CN114479712A

CN114479712A - Adhesive composition and method for producing connected body

Info

Publication number: CN114479712A
Application number: CN202210094165.4A
Authority: CN
Inventors: 筱原研吾; 川端泰典; 松田和也; 松泽光晴; 饭岛由祐
Original assignee: Showa Denko KK
Current assignee: Resonac Holdings Corp
Priority date: 2017-04-28
Filing date: 2018-04-27
Publication date: 2022-05-13
Also published as: JP7287275B2; KR102573777B1; WO2018199329A1; KR20200002953A; TW201843276A; CN110546222A; JPWO2018199329A1

Abstract

The invention provides an adhesive composition and a method for producing a connected body. The adhesive composition contains an adhesive component and conductive particles, wherein the conductive particles comprise plastic particles and a metal layer covering the plastic particles, a plurality of protrusions are formed on the surface of the conductive particles, the height of the protrusions is 90-1200 nm on average, and the ratio of the area of the protrusions to the area of the surface of the conductive particles in a projected image of the conductive particles is 8-60%.

Description

Adhesive composition and method for producing connected body

The present application is a divisional application of a chinese patent application having an application date of 2018, month 4 and month 27, an application number of 201880027673.2, and an invention name of "adhesive composition and method for manufacturing a connecting body".

Technical Field

The present invention relates to an adhesive composition and a method for producing a connected body.

Background

In recent years, electronic components have been reduced in size, thickness, and performance, and high-density mounting technology has been actively developed. In such high-density mounting, it is difficult to cope with the connection between the electronic component and the fine circuit electrode by using a conventional solder or rubber connector. Therefore, a connection method using an anisotropic conductive adhesive having excellent resolution and a film thereof is often used. In this connection method, for example, when a glass substrate of a Liquid crystal Display (Liquid crystal Display) and a Circuit member such as a Flexible Circuit substrate (FPC) are connected, by sandwiching an anisotropic conductive adhesive film containing conductive particles between opposing electrodes and heating and pressing the same, it is possible to electrically connect the electrodes of the two substrates while maintaining the insulation between the adjacent electrodes on the same substrate, and to bond and fix an electronic component having a fine electrode and the Circuit member.

In addition, in response to the demand for weight reduction and thickness reduction of the module, it is desirable to use a flexible substrate such as a plastic substrate instead of the glass substrate. When members using such substrates are connected to each other by an anisotropic conductive adhesive film, in order to reduce connection resistance, formation of protrusions on the surfaces of conductive particles included in the anisotropic conductive adhesive film has been studied, and evaluation of the shape of such conductive particles has also been performed (see patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-61722

Disclosure of Invention

Problems to be solved by the invention

As the electrode of the flexible substrate or the glass substrate, for example, a transparent electrode formed of a metal oxide or the like is used. When a circuit member such as an FPC is connected to the circuit member having the electrodes of metal oxide or the like, it tends to be difficult to ensure sufficient electrical connection. In particular, when the connection is performed using an adhesive containing conductive particles, there is room for improvement in reliability of electrical connection between electrodes.

Accordingly, a main object of the present invention is to obtain a more reliable electrical connection when a circuit member having a flexible substrate or a glass substrate is connected by an adhesive containing conductive particles.

Means for solving the problems

One aspect of the present invention is an adhesive composition containing an adhesive component and conductive particles, wherein the conductive particles have plastic particles and a metal layer covering the plastic particles, a plurality of protrusions are formed on the surface of the conductive particles, and the height of the plurality of protrusions is 85 to 1200nm on average.

Another aspect of the present invention is a method for producing a connected body, including the steps of: and a step of disposing a circuit connecting material between a first circuit member and a second circuit member disposed opposite to the first circuit member, the first circuit member having a first substrate and a first connecting terminal provided on the first substrate, and the second circuit member having a second substrate and a second connecting terminal provided on the second substrate, and heating and pressing the laminate to electrically connect the first circuit member and the second circuit member to each other, wherein the circuit connecting material contains an adhesive component and conductive particles, the conductive particles have plastic particles and a metal layer covering the plastic particles, a plurality of protrusions are formed on the surface of the conductive particles, and the height of the plurality of protrusions is 85 to 1200nm on average.

In each of the above aspects, in the projection image of the conductive particles, the ratio of the area of the protrusion to the area of the surface of the conductive particle may be 8 to 60%. The conductive particles may have a layer formed of Pd as a metal layer on the outermost surface of the conductive particles. The thickness of the layer formed of Pd may be 2 to 200 nm.

