JP2006233201A - Anisotropically electroconductive adhesive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropically electroconductive adhesive film having high connection reliability even under severe thermal conditions. <P>SOLUTION: The anisotropically electroconductive adhesive film is one in which electroconductive particles are arranged as a single layer to form an electroconductive layer on the surface layer of an insulation adhesive, an insulation layer lies on at least one surface of the electroconductive layer, and electroconductivity develops upon the exertion of pressure in the thickness direction, wherein (1) the intercentral distance between electroconductive particles is 2 to 20 μm on the average, is 1.5 to 5 times as large as the average particle diameter of the electroconductive particles, and has a coefficient of variation of 0.025 to 0.5, (2) the insulation adhesive contains insulation fibers in an amount of 50 vol.% or smaller based on 100 vol.% insulation adhesive, (3) the internal stress at 25°C is 10 MPa or lower after the insulation adhesive containing the insulation fibers is cured, and (4) the average particle diameter of the electroconductive particles is 1 to below 6 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides an anisotropic conductive adhesive having high connection reliability even in a severe thermal environment without causing connection failure, insulation failure, or short-circuiting between electrodes in electrical connection of fine patterns. Related to film.

Anisotropic conductive adhesive film is a film in which conductive particles are dispersed in an adhesive. It is used to easily connect a liquid crystal display and TCP or FPC and TCP, and FPC and printed wiring board. For example, it is widely used for connecting a liquid crystal screen of a television or a mobile phone and a control IC (Patent Documents 1, 2, and 3).
In recent years, the dimensions of connected wiring patterns and electrode patterns have been increasingly miniaturized in this field. When the size of the electrode pattern to be connected is reduced, in the anisotropic conductive adhesive film in which the conductive particles are randomly distributed, a deviation occurs in the distribution of the conductive particles, so that the pattern to be connected does not exist in the conductive particles. It is unavoidable as a probability theory that it is placed in the area and not electrically connected.

In order to solve this problem, it is effective to disperse smaller conductive particles in the film at a high density. However, when the size of the conductive particles is reduced, the surface area increases rapidly and secondary aggregation easily occurs. As a result, if the density of the conductive particles is lowered to maintain the insulation, a wiring pattern or an electrode pattern that is not connected is generated. It has been considered difficult to cope with miniaturization while maintaining (Patent Document 4).
Furthermore, when an epoxy resin is used for the insulating adhesive, cracks due to the curing stress that the epoxy resin holds inside when cured may be a problem. That is, when the resin is embracing internal stress with cure shrinkage and the connection part receives a thermal shock etc., cracks are generated from it, and further, moisture that has entered may condense or cause corrosion, Ion migration occurs, stress concentration moves due to the occurrence of cracks, causing new cracks, and various problems. Therefore, countermeasures against it were required.

Japanese Patent Laid-Open No. 03-107888 Japanese Patent Laid-Open No. 04-366630 JP-A-61-195179 JP 09-31176 A

  The present invention provides an anisotropic conductive adhesive having high connection reliability even in a severe thermal environment without causing connection failure, insulation failure, or short-circuiting between electrodes in electrical connection of fine patterns. The purpose is to provide a film.

As a result of intensive studies to solve the above problems, the present inventors have first determined that the distance between particles is a specific average value and a specific value for a problem corresponding to miniaturization while maintaining connection reliability. It has been found that the conductive particles are arranged as a single layer on the surface layer of the insulating adhesive so as to have a standard deviation, so that it can meet the above-mentioned purpose, and the skeleton of the present invention is made.
Furthermore, it has been found that mixing an insulating fibrous material with an insulating adhesive can absorb internal stress and maintain high connection reliability, thus completing the present invention.

