有しており、ほぼ所定通りであった。一方、得られたＥＢＳＰデータを用いて、隣り合う結晶粒の方位差が１５°以上であるものを結晶粒界として解析した、箔面法線方向から見た時の、結晶粒径の評価を行ない、多結晶体については平均粒径を求めた。結果を表３に示す。
Then, 20 copper foils H having the four-level heat treatment conditions and the five-level angle conditions prepared for the EBSP measurement as described above are polished in the substrate thickness direction. The foil surface of the copper foil H was exposed. Furthermore, it finished-polished using colloidal silica, and the structure of the copper foil H was evaluated by EBSP. The measurement area was 0.8 mm × 1.6 mm, and the measurement interval was 4 μm. That is, the number of measurement points in one area is 80000 points. As a result, all the samples heat-treated under the heat treatment conditions from condition a to condition d have a cubic texture, and have a copper foil plane orientation and a main orientation of {001} <100> in the rolling direction. I understood. Based on the obtained results, the number of points where the unit cell axis <001> is within 10 ° is counted in the thickness direction and the rolling direction of the copper foil, and the ratio to the total number of points is calculated. The average value was obtained. The results are shown in Table 3. The variation between samples under the same heating condition is 1% or less, and it can be said that the same heat treatment condition has the integration degree shown in Table 3 over the entire surface of the copper foil. It was found that the higher the maximum heat treatment temperature and the greater the thermal history, the more recrystallization progressed and the higher the degree of integration of the cubic recrystallization texture. Further, as a result of orientation analysis in the foil plane, the cutting direction of the sample cut at five angles of 0 °, 2.9 °, 30 °, 63.4 °, and 78.6 ° with respect to the rolling direction. The main orientations of [100], [20 1 0], [40 23 0], [120], and [150] were almost as specified. On the other hand, using the obtained EBSP data, the crystal grain size was evaluated when viewed from the normal direction of the foil surface, in which the crystal grain boundary was analyzed when the difference in orientation between adjacent crystal grains was 15 ° or more. The average particle size was determined for the polycrystal. The results are shown in Table 3.
ＩＰＣ試験は、図８にその模式図を示したように、携帯電話等に使用される屈曲形態のひとつであるスライド屈曲を模擬した試験である。ＩＰＣ試験は、図８のように、決められたギャップ長８で屈曲部を設け、片側を固定部９で固定し、反対側のスライド稼動部１０を図のように繰り返し往復運動させる試験である。したがって、往復運動させる部分のストローク量に応じた領域において、基板は繰り返しの屈曲を受ける。本実施例では、ポリイミド層（樹脂層）１を外側にして、キャップ長を１ｍｍ、すなわち屈曲半径を０．５ｍｍ、ストロークを３８ｍｍとして繰り返しスライドさせ試験を行なった。試験中、試験用可撓性回路基板の回路の電気抵抗の測定を行ない、電気抵抗の増加で銅箔回路の疲労クラックの進展の度合いをモニタリングした。本実施例では、回路の電気抵抗が初期値の２倍に達したストローク回数を回路破断寿命とした。
The IPC test is a test simulating slide bending, which is one of the bending forms used for mobile phones and the like, as shown in the schematic diagram of FIG. The IPC test is a test in which a bent portion is provided with a determined gap length 8 as shown in FIG. 8, one side is fixed by a fixing portion 9, and the slide operating portion 10 on the opposite side is repeatedly reciprocated as shown in the drawing. . Therefore, the substrate is repeatedly bent in a region corresponding to the stroke amount of the reciprocating portion. In this example, the test was conducted by repeatedly sliding the polyimide layer (resin layer) 1 with the cap length being 1 mm, that is, the bending radius being 0.5 mm and the stroke being 38 mm. During the test, the electrical resistance of the circuit of the test flexible circuit board was measured, and the progress of fatigue cracks in the copper foil circuit was monitored by increasing the electrical resistance. In this example, the circuit breakage life was defined as the number of strokes at which the electrical resistance of the circuit reached twice the initial value.
試験は、上記の条件ａ～条件ｄの４つの熱処理条件について、２２水準の角度を有する配線パターンを形成した合計８８水準について行なった。それぞれの試験水準では、４本の試験片について測定を行い、回路破断したストローク回数の平均を求めた。回路破断寿命後の銅箔について、スライド方向に直交するようにして銅箔を厚さ方向に切った断面を走査型電子顕微鏡で観察すると、程度の差はあるが、樹脂層側及びカバー材側のそれぞれの銅箔表面にはクラックが発生し、特に屈曲部の外側にあたる樹脂層側の銅箔表面には多数のクラックが導入されていることが観察された。
The test was conducted on a total of 88 levels in which wiring patterns having 22 levels of angles were formed under the four heat treatment conditions of the above conditions a to d. At each test level, four test pieces were measured, and the average number of strokes at which the circuit was broken was obtained. Regarding the copper foil after the circuit breaking life, when the cross section of the copper foil cut in the thickness direction so as to be orthogonal to the sliding direction is observed with a scanning electron microscope, there is a difference in degree, but the resin layer side and the cover material side It was observed that cracks occurred on the surfaces of the copper foils, and that many cracks were introduced on the surface of the copper foil on the resin layer side, which is outside the bent portion.
