JP2007217503A - Anisotropically electroconductive adhesive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropically electroconductive adhesive film excellent in preservation stability which film, in fine pattern electrical connection, gives excellent electrical connection of small area electrodes, hardly causes dielectric breakdown (short circuit) between fine wirings and can be electrically connected to semiconductor chips having different electrode patterns and give connection with long term reliability. <P>SOLUTION: The anisotropically electroconductive adhesive film comprises a binder resin disposed with electroconductive particles on its surface layer as a single layer, and an insulating adhesive superposed on at least one surface of the binder resin and having lower melt viscosity at 180°C than that of the binder resin, and has electroconductivity when pressured in the thickness direction, wherein the average distance between the centers of the electroconductive particles is ≥2 μm but ≤20 μm and is ≥1.5 times but ≤5 times based on the electroconductive particle diameter and the coefficient of variation thereof is ≥0.1 but ≤0.4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is excellent in electrical connection of electrodes having a small area in electrical connection of fine patterns, and is less likely to cause dielectric breakdown (short circuit) between fine wirings, and can be electrically connected to semiconductor chips having different electrode patterns. The present invention relates to an anisotropic conductive adhesive film having a high storage stability and capable of providing a long-term reliability.

  Anisotropic conductive adhesive film is a film in which conductive particles are dispersed in an insulating adhesive. Connection between liquid crystal display and semiconductor chip or TCP, connection between FPC and TCP, connection between FPC and printed wiring board. For example, it is widely used for connecting a liquid crystal display of a notebook personal computer or a mobile phone and a control IC. Recently, a semiconductor chip is directly connected to a printed circuit board or a flexible wiring board. It is also used for flip chip mounting to be mounted on (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. On the other hand, the width of the miniaturized wirings and electrodes has been increased to a level of a few tens of μm. On the other hand, the average particle size of the conductive particles used so far is the line width of the wirings and electrodes. The particles were at the same level of several μm to 10 μm. Then, when the dimension of the electrode pattern to be connected is reduced, in the anisotropic conductive adhesive film in which conductive particles are randomly dispersed and arranged, there is a deviation in the distribution of the conductive particles. A case where the particles are arranged at positions where no particles exist and are not electrically connected is inevitable as a probability theory.

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 is rapidly increased and secondary aggregation is likely to occur. 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, the smaller the conductive particle size, the longer the long-term connection reliability, depending on the insulating adhesive used, such as low insulation resistance, high connection resistance, or short-circuit between adjacent electrodes. It has been found that there are many cases in which the decrease in the number of cases, and countermeasures have also been required.

  On the other hand, as a technique corresponding to the connection of fine patterns, a technique for arranging particles has been proposed. For example, a method in which charged conductive particles are dispersed on the surface of an insulating adhesive and the conductive particles attached to the surface are embedded in the surface layer of the insulating adhesive (Patent Document 5), or suction holes arranged in a predetermined manner are provided. A method of arranging conductive particles and embedding them in an insulating adhesive using a conductive particle adsorption jig (Patent Document 6), A method of arranging conductive particles using stretching and embedding them in an insulating adhesive (Patent Document 7) However, in order to connect the conductive particles arranged at an angle against the flow of the insulating resin at the time of connection without greatly destroying the arrangement state, usable electrodes and connection conditions are limited. This is a major limitation in practical use. On the other hand, attempts are made to cope with the connection of fine patterns by suppressing the flow of conductive particles at the time of connection. For example, a technique comprising an insulating layer having high fluidity and an anisotropic conductive layer having low fluidity has been proposed. (Patent Documents 8 and 9), however, the actual condition is that the arrangement of the original conductive particles is low, so that it cannot cope with connection of very fine electrode patterns. On the other hand, when the arrangement is very high, the electrode pattern that matches the arrangement pitch of the conductive particles shows high connectivity, but the electrode pattern to be connected does not match the arrangement pattern of the conductive particles As a result, connection reliability is inferior. That is, in order to connect a plurality of semiconductor chips having different electrode patterns, it is necessary to use different kinds of anisotropic conductive adhesive films, which has a problem in productivity.

Japanese Patent Laid-Open No. 03-107888 Japanese Patent Laid-Open No. 04-366630 JP-A 61-195179 Japanese Patent Laid-Open No. 09-312176 JP 2000-151084 A JP 2002-332461 A International Application PCT / JP2004 / 017944 Japanese Patent Laid-Open No. 63-310581 JP 2000-178511 A

  The present invention is excellent in electrical connection of electrodes having a small area in electrical connection of fine patterns, and is less likely to cause dielectric breakdown (short circuit) between fine wirings, and can be electrically connected to semiconductor chips having different electrode patterns. It is an object of the present invention to provide an anisotropic conductive adhesive film having a high storage stability and capable of providing a long-term reliability.