That is, the present invention
1. Conductive particles are arranged as a single layer on the surface layer of the insulating adhesive to form a conductive layer, and an insulating layer made of an insulating adhesive is provided on at least one side of the conductive layer. In the anisotropic conductive adhesive film having conductivity by pressing,
(1) The average distance between the centers of the conductive particles is 2 μm or more and 20 μm or less, and is 1.5 times or more and 5 times or less with respect to the average particle diameter of the conductive particles. 5 or less,
(2) Insulating fibers are contained in the insulating adhesive in a range of 50% by volume or less when the insulating adhesive is 100% by volume,
(3) The internal stress at 25 ° C. after curing the insulating adhesive containing the insulating fiber is 10 Pa or less,
(4) The present invention relates to an anisotropic conductive adhesive film characterized in that the average particle diameter of the conductive particle diameter is 1 μm or more and less than 6 μm.
2. 2. The anisotropic conductive adhesive film according to 1 above, wherein the anisotropic conductive adhesive film has a thickness of 5 μm or more and 50 μm or less.
3. 3. The anisotropic conductive adhesive film according to 1 or 2 above, wherein the conductive layer contains insulating particles, and the average particle size of the insulating particles is smaller than the average particle size of the conductive particles.

  The anisotropic conductive adhesive film of the present invention is excellent in electrode adhesion even when it is a high aspect ratio electrode in a fine pattern electrical connection, causing connection failure, insulation failure, or High connection reliability without short circuit.

The present invention will be specifically described below.
The present invention relates to an anisotropic conductive adhesive film having conductivity by dispersing conductive particles in an insulating adhesive and applying pressure in the thickness direction.
In the anisotropic conductive adhesive film of the present invention, a conductive layer is formed by arranging conductive particles as a single layer on the surface layer of an insulating adhesive.
Here, the arrangement in the surface layer means a state in which a part or the whole of the conductive particles is embedded in the surface of the insulating adhesive, and the state in which the entire conductive particle is embedded is preferable because of high adhesion to the electrode. . When a part of the conductive particles are embedded, the conductive particles are less than 1/3 of the average particle size embedded in the insulating adhesive, so that the conductive particles are less likely to be detached from the insulating adhesive. preferable. More preferably 1/2 or more, more preferably 2/3 or more, more preferably 4/5 or more, and even more preferably 9 /. 10 or more are embedded. On the other hand, when the conductive particles are completely embedded in the insulating adhesive layer, the thickness of the insulating adhesive between the conductive particles and the surface of the insulating adhesive is determined during pressurization to obtain conductivity. In order to suppress the movement of the conductive particles, it is preferably less than 1.0 times the average particle size of the conductive particles. More preferably, it is less than 0.8 times, more preferably less than 0.5 times, more preferably less than 0.3 times, and still more preferably less than 0.1 times.

  In the present invention, the conductive particles are arranged in a single layer in the insulating adhesive layer in order to secure the conductivity in the thickness direction and the insulation in the plane direction (hereinafter often referred to as anisotropic conductivity) at a high level. . Here, being arranged in a single layer means that the thickness of the adhesive layer in which the conductive particles are present is less than twice the average particle diameter of the conductive particles. Preferably they are 1 time or more and less than 1.8 times, More preferably, they are 1 time or more and less than 1.5 times, More preferably, they are 1 time or more and less than 1.3 times. In the present invention, since the conductive particles are present as a single layer on the surface layer of the insulating adhesive, the connecting electrode has a high height and a substantially flat one such as a connection between a semiconductor chip and a liquid crystal panel. In this connection, it is possible to prevent the arranged conductive particles from largely moving during the connection.