The adhesive composition can be used for electrically connecting a first circuit member having a first substrate and a first connection terminal provided on the first substrate and a second circuit member having a second substrate and a second connection terminal provided on the second substrate to each other. In this case, the first substrate may be an IC chip or a flexible substrate, and the second substrate may be a flexible substrate containing at least one thermoplastic resin selected from the group consisting of polyimide, polyethylene terephthalate, polycarbonate, and polyethylene naphthalate. The first substrate may be an IC chip or a flexible substrate, and the second substrate may be a glass substrate or a composite substrate including a glass substrate and an insulating film provided on the glass substrate.

In the method of manufacturing a connected body, the first substrate may be an IC chip or a flexible substrate, and the second substrate may be a flexible substrate containing at least one thermoplastic resin selected from the group consisting of polyimide, polyethylene terephthalate, polycarbonate, and polyethylene naphthalate. The first substrate may be an IC chip or a flexible substrate, and the second substrate may be a glass substrate or a composite substrate including a glass substrate and an insulating film provided on the glass substrate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, when a circuit member having a flexible substrate or a glass substrate is connected by an adhesive containing conductive particles, more reliable electrical connection can be obtained.

Drawings

Fig. 1 is a sectional view schematically showing one embodiment of the adhesive composition.

Fig. 2 is a cross-sectional view schematically showing one embodiment of the conductive particles.

Fig. 3 is a sectional view schematically showing one embodiment of a method for manufacturing a connected body.

Fig. 4 is a sectional view schematically showing a main part of a connecting body of an embodiment.

Fig. 5 is a sectional view schematically showing a main part of a conventional connecting body.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

An adhesive composition according to one embodiment is an adhesive film formed in a film shape. In another embodiment, the adhesive composition may be in a state other than a film shape (e.g., paste).

Fig. 1 is a cross-sectional view schematically showing a film-like adhesive composition (adhesive film) according to an embodiment. As shown in fig. 1, in one embodiment, an adhesive film 1 includes an adhesive component (insulating adhesive) 2 and conductive particles 3 dispersed in the adhesive component 2. The thickness of the adhesive film 1 may be, for example, 10 to 50 μm.

In one embodiment, the adhesive component has an insulating property and contains a curable component that is cured by heat or light. The binder component may be defined as a solid component excluding the conductive particles in the binder composition.

The curable component may contain a radical polymerizable substance and a radical initiator, may contain a thermosetting resin, and may contain a radical polymerizable substance, a radical initiator and a thermosetting resin.

The radical polymerizable substance is a substance having a functional group that is polymerized by a radical, and examples thereof include acrylate, methacrylate, and maleimide compounds. The content of the radical polymerizable substance may be, for example, 50 to 80% by mass based on the total amount of the adhesive component.

As the acrylic acid ester and methacrylic acid ester, there may be mentioned, for example, urethane acrylate, urethane methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, dimethylol tricyclodecane diacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, 2-hydroxy-1, 3-diacryloyloxypropane, 2-bis [ 4- (acryloyloxymethyl) phenyl ] propane, 2-bis [ 4- (acryloyloxypolyethoxy) phenyl ] propane, dicyclopentenyl acrylate, tricyclodecyl acrylate, bis (acryloyloxyethyl) isocyanurate, epsilon-caprolactone-modified tris (acryloyloxyethyl) isocyanurate and tris (acryloyloxyethyl) isocyanurate. These radical polymerizable substances may be used alone or in combination of two or more. From the viewpoint of adhesiveness, the radical polymerizable substance is preferably urethane acrylate or urethane methacrylate.

Particularly preferred as the radical polymerizable substance is a radical polymerizable substance which is crosslinked with a urethane acrylate or a urethane methacrylate and an organic peroxide and which exhibits a Tg of 100 ℃ or higher by itself, in combination, from the viewpoint of improving heat resistance. Such a radical polymerizable substance may have a dicyclopentenyl group, a tricyclodecyl group and/or a triazine ring, and preferably has a tricyclodecyl group or a triazine ring.

The radical polymerizable substance may be at least one radical polymerizable substance having a viscosity of 100000 to 1000000 mPas at 25 ℃, and preferably at least one radical polymerizable substance having a viscosity of 100000 to 500000 mPas. The viscosity of the radical polymerizable substance can be measured using a commercially available E-type viscometer.

The radical initiator is a compound which is decomposed by heat or light to generate a radical, and is, for example, a peroxide compound or an azo compound. The free radical initiator is appropriately selected depending on the target linking temperature, linking time, pot life and the like. The free radical initiator may be one or more selected from, for example, benzoyl peroxide, diacyl peroxide, dicarbonate peroxide, peroxyester, peroxyketal, dialkyl peroxide, and hydrogen peroxide. From the viewpoint of high reactivity and pot life, the free radical initiator is preferably an organic peroxide having a half-life of 10 hours at a temperature of 40 ℃ or more and a half-life of 1 minute at a temperature of 180 ℃ or less. The radical initiator may be used in combination with a decomposition accelerator, an inhibitor, and the like. The content of the radical initiator may be, for example, 0.05 to 15% by mass based on the total amount of the adhesive component.