As a result of intensive studies to solve the above problems, the present inventors have determined that a specific layer in which conductive particles are arranged in a single layer on the surface layer so that the interparticle distance has a specific average value and a specific coefficient of variation. It has been found that an anisotropic conductive adhesive film comprising a binder resin and a specific insulating adhesive having a lower melt viscosity can meet the above-mentioned purpose.
From the above technical disclosure performed prior to the filing of the present application in order to solve the above problems, the above problems could be solved by simply controlling the arrangement of the conductive particles and embedding them in a binder resin having a high melt viscosity. This means that Patent Document 5 where the probabilistic problem remains inherent and jigs that are enormous and continue to increase in number must be prepared, and there is a limit to improving the productivity of the electrical connection process. In view of the technical disclosure of Patent Document 6, there was a surprising discovery that could not be anticipated by those skilled in the art.

That is, the present invention is as follows.
1) A binder resin in which conductive particles are arranged in a single layer on the surface layer, and an insulating adhesive that is laminated on at least one side of the binder resin and has a melt viscosity of 180 ° C. lower than that of the binder resin. In the anisotropic conductive adhesive film having conductivity by pressing, the average distance between the centers of the conductive particles is 2 μm or more and 20 μm or less, and 1.5 times or more and 5 times or less with respect to the average particle diameter of the conductive particles An anisotropic conductive adhesive film whose coefficient of variation is 0.1 or more and less than 0.4.
2) The anisotropic conductive adhesive film according to 1) above, wherein the binder resin has a melt viscosity at 180 ° C. of 50 Pa · s or more.
3) The anisotropic conductive adhesive film as described in 1) or 2) above, wherein the insulating adhesive is a thermosetting epoxy resin adhesive using a latent curing agent.
4) The anisotropic conductive adhesive film according to any one of 1) to 3), wherein the conductive particles have an average particle size of 0.5 μm or more and less than 10 μm.
5) The above 1 characterized in that after stretching a stretchable sheet in which conductive particles are fixed in a single layer by an adhesive, a binder resin is laminated on the conductive particle side and laminated, and the conductive particles are embedded in the binder resin. The manufacturing method of the anisotropically conductive adhesive film in any one of -5).

  The anisotropic conductive adhesive film of the present invention has high storage stability, excellent electrical connectivity of electrodes with a small area, and is less prone to dielectric breakdown (short) between fine wirings, and has a fine pitch connectivity. In addition to being excellent, there is no need to change the anisotropic conductive adhesive film for each semiconductor chip having a different electrode pattern, and the productivity is excellent, and there is an effect of enabling connection that gives long-term reliability.

The present invention will be specifically described below.
The present invention relates to an anisotropic conductive adhesive film having conductivity by applying pressure in the thickness direction.
In the anisotropic conductive adhesive film of the present invention, a binder resin in which conductive particles are arranged in a single layer on the surface layer is one of the constituent elements.

  Here, disposing in the surface layer means a state in which part or all of the conductive particles are embedded in the surface of the binder. Alternatively, the binder resin may be thinner than the particle size of the conductive particles, and the conductive particles may be exposed above and below the binder resin. When a part of the conductive particles are embedded, the conductive particles are embedded in the binder resin with 1/3 or more of the average particle size, and it is difficult for the conductive particles to be detached from the binder resin, resulting in poor connection. There is an effect of suppressing, which is preferable. More preferably, ½ or more are embedded, and more preferably 2/3 or more are embedded. On the other hand, when the conductive particles are completely embedded in the binder resin, the thickness of the binder resin between the conductive particles and the surface of the binder resin is to suppress the movement of the conductive particles during pressurization for connection. The average particle size of the conductive particles is preferably less than 1.0 times. 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 on the binder resin in order to ensure 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 variation in the center height of the conductive particles is less than twice the average particle size of the conductive particles. The variation in the center height with respect to the average particle diameter of the conductive particles is preferably close to 0, preferably less than 1 time, more preferably less than 0.8 time, and further preferably less than 0.6 time. Here, the variation in the center height of the conductive particles is a standard deviation of the distance from the binder resin surface to the center of the conductive particles. When the center of the conductive particles is not embedded in the binder resin, the center height is This is the value minus the distance.

  In the present invention, since the conductive particles exist as a single layer on the surface layer of the binder resin, in particular, the connection between a high connection height and a substantially flat connection, such as a connection between a semiconductor chip and a liquid crystal panel. In this case, it is possible to prevent the arranged conductive particles from largely moving at the time of connection.