  The anisotropic conductive adhesive film of the present invention has high anisotropic conductivity by arranging conductive particles at a specific center distance and further having a specific coefficient of variation. ing. That is, in the anisotropic conductive adhesive film of the present invention, the average distance between the centers of the conductive particles is 2 μm or more and 20 μm or less, and is 1.5 times or more and 5 times or less of the average particle diameter of the conductive particles. By setting the distance between centers to 2 μm or more and 1.5 times or more the average particle diameter of the conductive particles, the insulation in the plane direction, that is, the insulation between adjacent electrodes can be maintained at a high level. On the other hand, by setting the distance between centers to 20 μm or less and 5 times or less the average particle diameter of the conductive particles, a conductive particle density capable of maintaining the electrical conductivity in the thickness direction, that is, the electrical connectivity between the connection electrodes, is obtained. And exhibits high performance as an anisotropic conductive adhesive film. The average distance between the centers of the conductive particles is preferably 2.5 μm or more and 18 μm or less, more preferably 3 μm or more and 16 μm or less, further preferably 3.5 μm or more and 15 μm or less, and further preferably 4 μm or more and 13 μm or less. The average particle diameter is preferably 1.55 to 4.5 times, more preferably 1.6 to 4 times, and still more preferably 1.65 to 3.5 times. The variation coefficient of the distance between the centers of the conductive particles is a value obtained by dividing the standard deviation of the distance between the centers of the conductive particles by the average value, and is 0.025 or more and 0.5 or less in the present invention. Preferably they are 0.05 or more and 0.45 or less, More preferably, they are 0.07 or more and 0.4 or less, More preferably, they are 0.08 or more and 0.35 or less, More preferably, they are 0.1 or more and 0.3 or less. By setting it to 0.025 or more, stable connection is possible even with a semiconductor chip having a different electrode pattern. On the other hand, by setting it to 0.5 or less, the number of conductive particles captured between connection electrodes is stable. In addition, variations in connection resistance between electrodes are small, and a stable connection can be obtained.

In the anisotropic conductive adhesive of the present invention, for example, the following method is used to arrange the conductive particles as a single layer on the surface layer of the insulating adhesive.
That is, first, an adhesive is applied onto a stretchable film, and conductive particles are densely filled thereon. Next, by removing the conductive particles that do not reach the pressure-sensitive adhesive layer and are on other conductive particles, a single-layer conductive particle layer that is densely packed can be obtained. By stretching the film on which the conductive particle layer obtained here is stretched at a desired stretch ratio, the individual conductive particles are arranged so as to have a desired center-to-center distance with a standard deviation necessary for the present invention. The Next, the anisotropic conductive adhesive film of the present invention is obtained by overlaying the insulating adhesive layer on the side of the stretched film where the conductive particles are arranged and embedding the conductive particles in the insulating adhesive layer. In general, the anisotropic conductive adhesive film is slit to a desired width and wound into a reel.
Examples of the stretchable film include films of polyester such as polyethylene, polypropylene, polystyrene, PET, and PEN, nylon, vinyl chloride, and polyvinyl alcohol. Examples of the adhesive include urethane resin, acrylic resin, urea resin, melamine resin, phenol resin, vinyl acetate, chloroprene and the like. Preferable resin for film includes polypropylene and PET, and preferable adhesive includes acrylic resin-based adhesive.

Stretching is so-called biaxial stretching in which both longitudinal stretching and lateral stretching are performed, and can be performed by a known method. Examples of the method include a method of pulling between two or four sides of the film with a clip or the like, and a method of stretching by changing the rotation speed of the roll while sandwiching between two or more rolls. The stretching may be simultaneous biaxial stretching in which the longitudinal direction and the transverse direction are simultaneously stretched, or sequential biaxial stretching in which the other is stretched after stretching in one direction. Simultaneous biaxial stretching is preferred because it is difficult to cause disorder in the arrangement of the conductive particles during stretching. In order to perform stretching with high accuracy, it is preferable to soften a stretchable film. Depending on the stretchable film used, for example, it is preferable to perform stretching at 70 ° C. or higher and 250 ° C. or lower.
As a method of overlaying the insulating adhesive layer on the side where the conductive particles of the stretched film are arranged and embedding the conductive particles in the insulating adhesive layer, for example, a coating liquid containing an insulating adhesive and a solvent, On the side where the conductive particles of the stretched film are arranged, a method of applying a desired film thickness, a method of scattering and drying the solvent, and a film-like insulating adhesive formed on the separator, Examples include a method of laminating using a laminator or the like on the side of the stretched film where the conductive particles are arranged, and embedding the conductive particles in the insulating adhesive layer using a roller or the like. After peeling the stretched film as necessary, the anisotropic conductive adhesive film of the present invention is slit.

  One important requirement of the present invention is that the insulating adhesive contains insulating fibers. The insulating fiber is preferable because it can increase the strength of the adhesive and can be expected to prevent stress and peeling due to the difference in coefficient of thermal expansion from the substrate. For example, inorganic fibrous materials such as glass, ceramic, aluminum oxide, magnesium oxide, boron nitride, and organic fibrous materials such as polyester, acrylic, polyamide, kevlar, and silicone carbide are examples. Is done. One type of these fibers may be used, or a plurality of types may be used.