When the adhesive component contains a radical curing material, a polymerization inhibitor may be further contained. The polymerization inhibitor may be hydroquinone, methyl ether hydroquinones, etc. The content of the polymerization inhibitor may be 0.05 to 5% by mass based on the total amount of the binder component.

Examples of the thermosetting resin include epoxy resin, cyanate resin, maleimide resin, allyl nadimide resin (allyl nadimide resin), phenol resin, urea resin, melamine resin, alkyd resin, acrylic resin, unsaturated polyester resin, diallyl phthalate resin, silicone resin, resorcinol-formaldehyde resin, xylene resin, furan resin, polyurethane resin, ketone resin, triallyl cyanurate resin, polyisocyanate resin, resin containing tris (2-hydroxyethyl) isocyanurate, resin containing triallyl trimellitate, thermosetting resin synthesized from cyclopentadiene, thermosetting resin formed by trimerization of aromatic dicyandiamide, and the like. The thermosetting resins may be used alone or in combination of two or more. The content of the thermosetting resin may be, for example, 20 to 50% by mass based on the total amount of the binder component.

In the case where the adhesive component contains a thermosetting resin, the adhesive component may further contain a curing agent. The curing agent may be melamine or a derivative thereof, a hydrazide curing agent, a boron trifluoride-amine complex, a sulfonium salt, an aminimide (amine imide), diaminomaleonitrile, a polyamine salt, dicyandiamide, or a modified product thereof, and these may be used alone or in combination of two or more. The curing agent may be a polyaddition type curing agent such as polyamine, polythiol, polyphenol, acid anhydride, etc., and a polyaddition type curing agent and a catalyst type curing agent may be used in combination. The content of the curing agent may be 0.5 to 15% by mass based on the total amount of the binder component.

It is preferable that the curing agent is coated with a polymer such as urethane or polyester, or a metal film such as Ni or Cu, or an inorganic material such as calcium silicate, and encapsulated to give a product which can be used for a long time.

The adhesive component may further contain a filler such as silicone particles, a softening agent, an accelerator, an antioxidant, a colorant, a flame retardant, a thixotropic agent, a coupling agent, and the like.

When the adhesive composition is formed into a film, the adhesive component may contain a resin having a functional group such as a hydroxyl group in order to improve film formability. Such a resin may be polystyrene, polyethylene, polyvinyl butyral, polyvinyl formal, polyimide, polyamide, polyester, polyvinyl chloride, polyphenylene ether, urea resin, melamine resin, phenol resin, xylene resin, epoxy resin, polyisocyanate resin, phenoxy resin, polyimide resin, polyester urethane resin, polyurethane resin, or the like, and from the viewpoint of further improving the connection reliability, it may be a high molecular weight epoxy resin or phenoxy resin having a weight average molecular weight of 10000 or more as determined by High Performance Liquid Chromatography (HPLC). The adhesive component may contain a product obtained by modifying these resins with a radical polymerizable functional group, or may contain a mixture of these resins with a styrene resin or an acrylic resin in order to adjust melt viscosity or the like. In another embodiment, the adhesive component may contain rubber for improving film formability.

Fig. 2 is a cross-sectional view schematically showing an embodiment of the conductive particles 3 included in the adhesive film 1. As shown in fig. 2 (a), in one embodiment, the conductive particles 3A include plastic particles 31 and a metal layer 32A covering the plastic particles 31.

The surface of the plastic particle 31 is preferably substantially entirely coated with the metal layer 32A, but a part of the surface of the plastic particle 31 may be exposed without being coated with the metal layer 32A within a range in which a function as a circuit connecting material (a function of electrically connecting circuit members) can be maintained.

The plastic particles 31 may be, for example, particles containing a polymer containing at least one monomer selected from styrene and divinylbenzene as a monomer unit. The polymer may further comprise (meth) acrylate as a monomer unit.

The diameter of the plastic particles 31 may preferably be greater than or equal to 1 μm, on average, and may be less than or equal to 40 μm. From the viewpoint of high-density mounting, the diameter of the plastic particles 31 is more preferably 1 μm or more and 30 μm or less on average. From the viewpoint of more stably maintaining the connection state when there is variation in the surface irregularities of the electrode, the diameter of the plastic particles 31 is more preferably 2 μm or more and 20 μm or less on average.

The metal layer 32A includes, for example, a metal layer. The metal layer 32A is formed of, for example, Ni, Cu, NiB, Ag, or Ru. The thickness of the metal layer 32A may be, for example, 50nm or more, and may be 300nm or less. The thickness of the metal layer 32A is a thickness at a portion of the metal layer where a protrusion described later is not formed. The thickness of the metal layer 32A can be measured by an electron microscope.