  The anisotropic conductive adhesive film of the present invention has high anisotropic conductivity because the conductive particles are arranged with a specific center distance, and the center distance is arranged with a specific coefficient of variation. Yes. That is, the anisotropic conductive adhesive film of the present invention has an average distance between the centers of the conductive particles of 2 μm or more and 20 μm or less, and 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 surface 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. Preferably it is 1.55 times or more and 4.6 times or less with respect to the average particle diameter of particle | grains, More preferably, they are 1.6 times or more and 4.3 times or less, More preferably, they are 1.65 times or more and 4.0 or less. . 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 0.1 or more and less than 0.4 in the present invention. Preferably they are 0.11 or more and less than 0.36, More preferably, they are 0.12 or more and less than 0.34, More preferably, they are 0.13 or more and less than 0.32, More preferably, they are 0.14 or more and less than 0.3. By setting the coefficient of variation to 0.1 or more, it is possible to stably connect semiconductor chips having different electrode patterns without causing flow of conductive particles during connection that adversely affects the electrical connectivity between connection electrodes. On the other hand, by setting it to less than 0.4, the variation in the number of conductive particles trapped between the connection electrodes can be kept small, and the variation in connection resistance between the electrodes is small, so that a stable connection is obtained. It is done.

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.

  Particles in which a polymer thin film is coated on a polymer core material 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.

  The average particle diameter of the conductive particles is preferably in the range of 0.5 μm or more and less than 10 μm from the viewpoint of particle aggregation and anisotropic conductivity. More preferably, they are 1.0 micrometer or more and less than 7 micrometers, More preferably, they are 1.5 micrometers or more and less than 6 micrometers, More preferably, they are 2.0 micrometers or more and less than 5.5 micrometers, More preferably, they are 2.5 micrometers or more and less than 5.0 micrometers. The standard deviation of the particle diameter of the conductive particles is preferably as small as possible, and is preferably 50% or less of the average particle diameter. More preferably, it is 20% or less, more preferably 10 or less, and still more preferably 5% or less.

  The binder resin used in the present invention contains one or more kinds of 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 long-term reliability after connection is required, it is preferable to contain an epoxy resin.
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.

  When an epoxy resin is contained in the binder resin, it is preferable to contain an epoxy resin curing agent. The curing agent for the epoxy resin is preferably a latent curing agent from the viewpoint of storage stability. 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 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 0-100 mass parts with respect to 100 mass parts of epoxy resins.

The binder resin used in the present invention has low fluidity characteristics under connection conditions in order to prevent the conductive particles from moving at the time of connection and reducing the number of conductive particles captured between the connection electrodes. In view of long-term connection reliability, it is preferable to contain a phenoxy resin.
Examples of the phenoxy resin used herein include bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, bisphenol A bisphenol F mixed type phenoxy resin, bisphenol A bisphenol S mixed type phenoxy resin, fluorene ring-containing phenoxy resin, and caprolactone-modified bisphenol A type. Examples include phenoxy resin.

The weight average molecular weight of the phenoxy resin is preferably 20,000 or more and less than 100,000.
As the binder resin used in the present invention, it is preferable to use a phenoxy resin and an epoxy resin in combination, and in this case, the amount of the phenoxy resin used is preferably 50% by mass or more based on the entire binder resin. More preferably, it is 55 mass% or more and less than 95 mass%, More preferably, it is 60 mass% or more and less than 90 mass%.
The binder resin can further contain insulating particles, fillers, softeners, accelerators, anti-aging agents, colorants, flame retardants, thixotropic agents, coupling agents, and the like. When the insulating particles and the filler are contained, the maximum diameter is preferably less than the average particle diameter 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 binder resin, 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 binder resin can be produced, for example, by mixing each component in a solvent, creating a coating liquid, coating the substrate by applicator coating, etc., and evaporating the solvent in an oven.
Since the binder resin has a function of suppressing the flow of the conductive particles at the time of connection, the fluidity needs to be low under the connection conditions, and the melt viscosity at 180 ° C. is preferably 50 Pa · s or more. More preferably, it is 65 Pa · s or more and less than 20,000 Pa · s, and more preferably 80 Pa · s or more and less than 10,000 Pa · s. If the melt viscosity becomes too high, a high temperature is required when embedding the conductive particles in the binder layer, and the manufacturing difficulty level increases.

Here, when the binder resin is a thermosetting resin, the melt viscosity indicates a melt viscosity obtained by removing the curing agent from the binder resin or in a state where the curing agent is not blended.
The film thickness of the binder resin is preferably equal to or less than the average particle diameter of the conductive particles. Preferably, it is 10% or more and less than 200%, more preferably 20% or more and less than 170%, more preferably 25% or more and less than 140% of the average particle diameter of the conductive particles.
The thickness of the binder resin is preferably less than the average particle size of the conductive particles because it is easy to obtain a low connection resistance. In that case, the conductive particles are exposed above and below the film to obtain a low connection resistance. And more preferable.

In the anisotropic conductive adhesive film of the present invention, an insulating adhesive is laminated on at least one surface of a binder resin in which conductive particles are arranged.
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 long-term reliability after connection is required, it is preferable to contain an epoxy resin.
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.

