CN108603303B

CN108603303B - Surface-treated copper foil and copper-clad laminate produced using same

Info

Publication number: CN108603303B
Application number: CN201780008477.6A
Authority: CN
Inventors: 佐藤章; 宇野岳夫
Original assignee: Furukawa Electric Co Ltd
Current assignee: Furukawa Electric Co Ltd
Priority date: 2016-02-10
Filing date: 2017-01-23
Publication date: 2020-11-13
Anticipated expiration: 2037-01-23
Also published as: CN108603303A; JP6248231B1; TWI704048B; TW201800242A; WO2017138338A1; JPWO2017138338A1; KR102230999B1; KR20180112769A

Abstract

The invention provides a surface-treated copper foil and a copper-clad laminate manufactured by using the same, which ensure sufficient adhesion with an insulating substrate and have high reflow heat resistance and transmission characteristics. The surface-treated copper foil is characterized in that the roughened layer (120) is formed by roughening a copper foil substrate (110) to form a rough surface, the rough surface layer (120) has a ratio (Da/Db) of a length (Da) along the rough surface of the roughened layer (120) to a length (Db) along the copper foil substrate in a cross section perpendicular to the copper foil substrate surface, which is 1.05 to 4.00 times, the average height difference (H) of the roughness of the rough surface is 0.2 to 1.3 [ mu ] m, and the rough surface layer (120) has a thickness of 0.0003 to 0.0300mg/dm directly or through an intermediate layer²A silane coupling agent layer formed by the amount of silane deposited.

Description

Surface-treated copper foil and copper-clad laminate produced using same

Technical Field

The present invention relates to a surface-treated copper foil that ensures sufficient adhesion to an insulating substrate and has high reflow heat resistance and high transmission characteristics, and a copper-clad laminate produced using the same.

Background

In recent years, with the progress of high performance, and networking of computers and information communication devices, signals tend to be increasingly higher in frequency to perform high-speed transmission processing of large volumes of information. Such an information communication device uses a copper-clad laminate. The copper-clad laminate is produced by heating and pressing an insulating substrate (resin substrate) and a copper foil. In general, a resin having excellent dielectric properties is required for an insulating substrate constituting a high-frequency supporting copper-clad laminate, but a resin having a low relative permittivity and a low dielectric loss tangent tends to be as follows: the functional group having high polarity contributing to adhesion with the copper foil is small, and the adhesion property with the copper foil is deteriorated.

In addition, it is desirable to reduce the surface roughness of a copper foil used as a conductive layer for a high-frequency-supporting copper-clad laminate as much as possible. The reason why such a low profile of the copper foil is required is that, as the frequency increases, a current intensively flows in a surface portion of the copper foil, and the transmission loss tends to increase as the surface roughness of the copper foil increases.

In order to improve the adhesion of the copper foil constituting the copper-clad laminate to the insulating substrate, a roughened layer having a fine uneven surface (hereinafter, simply referred to as an uneven surface) formed by electrodeposition of roughened particles is generally formed on a copper foil base, and the adhesion force is improved by a physical effect (anchor effect). When the height difference (surface roughness) of the uneven surface is increased, the adhesion is improved, but the transmission loss is increased due to the above-mentioned reason. However, in the present situation, it is preferable to form the surface of the roughened layer formed on the copper foil substrate as a concave-convex surface to ensure the reliability of the transmission power and to allow a certain reduction in the transmission loss due to the formation of the concave-convex surface. However, development of a next-generation high-frequency circuit board supporting a frequency of 20GHz or more has been recently carried out, and it is desired that the transmission loss of the board be further reduced than before.

In general, in order to reduce the transmission loss, it is desirable to use, for example, a surface-treated copper foil in which the height difference (surface roughness) of the surface irregularities of the roughened layer is reduced or a smooth copper foil which is not roughened and has not been subjected to roughening treatment. In order to secure the adhesion of the copper foil having such a small surface roughness, it is preferable to form a silane coupling agent layer between the copper foil and the insulating substrate, and the silane coupling agent layer forms a chemical bond.

In the case of manufacturing a high-frequency circuit board using the copper foil, in addition to the adhesion and the transmission characteristics, it is recently necessary to take reflow heat resistance into consideration. Here, "reflow heat resistance" refers to heat resistance in a solder reflow step performed when manufacturing a high-frequency circuit board. The solder reflow step is a method of soldering by heating in a reflow furnace in a state where a paste-like solder is attached to a contact between a wiring of a circuit board and an electronic component. In recent years, from the viewpoint of reducing environmental load, solder used for an electrical joint portion of a circuit board has been developed to be lead (Pb) -free. Lead-free solder has a higher melting point than conventional solder, and when applied to a solder reflow process, a circuit board is exposed to a high temperature of, for example, about 260 ℃. Therefore, it has been a new problem to provide a copper foil used for such applications, which ensures sufficient adhesion to an insulating substrate and has high reflow heat resistance and high transmission characteristics.

The present applicant has proposed, for example, a method in patent document 1 for producing a metal-coated laminate as a circuit board having excellent transmission characteristics and adhesion by forming fine irregularities on the surface of a thermoplastic resin film using a potassium hydroxide solution and then sequentially performing electroless copper plating and electrolytic copper plating to form a copper layer having fine irregularities due to the surface shape of the thermoplastic resin film. However, the present applicant has further studied the invention described in patent document 1, and as a result, has found that: there are cases where reflow heat resistance is not sufficiently obtained and improvement is desired.

The present applicant also proposed, in patent document 2, a surface-treated copper foil having a roughened surface with protrusions formed of roughened particles and having a height of 1 to 5 μm on at least one surface of an electrolytic copper foil. The surface-treated copper foil described in patent document 2 has a high height of protrusions and is not intended to improve reflow heat resistance, and the formation of a silane coupling layer is arbitrary, so although it has excellent adhesion to a liquid crystal polymer film, it tends to increase transmission loss due to increased surface roughness by the adhesion of coarsened particles, and is not sufficient for application to an insulating substrate supporting a high frequency of 20GHz or more in recent years, and there is a case where reflow heat resistance cannot be sufficiently obtained, and thus improvement is desired.

Further, patent document 3 discloses a surface-treated copper foil for a copper-clad laminate, in which roughened particles are formed by a roughening treatment using copper-cobalt-nickel alloy plating. When such a copper foil is applied to a high-frequency circuit board, the contact area between the copper foil and the resin is increased, and therefore good adhesion can be secured, but the surface area of the copper foil is excessively increased, and therefore, it is expected that transmission characteristics will be deteriorated, and reflow heat resistance is not considered at all.

Patent document 4 discloses a copper foil having improved transmission characteristics, adhesion, and heat resistance by roughening treatment of copper. When such a copper foil is used, improvement of transmission characteristics can be expected, but delamination and peeling occur between the copper foil and an insulating substrate (resin substrate) under a heating condition of about 260 ℃ in a reflow test, and satisfactory characteristics cannot be exhibited.