各水準の回路破断寿命の平均値、及び引張試験における破断伸びを表４に示す。表４の角度欄には、回路の長さ方向（配線方向）、すなわち、屈曲部における稜線から厚み方向に切った際の配線の断面Ｐについて、低指数方向になる場合のみ面指数も示した。
Table 4 shows the average value of circuit break life at each level and the elongation at break in the tensile test. In the angle column of Table 4, the surface index is also shown only in the case of the low index direction of the cross section P of the wiring when the circuit is cut in the length direction (wiring direction), that is, the ridgeline at the bent portion in the thickness direction. .
ＩＰＣ試験における破断寿命（疲労寿命）は、回路長さ方向（Ｈ方向）と圧延方向（ＭＤ方向）とのなす角、すなわち屈曲部における稜線から厚み方向に切った際の配線断面の法線方向と［１００］とのなす角に大きく依存することがわかった。この方位依存性は、条件ｂ、条件ｃ、及び条件ｄにおいて発現し、立方体方位の集積度が高いほど、繰り返し屈曲に対する疲労寿命が大きく、また、方位依存性が大きい。この方位依存性については、金属箔の厚さ方向に対し、銅の［００１］が方位差１０°以内にある領域がＥＢＳＰ法による評価で面積比５０％以上を占めるように、＜００１＞主方位が金属箔の厚さ方向に優先配向していると共に、銅の［１００］軸から方位差１０°以内にある領域がＥＢＳＰ法による評価で面積比５０％以上を占めるように、［１００］主方位が金属箔面内で優先配向している場合に発現することが確認された。特に、厚さ方向、及び圧延方向が、それぞれ面積比７５％以上、及び８５％以上を示して立方体方位の集積度が高い条件ｃの場合には、疲労寿命が大きく、また、方位依存性の効果が大きくなり、厚さ方向、及び圧延方向が、それぞれ面積比９８％以上、及び９９％以上を示して立方体方位の集積度が極めて高い条件ｄでは、更に疲労寿命が大きく、方位依存性の効果が大きいことが分った。
The fracture life (fatigue life) in the IPC test is the angle between the circuit length direction (H direction) and the rolling direction (MD direction), that is, the normal direction of the cross section of the wiring when cutting from the ridge line at the bent portion in the thickness direction. And [100] were found to depend greatly on the angle. This orientation dependency is manifested under conditions b, c, and d. The higher the degree of integration of the cube orientation, the greater the fatigue life against repeated bending and the greater the orientation dependency. Regarding this orientation dependency, the <001> main direction is such that the area where the copper [001] is within an orientation difference of 10 ° occupies an area ratio of 50% or more in the evaluation by the EBSP method with respect to the thickness direction of the metal foil. [100] The orientation is preferentially oriented in the thickness direction of the metal foil, and the region within 10 ° of the orientation difference from the [100] axis of copper occupies an area ratio of 50% or more as evaluated by the EBSP method. It was confirmed that the main azimuth was expressed when preferentially oriented in the metal foil plane. In particular, when the thickness direction and the rolling direction show the area ratios of 75% or more and 85% or more, respectively, and the condition c has a high degree of integration of cube orientation, the fatigue life is large and the orientation dependency is also high. The effect becomes large, and in the condition d in which the thickness direction and the rolling direction show an area ratio of 98% or more and 99% or more, respectively, and the accumulation degree of the cube orientation is extremely high, the fatigue life is further increased and the orientation dependency is increased. It turns out that the effect is great.
条件ｂ、条件ｃ、及び条件ｄの結果を詳細に検討すると、屈曲部における稜線から厚み方向に切った際の配線断面Ｐの法線方向、すなわち主応力方向が銅箔の＜１００＞主方位からずれていたほうが、屈曲に対する回路の疲労寿命が高い。本実施例のＩＰＣ試験において、効果が見られたのは、屈曲部の主歪み方向に対し、すなわち屈曲部における稜線から厚み方向に切った際の配線の断面法線方向に対して、２．９°～８７．１°の角度を有する場合であった。これを面指数で表すと、屈曲部における稜線から厚み方向に切った際の配線の断面Ｐが、［００１］を晶帯軸として（20 １ ０）から（１１０）を通り、（１ 20 ０）までの範囲である。なかでも効果が大きいのは、屈曲部の主歪み方向に対し、すなわち屈曲部における稜線から厚み方向に切った際の配線の断面法線方向に対して、１１．４°～７８．６°の角度を有する場合であった。これを面指数で表すと、屈曲部における稜線から厚み方向に切った際の配線の断面Ｐが、［００１］を晶帯軸として（５１０）から（１１０）を通り、（１５０）までの範囲である。屈曲特性は、更に屈曲部の主歪み方向に対し、すなわち屈曲部における稜線から厚み方向に切った際の配線の断面法線方向に対して、２６．６°～６３．４°の角度を有する場合に高くなり、最も優れるのは３０°と６０°の場合であった。これを面指数で表すと、断面Ｐが、［００１］を晶帯軸として（２１０）から（１１０）を通り、（１２０）までの範囲であり、最も優れるのは（40 23 ０）及び（23 40 ０）近傍にあるときであった。
When the results of conditions b, c, and d are examined in detail, the normal direction of the wiring cross section P when cutting in the thickness direction from the ridgeline at the bent portion, that is, the main stress direction is the <100> main orientation of the copper foil. The fatigue life of the circuit against bending is higher when it deviates from the above. In the IPC test of this example, the effect was observed with respect to the main strain direction of the bent portion, that is, with respect to the cross-sectional normal direction of the wiring when cutting from the ridge line in the bent portion in the thickness direction. This was the case with an angle of 9 ° to 87.1 °. Expressing this in terms of a plane index, the cross section P of the wiring when cut in the thickness direction from the ridgeline at the bent portion passes from (20 1 0) to (110) with [001] as the zone axis, and (1 20 0 ). In particular, the effect is large at 11.4 ° to 78.6 ° with respect to the main strain direction of the bent portion, that is, with respect to the normal direction of the cross section of the wiring when cut from the ridge line in the bent portion in the thickness direction. It was the case with an angle. When this is expressed in terms of a plane index, the cross section P of the wiring when it is cut in the thickness direction from the ridgeline at the bent portion ranges from (510) to (110) to (150) with [001] as the zone axis. It is. The bending characteristic further has an angle of 26.6 ° to 63.4 ° with respect to the main strain direction of the bent portion, that is, with respect to the normal direction of the cross section of the wiring when cut from the ridge line in the bent portion in the thickness direction. In the case of 30 ° and 60 °, the best results were obtained. When this is expressed in terms of a plane index, the cross section P is in the range from (210) to (110) to (120) with [001] as the zone axis, and the most excellent is (40 23 0) and ( 23 40 0) Near.