The length of the insulating fiber is preferably a fiber having an average fiber length longer than the distance between the electrodes, and the thickness is preferably such that the diameter of the single fiber is smaller than the thickness of the conductive layer.
The insulating fibers are also preferable in a state where each of the insulating fibers is dispersed in the insulating adhesive, and a state where the fibers are intertwined in a network is also preferable.
With respect to the method for producing an insulating adhesive that exists in a state in which such fibers are dispersed or entangled in a network, it may be based on a general method for producing a resin composition. Insulating fibers may be mixed and kneaded with an extruder, etc., or may be sufficiently stirred using an appropriate mixer, or the insulating adhesive may be dissolved after being dissolved in an appropriate solvent. Insulative adhesion in which fibers may be mixed with stirring, or those in which the insulating fibers are intertwined are placed in a formwork and fluidized by heating above the melting point or using a solvent. It can also be produced by a method of pouring the agent.

The content of the insulating fiber is preferably 50% by volume or less, more preferably 45% by volume or less, and still more preferably 40% by volume or less when the insulating adhesive is 100% by volume. The lower limit is generally 0.01% by volume or more in many cases. The content rate at which the effect of relieving internal stress most effectively varies depending on the insulating fiber used, but is often about 30% by volume. If insulating fibers are contained in a proportion exceeding 50% by volume, the effect of relieving internal stress may not be expected, which is not preferable.
Thus, the value of the internal stress reduced by containing the insulating fiber is preferably 10 Mpa or less, more preferably 8 MPa or less, and further preferably 6 MPa or less. The lower the value, the better. Insulating adhesives that incorporate internal stresses exceeding 10 MPa are susceptible to minute cracks during use that is susceptible to thermal history or for long periods of time, and from which moisture and dust can enter, resulting in poor insulation and the same. This is not preferable because it causes problems such as poor communication and dielectric breakdown.

As described in the Examples section, the internal stress is determined by the tensile modulus, linear expansion coefficient, glass transition point after the insulating adhesive is cured under predetermined conditions according to the method described in JIS-K-7162. It is derived as the product of the temperature difference between the temperature and the measured temperature.
As a method for reducing or alleviating the internal stress, a conventionally known method can be used in addition to the method using a fibrous reinforcing agent as already shown, and these methods further enhance the effects of the present invention. For the purpose of increasing, it is also preferable to use it together with a fibrous reinforcing agent.
For example, since internal stress is caused by shrinkage at the time of curing, it is effective to mix a resin that expands at the time of curing. As a resin for that purpose, spiro ortho obtained by reacting bisphenol A type epoxy resin with γ-butyrolactone is effective. Examples thereof include a resin having a spiro structure such as an esterified bisphenol A resin.

In the present invention, the anisotropic conductive adhesive film contains conductive particles in the insulating adhesive, which makes it difficult to measure the internal stress of the insulating adhesive, and the measured values vary and are reproducible. There is a concern that may not be obtained. Therefore, in the present invention, with the same composition as the adhesive film, except for the conductive particles, the internal stress of the film when cured under the same conditions as at the time of connection, the internal stress value of the adhesive film and To do.
As the conductive particles used in the present invention, metal particles, particles composed of carbon, particles obtained by coating a polymer thin film with a metal thin film, and the like can be used.
As the metal particles, for example, a simple substance such as gold, silver, copper, nickel, aluminum, zinc, tin, lead, solder, indium, palladium, etc., or two or more of these metals are combined in a layered or inclined manner. Particles are exemplified. Preferable metal particles include nickel particles and silver / copper inclined particles.