In patent document 5, a surface-treated copper foil with an extremely thin primer resin layer is subjected to silane treatment for improving the adhesion between the resin and the copper foil, thereby improving the adhesion in a normal state. However, when such silane treatment is performed, the uniform treatment of silane tends to be insufficient, and the heat-resistant reflow property tends to be adversely affected.

Patent document 6 discloses an electromagnetic wave shielding copper foil in which a black or brown treated layer made of fine roughened particles is provided on one surface of a copper foil. As an example of forming fine coarsened particles, electrolysis is performed, for example, in a bath to which a chelating agent such as trisodium citrate is added. When the copper foil of this example is used for a high-frequency substrate, the transmission loss characteristics are degraded by the influence of fine irregularities on the surface, and the required characteristics are insufficient, although the copper foil is excellent in adhesion and the like.

Patent document 7 discloses a copper foil having at least one surface of the copper foil provided with a copper fine roughened particle treated layer. In the examples, the roughening particles were made fine by adding pentasodium diethylenetriaminepentaacetate as a chelating agent to the roughening plating bath. However, when the copper foil of the present example is used for a high-frequency substrate, the transmission loss characteristics are degraded by the influence of fine irregularities on the surface, and the desired characteristics are not sufficient.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-158935

Patent document 2: japanese patent No. 4833556

Patent document 3: japanese patent laid-open publication No. 2013-147688

Patent document 4: international publication No. 2011/090175 pamphlet

Patent document 5: international publication No. 2006/134868 pamphlet

Patent document 6: japanese patent laid-open No. 2006-278881

Patent document 7: japanese patent laid-open No. 2007-332418

Disclosure of Invention

The present invention addresses the need for higher performance and higher functionality of information communication equipment that processes large volumes of information for high-speed transmission and has higher frequencies, and an object of the present invention is to provide a surface-treated copper foil that ensures sufficient adhesion to an insulating substrate having excellent dielectric properties due to low relative permittivity and low dielectric loss tangent, and that has high reflow heat resistance and transmission properties, and a copper-clad laminate produced using the same.

The present inventors have made extensive studies and, as a result, have found that: in a cross section perpendicular to the copper foil base surface, a ratio Da/Db (hereinafter also referred to as "line length ratio") of a surface length Da measured along the uneven surface of the roughened layer to a surface length Db measured along the copper foil base surface greatly affects reflow heat resistance. Further, the present inventors have also found that: in the case of the roughening treatment for forming a roughened layer having an uneven surface on a copper foil substrate by electrodeposition of roughening particles, a copper foil exhibiting excellent characteristics in terms of reflow heat resistance, adhesiveness, and transmission characteristics can be obtained by controlling the average height difference H between the unevenness of the uneven surface and the amount of silane adhesion of the silane coupling agent layer formed directly or via an intermediate layer on the roughened layer, and the present invention has been completed.

That is, the gist of the present invention is as follows.

(1) A surface-treated copper foil having a roughened layer provided on a copper foil substrate, wherein the roughened layer has an uneven surface formed by roughening particles, and wherein, in a cross section orthogonal to the copper foil substrate surface, the ratio (Da/Db) of the length (Da) along the uneven surface of the roughened layer to the length (Db) along the copper foil substrate surface is in the range of 1.05 to 4.00, the average height difference (H) of the unevenness of the uneven surface is in the range of 0.2 to 1.3 [ mu ] m, and the roughened layer has a thickness of 0.0003 to 0.0300mg/dm directly or with an intermediate layer interposed therebetween²A silane coupling agent layer formed by the amount of silane deposited.

(2) The surface-treated copper foil is characterized in that the uneven surface has a necked-down shape.

(3) According to the surface-treated copper foil, the ratio of length along the surface (Da/Db) is in the range of 1.05 to 3.20, the average height difference (H) of the irregularities is in the range of 0.2 to 0.8 μm, and the number of bubbles at the interface of the rough-surfaced layer and the insulating substrate is 2 or less on a line of 2.54 μm in the width direction, which is a direction perpendicular to the production direction of the copper foil, on the copper foil base when the copper foil is laminated with the insulating substrate. The direction of production of the copper foil is the longitudinal direction of the roll in the case of electrolytic copper foil, and the rolling direction in the case of rolled copper foil.

(4) According to the surface-treated copper foil, wherein the ratio of length along the surface (Da/Db) is in the range of 1.05 to 1.60, the average height difference (H) of the irregularities is in the range of 0.2 to 0.3 μm, and the number of bubbles at the interface between the roughened layer and the insulating substrate is 1 or less on a line of 2.54 μm in the width direction of the copper foil base.

(5) The surface-treated copper foil, wherein the silane coupling agent layer has a silane adhesion amount of 0.0005 to 0.0120mg/dm²。

(6) The surface-treated copper foil is characterized in that the intermediate layer comprises at least 1 layer selected from a base layer containing Ni, a heat-resistant treated layer containing Zn, and a rust-proofing treated layer containing Cr.

(7) The surface-treated copper foil is characterized in that the silane coupling agent layer is composed of at least 1 selected from the group consisting of epoxy silane, amino silane, vinyl silane, methacrylic silane, acrylic silane, styrene silane, ureide silane, mercapto silane, sulfide silane, and isocyanate silane.

(8) A copper-clad laminate is produced using the surface-treated copper foil, and has an insulating substrate on the surface of the surface-treated copper foil on the roughened layer side.

(9) A copper-clad laminate comprising an insulating substrate on the roughened layer side of a surface-treated copper foil having the roughened layer provided on a copper foil base, characterized in that, in a cross section orthogonal to the copper foil base surface, the ratio (Da '/Db) of the interface length (Da ') measured along the interface between the roughened layer and the insulating substrate to the surface length (Db) measured along the copper foil base surface is in the range of 1.05 to 4.00, the average height difference (H ') of irregularities on the interface is in the range of 0.2 to 1.3 [ mu ] m, and further 0 is provided directly between the roughened layer and the insulating substrate or with an intermediate layer interposed therebetween.0003 to 0.0300mg/dm²The silane coupling agent layer having a silane adhesion amount of (3).

(10) According to the copper-clad laminate, the number of bubbles at the interface between the roughened layer and the insulating substrate is 2 or less on a 2.54 μm line in the width direction of the copper foil base.

Effects of the invention

According to the present invention, it is possible to provide a surface-treated copper foil which ensures sufficient adhesion to an insulating substrate having excellent dielectric characteristics due to low relative permittivity and low dielectric loss tangent and which can support high-frequency information communication devices capable of processing large volumes of information for high-speed transmission and which has high reflow heat resistance and high transmission characteristics. The present invention also provides a copper-clad laminate produced using the surface-treated copper foil.