As shown in fig. 2 (B), in the conductive particle 3B according to another embodiment, the metal layer 32B may be a metal layer including two layers, i.e., a first metal layer 32a and a second metal layer 32B. That is, the conductive particle 3B according to another embodiment includes a plastic particle 31, a first metal layer 32a covering the plastic particle 31, and a second metal layer 32B covering the first metal layer 32 a.

The first metal layer 32a is formed of Ni, for example. The second metal layer 32b may be formed of, for example, Au or Pd, and is preferably formed of Pd in view of further improving reliability. That is, the conductive particles 3B may have a layer made of Au or Pd as a metal layer on the outermost surface of the conductive particles 3B, and preferably have a layer made of Pd from the viewpoint of further improving reliability.

The thickness of the first metal layer 32a may be, for example, 50nm or more, and may be 300nm or less. The thickness of the second metal layer 32b may be, for example, greater than or equal to 2nm, greater than or equal to 5nm, or greater than or equal to 10nm, less than or equal to 200nm, less than or equal to 100nm, or less than or equal to 50nm, and may be 2 to 200nm, 2 to 100nm, 2 to 50nm, 5 to 200nm, 5 to 100nm, 5 to 50nm, 10 to 200nm, 10 to 100nm, or 10 to 50 nm. The thicknesses of the first metal layer 32a and the second metal layer 32b respectively refer to thicknesses at portions of the metal layers where the later-described protrusions are not formed. The thicknesses of the first metal layer 32a and the second metal layer 32b can be measured by an electron microscope.

A plurality of protrusions 33 are formed on the surface of the conductive particle 3. In the conductive particles 3A shown in fig. 2 (a), the protrusion 33A is formed of a metal layer 32A including one layer. In the conductive particles 3B shown in fig. 2 (B), the protrusion 33B is formed of a metal layer 32B including two layers, i.e., a first metal layer 32a and a second metal layer 32B.

From the viewpoint of improving the reliability of electrical connection, the height of the protrusion 33 is 85nm or more, 90nm or more, or 100nm or more, 1200nm or less, 1000nm or less, 600nm or less, 500nm or less, 400nm or less, 300nm or less, or 200nm or less. From the same viewpoint, the height of the protrusion 33 may be 85 to 1200nm, 85 to 1000nm, 85 to 600nm, 85 to 500nm, 85 to 400nm, 85 to 300nm, 85 to 200nm, 90 to 1200nm, 90 to 1000nm, 90 to 600nm, 90 to 500nm, 90 to 400nm, 90 to 300nm, 90 to 200nm, 100 to 1200nm, 100 to 1000nm, 100 to 600nm, 100 to 500nm, 100 to 400nm, 100 to 300nm, or 100 to 200 nm.

Here, the height of the protrusion 33 is determined by analyzing a two-dimensional image of a projected image including conductive particles. The analysis of the two-dimensional image can be performed according to the method described in japanese patent application laid-open No. 2016-61722.

Specifically, for example, the determination can be made by a method including the steps of: detecting a particle edge which is a boundary between a projected image of each conductive particle and another region in a two-dimensional image in which a plurality of conductive particles are captured; calculating center coordinates of the conductive particles on the two-dimensional image based on the edges of the particles; dividing the edge of the particle into a plurality of edge portions (for example, 12) of the particle at predetermined angles around the center coordinate, calculating a difference between a maximum value and a minimum value of distances between the center coordinate and the edge of the particle for each of the plurality of edge portions of the particle, and calculating an average value of the differences as a height of the protrusion; and calculating an average value of the heights of the protrusions calculated for a plurality of conductive particles (for example, an arbitrary number of 5 to 100).

In the analysis of the two-dimensional image, the particle edge substantially corresponds to the outer periphery of the two-dimensional projection image of the conductive particle including the unevenness derived from the protrusion. In general, the frequency distribution display of the luminance obtained from the two-dimensional image reflects the minimum value of the edge portion of the particle. And binarizing the two-dimensional image by taking the brightness corresponding to the minimum value as a first threshold value to generate a binarized image. The edge formed in the obtained binary image is detected as a particle edge. The center coordinates of the conductive particles on the two-dimensional image are calculated based on the particle edges. A circle fitted to the edge of the particle is obtained by the least square method, and the center of the circle is regarded as the center coordinate of the conductive particle.

From the viewpoint of further improving the reliability of the electrical connection, the area ratio of the projection image of the projection 33 to the surface of the conductive particle 3 (the area ratio of the projection 33) is preferably 8% or more, 9% or more, or 20% or more, preferably 60% or less, or 50% or less, preferably 8 to 60%, 8 to 50%, 9 to 60%, 9 to 50%, 20 to 60%, or 20 to 50%.