これらの結果と破断伸びとを比較したとき、面心立方構造の単位格子の基本結晶軸＜１００＞が、金属箔の厚さ方向と箔面内に存在するある一方向との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で５０％以上を占めるように、主方位を有していた場合、屈曲部における稜線から金属箔の厚み方向に切った配線の断面Ｐに対する法線方向の金属箔の破断伸びが３．５％以上であれば、その方位に主応力、主歪みを発生させる屈曲に対して、良好な屈曲疲労特性を有することが分かった。一方、＜１００＞優先配向領域の面積率が４９％以下の場合、その方向の破断伸びが３．５％以上の値を示しても、良好な屈曲疲労特性は得られなかった。
When these results are compared with the elongation at break, the basic crystal axis <100> of the unit cell having a face-centered cubic structure has two orthogonal axes of the thickness direction of the metal foil and a certain direction existing in the foil surface. On the other hand, when the main orientation is such that the preferential orientation regions having an orientation difference of 10 ° or less each occupy 50% or more in area ratio, the wiring cut from the ridge line in the bent portion in the thickness direction of the metal foil It was found that when the breaking elongation of the metal foil in the normal direction relative to the cross section P is 3.5% or more, the metal foil has good bending fatigue characteristics with respect to bending that generates principal stress and principal strain in the direction. On the other hand, when the area ratio of the <100> preferentially oriented region was 49% or less, even if the elongation at break in that direction showed a value of 3.5% or more, good bending fatigue characteristics were not obtained.
［実施例４］
純度９９．９９％の銅箔ＣにＡｒ気流中で１８０℃～４００℃の５水準の温度で３０分間の熱処理（予備熱処理）を加え、実施例１と同じ方法でポリアミド酸溶液aを塗布し、乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、その上にポリアミド酸ｂを塗布し、乾燥させ（硬化後は膜厚9μmの低熱熱膨張性ポリイミドを形成）、更にその上にポリアミド酸aを塗布し乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、３００～３６０℃の温度が積算時間で５分以上負荷されるような加熱条件を経て３層構造からなるポリイミド層を形成した。次いで、銅箔の圧延方向（MD方向）に沿って長さ２５０ｍｍ、圧延方向に対して直交する方向（TD方向）に幅１５０ｍｍの長方形サイズとなるように切り出し、図５に示すように、厚さ１３μｍのポリイミド層（樹脂層）１と厚さ９μｍの銅箔２とを有した片面銅張積層板４を得た。そのときの樹脂層全体の引張弾性率は７．５ＧＰａであった。 [Example 4]
A heat treatment (preliminary heat treatment) for 30 minutes was applied to copper foil C having a purity of 99.99% at five levels of 180 ° C. to 400 ° C. in an Ar stream, and the polyamic acid solution a was applied in the same manner as in Example 1. , Dried (after forming a 2 μm-thick thermoplastic polyimide film after curing), coated with polyamic acid b and dried (after curing, formed a 9 μm-thick low thermal expansion polyimide), and further The polyamic acid a is applied and dried (forms a thermoplastic polyimide with a film thickness of 2 μm after curing), and is heated to a temperature of 300 to 360 ° C. for a total time of 5 minutes or more. A polyimide layer was formed. Next, the copper foil was cut out to a rectangular size of 250 mm in length along the rolling direction (MD direction) and 150 mm in the direction perpendicular to the rolling direction (TD direction), as shown in FIG. A single-sided copper cladlaminate 4 having a 13 μm thick polyimide layer (resin layer) 1 and a 9 μm thick copper foil 2 was obtained. At that time, the tensile elastic modulus of the entire resin layer was 7.5 GPa.