Drawings

Fig. 1 (a) is a cross-sectional view showing a state of a roughened layer having a necked shape according to the present invention. The necking shape is a shape as shown in fig. 1, that is, a shape in which the width of the root of the roughened particle is narrower than the maximum width of the roughened particle, and the root of the roughened particle has a recess. Fig. 1 (b) is a cross-sectional view showing a state of a conventional rough-surface layer.

Fig. 2 is a cross-sectional view schematically showing an average height difference H of the irregularities constituting the irregular surface constituting the rough surface layer.

Fig. 3 is a cross-sectional view schematically showing the surface-following length Da on the uneven surface of the rough-surface layer shown in fig. 1.

Fig. 4 (a) is a cross-sectional view of a base line BL1 for measuring an average height difference H of the irregularities constituting the uneven surface constituting the rough-surface layer. Fig. 4 (b) is a sectional view similarly showing the base line BL 2.

Fig. 5 is a cross-sectional view schematically showing bubbles existing at the interface between the rough-surface layer and the insulating substrate.

Detailed Description

Hereinafter, an embodiment of the surface-treated copper foil according to the present invention will be described with reference to the drawings. Fig. 1 (a) shows a cross-sectional structure when a roughened layer is formed on the surface of a copper foil constituting a representative surface-treated copper foil according to the present invention.

The surface-treated copper foil of the present invention is mainly composed of a copper foil 110, a roughened layer 120, and a silane coupling agent layer (not shown). That is, in the present invention, a copper foil subjected to surface treatment by forming the rough-surface layer 120 on the copper foil 110 and further forming a silane coupling agent layer (not shown) is referred to as a surface-treated copper foil.

The copper foil 110 may be appropriately selected from an electrolytic copper foil, an electrolytic copper alloy foil, a rolled copper foil, and a rolled copper alloy foil according to the use and the like.

The roughened layer 120 is formed by performing a roughening treatment on the copper foil base 110, and has substantially granular fine irregularities formed on the surface. In the roughening treatment, copper electrodeposition is performed at a current density exceeding the limiting current density while generating hydrogen gas to form a state called a scorched plating layer, thereby forming particulate electrodeposition and forming a micro uneven surface of a micron order. In the present invention, such a fine uneven surface is simply referred to as an uneven surface. The term "coarsened particles" as used herein refers to the particulate analytes.

In the present invention, in a cross section perpendicular to the surface of the copper foil base, the ratio (linear length) of the surface length Da of the roughened layer 120 measured along the uneven surface to the surface length Db of the copper foil base (linear length) Da/Db is in the range of 1.05 to 4.00. The line length ratio Da/Db may be in the range of 1.05 to 3.20, and the line length ratio Da/Db may also be in the range of 1.05 to 1.60.

If the line length ratio Da/Db is less than 1.05, the reflow heat resistance is lowered and satisfactory performance cannot be obtained. If the line length ratio Da/Db exceeds 4.00, the unevenness of the surface increases excessively, so that the transmission loss becomes large due to the skin effect to deteriorate the transmission characteristic, and thus the line length ratio Da/Db is in the range of 1.05 to 4.00. Note that, the method of measuring the line length ratio Da/Db will be described below.

The present inventors made an effort to investigate the reason why the line length ratio Da/Db affects the reflow heat resistance, and as a result, obtained the following new findings. First, a method for manufacturing a test piece for a reflow heat resistance test will be described. An insulating substrate (base material) having copper foils laminated on both surfaces thereof was used as a core layer. The core layer is etched with a copper (II) chloride solution or the like to dissolve and remove all the copper foil. Next, on both surfaces of the insulating substrate (base material) remaining after etching of the core layer, a prepreg layer made of an insulating material and a copper foil were laminated to prepare a reflow test piece. The cross section of the reflow test piece was observed, and as a result, it was confirmed that: the surface shape of the copper foil constituting the core layer is replicated at the interface where the insulating substrate (base material) of the core layer contacts the prepreg layer. And confirming that: in the reflow heat resistance test, since the sample (test piece) is exposed to a high temperature of about 260 ℃, a low molecular weight component in the insulating substrate (base material) volatilizes, and the volatilized gas accumulates in a region where the adhesiveness between the insulating substrate and the prepreg layer is weak, thereby causing delamination. Thus, it is generally believed that: if the line length ratio Da/Db is less than 1.05, the area to be transferred by etching is reduced, and as a result, the area where the insulating substrate (base material) and the prepreg layer are in contact with each other is reduced, and thus an area with low adhesion between both layers is generated, and gas volatilized from the base material during heating accumulates in the area between the layers, and peeling is likely to occur.

In the invention, through diligent research, the following results are found: by controlling the line length ratio Da/Db and the average height difference H of the irregularities within an appropriate range, a roughened shape having a necked shape can be obtained, and the heat resistance is significantly improved as compared with the copper foil controlled by the surface area in the known example. That is, if Da/Db is increased within the range of the average height difference H of the irregularities of the present application to such an extent that the transmission characteristic is not lowered, the contour length of the roughened layer becomes long, and as a result, a roughened shape having a large number of neck shapes can be obtained. By increasing the neck-down shape, although the roughening is fine, a strong anchor effect is exhibited, and the adhesion between the copper foil and the insulating substrate (resin substrate) is enhanced, thereby improving the heat resistance. Therefore, within the scope of the present application, by controlling Da/Db and the average height difference H, the heat resistance is significantly improved as compared with the conventional examples while maintaining high transmission characteristics.

As a parameter for quantifying the roughened shape, a surface area ratio measured by a laser microscope is known as shown in patent document 4(WO 2011-090175). However, as shown in fig. 1, for example, when (a) roughening with a necked shape 11 and (b) roughening with no necked shape are present, theoretically, when the surface area is measured by a laser microscope, the height is measured by projecting laser light from the perpendicular direction of the copper foil, and therefore, it is difficult to measure the difference between the necked shape and the necked shape of fig. 1 (a) and fig. 1 (b). That is, although the shape of the surface directly irradiated with the laser light can be measured, the laser light projected from the vertical direction becomes a shadow in the constricted portion, and thus the shape of the portion not directly irradiated with the laser light cannot be measured.

Therefore, as shown in the embodiment of patent document 4, when the surface area ratio is measured by a laser microscope, the presence or absence of the necking shape cannot be reflected in the measured value, and therefore, it is not suitable for the present application to control the surface shape of the copper foil by the surface area ratio measured by the laser microscope. The aspect ratio shown in patent document 4 only indicates the ratio of the "height" to the "width" of the coarsened particles, and the shape of the neck is not considered at all.