  When an epoxy resin is contained in the insulating adhesive, it is preferable to contain a curing agent for the epoxy resin. As the curing agent for the epoxy resin, a latent curing agent is preferable from the viewpoint of storage stability. 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 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 1,000,000. The content of the polymer component is preferably 2 to 80% by mass with respect to the entire insulating adhesive.

These polymer components are preferably phenoxy resins from the viewpoint of long-term connection reliability.
Examples of the phenoxy resin used herein include bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, bisphenol A bisphenol F mixed type phenoxy resin, bisphenol A bisphenol S mixed type phenoxy resin, fluorene ring-containing phenoxy resin, and caprolactone-modified bisphenol A type. Examples include phenoxy resin.
The weight average molecular weight of the phenoxy resin used here is preferably 20,000 or more and less than 100,000.
As the insulating adhesive used in the present invention, a thermosetting epoxy resin adhesive containing an epoxy resin and a latent curing agent having high storage stability and high connection reliability is preferable. An epoxy resin-based adhesive containing a phenoxy resin is more preferable. In that case, the amount of the phenoxy resin used is preferably less than 50% by mass with respect to the entire insulating adhesive. More preferably, they are 20 mass% or more and less than 46 mass%, More preferably, they are 30 mass% or more and less than 44 mass%.

The insulating adhesive may further contain insulating particles, fillers, softeners, accelerators, anti-aging agents, colorants, flame retardants, thixotropic agents, coupling agents and the like. When the insulating particles and the filler are contained, the maximum diameter is preferably less than the average particle diameter of the conductive particles. Furthermore, the conductive particles may contain, for example, for the purpose of preventing charging, as long as the insulating adhesive does not impair the insulating properties.
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 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.
Since the insulating adhesive has a function of flowing at the time of connection and sealing the connection region, it needs to have high fluidity under the connection conditions. For the high fluidity, the relative value with the fluidity of the binder resin is important, and the melt viscosity at 180 ° C. needs to be lower than that of the binder resin. Preferably, it is less than 50% of the binder resin viscosity, more preferably less than 25%, more preferably less than 15%, and even more preferably less than 10%.
A preferable range of the melt viscosity at 180 ° C. of the insulating adhesive is 1 Pa · s or more and less than 100 Pa · s. More preferably, it is 2 Pa · s or more and less than 50 Pa · s, and more preferably 4 Pa · s or more and less than 30 Pa · s. If the melt viscosity is too high, a high pressure is required at the time of connection. On the other hand, if the melt viscosity is low, it is necessary to store at a low temperature in order to suppress deformation before use.

Here, when the insulating adhesive is a thermosetting resin, the melt viscosity refers to the melt viscosity obtained by removing the curing agent from the insulating adhesive or in the state where the curing agent is not blended.
The insulating adhesive may be formed only on one side of the binder resin, or may be formed on both sides. In order to improve the temporary sticking property of the anisotropic conductive adhesive film, it is preferable to form it on both sides.
When laminating the insulating adhesive on both surfaces of the binder resin, the insulating adhesive on each surface may be the same or different. While different ones can be formulated according to the connected member, it is necessary to prepare two types of formulations.

  When the insulating adhesive is formed on both sides of the binder resin, it is preferable that the conductive particles do not enter the inside from the surface on one side of the anisotropic conductive adhesive film in order to suppress the movement of the conductive particles due to the pressure at the time of connection. The center position of the conductive particles is preferably located less than 2.0 times the average particle diameter of the conductive particles from the surface on one side of the anisotropic conductive adhesive film. More preferably, it is less than 1.5 times, More preferably, it is less than 1.0 time, More preferably, it is less than 0.8 time. On the other hand, when it is less than 0.5 times, the conductive particles are exposed from the anisotropic conductive adhesive film, and when the goodness of exposure increases, the temporary sticking property of the anisotropic conductive adhesive film decreases, 0.1 times or more is preferable because it may cause loss of particles. More preferably, it is 0.2 times or more, and more preferably 0.3 times or more.

The total thickness of the insulating adhesive is preferably 4 μm or more and less than 50 μm. More preferably, they are 5 micrometers or more and less than 30 micrometers, More preferably, they are 6 micrometers or more and less than 25 micrometers, More preferably, they are 7 micrometers or more and less than 22 micrometers.
The total film thickness of the insulating adhesive is preferably 2 to 100 times the film thickness of the binder resin, more preferably 3 to 75 times, more preferably 4 to 50 times, and still more preferably. Is 5 times or more and 30 times or less.
The thickness of the anisotropic conductive adhesive film of the present invention is preferably 5 μm or more and 50 μm or less, more preferably 6 μm or more and 35 μm or less, further preferably 7 μm or more and 25 μm or less, and further preferably 8 μm or more and 22 μm or less.