The area ratio of the projection can also be determined by analyzing a two-dimensional image of the conductive particles according to the method described in japanese patent application laid-open No. 2016-61722. For example, the area ratio of the protrusions can be determined by a method including the steps of: calculating a second threshold value corresponding to a boundary between the protrusion and a portion other than the protrusion, based on a frequency distribution of luminance in a region inside the particle edge; a step of generating a binarized image by binarizing an area inside the edge of the particle by using the obtained second threshold value; and calculating a ratio of an area of a region corresponding to the protrusion to an area of an inner side of the edge of the particle as an area ratio of the protrusion in the obtained binary image.

The conductive particles 3 having the protrusions as described above can be obtained by forming the

metal layers

32A and 32B on the surface of the plastic particle 31 by metal plating, for example. The projection 33 can be formed by changing the plating conditions during metal plating to change the thickness of the

metal layers

32A and 32B. For example, the protrusions 33 can be formed by increasing the concentration of the plating solution in stages during the metal plating process.

Alternatively, the metal layer having the nodular protrusions can be formed by adjusting the pH of the plating solution (for example, the pH of the nickel plating solution is set to 6) (see tomayu et al, surface technology, vol.48, No.4, pages 429 to 432, 1997). While a metal layer having a flat surface can be formed when glycine is used as a complexing agent contributing to the stability of the plating bath, a nodular protrusion can be formed when tartaric acid or DL-malic acid is used as a complexing agent (see, for example, triarrhena et al, amorphous plated (amorphous plated) en-sul メッキ, Vol.36, pp.35-37, 1994; triarrhena et al, J.L.Soc. (American society for Circuit Assembly ), Vol.10, No.3, pp.148-152, 1995). By using these methods, the

metal layers

32A and 32B of the protruding portion 33 having a desired height and area ratio can be formed.

In the case of producing the conductive particles 3B shown in fig. 2 (B), for example, the second metal layer 32B can be obtained by forming the first metal layer 32a having the protruding portion by the above-described method, and then forming a layer of Au or Pd by displacement plating.

The content of the conductive particles 3 contained in the adhesive film 1 depends on the fineness of the electrode to be connected. For example, the content of the conductive particles 3 may be 1 part by volume or more and 50 parts by volume or less with respect to 100 parts by volume of the adhesive component, and is preferably 30 parts by volume or less from the viewpoint of insulation properties and production cost.

The adhesive composition may be in the form of a multilayer film (multilayer adhesive film). The multilayer adhesive film may be composed of two layers including a layer containing conductive particles and a layer not containing conductive particles, or may be composed of three layers including a layer containing conductive particles and layers not containing conductive particles provided on both sides thereof. The multilayer adhesive film may include a plurality of layers containing conductive particles. The multilayer adhesive film may be provided with an adhesive layer exhibiting high adhesiveness to the circuit member to be connected, in consideration of adhesiveness to the circuit member. When these multilayer adhesive films are used, the conductive particles can be efficiently trapped on the connection electrodes, and therefore, the connection of circuit members with a narrow pitch is facilitated.

The adhesive composition (adhesive film) described above is suitably used as a material for connecting circuit members (circuit connecting material), and particularly suitably used as an anisotropic conductive adhesive composition (anisotropic conductive adhesive film) for connecting circuit members.

Next, a method for producing a connected body using the adhesive film 1 will be described. Fig. 3 is a sectional view schematically showing a method for manufacturing a connected body according to an embodiment. First, as shown in fig. 3 (a), a first circuit member 4, a second circuit member 5, and an adhesive film 1 (circuit connecting material) are prepared. The first circuit member 4 has a first substrate 6 and a first connection terminal 7 provided on one surface 6a of the first substrate 6. The second circuit member 5 has a second substrate 8 and a second connection terminal 9 provided on one surface 8a of the second substrate 8.

Next, the first circuit member 4 and the second circuit member 5 are arranged so that the first connection terminal 7 and the second connection terminal 9 face each other, and the adhesive film 1 is arranged between the first circuit member 4 and the second circuit member 5 to produce a laminate.

Then, the adhesive film 1 is cured while pressing the entire laminate in the direction indicated by the arrow in fig. 3 (a). The pressure during pressurization may be, for example, 1 to 10MPa with respect to the total connection area. The method of curing the adhesive film 1 may be a method of heating, or a method of irradiating light in addition to heating. The heating may be performed at, for example, 100 to 170 ℃. The pressurization and heating (irradiation with light as needed) may be performed for, for example, 1 to 160 seconds. Thereby, the first circuit member 4 and the second circuit member 5 are pressure-bonded via the cured product of the adhesive composition constituting the adhesive film 1.

In the present embodiment, the adhesive film 1 is disposed between the first circuit member 4 and the second circuit member 5, but in another embodiment, instead of the adhesive film, a paste-like adhesive composition may be applied to the first circuit member 4 or the second circuit member 5, or to both of them.