純度９９．９９％の銅箔ＣにＡｒ気流中で１８０℃～４００℃の５水準の温度で３０分間の熱処理（予備熱処理）を加え、実施例１と同じ方法でポリアミド酸溶液aを塗布し、乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、その上にポリアミド酸ｂを塗布し、乾燥させ（硬化後は膜厚9μmの低熱熱膨張性ポリイミドを形成）、更にその上にポリアミド酸aを塗布し乾燥させ（硬化後は膜厚2μmの熱可塑性ポリイミドを形成）、３００～３６０℃の温度が積算時間で５分以上負荷されるような加熱条件を経て３層構造からなるポリイミド層を形成した。次いで、銅箔の圧延方向（MD方向）に沿って長さ２５０ｍｍ、圧延方向に対して直交する方向（TD方向）に幅１５０ｍｍの長方形サイズとなるように切り出し、図５に示すように、厚さ１３μｍのポリイミド層（樹脂層）１と厚さ９μｍの銅箔２とを有した片面銅張積層板４を得た。そのときの樹脂層全体の引張弾性率は７．５ＧＰａであった。 [Example 4]
A heat treatment (preliminary heat treatment) for 30 minutes was applied to copper foil C having a purity of 99.99% at five levels of 180 ° C. to 400 ° C. in an Ar stream, and the polyamic acid solution a was applied in the same manner as in Example 1. , Dried (after forming a 2 μm-thick thermoplastic polyimide film after curing), coated with polyamic acid b and dried (after curing, formed a 9 μm-thick low thermal expansion polyimide), and further The polyamic acid a is applied and dried (forms a thermoplastic polyimide with a film thickness of 2 μm after curing), and is heated to a temperature of 300 to 360 ° C. for a total time of 5 minutes or more. A polyimide layer was formed. Next, the copper foil was cut out to a rectangular size of 250 mm in length along the rolling direction (MD direction) and 150 mm in the direction perpendicular to the rolling direction (TD direction), as shown in FIG. A single-sided copper clad
上記で得られた片面銅張積層板４について、銅箔２の圧延面2aに対してコロイダルシリカを使用し、機械的、化学的研磨を行なった後、ＥＢＳＰ装置にて方位解析を行った。使用した装置は、日立製作所製ＦＥ－ＳＥＭ（S-4100）、ＴＳＬ社製のＥＢＳＰ装置、及びソフトウエア（OIM Analysis 5.2）である。測定領域はおよそ８００μｍ×１６００μｍの領域であり、測定時加速電圧２０ｋＶ、測定ステップ間隔４μｍとした。配向性の評価は、箔の厚さ方向、及び箔の圧延方向に対して＜１００＞が１０°以内に入っている測定点の全体の測定点に対する割合で示した。測定数は各品種個体の異なる５つの試料について実施し、百分率の小数点２桁目以下を四捨五入した。また、得られたデータを用いて、隣り合う結晶粒の方位差が１５°以上であるものを結晶粒界として結晶粒径の評価を行ない、多結晶体については平均粒径を求めた。結果を表５に示す。
For the single-sided copper-clad laminate 4 obtained above, colloidal silica was used on the rolled surface 2a of the copper foil 2, mechanically and chemically polished, and then subjected to orientation analysis using an EBSP apparatus. The apparatuses used were FE-SEM (S-4100) manufactured by Hitachi, Ltd., EBSP apparatus manufactured by TSL, and software (OIM Analysis 5.2). The measurement area was an area of approximately 800 μm × 1600 μm, and the measurement acceleration voltage was 20 kV and the measurement step interval was 4 μm. The evaluation of the orientation was shown by the ratio of the measurement points where <100> is within 10 ° with respect to the thickness direction of the foil and the rolling direction of the foil to the total measurement points. The number of measurements was performed on five different samples of each variety, and the percentages after the second decimal place were rounded off. Further, using the obtained data, the crystal grain size was evaluated by setting the crystal grain boundaries to those having an orientation difference of 15 ° or more between adjacent crystal grains, and the average grain size was determined for the polycrystal. The results are shown in Table 5.
銅箔Ｃはいずれも立方体集合組織を形成しており、銅箔面方位、圧延方向ともに｛００１｝＜１００＞の主方位を有していることが分った。これは、圧延加工された銅箔が、予備熱処理とポリイミドの硬化の際の熱によって再結晶し、再結晶集合組織が形成されたためである。ここでは、予備熱処理温度が高い程、｛００１｝＜１００＞の配向度は大きくなった。また、＜１００＞方位以外の方位は、上記と同様にＥＢＳＰ装置によって確認したところ、圧延方向に対して＜２１２＞の方位を有し、円相当径が５μｍ以下の再結晶残留方位が島状に分散していた。但し、４００℃で予備熱処理を行った銅箔では、このような島状の組織は殆ど見られなかった。なお、確認された島状組織の面積率は２％以下と小さいため、立方体方位を有する再結晶粒は同じ方位を有して一体化していた。また、再結晶粒の大きさは、厚さ方向に箔厚と同じ９μｍであり、箔面内に８００μｍ以上であった。
It was found that each of the copper foils C had a cubic texture, and both the copper foil surface orientation and the rolling direction had a main orientation of {001} <100>. This is because the rolled copper foil was recrystallized by pre-heat treatment and heat at the time of curing of the polyimide, and a recrystallized texture was formed. Here, the higher the preliminary heat treatment temperature, the greater the degree of orientation of {001} <100>. In addition, the orientation other than the <100> orientation was confirmed by the EBSP apparatus in the same manner as described above. As a result, the recrystallized residual orientation having an orientation of <212> with respect to the rolling direction and an equivalent circle diameter of 5 μm or less was island-like. Was dispersed. However, such an island-like structure was hardly observed in the copper foil subjected to the preliminary heat treatment at 400 ° C. In addition, since the area ratio of the confirmed island-like structure was as small as 2% or less, the recrystallized grains having the cubic orientation were integrated with the same orientation. Moreover, the size of the recrystallized grains was 9 μm, which was the same as the foil thickness in the thickness direction, and was 800 μm or more in the foil surface.