Particles with a polymer core coated with a metal thin film include epoxy resin, styrene resin, silicone resin, acrylic resin, polyolefin resin, melamine resin, benzoguanamine resin, urethane resin, phenol resin, polyester resin, divinylbenzene crosslinked product, NBR , SBR and other polymer core materials combined with one or more polymers, gold, silver, copper, nickel, aluminum, zinc, tin, lead, solder, indium, palladium, etc. The particle | grains which metal-coated by plating etc. in combination of 2 or more types are illustrated. The thickness of the metal thin film is preferably in the range of 0.005 μm to 1 μm from the viewpoint of connection stability and particle cohesion. It is preferable in terms of connection stability that the metal thin film is uniformly coated. Particles obtained by further insulating coating the surfaces of these conductive particles can also be used. Preferred examples include particles in which gold or nickel is coated on a polystyrene resin having a predetermined particle size.
The average particle diameter of the conductive particles has an upper limit of less than 10 μm, preferably less than 8 μm, more preferably less than 6 μm, more preferably less than 5 μm, and a lower limit of 0.5 μm or more, preferably 0.7 μm or more, more preferably 1 μm. More preferably, it is 1.5 μm or more. The standard deviation of the particle size distribution of the conductive particles is preferably 50% or less of the average particle size.

The insulating adhesive used in the present invention contains one or more resins selected from thermosetting resins, thermoplastic resins, photocurable resins, and electron beam curable resins. Examples of these resins include epoxy resins, phenol resins, silicone resins, urethane resins, acrylic resins, polyimide resins, phenoxy resins, polyvinyl butyral resins, SBR, SBS, NBR, polyether sulfone resins, polyether terephthalate resins, polyphenylenes. Sulfide resin, polyamide resin, polyether oxide resin, polyacetal resin, polystyrene resin, polyethylene resin, polyisobutylene resin, alkylphenol resin, styrene butadiene resin, carboxyl modified nitrile resin, polyphenylene ether resin, polycarbonate resin, polyether ketone resin, etc. Of the modified resin. In particular, when adhesiveness with a substrate is required, an epoxy resin is preferably contained.
Examples of the epoxy resin used here include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, tetramethylbisphenol A type epoxy resin, biphenol type epoxy resin, naphthalene type epoxy resin, and fluorene type epoxy. Resin, phenol novolac epoxy resin, cresol novolac epoxy resin, bisphenol A novolac epoxy resin, glycidyl ether epoxy resin such as aliphatic ether epoxy resin, glycidyl ether ester epoxy resin, glycidyl ester epoxy resin, glycidyl amine Type epoxy resin, hydantoin type epoxy resin, alicyclic epoxide, etc., these epoxy resins may be halogenated or hydrogenated Further, it may urethane-modified, rubber-modified, even modified epoxy resins such as silicone-modified.

The anisotropic conductive adhesive film of the present invention is characterized by having an insulating layer on at least one side of the conductive layer.
The insulating layer is made of an insulating adhesive, and the insulating adhesive is appropriately selected from the insulating adhesives for the conductive layer described above.
As a method for producing the insulating layer, the conductive layer may be adhered to at least one side of the conductive layer by a method such as laminating. The conductive layer is formed by arranging conductive particles as a single layer on the surface layer of the insulating adhesive. Therefore, the portion inside the surface layer of the insulating adhesive is an insulating layer, which may be used as the insulating layer.
Further, the conductive layer and the insulating layer may be repeated over several layers, or an intermediate layer made of, for example, a thermoplastic resin may be provided between the conductive layer and the insulating layer. good.
The insulating layer can appropriately contain insulating particles, inorganic fine particles, and the like. Insulating particles are preferable since they can be expected to improve the insulation between adjacent electrodes and adjust the gap of the connecting electrode. For example, for inorganic materials, mica powder, silica or quartz powder, calcium carbonate, alumina, zirconium silicate, oxidation Examples of the material are iron and glass powder, and examples of the organic material include pulp powder, nylon powder, tetron powder, and benzoguanamine particles. The insulating particles are preferably particles whose average particle size is smaller than that of the conductive particles and whose hardness is harder than that of the conductive particles.