Further, when the copper-clad laminated board is formed by closely adhering the insulating substrate to the roughened layer side of the copper foil having the roughened layer obtained in the above embodiment, the interface length (Da') measured along the interface between the roughened layer and the insulating substrate tends to be slightly reduced by the close adhesion under pressure with the insulating substrate. Therefore, it is necessary to maintain the line length ratio in the above range even after the insulating substrates are closely adhered, and by setting the ratio (Da '/Db) of the interface length (Da') measured along the interface between the roughened layer and the insulating substrate to the surface length (Db) measured along the surface of the copper foil base in the range of 1.05 to 4.00 on the cross section orthogonal to the surface of the copper foil base after the insulating substrates are closely adhered, the same effect as in the case of (Da/Db) can be obtained.

Therefore, in the present invention, the average height difference H of the irregularities (corresponding to the average height of the roughening particles) on the irregular surface of the copper foil is set to be in the range of 0.2 to 1.3 μm. If the average height difference H of the irregularities on the irregular surface is less than 0.2 μm, the anchoring effect is weak, and sufficient adhesion between the copper foil and the insulating substrate cannot be obtained. When the average height difference H of the irregularities on the uneven surface exceeds 1.3 μm, the surface irregularities become excessively large, and the transmission loss increases due to the skin effect. Further, the average height difference H of the irregularities of the uneven surface may be in the range of 0.2 to 0.8. mu.m, and the average height difference H of the irregularities of the uneven surface may be in the range of 0.2 to 0.3. mu.m.

Further, when the copper-clad laminate is formed by closely adhering the insulating substrate to the roughened layer side of the copper foil having the roughened layer obtained in the above embodiment, the difference in roughness H of the roughened layer tends to be slightly reduced by the pressure close adhesion to the insulating substrate. Therefore, it is necessary to maintain the average height of the irregularities within the above range even after the insulating substrates are closely bonded, and the same effect as in the case of H can be obtained by setting the average height difference H' of the irregularities on the surface of the irregularities (corresponding to the average height of the roughening particles) within the range of 0.2 to 1.3 μm in the cross section perpendicular to the copper foil base surface after the insulating substrates are closely bonded.

The present inventors investigated a method of controlling Da/Db in a range of an appropriate average height difference (H) between irregularities, and found that: in the roughening methods of documents 6 and 7, since the chelating agent concentration is high, Da/Db is excessively increased by forming a large number of fine roughened particles on the surface of the copper foil, and as a result, transmission loss is increased. The present inventors have made an effort to solve the above problems, and as a result, have found that: by setting the concentration of the chelating agent to a lower concentration than in the conventional case, the particle size becomes appropriate, and Da/Db can be controlled to an optimum range, whereby the transmission loss characteristics can be improved while maintaining high adhesion and heat resistance. Specifically, the concentration of the chelating agent added to the plating bath may be made to be in the range of 0.1 to 5 g/L.

As a mechanism of the reaction, it is presumed that the overvoltage phase at the time of electrolysis is lowered as compared with the high concentration condition by making the chelating agent low in concentration, thereby lowering the nucleation frequency, and therefore, the effect of the pulverization can be appropriately suppressed and coarsened particles having an appropriate size can be formed. In addition, it is generally considered that: when the chelating agent is used at a low concentration, the number of chelate molecules in the bath is small, so that most of the metal ions (such as Cu) coordinated to the chelate complex and the metal ions not coordinated to the chelate complex are mixed in the bath, and the difference in the coordination state of the chelate complex causes particles having different precipitation patterns to be formed simultaneously, thereby forming a complex particle shape having a neck shape, and achieving both high heat resistance and adhesion even in an appropriate Da/Db range. When the chelating agent is used at a low concentration, the growth of the coarse particles in the height direction is appropriately suppressed, and the average height difference H of the irregularities falls within an appropriate range. According to the precipitation mode in which most of the coordinated metal ions (Cu, etc.) of the chelate complex and the metal ions not coordinated to the chelate complex are mixed in the bath, the orientation of precipitation is random, and thus the growth in the height direction is suppressed.

In addition, the present inventors found that: as a method for controlling Da/Db appropriately, a method of adding two kinds of chelating agents to the roughening treatment bath is also effective. Presumably: by adding two kinds of chelating agents, metals having different coordination states of the chelate compound are electrolyzed at the same time, and particles having different shapes are precipitated at the same time, whereby the shape of the coarsened particle becomes complicated, and the anchoring effect is easily exhibited.

As another method for properly managing Da/Db, 70 to 90A/dm which has not been used conventionally due to a trouble such as powder falling is used²The current density of (2) is also effective in forming coarse particles. However, if the treatment time is long, the particles excessively grow in the vertical direction and the powder easily falls off, so that the treatment time needs to be short. At a high current density, the amount of hydrogen produced at the cathode increases. Presume that: since hydrogen gas is not plated until it is released from the cathode and enters the solution, the time point of coarsening and precipitation becomes discontinuous, and as a result, a surface shape with a suitable large number of irregularities can be obtained.

Further, in the present invention, the roughness layer 120 has a thickness of 0.0003 to 0.0300mg/dm directly or through an intermediate layer²A silane coupling agent layer formed by the amount of silane deposited. When the silane adhesion amount of the silane coupling agent constituting the silane coupling agent layer is less than 0.0003mg/dm²The reflow heat resistance will beAnd decreases. Further, if the adhesion amount exceeds 0.0300mg/dm²The silane coupling agent layer becomes too thick, and the adhesion strength is reduced. The silane adhesion amount of the silane coupling agent constituting the silane coupling agent layer may be 0.0005 to 0.0120mg/dm²。

Further, examples of the method for forming the silane coupling agent layer include the following methods: the rough-surface layer 120 is formed by applying a silane coupling agent solution directly or indirectly via an intermediate layer on the uneven surface, and then air-drying or heat-drying the resultant. The effect of the present invention can be sufficiently exhibited by evaporation of water in drying the applied coupling agent layer, but from the viewpoint of promoting the reaction between the silane coupling agent and the copper foil, it is preferable to heat-dry at a temperature of 50 to 180 ℃.

Preferably, the silane coupling agent layer contains at least one of epoxy silane, amino silane, vinyl silane, methacrylic silane, acrylic silane, styrene silane, ureide silane, mercapto silane, sulfide silane, and isocyanate silane.

The concave-convex surface of the present invention preferably has a large number of neck shapes. Although the copper foil has a large number of neck-shaped portions and the roughening is fine, the copper foil exhibits a strong anchor effect, and the adhesion between the copper foil and the insulating substrate is enhanced, thereby improving the heat resistance. To form the uneven surface having a large number of necking shapes, as described above, by making the average height difference H of the unevenness in the range of 0.2 to 1.3 μm and controlling Da/Db in the range of 1.4 to 4.0, the profile length of the roughened layer can be made long, and as a result, a roughened shape having a large number of necking shapes can be obtained.