  The anisotropic conductive adhesive film of the present invention may be formed on a release sheet. Examples of the release sheet include films such as polyesters such as polyethylene, polypropylene, polystyrene, PET, and PEN, nylon, vinyl chloride, and polyvinyl alcohol. Preferred resins for the release sheet include polypropylene and PET. The release sheet is preferably subjected to surface treatment such as fluorine treatment, silicone treatment or alkyd treatment.

The anisotropic conductive adhesive film of the present invention is produced, for example, by the following method.
That is, first, a conductive particle array sheet in which conductive particles arranged in a single layer are fixed on a sheet with an adhesive is manufactured. In order to manufacture the array sheet, for example, an adhesive is preferably applied on a stretchable sheet so that the film thickness is equal to or less than the average particle diameter of the conductive particles, and the conductive particles are filled thereon. Thereafter, the conductive particles that have not reached the pressure-sensitive adhesive layer are removed by air blowing or the like, thereby forming a single conductive particle layer in which the conductive particles are densely packed. If necessary, the conductive particles arranged in a single layer are embedded in the adhesive. The filling rate defined by the ratio of the projected area of the conductive particles to the total area at this time is preferably 60% or more and 90% or less. More preferably, they are 65% or more and 88% or less, More preferably, they are 68% or more and 85% or less. The filling factor greatly affects the coefficient of variation of the distance between the centers of the conductive particles, which is an important factor in the present invention.

Next, the sheet on which the conductive particles are fixed is drawn at a desired draw ratio so that each conductive particle has a desired center-to-center distance with a coefficient of variation necessary for the present invention. As a result, an array sheet of conductive particles arranged on the substrate is obtained.
Examples of the stretchable sheet include sheets 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.

  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 stretched simultaneously, or may be 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 sheet used, for example, it is preferable to perform stretching at 70 ° C. or more and less than 250 ° C. More preferably, it is 75 degreeC or more and less than 200 degreeC, More preferably, it is 80 degreeC or more and less than 160 degreeC, More preferably, it is 85 degreeC or more and less than 145 degreeC. If the stretching temperature is too high, the adhesive force of the pressure-sensitive adhesive is reduced, the arrangement of the conductive particles is disturbed, and the coefficient of variation in the distance between the centers of the conductive particles is increased.

Next, a binder resin is stacked on the conductive particle side of the array sheet, and the conductive particles are embedded in the binder resin. Examples of the embedding method include a method in which a film-like binder resin is laminated on the conductive particle side of the array sheet and laminated, and the conductive particles are embedded using a heat roll or the like.
The binder resin may be bonded with an insulating adhesive on the surface opposite to the surface on which the conductive particles are embedded, or after the conductive particles are embedded on the surface of the binder resin opposite to the surface on which the conductive particles are embedded. An insulating adhesive may be bonded together with a laminate or the like.
The stretchable sheet and the adhesive of the array sheet are peeled from the conductive particles embedded in the binder. If necessary, another insulating adhesive is laminated on the surface of the binder resin in which the conductive particles are embedded.

In the present invention, the conductive particles are preferably embedded at a temperature as low as possible. In particular, in the case where the binder resin or the insulating adhesive is a thermosetting resin containing a latent curing agent, when it is embedded at a high temperature, low temperature storage is required to suppress the progress of the curing reaction. However, if the temperature is low, embedding becomes difficult because the viscosity of the binder resin is high.
The embedding temperature of the conductive particles is preferably 35 ° C. or higher and 120 ° C. or lower. More preferably, it is 40 degreeC or more and 100 degrees C or less, More preferably, it is 45 degreeC or more and 80 degrees C or less.

When embedding the conductive particles in the binder resin, after peeling the stretchable sheet and the adhesive from the binder resin in which the conductive particles are embedded, the film having a high elastic modulus is stacked on the conductive particle side, and further using a heat roll or the like. It is preferable to embed the conductive particles in the binder resin. Examples of the film having a high elastic modulus include an aramid film.
When the conductive particles are not sufficiently embedded in the binder resin, the conductive particles are missing from the binder resin before use, causing connection failure.

The anisotropic conductive adhesive film of the present invention is obtained by the above method and the like. Generally, an anisotropic conductive adhesive film is slit to a desired width and wound up in a reel shape.
The anisotropic conductive adhesive film of the present invention thus produced can be suitably used for fine pitch connection with a line width of a few tens of μm class, and includes a liquid crystal display and TCP, TCP and FPC, and FPC and print. It can be suitably used for connection to a wiring substrate 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.
a. Melt viscosity measurement It measured at 180 degreeC using 20mm diameter cone (PP20H) using the product made from HAAKE, RHeoStress600 Thermo.