次に、上記で得られた片面銅張積層板４の銅箔２側に所定のマスクを被せ、塩化鉄／塩化銅系溶液を用いてエッチングを行い、図６に示したように（但し、配線方向ＨとＭＤ方向とのなす角は０°である）、線幅（ｌ）が１５０μｍの直線状の配線２の配線方向Ｈ（Ｈ方向）が、ＭＤ方向（＜１００＞軸）に平行になるように、かつ、スペース幅（ｓ）が２５０μｍとなるように配線パターンを形成した。そして、後述する耐屈曲試験用のサンプルを兼ねるように、JIS 6471に準じて、回路基板の配線方向Ｈに沿って長手方向に１５０ｍｍ、配線方向Ｈに直交する方向に幅１５ｍｍを有した試験用可撓性回路基板５を得た。
Next, a predetermined mask is put on the copper foil 2 side of the single-sided copper clad laminate 4 obtained above, and etching is performed using an iron chloride / copper chloride solution, as shown in FIG. The angle between the wiring direction H and the MD direction is 0 °), and the wiring direction H (H direction) of the linear wiring 2 having a line width (l) of 150 μm is parallel to the MD direction (<100> axis). The wiring pattern was formed so that the space width (s) was 250 μm. And in order to serve as a sample for bending resistance test to be described later, in accordance with JIS 6471, for test having 150 mm in the longitudinal direction along the wiring direction H of the circuit board and 15 mm in the direction orthogonal to the wiring direction H A flexible circuit board 5 was obtained.
上記で得られた試験用可撓性回路基板を用い、JIS C5016に準じてＭＩＴ屈曲試験を行った。試験の模式図を図７に示す。装置は東洋精機製作所製（STROGRAPH-R1）を使用し、試験用可撓性回路基板５の長手方向の一端を屈曲試験装置のくわえ治具に固定し、他端をおもりで固定して、くわえ部を中心として、振動速度１５０回／分の条件で左右に交互に１３５±５度ずつ回転させながら、曲率半径０．８ｍｍとなるように屈曲させ、回路基板５の配線２の導通が遮断されるまでの回数を屈曲回数として求めた。
MIT flex test was performed according to JIS C5016 using the test flexible circuit board obtained above. A schematic diagram of the test is shown in FIG. The equipment is manufactured by Toyo Seiki Seisakusho (STROGRAPH-R1), one end of the test flexible circuit board 5 in the longitudinal direction is fixed to the holding jig of the bending test apparatus, and the other end is fixed with a weight. The wire 2 on the circuit board 5 is cut off from conduction while being rotated to 135 ± 5 degrees alternately left and right at a vibration speed of 150 times / min. Was determined as the number of flexing.
この試験条件において、屈曲部に形成される稜線が試験用可撓性回路基板５の配線２の配線方向Ｈに対して直交するよう屈曲を受けることかから、銅回路に印加される主応力、主歪みは、圧延方向に平行な引張応力、引張歪みとなる。屈曲試験後に銅箔の厚さ方向から回路を観察すると屈曲部の稜線付近で圧延方向とほぼ垂直にクラックが入り、破線したことが確認された。屈曲寿命の結果を表５に示す。表５の屈曲寿命は、銅箔の予備熱処理温度ごとにそれぞれ５つ用意した試験用可撓性回路基板の結果の平均である。表５に示した結果から、屈曲疲労寿命は、立方体集合組織の集積度が、９８．０％以上、９９．８％の時に特に大きくなることが分かった。
Under this test condition, the main stress applied to the copper circuit is obtained because the ridge line formed in the bent portion is bent so as to be orthogonal to the wiring direction H of the wiring 2 of the test flexible circuit board 5. The main strain is a tensile stress or tensile strain parallel to the rolling direction. When the circuit was observed from the thickness direction of the copper foil after the bending test, it was confirmed that a crack occurred in the vicinity of the ridgeline of the bent portion, almost perpendicular to the rolling direction, and a broken line. The results of the bending life are shown in Table 5. The flex life in Table 5 is an average of the results of five test flexible circuit boards prepared for each copper foil pre-heat treatment temperature. From the results shown in Table 5, it was found that the bending fatigue life becomes particularly large when the degree of cube texture accumulation is 98.0% or more and 99.8%.
次に、屈曲寿命の支配因子を調べるために、屈曲の主応力、主歪み方向、すなわち圧延方向と平行に引張試験を行った。予備熱処理温度による銅箔単体の特性を調べるために、エッチングする前の片面銅張積層板４から樹脂層を溶解して、銅箔単体での引張試験を行った。ポリイミドを溶解する過程で、銅箔の組織に変化がないことを確認した。
Next, in order to investigate the governing factor of the bending life, a tensile test was performed in parallel with the main stress of bending, the main strain direction, that is, the rolling direction. In order to investigate the characteristics of the copper foil alone according to the preliminary heat treatment temperature, the resin layer was dissolved from the single-sided copper clad laminate 4 before etching, and a tensile test was conducted on the copper foil alone. In the process of dissolving the polyimide, it was confirmed that there was no change in the structure of the copper foil.