In the present invention, when the copper foil and the insulating substrate are laminated, the number of bubbles at the interface between the roughened layer and the insulating substrate is preferably 2 or less across the width of the substrate (for example, 2.54 μm). In the present case, in the process of investigating factors affecting the reflow heat resistance, it is found that: in addition to the line length ratio Da/Db and the average height difference H, the number of bubbles at the interface between the roughened layer of the copper foil and the insulating substrate in the reflow test piece is also greatly affected. Here, the air bubbles in the present invention mean a region where the insulating substrate is not filled in the interface between the rough-surface layer and the insulating substrate, and the size of the air bubbles is 1.0 μm or less in terms of the major axis. When the number of bubbles at the interface between the roughened layer of the copper foil and the insulating substrate is large, gas volatilized from the insulating substrate is concentrated in the bubble portion during heating in the reflow test, so that the gas pressure in the bubble is increased, and thus interlayer peeling is likely to occur.

Therefore, the present inventors have made an effort to investigate a method for reducing the number of bubbles at the interface between the rough-surface layer and the substrate, and as a result, have found that: it is an effective method to appropriately control the treatment conditions of the silane coupling agent. Specifically, first, an alcohol is added to an aqueous silane coupling agent solution. Examples of the alcohol include methanol, ethanol, isopropanol, and n-propanol. By adding alcohol, the dispersibility of silane molecules in the solution becomes good, and the silane coupling agent can be uniformly treated on the rough surface layer of the copper foil, so that the wettability to the resin is improved. And it is presumed that: when the substrate and the copper foil are pressed together at a high temperature, the molten resin sufficiently infiltrates the roughened layer to improve the filling property, thereby reducing the number of bubbles at the interface between the roughened layer and the substrate. In addition, it is also effective to extend the time from the treatment of the copper foil with the silane aqueous solution to the drying with warm air. Presumably: the time from the treatment with the silane aqueous solution to the drying with warm air is prolonged, silane molecules are regularly oriented on the surface of the roughened layer of the copper foil to improve the wettability to the resin, and as a result, the number of bubbles at the interface between the roughened layer and the insulating substrate is reduced. For example, in the case of the silane treatment described in patent document 4, the wettability of the resin to the rough-surface layer is not considered, and the number of bubbles at the interface between the rough-surface layer and the insulating substrate tends to increase.

The number of bubbles at the interface between the roughened layer of the copper foil and the insulating substrate may be 2 or less in the width direction of the substrate, that is, on a line of 2.54 μm. The number of bubbles may be 1 or less or 0 on the line. If the number of bubbles at the interface between the roughened layer of the copper foil and the insulating substrate is 3 or more on the line, gas generated from the insulating substrate during the reflow test tends to concentrate on the bubble portion, causing easy occurrence of phase separation, and reflow heat resistance (between the copper foil and the prepreg layer) tends to decrease.

In another embodiment, at least 1 intermediate layer selected from a Ni-containing base layer, a Zn-containing heat-resistant treated layer, and a Cr-containing rust-preventive treated layer may be further provided between the rough-surface layer 120 and the silane coupling agent layer.

For example, if copper (Cu) in the copper foil base 110 or the rough-surface layer 120 diffuses to the insulating substrate side and causes a copper hazard, and adhesion is reduced, it is preferable to form a base layer containing nickel (Ni) between the rough-surface layer 120 and the silane coupling agent layer. The Ni-containing underlayer contains at least 1 or more of nickel (Ni), nickel (Ni) -phosphorus (P), and nickel (Ni) -zinc (Zn). Among these, nickel-phosphorus is preferable from the viewpoint of suppressing nickel residue during etching of the copper foil during formation of the circuit wiring.

It is preferable to form a heat-resistant treated layer containing zinc (Zn) when it is necessary to further improve heat resistance. Preferably, the heat-resistant treatment layer is formed of, for example, zinc or an alloy containing zinc, that is, at least 1 or more zinc-containing alloys selected from zinc (Zn) -tin (Sn), zinc (Zn) -nickel (Ni), zinc (Zn) -cobalt (Co), zinc (Zn) -copper (Cu), zinc (Zn) -chromium (Cr), and zinc (Zn) -vanadium (V). Among these, zinc-vanadium is particularly preferable from the viewpoint of suppressing undercut during etching when forming circuit wiring. The term "heat resistance" as used herein refers to a property that the adhesion strength between the surface-treated copper foil and the insulating substrate is not easily reduced after the insulating substrate is laminated on the surface-treated copper foil and heated to cure the resin, and is different from reflow heat resistance.

If corrosion resistance is required to be further improved, a rust-preventive treatment layer containing Cr may be formed. Examples of the rust-preventive treatment layer include a chromium layer formed by chromium plating and a chromate layer formed by chromate treatment.

When the three layers, that is, the base layer, the heat-resistant treated layer, and the rust-preventive treated layer are all formed, they may be formed in this order on the rough-surface layer, or only one or two of the three layers may be formed depending on the characteristics of the intended use or purpose.

The surface-treated copper foil of the present invention is preferably used for producing a copper-clad laminate. The copper-clad laminate has an insulating substrate on the surface of the surface-treated copper foil on the roughened layer side.

The insulating substrate used for the copper-clad laminate may use an insulating resin selected from thermosetting polyphenylene ether resins, thermosetting polyphenylene ether resins containing polystyrene-based polymers, resin compositions containing polymers or copolymers of triallylcyanurate, epoxy resin compositions modified with methacrylic acid or acrylic acid, phenol addition butadiene polymers, diallyl phthalate resins, divinylbenzene resins, polyfunctional methacryl resins, unsaturated polyester resins, polybutadiene resins, styrene-butadiene, crosslinked polymers of styrene-butadiene and styrene-butadiene, and the like.

In the case of producing a copper-clad laminate, it is sufficient if the surface-treated copper foil having a silane coupling agent layer and the insulating substrate are pressed by heating and are brought into close contact with each other. Further, a copper-clad laminate produced by applying a silane coupling agent to an insulating substrate and then heating and pressing the insulating substrate and a copper foil having an anticorrosive treatment layer on the outermost surface thereof to be in close contact with each other has the same effect as that of the present invention.

[ production of surface-treated copper foil ]

(1) Process for Forming roughened layer

A roughened layer having an uneven surface is formed on the copper foil by electrodeposition of the roughened particles.

Preferably: in addition to controlling the line length ratio Da/Db, (i) the size of the coarse particles is appropriately controlled, and (ii) the coarse particles having different shapes are easily precipitated simultaneously.

From the viewpoint of (i), for example, a method of reducing the overvoltage at the time of electrolysis to decrease the nucleation frequency can be employed, and a specific example thereof is a method of making the chelating agent at a low concentration. Alternatively, the current density at the time of roughening treatment may be as high as 70 to 90A/dm²Thereby shortening the processing time.

Here, it is appropriate that the concentration of the chelating agent added to the plating bath for roughening treatment is 0.1 to 5 g/L. Examples of the chelating agent include DL-malic acid, a sodium EDTA solution, sodium gluconate, and a chelating agent such as pentasodium Diethylenetriaminepentaacetate (DTPA).