As shown in fig. 3 (b), the connected body 10 according to one embodiment obtained by the above-described operation includes: a first circuit member 4 having a first substrate 6 and a first connection terminal 7 provided on the first substrate 6; a second circuit member 5 having a second substrate 8 and a second connection terminal 9 provided on the second substrate 8; and a connection portion 11 that is provided between the first circuit member 4 and the second circuit member 5 and that electrically connects the first circuit member 4 (the first connection terminal 7) and the second circuit member 5 (the second connection terminal 9) to each other. The connection portion 11 is composed of a cured product of an adhesive composition, and includes a cured product 12 of an adhesive component 2 and conductive particles 3 dispersed in the cured product 12. In the connected body 10, the first connection terminal 7 and the second connection terminal 9 are electrically connected to each other by interposing the conductive particles 3 between the first connection terminal 7 and the second connection terminal 9.

The first substrate 6 may be, for example, an IC chip or a flexible substrate. The second substrate 8 may be, for example, a flexible substrate, a glass substrate, or a composite substrate having a glass substrate and an insulating film provided on the glass substrate.

As a combination of the first substrate 6 and the second substrate 8, more specifically, the first substrate 6 may be an IC chip or a flexible substrate, and the second substrate 8 may be a flexible substrate. Alternatively, the first substrate 6 may be an IC chip or a flexible substrate, and the second substrate 8 may be a glass substrate or a composite substrate. In other words, when the second substrate 8 is a flexible substrate, the first substrate 6 may be an IC chip or a flexible substrate. When the first substrate 6 is an IC Chip and the second substrate 8 is a flexible substrate, COP (Chip on Plastic substrate) connection is performed using the adhesive film 1. When the first substrate 6 and the second substrate 8 are flexible substrates, the adhesive Film 1 is used to connect films on Plastic substrates (FOP).

The flexible substrate contains, for example, at least one thermoplastic resin selected from the group consisting of Polyimide (PI), polyethylene terephthalate (PET), Polycarbonate (PC), and polyethylene naphthalate (PEN).

The flexible substrate may further have a modification treatment film such as a hard coat layer and/or a protective film formed on the surface of the organic base material for improving optical and mechanical properties. In order to facilitate handling and transportation of the flexible substrate, a reinforcing material selected from a glass base material and SUS may be bonded to the organic base material.

The thickness of the flexible substrate is preferably 10 μm or more, 200 μm or less or 125 μm or less from the viewpoint of ensuring strength and ease of bending as a film with the substrate alone.

When a conventional circuit connecting material is used, the electrodes on the flexible substrate are likely to be broken or cracks are likely to be generated by heating and pressing for pressure bonding of circuit members. In addition, in connection of electrodes that are difficult to form sufficient electrical connection, it is necessary to crimp a circuit member at a lower temperature or a lower stress in order to suppress breakage of the electrodes. The circuit connecting material (adhesive film) of the present embodiment can also have advantageous effects in these respects as compared with conventional materials.

The glass substrate may be formed of soda lime glass, quartz glass, or the like, and may be a substrate subjected to chemical strengthening treatment from the viewpoint of preventing breakage due to external stress. The composite substrate may have a glass substrate and an insulating film provided on a surface of the glass substrate and composed of polyimide or a colored organic material or inorganic material for decoration, and in the composite substrate, the electrode may be formed on the insulating film thereof.

In the case where the second substrate 8 is a flexible substrate, the first substrate 6 may be an active element such as a semiconductor chip, a transistor, a diode, or a thyristor; electronic components such as passive elements including capacitors, resistors, and coils; a printed substrate, and the like. When the first substrate 6 is an IC chip, a bump formed by plating or a protruding electrode (first connection terminal 7) such as a wire bump (wire bump) formed by melting the tip of a gold wire with a welding torch or the like to form a gold ball, pressing the ball onto an electrode pad, and then cutting the wire can be provided and used as the first circuit member 4.

Examples of the electrode material forming the first connection terminal 7 and the second connection terminal 9 include Ag paste, metals such as Ni, Al, Au, Cu, Ti, and Mo; metal oxides such as ITO and IZO; and electrical conductors such as silver nanowires and carbon nanotubes. The first connection terminal 7 and the second connection terminal 9 may be formed of the same material or different materials, but are preferably formed of the same material. From the viewpoint of preventing disconnection, a surface layer formed of an oxide, a nitride, an alloy, an organic substance, or the like may be further provided on the first connection terminal 7 and the second connection terminal 9. One first connection terminal 7 or second connection terminal 9 may be provided at each of the first circuit member 4 and the second circuit member 5, but it is preferable to provide a plurality thereof with a predetermined interval.