Inorganic fine particles are also preferable because they can increase the strength of the insulating layer, and can be expected to prevent the effects of stress and peeling due to the difference in thermal expansion coefficient from the substrate. For example, silica, calcium silicate, calcium carbonate, alumina , Fine particles such as sand, talc, metal powder, and erogen.
In most cases, the anisotropic conductive adhesive film disclosed in the present invention has a protective film. Examples of the protective film include polyethylene, polypropylene, polystyrene, PET, PEN and other polyester, nylon, vinyl chloride, polyvinyl alcohol, and other films. Is exemplified. Preferred resins for the protective film include polypropylene and PET.
The insulating adhesive may be heated at the time of connection, or may be stressed or peeled off due to the difference in thermal conductivity between the insulating adhesive and the substrate. Illustrated. As typical physical properties, for example, when the insulating adhesive has a clear melting point, the melting point is generally preferably 25 ° C. or higher and 250 ° C. or lower, and measured by the method described in JIS-K-6877. strength is generally 0.3 kgf / mm ² or more 10 kgf / mm ² or less is preferable tensile, it is preferable elongation is generally 300% or less than 0%.

As the curing agent for the epoxy resin, a latent curing agent is preferable. As the latent curing agent, curing agents such as boron compounds, hydrazides, tertiary amines, imidazoles, dicyandiamides, inorganic acids, carboxylic acid anhydrides, thiols, isocyanates, boron complex salts and derivatives thereof are preferable. Among latent curing agents, microcapsule type curing agents are preferred. The microcapsule-type curing agent is a material in which the surface of the curing agent is stabilized with a resin film, etc., and the resin film is destroyed by the temperature and pressure during connection work, the curing agent diffuses outside the microcapsule, and the epoxy resin and react. Among the microcapsule type latent curing agents, a latent curing agent obtained by microencapsulating an adduct type curing agent such as an amine adduct or an imidazole adduct is preferable because of excellent balance between stability and curability. Generally these epoxy resin hardening | curing agents are used in the quantity of 2-100 mass parts with respect to 100 mass parts of epoxy resins.
The insulating adhesive used in the present invention is a phenoxy resin, a polyester resin, an acrylic rubber, SBR, NBR, a silicone resin, a polyvinyl butyral resin for the purpose of imparting film formability, adhesiveness, stress relaxation during curing, etc. Polyurethane resin, polyacetal resin, urea resin, xylene resin, polyamide resin, polyimide resin, rubber containing functional groups such as carboxyl group, hydroxyl group, vinyl group, amino group, and polymer components such as elastomers Is preferred. These polymer components preferably have a molecular weight of 10,000 to 10,000,000. The content of the polymer component is preferably 2 to 80% by mass with respect to the insulating adhesive.

The insulating adhesive may further contain a filler, a softener, an accelerator, an anti-aging agent, a colorant, a flame retardant, a thixotropic agent, a coupling agent, and the like. When the filler is contained, the maximum diameter of the filler is preferably less than the average particle size of the conductive particles. As the coupling agent, ketimine group, vinyl group, acrylic group, amino group, epoxy group, and isocyanate group-containing silane coupling agent are preferable from the viewpoint of improving adhesiveness.
When mixing each component of an insulating adhesive, a solvent can be used as needed. Examples of the solvent include methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, ethyl acetate, butyl acetate, ethylene glycol monoalkyl ether acetate, propylene glycol monoalkyl ether acetate, and the like.
The insulating adhesive may have a single composition, or two or more layers of adhesives having different compositions may be laminated. A single composition is preferred because there is no accumulation of internal stress.
The insulating adhesive can be produced, for example, by mixing each component in a solvent, preparing a coating solution, coating the substrate by applicator coating, etc., and evaporating the solvent in an oven.

The thickness of the anisotropic conductive adhesive film of the present invention is preferably 5 μm to 50 μm, more preferably 6 μm to 35 μm, still more preferably 7 μm to 25 μm, and still more preferably 8 μm to 20 μm.
The anisotropic conductive adhesive film may have a protective film. Examples of the protective film include films of polyester such as polyethylene, polypropylene, polystyrene, PET, PEN, nylon, vinyl chloride, and polyvinyl alcohol. Preferred resins for the protective film include polypropylene and PET. The protective film is preferably subjected to surface treatment such as fluorine treatment, Si treatment or alkyd treatment.
The anisotropic conductive adhesive film of the present invention thus produced can be suitably used for fine pitch connection having a line width of 10 μm, and includes a liquid crystal display and TCP, TCP and FPC, FPC and printed wiring board. Or flip chip mounting in which a semiconductor silicon chip is directly mounted on a substrate.