[Example 1]
100 parts by mass of phenoxy resin (InChem, trade name: PKHC, weight average molecular weight 43000), 50 parts by mass of bisphenol A type liquid epoxy resin (trade name: AER2603, manufactured by Asahi Kasei Chemicals), microcapsule type latent curing agent 15 parts by mass (a product name: NovaCure, manufactured by Asahi Kasei Chemicals Co., Ltd.) and a silane coupling agent (product name: A-187, manufactured by Nihon Unicar Company) 25 parts by mass and 300 parts by mass of ethyl acetate were mixed to obtain a binder varnish. The binder varnish was applied onto a release sheet made of 50 μm PET film using a blade coater, and the solvent was removed by drying to obtain a film-like binder resin A having a thickness of 4 μm. Separately, instead of 15 parts by mass of the mixture of the microcapsule type latent curing agent and the liquid epoxy resin, the melt viscosity of the binder resin similarly prepared by blending 10 parts by mass of the liquid epoxy resin was measured, and the binder resin A was melted at 180 ° C. The viscosity was 78.4 Pa · s.

  100 parts by mass of phenoxy resin (InChem, trade name: PKHC, weight average molecular weight 43000), 90 parts by mass of bisphenol A type liquid epoxy resin (trade name: AER2603, manufactured by Asahi Kasei Chemicals), microcapsule type latent curing agent 60 parts by mass (a product name: Novacure, manufactured by Asahi Kasei Chemicals Co., Ltd.) and a silane coupling agent (product name: A-187, manufactured by Nihon Unicar Co., Ltd.) 25 parts by mass and 200 parts by mass of ethyl acetate were mixed to obtain an adhesive varnish. The adhesive varnish was applied onto a release sheet made of 50 μm PET film using a blade coater, and the solvent was removed by drying to obtain a film-like insulating adhesive A having a film thickness of 15 μm. Separately, instead of 60 parts by mass of a mixture of a microcapsule type latent curing agent and a liquid epoxy resin, 40 parts by mass of a liquid epoxy resin was blended, and the melt viscosity of an insulating adhesive similarly prepared was measured. The 180 ° C. melt viscosity was 11.6 Pa · s.

  An acrylic polymer diluted with ethyl acetate to a resin content of 5% by mass using a blade coater was applied onto a 100 μm unstretched copolymerized polypropylene film and dried at 80 ° C. for 10 minutes to form an adhesive layer having a thickness of 2 μm. The acrylic polymer used here was 62 parts by mass of methyl acrylate, 30.6 parts by mass of 2-ethylhexyl acrylate, and 7 parts by mass of 2-hydroxyethyl acrylate in 233 parts by mass of ethyl acetate. The weight average molecular weight obtained by polymerizing 0.2 parts by mass of nitrile at 65 ° C. for 8 hours in a nitrogen gas stream is 950,000. The weight average molecular weight was measured by gel permeation chromatography (GPC).

On this pressure-sensitive adhesive, conductive particles having an average particle diameter of 3 μm were filled on one side, and conductive particles that did not reach the pressure-sensitive adhesive were eliminated by air blowing. As a result, a single-layer conductive particle layer having a filling rate of 70% was formed. Here, the conductive particles have a core of divinylbenzene resin, a nickel layer of 0.07 μm is formed on the surface layer by electroless plating, and a gold layer of 0.04 μm is further formed by electroplating. The one with a ratio of 0.95 and a standard deviation of particle diameter of 0.2 μm was used.
Next, the conductive film is fixed to the polypropylene film with the adhesive by using a test biaxial stretching apparatus, and stretched to 3.8 times at 135 ° C. at a rate of 10% / second in both length and width. The array sheet A was obtained by cooling to room temperature.

  The binder resin A was stacked on the conductive particle side of the array sheet A, and lamination was performed at 55 ° C. and 0.3 MPa. Furthermore, after peeling off the release sheet laminated on the binder resin, the insulating adhesive A was overlapped on the surface of the binder resin opposite to the surface where the conductive particles were embedded, and lamination was performed under the same conditions. Next, the polypropylene film and the adhesive of the array sheet A were peeled from the binder resin surface in which the conductive particles were embedded. When a part of the sample was sampled and the embedding depth of the conductive particles was observed using a laser microscope (manufactured by Keyence Corporation, trade name VK-9500, the same applies hereinafter), the conductive particles were exposed from the 2.25 μm binder resin. In the middle of handling, the absence of particles was observed.

  Next, a film obtained by treating a 16 μm aramid film (manufactured by Teijin Ltd., trade name: Aramika, elastic modulus: 15 Gpa) with a release agent on the binder resin surface in which the conductive particles are embedded is superposed at 60 ° C. and 1.0 MPa. After embedding the conductive particles with a heat roll under the conditions, the aramid film was peeled off to obtain an anisotropic conductive adhesive film A.