引張試験は、銅箔の圧延方向（ＭＤ方向）に長さ１５０ｍｍ、箔面内垂直方向に幅１０ｍｍに切り出した試料を使用し、標点間距離１００ｍｍ、長さ方向に引張速さ１０ｍｍ／ｍｉｎ．で測定した。測定には銅箔の予備熱処理温度ごとにそれぞれ試料を７本用意し、これらを測定して求めた破断応力（破断強度）、及び破断伸びの平均値を表５に示した。
The tensile test uses a sample cut to a length of 150 mm in the rolling direction (MD direction) of the copper foil and a width of 10 mm in the vertical direction in the foil plane, the distance between the gauge points is 100 mm, and the tensile speed is 10 mm / min in the length direction. . Measured with For the measurement, seven samples were prepared for each preliminary heat treatment temperature of the copper foil, and the breaking stress (breaking strength) and the average value of breaking elongation obtained by measuring these were shown in Table 5.
これまでの結果とは逆に、破断伸びは、＜１００＞集積度（％）が９８．０％以上９９．８％以下の領域において集積度が増すごとに大きくなった。一方で、島状組織が消失した銅箔では、破断伸びが小さくなった。これは、すべり面が関係しているものと推察される。以上から、破断伸びと屈曲疲労寿命は強い相関があることが確認された。すなわち、＜１００＞集積度（％）が、９８．０％以上９９．８％以下の集合組織が高度に発達し、かつ破断伸びが３．５％以上のところで屈曲疲労寿命が大きくなることが分った。
Contrary to the results so far, the elongation at break increased as the integration degree increased in the region where the <100> integration degree (%) was 98.0% or more and 99.8% or less. On the other hand, the elongation at break was small in the copper foil from which the island-like structure disappeared. This is presumed to be related to the slip surface. From the above, it was confirmed that the elongation at break and the bending fatigue life have a strong correlation. That is, a texture with a <100> accumulation degree (%) of 98.0% or more and 99.8% or less is highly developed, and the flexural fatigue life is increased when the elongation at break is 3.5% or more. I understand.
一方、同じ条件で酸素を０．０３５質量％含む、純度９９．９％のタフピッチ銅にて同じ条件で銅箔を作製して同じ条件で試験を実施したところ、＜１００＞集積度（％）が、９８．０％以上でも破断伸びは集積度が大きくなるに従って減少し、３．５％以上の銅箔は得られず、１０００回以上の疲労寿命は得られなかった。
On the other hand, when a copper foil was produced under the same conditions using tough pitch copper containing 0.035% by mass of oxygen under the same conditions and under the same conditions, the test was performed under the same conditions. <100> Degree of integration (%) However, even at 98.0% or more, the breaking elongation decreased as the degree of integration increased, and a copper foil of 3.5% or more could not be obtained, and a fatigue life of 1000 times or more could not be obtained.
本発明による可撓性回路基板は、各種電子・電気機器で幅広く使用することができ、回路基板自体が折り曲げられたり、ねじ曲げられたり、或いは搭載された機器の動作に応じて変形したりして、いずれかに屈曲部を有して使用するのに適している。特に、本発明の可撓性回路基板は屈曲耐久性に優れた屈曲部構造を有することから、摺動屈曲、折り曲げ屈曲、ヒンジ屈曲、スライド屈曲等の繰り返し動作を伴い頻繁に折り曲げられたりする場合や、或いは搭載される機器の小型化に対応すべく、曲率半径が極めて小さくなることが求められるような屈曲部を形成するような場合に好適である。そのため、耐久性が要求される薄型携帯電話、薄型ディスプレー、ハードディスク、プリンター、ＤＶＤ装置をはじめ、各種電子機器に好適に利用することができる。
The flexible circuit board according to the present invention can be widely used in various electronic and electrical devices. The circuit board itself is bent, twisted, or deformed according to the operation of the mounted device. , Suitable for use with a bent portion in either. In particular, since the flexible circuit board of the present invention has a bent portion structure with excellent bending durability, it is frequently bent with repeated operations such as sliding bending, bending bending, hinge bending, and sliding bending. Alternatively, it is suitable for the case where a bent portion is required in which the radius of curvature is required to be extremely small in order to cope with downsizing of the equipment to be mounted. Therefore, it can be suitably used for various electronic devices such as thin mobile phones, thin displays, hard disks, printers, and DVD devices that require durability.