The invention is explained in more detail by means of examples.
<Measurement of internal stress>
Tensile modulus was measured according to ASTM-D638 using a fully automatic plastic tensile bending tester (AGS-J, manufactured by Shimadzu Corporation) at a tensile speed of 5 mm / min and a distance between marked lines of 50.8 mm. did.
The linear expansion coefficient was measured using a quartz tube dilatometer on a test piece having a width of 5 mm, a length of 50 mm, and a thickness of 3 mm in accordance with ASTM-D696.
The glass transition point temperature was measured using a differential thermal analyzer (Shimadzu Corporation DTA-50).
The internal stress was calculated using the following formula.
P = ε × E
ε = Δt × α
Δt = Tg−t
P: Internal stress (MPa)
Tg: Glass transition temperature (° C)
t: Measurement temperature (° C)
α: Linear expansion coefficient (m / m · ° C)
E: Tensile modulus (MPa)

<Thermal shock test>
The thermal shock test (conforming to JIS-C-0025) of -55 ° C to 125 ° C and 1000 cycles was performed and evaluated.
<PCT test>
A PCT test (conforming to JIS-C-0096) at 121 ° C., 2 atm, 200 hours was performed and evaluated.
<Solder heat resistance test>
A 260 ° C. solder bath, 10 second immersion test (based on JIS-C-7021) was performed and evaluated.

[Example 1]
100 parts by mass of phenoxy resin (E1256; manufactured by Japan Epoxy Resin Co., Ltd.), 50 parts by mass of bisphenol A type liquid epoxy resin (manufactured by Asahi Kasei Chemicals Corporation, trade name: AER2603), mixture of microcapsule type latent curing agent and liquid epoxy resin (Made by Asahi Kasei Chemicals Corporation, trade name: Novacure HX-3941HP) 50 parts by mass and 200 parts by mass of ethyl acetate are mixed, and glass fiber (average fiber length: 100 μm, diameter: 2 μm) is further added to 100% by volume of the mixture. Volume% was mixed to obtain an adhesive varnish. The adhesive varnish was applied onto a 50 μm thick PET film separator subjected to a release treatment using a blade coater, and the solvent was removed by drying to obtain a film-like insulating adhesive A having an average film thickness of 20 μm.
The internal stress of the test piece obtained by curing the insulating adhesive A at 190 ° C. for 1 minute was 6 MPa.

An acrylic pressure-sensitive adhesive was applied on a 250 μm-thick unstretched polypropylene film and dried to obtain a film having a 2 μm pressure-sensitive adhesive layer. Ni conductive particles having an average particle diameter of 5 μm were densely arranged on this film, and then the conductive particles that did not reach the pressure-sensitive adhesive layer were removed by air blowing. Next, the film to which the conductive particles were adhered was stretched twice at 150 ° C. at a rate of 3% / second in both longitudinal and lateral directions using a test biaxial stretching apparatus to obtain a film in which the conductive particles were arranged. After laminating the insulating adhesive A attached to the separator on the conductive particle side of the film in which the conductive particles are arranged, the conductive particles are embedded and fixed in the surface layer of the insulating adhesive by using a roller to conduct anisotropic conduction. An adhesive film a was obtained.
As a result of observing the obtained anisotropic conductive adhesive film a with a microscope (manufactured by Keyence Corporation, trade name: VHX-100, the same shall apply hereinafter), the conductive particles are arranged in a single layer on the surface of the insulating adhesive A. The conductive particle portion protruding from the insulating adhesive A was 0.2 μm or less. In addition, from the image obtained with a microscope, using image processing software (trade name: A image-kun, manufactured by Asahi Kasei Co., Ltd., the same shall apply hereinafter), the average value of the distance between the centers of the conductive particles and the standard deviation thereof were obtained. The average value was 9.9 μm, and the standard deviation was 2.1 μm. The distance between the centers of the conductive particles was measured for particles within 0.06 mm ² using the length of the sides of the triangle formed by Deloni triangulation using the center point of each particle.