From the viewpoint of (ii), for example, a method of simultaneously electrolyzing metals having different coordination states of the chelate compound can be adopted, and a specific example thereof is a method of adding two kinds of chelating agents to the roughening treatment bath. As an example, there is a combination of DL-malic acid and DTPA.

In addition, in order to make the number of bubbles in the interface between the rough-surface layer and the insulating substrate 2 or less on a line of 2.54 μm, which is the width direction of the copper foil base, a method such as increasing the wettability of the rough-surface layer to the surface of the insulating substrate may be employed. Therefore, there are methods such as (i) performing a silane coupling treatment so that a silane coupling agent layer is uniformly formed on the roughened layer, and (ii) performing a silane coupling treatment so that silane molecules in the silane coupling agent layer are regularly oriented. Specific examples of (i) include a method of adding an alcohol to an aqueous solution of a silane coupling agent, and specific examples of (ii) include a method of extending the time from after the copper foil is treated with the aqueous solution of silane to before it is dried with warm air.

(2) Formation step of base layer

If necessary, an underlayer containing Ni is formed on the rough-surface layer.

(3) Process for Forming Heat-resistant treatment layer

If necessary, a heat-resistant treatment layer containing Zn is formed on the rough-surface layer or the base layer.

(4) Process for Forming Rust-preventive treatment layer

The copper foil with the layer formed thereon was immersed in an aqueous solution containing a Cr compound at a pH of less than 3.5 at a ratio of 0.3A/dm, as required²The chromium plating treatment is performed at the current density as above, whereby the rust-preventive treatment layer is formed on the rough-surface layer, the foundation layer, or the heat-resistant treatment layer.

(5) Process for Forming silane coupling agent layer

A silane coupling agent layer is formed on the rough-surface layer, the base layer, the heat-resistant treated layer, or the rust-preventive treated layer.

[ production of copper-clad laminate ]

The copper-clad laminate of the present embodiment is produced by the following steps.

(1) Production of surface-treated copper foil

A surface-treated copper foil was produced in accordance with the above (1) to (5).

(2) Process for producing (laminating) copper-clad laminate

The surface-treated copper foil thus produced and an insulating substrate are stacked together, the surface of the silane coupling agent layer constituting the surface-treated copper foil and the bonding surface of the insulating substrate are opposed to each other, and then heat and pressure treatment are performed to bring them into close contact with each other, thereby producing a copper-clad laminate.

The above description is merely an example of the embodiment of the present invention, and various modifications can be made without departing from the scope of the present invention.

Examples

(example 1)

The surface-treated copper foil was fabricated into an ungrased (surface roughness Rz about 0.8 μm) copper foil substrate having a thickness of 18 μm under the following conditions.

(1) Formation of a roughened layer

The surface roughening treatment for the surface of the copper foil base is performed in the following order to form a roughened layer: the surface roughening plating treatment 1 was performed under the conditions shown in table 1, and then the surface roughening plating treatment 2 shown below was performed.

(roughening plating treatment 2)

Copper sulfate: in terms of copper concentration of 13 to 72g/L

Concentration of sulfuric acid: 26 to 133g/L

Liquid temperature: 18 to 67 deg.C

Current density: 3 to 67A/dm²

Treatment time: 1 second to 1 minute 55 seconds

(2) Formation of Ni-containing base layer

After a rough-surface layer was formed on the surface of the copper foil substrate, the rough-surface layer was plated under the following nickel plating conditions to form a base layer (Ni deposition amount: 0.06 mg/dm)²)。

< Nickel plating Condition >

Nickel sulfate: 5.0g/L calculated by nickel metal

Ammonium persulfate 40.0g/L

Boric acid 28.5g/L

Current density 1.5A/dm²

pH 3.8

The temperature is 28.5 DEG C

For a period of 1 second to 2 minutes

(3) Formation of heat-resistant treatment layer containing Zn

After the formation of the base layer, the base layer was electroplated under the following galvanizing conditions to form a heat-resistant treated layer (Zn adhesion amount: 0.05 mg/dm)²)。

< galvanizing Condition >

Zinc sulfate heptahydrate 1-30 g/L

10 to 300g/L of sodium hydroxide

Current density of 0.1 to 10A/dm²

The temperature is 5-60 DEG C

For a period of 1 second to 2 minutes

(4) Formation of anticorrosive coating layer containing Cr

After the heat-resistant treated layer was formed, the heat-resistant treated layer was treated under the following chromium plating conditions to form a rust-preventive treated layer (amount of Cr deposited: 0.02 mg/dm)²)。

< conditions of chromium plating >

(chromium plating bath)

Chromic anhydride CrO₃ 2.5g/L

pH value of 2.5

Current density 0.5A/dm²

The temperature is 15-45 DEG C

For a period of 1 second to 2 minutes

(5) Formation of silane coupling agent layer

After the rust-preventive treatment layer was formed, methanol or ethanol was added to the silane coupling agent aqueous solution under the conditions shown in table 2, and a treatment liquid adjusted to a predetermined pH value was applied on the rust-preventive treatment layer. Thereafter, the samples were stored for a predetermined period of time, and then dried with warm air, thereby forming a silane coupling agent layer having a silane adhesion amount shown in table 3. In table 3, underlined values indicate values outside the appropriate range of the present invention.

[ Table 2]

(examples 2 to 18)

The surface roughening plating treatment 1 was performed in the same manner as in example 1 except that the surface roughening plating treatment 1 was performed according to the contents of table 1 and the silane coupling agent treatment was performed according to the contents of table 2.

(comparative examples 1 to 7 and comparative examples 9 to 14)

[ comparative example 8 ]

A roll of a liquid crystal polymer film (Vecster (registered trademark) CT-Z manufactured by Kuraray corporation) was immersed in a potassium hydroxide solution (liquid temperature 80 ℃ C.) for a treatment time of 10 minutes, and then etched to roughen the surface. Next, an electroless copper plating layer was formed on the roughened thermoplastic resin film by an electroless copper plating bath described below.

< electroless copper plating bath >

Copper sulfate pentahydrate (calculated as copper component) 19g/L

HEEDTA (chelating agent) 50g/L

Sodium phosphinate (reducing agent) 30g/L

Sodium chloride 20g/L

Disodium hydrogen phosphate 15g/L

Thereafter, an electroplated copper layer including an electroless copper plating layer formed on the thermoplastic resin film by a copper sulfate bath was formed so that the thickness of the entire copper plating layer was 20 μm. In addition, comparative example 8 was produced under the condition that the scope of the invention described in patent document 1 was satisfied.

Evaluation of Properties of test piece

The results of various measurements and evaluations of each test piece are shown in table 3.