When the embedding depth of the conductive particles of the obtained anisotropic conductive adhesive film A was measured, the exposure from the binder resin was an average of 0.1 μm, and the embedding depth was 97% of the average particle diameter of the conductive particles. It was equivalent. Further, the variation in the center height of the conductive particles calculated from the exposure amount was less than 0.5 μm. Furthermore, as a result of observing the anisotropic conductive adhesive A with a microscope (manufactured by Keyence Corporation, trade name: VHX-100, the same shall apply hereinafter), conductive particles are arranged in a single layer on the surface layer of the binder resin A. From the image obtained with the microscope, using image processing software (trade name: A image kun, manufactured by Asahi Kasei Co., Ltd., the same applies hereinafter), the average value of the center-to-center distance of the conductive particles and the coefficient of variation thereof were determined. The average value was 11.9 μm and the coefficient of variation was 0.34. As the distance between the centers of the conductive particles, the length of a side of a triangle formed by Deloni triangulation using the center point of each particle was used, and the observation of the conductive particles was performed for particles within 0.06 mm ² .

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 × 100 μm are arranged at a pitch of 30 μm, and a bare chip 3 in which gold bumps of 13 μm × 150 μm are arranged at a pitch of 25 μm. An ITO glass substrate having a connection pitch corresponding to a bare chip is prepared, and an anisotropic conductive adhesive film A is thermocompression bonded to three kinds of ITO glass substrates at 70 ° C., 5 kg / cm ² for 2 seconds, and a release sheet After peeling off, the bare chip corresponding to each ITO glass substrate was aligned using a flip chip bonder (FC2000 manufactured by Toray Engineering Co., Ltd., the same applies hereinafter), and reached 180 ° C. after 2 seconds with constant heat, and then Heating and pressing at 30 Kg / cm ² for 20 seconds under the condition of a constant temperature, The tip was connected to an ITO glass substrate.

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 consisting of the three types of bare chips and ITO glass electrodes, the daisy chain circuit was turned on, indicating that all connections were made. On the other hand, the insulation resistance of the comb electrode was 10 ⁹ Ω or more, and no short circuit occurred between adjacent electrodes. Furthermore, using the anisotropic conductive adhesive film A stored at 5 ° C. for 6 months, the bare chip 1 and the ITO glass substrate were connected in the same manner as described above.

[Example 2]
100 parts by mass of phenoxy resin (InChem, product name: PKHC, weight average molecular weight 43000), 35 parts by mass of bisphenol A type liquid epoxy resin (Asahi Kasei Chemicals Co., Ltd., product name: AER2603), and 300 parts by mass of ethyl acetate are mixed. And a binder varnish was obtained. The binder varnish was applied onto a release sheet made of 50 μm PET film using a blade coater, and the solvent was removed by drying to obtain a film-like binder resin B having a film thickness of 1.5 μm. As a result of measuring the 180 ° C. melt viscosity of the binder resin B, it was 280 Pa · s.

A film in which only the film thickness of the insulating adhesive used in Example 1 was changed was formed on a 50 μm PET film release sheet to obtain an insulating adhesive B having a film thickness of 1 μm.
An array sheet was prepared in the same manner as in Example 1 except that the conductive particle filling rate was 82% and the draw ratio was 2.5 times, and an array sheet B was obtained.

  The binder resin B and the insulating adhesive A were laminated at 50 ° C. and 0.1 MPa, and the release sheet on the binder resin B side was peeled off. Next, the conductive particle side of the array sheet B was overlaid on the binder resin B, and lamination was performed under the conditions of 55 ° C. and 0.3 Mpa. Next, a film obtained by treating a 16 μm aramid film (manufactured by Teijin Ltd., trade name: Aramika, elastic modulus: 15 Gpa) with a release agent on the binder resin surface in which the conductive particles are embedded is superposed at 60 ° C. and 1.0 MPa. After conducting the conductive particle embedding with a heat roll under the conditions, the aramid film was peeled off and the conductive particle embedding depth was measured in the same manner as in Example 1. As a result, the exposure from the binder resin was 0.8 μm, It was found that the particles passed through the binder resin and partly reached the insulating adhesive layer. Further, the variation in the center height of the conductive particles calculated from the exposure amount was less than 0.5 μm. Furthermore, the insulating adhesive B was laminated on the side where the conductive particles were exposed, and was laminated under the conditions of 55 ° C. and 0.3 Mpa to obtain an anisotropic conductive adhesive film B.