If the circuit connecting material (adhesive film) is used, even when the first circuit member 4 is an FPC circuit board and the second connecting terminal 9 of the second circuit member 5 is formed of a metal oxide which tends to make it difficult to ensure sufficient electrical connection, electrical connection with higher reliability can be obtained.

Fig. 4 is a sectional view schematically showing a main part of one embodiment of the connected body 10. As shown in fig. 4, when the height of the protruding portion 33 of the conductive particle 3 is within a predetermined range, when the circuit members are connected to each other, the conductive particle 3 interposed between the first connection terminal 7 and the second connection terminal 9 can apply sufficient pressure to the first connection terminal 7 and the second connection terminal 9 (and the second substrate 8) via the protruding portion 33, and therefore, it is possible to obtain more reliable electrical connection, and for example, it is considered that an increase in connection resistance under high temperature and high humidity is less likely to occur.

On the other hand, as shown in fig. 5 (a sectional view schematically showing a main portion of a conventional connected body), in the conventional connected body 20, since the conductive particles 23 have relatively low protrusions 23a, a sufficient pressure cannot be applied to the first connection terminal 7 and the second connection terminal 9 (and the second substrate 8). Therefore, the conventional connector 20 is poor in reliability of electrical connection.

Examples

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples.

(preparation of conductive particles)

(1) Plastic particle

Using tetramethylolmethane tetraacrylate, divinylbenzene and styrene as monomers, they were polymerized by suspension polymerization using a polymerization initiator (benzoyl peroxide), to thereby obtain plastic particles.

(2-1) conductive particles 1-1 to 1-3

The obtained plastic particles were subjected to electroless Ni plating to obtain conductive particles 1 to 3 having a metal layer (Ni layer, thickness 0.2 μm) made of Ni and having a protrusion. In the Ni plating treatment, the thickness of the Ni layer is changed by appropriately adjusting the amount of plating solution added, the treatment temperature, and the treatment time, thereby forming the projections having different heights and area ratios.

(2-2) conductive particles 1-4 to 1-6

On the Ni layers of the conductive particles 1 to 3, layers (Au layers) made of Au having protrusions were formed by displacement plating, and conductive particles 4 to 6 were obtained, respectively.

(2-3) conductive particles 1-7

An Ni layer having a flat surface was formed on the obtained plastic particles, and an Au layer having a flat surface was further formed on the Ni layer, thereby producing conductive particles.

(2-4) conductive particles 2-1 to 2-4

The obtained plastic particles were subjected to electroless Ni plating treatment, thereby obtaining conductive particles having a Ni layer (thickness of 0.2 μm) with protrusions. In the Ni plating treatment, the plating thickness is changed by appropriately adjusting the amount of plating solution to be added, the treatment temperature, and the treatment time, thereby forming the projections having different heights and area ratios. On the Ni layer of these conductive particles, a layer (Pd layer) made of Pd having a protrusion was formed by displacement plating, and conductive particles 2-1 to 2-4 were obtained.

(3) Height and area ratio of the projections

Two-dimensional images containing the conductive particles were obtained by a scanning electron microscope. The obtained two-dimensional image was analyzed by the method described in japanese patent application laid-open No. 2016-61722, whereby the height and area ratio of the protrusions of 100 conductive particles were calculated, and the average value of these was obtained.

(preparation of adhesive film (Circuit connecting Material))

A urethane acrylate (product name: UA-5500T, manufactured by NinghamｃA chemical industries Co., Ltd.) as ｃA radical polymerizable substance 20 parts by mass, bis (acryloyloxyethyl) isocyanurate (product name: M-215, manufactured by Toyo chemical Co., Ltd.) 15 parts by mass, dimethylol tricyclodecane diacrylate (product name: DCP-A, manufactured by Kyodo chemical Co., Ltd.) 5 parts by mass, 2-methacryloyloxyethyl acid phosphate (product name: P-2M, manufactured by Kyodo chemical Co., Ltd.) 1 part by mass, benzoyl peroxide (product name: Nyper BMT-K, manufactured by Nichio oil Co., Ltd.) 8 parts by mass, and ｃA solution containing ｃA polyester urethane resin (product name: UR4800, manufactured by Toyo Seiki Co., Ltd.) 60 parts by mass at ｃA concentration of 40% were mixed and stirred, a solution of the binder resin was obtained. The solution of the polyester urethane resin was prepared by dissolving the polyester urethane resin in a mixed solvent of toluene/methyl ethyl ketone 50/50.