１：樹脂層
２：配線（金属箔）
2a：圧延面
2b：側面
３：コネクタ端子
４：片面銅張積層板
５：試験用可撓性回路基板
６：接着層
７：カバー材
８：ギャップ長
９：固定部
１０：スライド稼動部
２１：断面Ｐの法線方向
Ｌ：稜線
Ｐ：屈曲部における稜線から厚み方向に切った際の配線の断面 1: Resin layer 2: Wiring (metal foil)
2a: Rolled surface
2b: Side surface 3: Connector terminal 4: Single-sided copper clad laminate 5: Test flexible circuit board 6: Adhesive layer 7: Cover material 8: Gap length 9: Fixing part 10: Slide operating part 21: Method of section P Line direction L: Ridge line P: Cross section of wiring when cut in the thickness direction from the ridge line at the bent portion
２：配線（金属箔）
2a：圧延面
2b：側面
３：コネクタ端子
４：片面銅張積層板
５：試験用可撓性回路基板
６：接着層
７：カバー材
８：ギャップ長
９：固定部
１０：スライド稼動部
２１：断面Ｐの法線方向
Ｌ：稜線
Ｐ：屈曲部における稜線から厚み方向に切った際の配線の断面 1: Resin layer 2: Wiring (metal foil)
2a: Rolled surface
2b: Side surface 3: Connector terminal 4: Single-sided copper clad laminate 5: Test flexible circuit board 6: Adhesive layer 7: Cover material 8: Gap length 9: Fixing part 10: Slide operating part 21: Method of section P Line direction L: Ridge line P: Cross section of wiring when cut in the thickness direction from the ridge line at the bent portion
Claims (11)
- 樹脂層と金属箔から形成された配線とを備え、配線の少なくとも一箇所に屈曲部を有して使用される可撓性回路基板であって、
金属箔は、面心立方構造を有する金属からなると共に、面心立方構造の単位格子の基本結晶軸＜１００＞が、金属箔の厚さ方向と箔面内に存在するある一方向との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で５０％以上を占め、かつ屈曲部における稜線から金属箔の厚み方向に切った配線の断面Ｐに対する法線方向の金属箔の破断伸びが３．５％以上、２０％以下であることを特徴とする可撓性回路基板。 A flexible circuit board comprising a resin layer and a wiring formed from a metal foil, and having a bent portion in at least one part of the wiring,
The metal foil is made of a metal having a face-centered cubic structure, and the basic crystal axis <100> of the unit cell of the face-centered cubic structure is 2 in the thickness direction of the metal foil and a certain direction existing in the foil surface. With respect to two orthogonal axes, the preferential orientation regions having an azimuth difference of 10 ° or less occupy 50% or more in area ratio, and the normal direction with respect to the cross section P of the wiring cut from the ridge line in the bent portion in the thickness direction of the metal foil A flexible circuit board, wherein the breaking elongation of the metal foil is 3.5% or more and 20% or less. - 金属箔が、純度９９．９９９質量％以上の銅箔からなる請求項１に記載の可撓性回路基板。 The flexible circuit board according to claim 1, wherein the metal foil is made of copper foil having a purity of 99.999 mass% or more.
- 金属箔が銅箔であり、箔面法線方向から見たときの結晶粒径が２５μｍ以上である請求項１又は２に記載の可撓性回路基板。 The flexible circuit board according to claim 1 or 2, wherein the metal foil is a copper foil, and the crystal grain size when viewed from the normal direction of the foil surface is 25 µm or more.
- 金属箔の厚みが５μｍ以上、１８μｍ以下である請求項１～３のいずれかに記載の可撓性回路基板。 4. The flexible circuit board according to claim 1, wherein the thickness of the metal foil is 5 μm or more and 18 μm or less.
- 配線の断面Ｐが、［００１］を晶帯軸として（１００）から（１１０）への回転方向における（20 １ ０）から（１ 20 ０）の範囲に含まれたいずれかの面に主方位をなす請求項１～４のいずれかに記載の可撓性回路基板。 The cross section P of the wiring has a main orientation on any surface included in the range of (20 1 0) to (1 20 0) in the rotation direction from (100) to (110) with [001] as the zone axis The flexible circuit board according to any one of claims 1 to 4, wherein:
- 配線の断面Ｐが、（１００）標準投影図のステレオ三角形において（20 １ ０）を表す点と（１１０）を表す点とで結ばれた線分上にあるいずれかの面である請求項５に記載の可撓性回路基板。 6. The cross section P of the wiring is any surface on a line segment connected by a point representing (20 1 0) and a point representing (110) in a stereo triangle of (100) standard projection. A flexible circuit board according to claim 1.
- 屈曲部における稜線に対して直交する方向に沿って配線が形成されている請求項１～６のいずれかに記載の可撓性回路基板。 The flexible circuit board according to any one of claims 1 to 6, wherein a wiring is formed along a direction orthogonal to the ridge line in the bent portion.
- 樹脂層がポリイミドからなる請求項１～７のいずれかに記載の可撓性回路基板。 8. The flexible circuit board according to claim 1, wherein the resin layer is made of polyimide.
- 摺動屈曲、折り曲げ屈曲、ヒンジ屈曲及びスライド屈曲からなる群から選ばれたいずれかの繰り返し動作を伴う屈曲部が形成されるように使用される請求項１～８のいずれかに記載の可撓性回路基板。 The flexibility according to any one of claims 1 to 8, which is used so as to form a bent portion with any repetitive motion selected from the group consisting of sliding bending, bending bending, hinge bending, and sliding bending. Circuit board.
- 請求項１～９のいずれかに記載の可撓性回路基板を搭載した電子機器。 An electronic device on which the flexible circuit board according to any one of claims 1 to 9 is mounted.