(1) Measurement of line length ratio Da/Db and average height difference H between irregularities on irregular surface

In a cross section perpendicular to the surface (surface direction P) of the copper foil base shown by a double-headed arrow in fig. 3, a ratio Da/Db of a surface length Da measured along the uneven surface 120 of the roughened layer to a surface length Db measured along the surface of the copper foil base 110 is defined as a line length ratio. If the uneven surface of the rough-surface layer on the cross section is formed into a shape having more or larger unevenness, the line length ratio becomes large.

Each test piece was treated by an ion polishing apparatus (IM 4000, manufactured by Hitachi Ltd.), the cross section of each treated test piece was observed by a Scanning Electron Microscope (SEM) SU8020, manufactured by Hitachi Ltd.), and the line length ratio Da/Db was measured in the following order. Calculated from an observation image enlarged at a magnification of 10000 times (the actual width of the visual field in the image of the present case is 12.7 μm). The observation image of the SEM was analyzed using image analysis software Winroof (three-valley business), whereby the face length Da on the uneven surface of the rough-surfaced layer was measured as indicated by a thick line in fig. 3. In addition, other image analysis software can be used to perform the measurement in the same manner. Regarding the magnification of the SEM, it is preferable to make the width of the SEM image in the range of 5 to 15 μm. In this case, Dan/Dbn (n is 1 to 10) was measured in a visual field at 10 points, and the average value thereof was defined as Da/Db.

Next, the average height difference of the uneven surface was measured as follows. First, the observation magnification was increased to 200 times (the actual width of the visual field in the image in this case was 63.5 μm), and the extending direction of the uneven surface was aligned with the horizontal direction of the screen at an arbitrary position within a range of ± 1 °. Next, the observation magnification was increased to 10000 times (the actual width of the field of view in the image in this case was 12.7 μm), and the bottom position of the 1 st concave portion, which is the lowest point position among the irregularities on the uneven surface formed on the arbitrary position displayed in the SEM image, was defined as the a point. Then, of the remaining concave portions except for the 1 st concave portion and the concave portion adjacent to the 1 st concave portion, the bottom position of the 2 nd concave portion whose bottom position is the lowest point position is defined as point B. Then, a straight line connecting the points a and B is defined as a base line BL1 (fig. 4 (a)). Then, in an SEM image enlarged to 50000 times (the actual width of the field of view in the image in this case is 2.54 μm), a base line BL2 parallel to the base line BL1 is drawn, and passes through the bottom position of the 3 rd recessed portion, which is the lowest point position among the irregularities forming the uneven surface at an arbitrary position, and the distance from the base line BL2 to the apex of the convex portion farthest away in the vertical direction is measured as a step H (fig. 4 (b)). In this example, the height differences were measured in the visual field at 5 points, and the average value thereof was defined as the average height difference H.

(2) Number of bubbles at interface between roughened layer and insulating substrate

As shown in fig. 5, the number of bubbles at the interface between rough-surface layer 43 and insulating substrate 42 was measured in the following procedure. First, a laminate was produced by laminating an insulating substrate 42 (prepreg layer) and a copper foil 43 under standard lamination conditions recommended by insulating substrate manufacturers using a laminator (in this case, MEGTRON 6: R-5670 from Songhou Co., Ltd. was used as the insulating substrate 42, and lamination was carried out under lamination conditions of a lamination temperature of 200 ℃ and a lamination pressure of 35kgf/cm²And the pressing time is 160 minutes). Next, the laminate was processed using the ion polishing apparatus, and the cross section of the processed laminate was enlarged to 50000 times (the actual width of the field of view in the image in this case was 2.54 μm) with the scanning electron microscope, and the interface between rough-surface layer 43 of the laminate and insulating substrate 42 was observed. As shown in fig. 5, at 1The number of bubbles 41 existing at the interface between rough-surface layer 43 and insulating substrate 42 on the line having a width of 2.54 μm was measured at 0, and the average value of the number of bubbles at 10 was defined as the number of bubbles Vi at the interface between rough-surface layer 43 and insulating substrate 42. The air bubbles in this case are regions where the insulating substrate is not filled in the interface between the rough-surface layer and the insulating substrate, and have a size of 1.0 μm or less in terms of the major axis.

(3) Measurement of the amount of silane adhered

The analysis was carried out using a fluorescent X-ray analyzer (ZSXPrimus, analysis diameter: phi 35mm, manufactured by RIGAKU, Ltd.).

(4) Measurement of line length ratio Da '/Db and average height difference H' of unevenness on uneven surface after adhesion of insulating substrates

After the copper foils and the insulating substrate were bonded, the line length ratio Da '/Db and the average height difference H' of the irregularities on the irregular surface were measured in the same manner as the measurement of Da/Db and H.

(5) Transmission characteristics (measurement of transmission loss at high frequency)

After the copper foils were bonded to the insulating substrate, a sample for transmission characteristic measurement was prepared, and the transmission loss in the high frequency band was measured. A commercially available polyphenylene ether insulating substrate (MEGTRON 6 manufactured by songhua corporation) was used as the insulating substrate. The transmission loss measurement substrate had a strip line structure, and the conductor length was 400mm, the conductor thickness was 18 μm, the conductor width was adjusted to 0.14mm, the overall thickness was adjusted to 0.31mm, and the characteristic impedance was adjusted to 50 Ω. For the evaluation, the transmission loss at 10GHz and 40GHz was measured using a vector network analyzer E8363B (manufactured by KEYSIGHT TECHNOLOGIES Co., Ltd.). The transmission loss measured at a conductor length of 400mm was converted into a value at a conductor length of 1000mm, and the value was measured as a transmission loss in dB/m. Specifically, the value obtained by multiplying the value of the transmission loss measured when the conductor length is 400mm by 2.5 was used as the measured value of the transmission loss. As a result, as shown in Table 3, regarding the transmission characteristics, the case where the transmission loss was less than 19.5dB/m was regarded as passed at 10GHz, and the case where the transmission loss was less than 66.0dB/m was regarded as passed at 40 GHz.

(6) Joint sealing strength

The adhesion strength between the surface-treated copper foil and the insulating substrate was measured. A commercially available polyphenylene ether substrate was used as the insulating substrate. The curing conditions of the insulating (resin) substrate were set at 210 ℃ for 1 hour. The copper foil and the insulating substrate were bonded using a universal material tester (tensilion, manufactured by a & D), then the test piece was etched into a circuit wiring having a width of 10mm, the insulating side was fixed to a stainless steel plate with a double-sided tape, and then the circuit wiring was peeled off at a speed of 50 mm/min in a 90-degree direction, thereby obtaining the adhesion strength. Regarding the initial adhesion, a peel strength of 0.4kN/m or more was regarded as acceptable, and a peel strength of less than 0.4kN/m was regarded as unacceptable.