Next, a bare chip 1 in which gold bumps of 20 μm × 100 μm are arranged at a pitch of 30 μm, a bare chip 2 in which gold bumps of 15 μm × 130 μm are arranged at a pitch of 30 μm, a bare chip 3 in which gold bumps of 16 μm × 125 μm are arranged at a pitch of 25 μm, and A bare chip 4 in which gold bumps of 13 μm × 150 μm are arranged at a pitch of 25 μm and an ITO glass substrate having a connection pitch corresponding to each bare chip are prepared, and the anisotropic conductive adhesive film a is peeled off from the stretched polypropylene film, and the four types After pressure bonding to the ITO glass substrate at 80 ° C., 5 kg / cm ² for 3 seconds and peeling off the separator, the bare chip corresponding to each ITO glass substrate was flip chip bonder (FC2000 manufactured by Toray Engineering Co., Ltd., and so on) ) To align , 200 ° C., 30 kg / cm ² , heat-pressed for 20 seconds, and the bare chip was connected to the ITO glass substrate by pressure bonding. From each bare chip and ITO glass substrate, a daisy chain circuit having 64 joints and a comb-shaped electrode having 20 pairs of combs were formed, and connection resistance measurement and insulation resistance measurement were performed. In all of the circuits composed of four types of bare chips and ITO glass electrodes, the daisy chain circuit is conductive and all connections are made.
This connected product was subjected to a thermal shock test, a PCT test, and a solder heat resistance test, and both conduction and insulation were good.
Furthermore, there was no peeling of the electrode, no lifting of the chip from the substrate, and no peeling from the substrate.

[Example 2]
Except for using 50 parts by mass of bisphenol A type liquid epoxy resin (manufactured by Asahi Kasei Chemicals Corporation, trade name: AER2603) in the same manner as in Example 1 except that 25 parts by mass of spiroorthoesterified bisphenol A type liquid epoxy resin was used. Manufactured.
The internal stress of the test piece obtained by curing the film adhesive obtained from the adhesive varnish at 200 ° C. for 20 seconds was about 2 MPa.
This connected product was subjected to a thermal shock test, a PCT test, and a solder heat resistance test, and both conduction and insulation were good.
Furthermore, there was no peeling of the electrode, no lifting of the chip from the substrate, and no peeling from the substrate.
[Comparative Example 1]
An anisotropic conductive adhesive film was prepared in the same manner as in Example 1 except that the fiber addition amount was 70% by volume, and was evaluated in the same manner as in Example 1.
The insulation was good, but there were places where connection was not possible.
After the solder heat test, peeling of the chip and the substrate was observed, and minute cracks were also observed in the foot portion of the chip.

  The anisotropic conductive adhesive film of the present invention has high connection reliability without causing connection failure, insulation failure, or short-circuiting between electrodes even under severe thermal environment. It can be suitably used in pattern electrical connection applications.

Claims (3)

Conductive particles are arranged as a single layer on the surface layer of the insulating adhesive to form a conductive layer, and an insulating layer made of an insulating adhesive is provided on at least one side of the conductive layer. In the anisotropic conductive adhesive film having conductivity by pressing,
(1) The average distance between the centers of the conductive particles is 2 μm or more and 20 μm or less, and is 1.5 times or more and 5 times or less with respect to the average particle diameter of the conductive particles. 5 or less,
(2) Insulating fibers are contained in the insulating adhesive in a range of 50% by volume or less when the insulating adhesive is 100% by volume,
(3) The internal stress at 25 ° C. after curing the insulating adhesive containing the insulating fiber is 10 MPa or less,
(4) An anisotropic conductive adhesive film, wherein the conductive particles have an average particle size of 1 μm or more and less than 6 μm.   The anisotropic conductive adhesive film according to claim 1, wherein the anisotropic conductive film has a thickness of 5 μm to 50 μm.   The anisotropic conductive adhesive film according to claim 1, wherein the insulating layer contains insulating particles, and the average particle size of the insulating particles is smaller than the average particle size of the conductive particles.