In the prepared solution of the binder resin, each conductive particle was dispersed in a proportion of 10 parts by volume with respect to 100 parts by volume of the binder resin. In which silicone fine particles (product name: KMP-605, manufactured by shin-Etsu chemical Co., Ltd.) having an average particle diameter of 2 μm were dispersed at a ratio of 20 parts by mass to 100 parts by mass of the binder resin to obtain a coating liquid containing the binder resin, conductive particles and silicone fine particles. The coating liquid was applied to a polyethylene terephthalate (PET) film (thickness 50 μm) having one surface treated, using a coating apparatus. The coating film was dried by hot air at 70 ℃ to prepare an anisotropic conductive adhesive film (thickness: 18 μm) as a circuit connecting material.

(preparation of Circuit Member)

Glass member

A glass member having a glass substrate and a connecting terminal (thickness 40nm) of a Cu film (thickness 30nm) and amorphous ITO sequentially laminated on the glass substrate was prepared.

Flexible component

A flexible member having a polyethylene terephthalate (PET) film (elastic modulus at 25 ℃ C.: 4600MPa) and a connection terminal (thickness 20nm) of ITO formed on the PET film was prepared.

Flexible Circuit Board (FPC)

An FPC having a resin film substrate made of polyethylene terephthalate (PET) and wiring provided on the resin film substrate was prepared. The wiring of the FPC had a connection terminal including a Cu layer with a pitch of 0.3mm (gap 0.15mm, electrode width 0.15mm, height 18 μm), and a Ni plating layer with a thickness of 3 μm and an Au plating layer with a thickness of 0.03 μm formed in this order on the Cu layer.

An anisotropic conductive adhesive film is interposed between the flexible member and the FPC. In this state, the entire assembly was pressurized at a pressure of 2MPa for 10 seconds with respect to the total connection area while heating the anisotropic conductive adhesive film so that the reaching temperature of the anisotropic conductive adhesive film became 160 ℃.

Similarly, the glass member and the FPC are connected to each other with an anisotropic conductive adhesive film interposed therebetween, thereby obtaining a glass/FPC connection body.

Each of the obtained linkers was subjected to a reliability test at 85 ℃ and 85% RH for 72 hours. The connection resistance between the opposing circuit members was measured for the connectors before and after the test.

The characteristics and evaluation results of the outermost surface layer, the height of the protrusions, the area ratio of the protrusions, and the like of each of the obtained conductive particles are shown in tables 1 and 2.

[ Table 1]

[ Table 2]

Description of the symbols

1 … adhesive film, 2 … adhesive composition, 3 … conductive particles, 4 … first circuit member, 5 … second circuit member, 6 … first substrate, 7 … first connection terminal, 8 … second substrate, 9 … second connection terminal, 10 … connector, 11 … connector, 31 … plastic particles, 32A, 32B … metal layer, 33A, 33B … protrusion.

Claims

1. An adhesive composition comprising an adhesive component and conductive particles,

the conductive particles comprise plastic particles and a metal layer covering the plastic particles,

a plurality of protrusions are formed on the surface of the conductive particle, the height of the plurality of protrusions is 90-1200 nm on average,

in the projection image of the conductive particles, the ratio of the area of the protrusion to the area of the surface of the conductive particles is 8-60%.

2. The adhesive composition according to claim 1, wherein the conductive particles have a layer formed of Pd as the metal layer on the outermost surface of the conductive particles.

3. The adhesive composition according to claim 2, wherein the thickness of the layer made of Pd is 2 to 200 nm.

4. The adhesive composition according to any one of claims 1 to 3, for electrically connecting a first circuit member and a second circuit member to each other,

the first circuit member has a first substrate and a first connection terminal provided on the first substrate,

the second circuit member has a second substrate and a second connection terminal provided on the second substrate,

the first substrate is an IC chip or a flexible substrate,

the second substrate is a flexible substrate including at least one thermoplastic resin selected from the group consisting of polyimide, polyethylene terephthalate, polycarbonate, and polyethylene naphthalate.

5. The adhesive composition according to any one of claims 1 to 3,

for electrically connecting the first circuit member and the second circuit member to each other,

the first substrate is an IC chip or a flexible substrate,

the second substrate is a glass substrate or a composite substrate having a glass substrate and an insulating film provided on the glass substrate.

6. A method for manufacturing a connected body, comprising the steps of:

a step of disposing a circuit connecting material between a first circuit member and a second circuit member disposed opposite to the first circuit member to produce a laminate, and heating and pressing the laminate to electrically connect the first circuit member and the second circuit member to each other,

the circuit connecting material contains an adhesive component and conductive particles,

7. The method for producing a connected body according to claim 6, wherein the conductive particles have a layer formed of Pd as the metal layer on an outermost surface of the conductive particles.

8. The method for manufacturing a connection body according to claim 7, wherein the thickness of the layer made of Pd is 2 to 200 nm.

9. The method for producing a connected body according to any one of claims 6 to 8,

the first substrate is an IC chip or a flexible substrate,

10. The method for producing a connected body according to any one of claims 6 to 8,

the first substrate is an IC chip or a flexible substrate,