(7) Reflow Heat resistance (between copper foil and prepreg layer)

First, a method for manufacturing a test piece for reflow heat resistance test (between a copper foil and a prepreg layer) will be described. Copper foils were laminated on both sides to prepare a reflow test piece (between the copper foil and the prepreg layer). In this case, the size of the reflow test piece (between the copper foil and the prepreg layer) was 100mm × 100 mm. Then, the prepared test piece was introduced into a reflow furnace and heated 10 times at a top temperature of 260 ℃ for 10 seconds. After heating under the above conditions, the swollen region was observed with a microscope for the cross section, and it was confirmed whether or not there was delamination between the copper foil and the prepreg layer. The one in which no delamination occurred between the copper foil and the prepreg layer was judged as "good", the one in which delamination occurred at 1 place between the copper foil and the prepreg layer was judged as "Δ (good)", and the one in which delamination occurred at 2 or more places between the copper foil and the prepreg layer was judged as "x (bad)". The contents of the reflow test were in accordance with JIS C60068-2-58.

(8) Heat resistance to reflow (between core and prepreg layers)

The following describes a method for producing a test piece for reflow heat resistance test (between the core layer and the prepreg layer). An insulating substrate having copper foils laminated on both surfaces thereof was used as a core layer. The core layer is etched with a copper (II) chloride solution or the like to dissolve all the copper foil. A reflow test piece was produced by laminating a prepreg layer as an insulating substrate and a copper foil on both surfaces of the etched core layer. In the present case, the dimensions of the reflow test piece (between the core layer and the prepreg layer) were 100mm × 100 mm.

Then, the prepared test piece was introduced into a reflow furnace and heated 10 times at a top temperature of 260 ℃ for 10 seconds. After heating under the above conditions, the one in which no interlayer peeling occurred between the core layer and the prepreg layer was judged as "o (pass)", the one in which interlayer peeling occurred at 1 place between the core layer and the prepreg layer was judged as "Δ (pass)", and the one in which interlayer peeling occurred at 2 or more places between the core layer and the prepreg layer was judged as "x (fail)". The contents of the reflow test were in accordance with JIS C60068-2-58.

As is clear from table 3, examples 1 to 18 were of acceptable grade in all of the properties of adhesiveness to an insulating substrate, transmission characteristics, and reflow heat resistance. On the other hand, in comparative example 1, the line length was smaller than Da/Db and Da '/Db, and the average height differences H and H' of the irregularities on the uneven surface were also low, so that the adhesion strength was low and the reflow heat resistance was also poor. In comparative example 2, the linear length is larger than Da/Db and Da '/Db, and the average height differences H and H' of the irregularities on the uneven surface are also high, so that the transmission loss is large and the transmission characteristics are poor. In comparative example 3, the line length was smaller than Da/Db and Da/Db', and the amount of silane adhering was small, so that the reflow heat resistance was poor. In comparative example 4, the linear length was smaller than Da/Db and Da '/Db, the average height differences H and H' of the irregularities on the uneven surface were low, and the adhesion amount of silane was large, so that the adhesion strength was low. In comparative examples 5 to 7, the line length is larger than Da/Db and Da/Db ', the average height difference H and H' is larger, and the number of bubbles at the interface between the rough-surface layer and the insulating substrate is large, so that the reflow heat resistance is poor. In comparative example 8, the linear length was smaller than Da/Db and Da'/Db, and the average height difference H between the irregularities on the uneven surface was low, so the adhesion strength was low. In comparative examples 9 to 14, the line length is larger than Da/Db and Da '/Db, and particularly in comparative examples 9 to 11, the average height differences H and H' of the irregularities on the uneven surface are also high, so that the transmission loss is large and the transmission characteristics are poor. Industrial applicability

According to the present invention, it is possible to provide a surface-treated copper foil which ensures sufficient adhesion to an insulating substrate having excellent dielectric characteristics due to low relative permittivity and low dielectric loss tangent and which can support high-performance and high-functionality high-frequency information communication devices capable of processing large volumes of information for high-speed transmission, and a copper-clad laminate produced using the surface-treated copper foil.

Description of reference numerals:

11 necked down shape

110 copper foil base

120 rough surface layer

Surface length of Da measured along uneven surface of roughened layer

Db along the surface of the copper foil substrate

Width of P substrate

41 bubbles

42 insulating substrate

43 roughen the layer.

Claims

1. A surface-treated copper foil comprising a copper foil base and a roughened layer formed thereon,

the roughened layer has a plurality of roughened particles, the surface of the roughened layer is configured as an uneven surface, the ratio Da/Db of the length Da along the surface of the roughened layer measured along the uneven surface of the roughened layer to the length Db along the surface of the copper foil substrate is in the range of 1.05 to 4.00, the average height difference H of the unevenness of the uneven surface is in the range of 0.2 to 1.3 [ mu ] m, the uneven surface has a necked shape, and the roughened layer has a thickness of 0.0003 to 0.0300mg/dm directly or through an intermediate layer²A silane coupling agent layer formed by the amount of silane deposited.

2. The surface-treated copper foil according to claim 1,

Da/Db, which is the ratio of the surface length Da to the surface length Db, is in the range of 1.05 to 3.20 times, the average height difference H of the irregularities is in the range of 0.2 to 0.8 [ mu ] m, and the number of bubbles at the interface between the rough-surface layer and the insulating substrate is 2 or less per 2.54 [ mu ] m of length on a straight line in an arbitrarily selected width direction, which is a direction perpendicular to the production direction of the copper foil, on the copper foil base when the copper foil is laminated with the insulating substrate.

3. The surface-treated copper foil according to claim 1,

Da/Db, which is the ratio of the surface length Da to the surface length Db, is in the range of 1.05 to 1.60 times, the average height difference H of the irregularities is in the range of 0.2 to 0.3 [ mu ] m, and the number of bubbles at the interface between the rough-surface layer and the insulating substrate is 1 or less per 2.54 [ mu ] m of length on a straight line in an arbitrarily selected width direction, which is a direction perpendicular to the production direction of the copper foil, of the copper foil base when the copper foil is laminated with the insulating substrate.

4. The surface-treated copper foil according to claim 1,

the silane adhesion amount of the silane coupling agent layer is 0.0005 to 0.0120mg/dm²。

5. The surface-treated copper foil according to claim 1,

the intermediate layer is composed of at least 1 layer selected from a base layer containing Ni, a heat-resistant treated layer containing Zn, and a rust-preventive treated layer containing Cr.

6. The surface-treated copper foil according to claim 1,

the silane coupling agent layer is composed of at least 1 selected from the group consisting of epoxy silane, amino silane, vinyl silane, methacrylic silane, acrylic silane, styrene silane, ureide silane, mercapto silane, sulfide silane, and isocyanate silane.

7. A copper-clad laminate characterized in that,

the surface-treated copper foil according to any one of claims 1 to 6, which has an insulating substrate on the roughened layer side surface.