- 樹脂層と金属箔から形成された配線とを備え、配線の少なくとも一箇所に屈曲部を有して使用される可撓性回路基板の屈曲部構造であって、
金属箔は、面心立方構造を有する金属からなると共に、面心立方構造の単位格子の基本結晶軸＜１００＞が、金属箔の厚さ方向と箔面内に存在するある一方向との２つの直交軸に対して、それぞれ方位差１０°以内の優先配向領域が面積率で５０％以上を占め、かつ、屈曲部における稜線から金属箔の厚み方向に切った配線の断面Ｐに対する法線方向の金属箔の破断伸びが３．５％以上、２０％以下であることを特徴とする可撓性回路基板の屈曲部構造。 A flexible circuit board bent portion structure comprising a resin layer and a wiring formed from a metal foil, and having a bent portion in at least one portion of the wiring;
The metal foil is made of a metal having a face-centered cubic structure, and the basic crystal axis <100> of the unit cell of the face-centered cubic structure is 2 in the thickness direction of the metal foil and a certain direction existing in the foil surface. The normal orientation direction with respect to the cross section P of the wiring cut in the thickness direction of the metal foil from the ridgeline in the bent portion with respect to the two orthogonal axes, the preferential orientation region having an azimuth difference of 10 ° or less occupies 50% or more in area ratio Bending part structure of flexible circuit board, wherein elongation at break of metal foil is 3.5% or more and 20% or less.
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| KR1020127019575A KR101690491B1 (en) | 2009-12-25 | 2010-12-22 | Flexible circuit board and structure of bend section of flexible circuit board |
| JP2011547609A JP5732406B2 (en) | 2009-12-25 | 2010-12-22 | Flexible circuit board and bent portion structure of flexible circuit board |
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| JP5243892B2 (en) * | 2008-08-26 | 2013-07-24 | 新日鉄住金化学株式会社 | A method for manufacturing a flexible wiring board. |
| JP4763068B2 (en) * | 2008-06-30 | 2011-08-31 | 新日鐵化学株式会社 | Flexible circuit board, manufacturing method thereof, and bent portion structure of flexible circuit board |
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- 2010-12-22 CN CN201080054314.XA patent/CN102782174B/en active Active
- 2010-12-22 JP JP2011547609A patent/JP5732406B2/en active Active
- 2010-12-22 KR KR1020127019575A patent/KR101690491B1/en active IP Right Grant
- 2010-12-22 WO PCT/JP2010/073198 patent/WO2011078259A1/en active Application Filing
- 2010-12-24 TW TW099145831A patent/TWI571183B/en active
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| JPH04173943A (en) * | 1990-11-02 | 1992-06-22 | Dowa Mining Co Ltd | High purity rolled copper foil having high flexibility and body utilizing same |
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| JP2013207145A (en) * | 2012-03-29 | 2013-10-07 | Jx Nippon Mining & Metals Corp | Copper foil, copper-clad laminate, flexible wiring board, and three-dimensional molding |
| CN103358618A (en) * | 2012-03-29 | 2013-10-23 | Jx日矿日石金属株式会社 | Copper foil, copper plated film stacking body, flexible distributing board and stereoscopic forming body |
| CN103358618B (en) * | 2012-03-29 | 2015-04-22 | Jx日矿日石金属株式会社 | Copper foil, copper plated film stacking body, flexible distributing board and stereoscopic forming body |
| JP2013247017A (en) * | 2012-05-28 | 2013-12-09 | Jx Nippon Mining & Metals Corp | Rolled copper foil for secondary battery negative electrode collector, negative electrode material for lithium ion secondary battery including the same, and lithium ion secondary battery |
| KR20140042684A (en) * | 2012-09-28 | 2014-04-07 | 신닛테츠 수미킨 가가쿠 가부시키가이샤 | Flexible copper-clad laminate |
| KR102045089B1 (en) * | 2012-09-28 | 2019-11-14 | 닛테츠 케미컬 앤드 머티리얼 가부시키가이샤 | Flexible copper-clad laminate |
| KR20160038827A (en) * | 2014-09-30 | 2016-04-07 | 신닛테츠 수미킨 가가쿠 가부시키가이샤 | Flexible printed circuit board and electronic device |
| JP2016072405A (en) * | 2014-09-30 | 2016-05-09 | 新日鉄住金化学株式会社 | Flexible circuit board, method of use thereof and electronic apparatus |
| TWI660649B (en) * | 2014-09-30 | 2019-05-21 | 日商日鐵化學材料股份有限公司 | Flexible circuit board and electronic equipment |
| KR102404294B1 (en) * | 2014-09-30 | 2022-05-31 | 닛테츠 케미컬 앤드 머티리얼 가부시키가이샤 | Flexible printed circuit board and electronic device |
| WO2024014169A1 (en) * | 2022-07-14 | 2024-01-18 | Ｊｘ金属株式会社 | Copper foil, and copper-clad laminate and flexible printed wiring board each using same |
Also Published As
| Publication number | Publication date |
|---|---|
| KR101690491B1 (en) | 2016-12-28 |
| JPWO2011078259A1 (en) | 2013-05-09 |
| CN102782174A (en) | 2012-11-14 |
| KR20120108032A (en) | 2012-10-04 |
| TWI571183B (en) | 2017-02-11 |
| CN102782174B (en) | 2015-11-25 |
| JP5732406B2 (en) | 2015-06-10 |
| TW201146101A (en) | 2011-12-16 |
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