When the appearance of the obtained anisotropic conductive adhesive film B was observed in the same manner as in Example 1, the conductive particles were not exposed from the binder resin, the conductive particles were arranged in a single layer, and the distance between the centers of the conductive particles. The average value was 8.3 μm and the coefficient of variation was 0.17.
Next, in the same manner as in Example 1, three types of bare chips and ITO glass connection were performed using the anisotropic conductive adhesive film B, and the connection resistance measurement and the insulation resistance measurement were performed in the same manner as in Example 1. As a result, the connection of any bare chip and ITO glass showed that the daisy chain circuit was conductive and all connections were made. Moreover, the conduction resistance (including wiring resistance) was lower than that of Example 1. On the other hand, the insulation resistance of the comb electrode was 10 ⁹ Ω or more, and no short circuit occurred between adjacent electrodes.

[Comparative Example 1]
An anisotropic conductive adhesive film was obtained in the same manner as in Example 1 except that the packing density of the conductive particles on the unstretched copolymerized polypropylene film coated with the pressure-sensitive adhesive was lowered. As a result of observation and measurement of the distance between the centers of the conductive particles, the conductive particles were exposed to 0.1 μm from the binder resin and arranged in a single layer, and the average value of the distance between the centers of the conductive particles was 12.6 μm, The coefficient of variation was 0.48. Furthermore, connection resistance measurement and insulation resistance measurement were performed in the same manner as in Example 1. As a result, no current flowed through any daisy chain circuit, and connection failure was observed. Further, the insulation resistance between the bare chip 3 and the comb-shaped electrode made of ITO glass was less than 10 ⁸ Ω, occurrence of short circuit was observed, and it was not suitable for fine pitch use.

[Comparative Example 2]
An anisotropic conductive adhesive film was obtained in the same manner as in Example 1 except that the filling rate of the conductive particles on the unstretched copolymerized polypropylene film coated with the pressure-sensitive adhesive was increased. As a result of measuring the distance between the centers of the conductive particles, the conductive particles are exposed by 0.1 μm from the binder resin and arranged in a single layer, and the average distance between the centers of the conductive particles is 11.7 μm, The coefficient of variation was 0.06. Further, the connection resistance measurement and the insulation resistance measurement were performed in the same manner as in Example 1. As a result, there was no problem in the insulation resistance measurement value, but the daisy chain circuit made of the bare chip 3 and ITO glass did not flow current. A poor connection was observed. In the anisotropic conductive adhesive film used in Comparative Example 2, the coefficient of variation in the distance between the centers of the conductive particles is too small. Therefore, in the circuit using the electrode width close to the average value of the distance between the centers of the conductive particles, the conductive particles There was a connection part that did not intervene, causing problems due to poor connection.

[Comparative Example 3]
The insulating adhesive A was stacked on the conductive particle side of the array sheet A prepared in Example 1, and lamination was performed at 55 ° C. and 0.3 MPa. Thereafter, the conductive particles were embedded in an insulating adhesive in the same manner as in Example 1 in which the conductive particles were embedded in the binder resin, and an anisotropic conductive adhesive film was obtained. As a result of measuring the distance between the centers of the conductive particles, the conductive particles are not exposed from the insulating adhesive, and are disposed as a single layer on the surface layer, and the average distance between the centers of the conductive particles is 11.9 μm. The coefficient of variation was 0.36. Further, as a result of conducting the connection resistance measurement and the insulation resistance measurement in the same manner as in Example 1, the daisy chain circuit composed of the bare chip 2 and the ITO glass was observed to have poor connection because no current flowed, and from the bare chip 3 and the ITO glass. The insulation resistance between the comb electrodes was less than 10 ⁸ Ω, and occurrence of short circuit was observed.

  Since the anisotropic conductive adhesive film used in Comparative Example 3 does not contain a binder resin, the conductive particles move at the time of connection, and a connection portion without conductive particles is formed, resulting in poor connection. On the other hand, there may be a case where conductive particles stay between the electrodes and cause dielectric breakdown.

  The anisotropic conductive adhesive film of the present invention has high storage stability, excellent electrical connectivity of electrodes with a small area, and is less prone to dielectric breakdown (short) between fine wirings, and has a fine pitch connectivity. In addition to being excellent, it is not necessary to change the anisotropic conductive adhesive film for each semiconductor chip having a different electrode pattern, so that the productivity is excellent, the connection stability can be maintained for a long time, and it can be suitably used in the electrical connection application of a fine pattern.

Claims (5)

  It consists of a binder resin in which conductive particles are arranged in a single layer on the surface layer, and an insulating adhesive that is laminated on at least one side of the binder resin and has a melt viscosity of 180 ° C. lower than that of the binder resin, and pressurizes in the thickness direction. In the anisotropic conductive adhesive film having electrical conductivity, the average distance between the centers of the conductive particles is 2 μm or more and 20 μm or less, and the average particle diameter of the conductive particles is 1.5 times or more and 5 times or less, An anisotropic conductive adhesive film having a coefficient of variation of 0.1 or more and less than 0.4.   The anisotropic conductive adhesive film according to claim 1, wherein the binder resin has a melt viscosity at 180 ° C. of 50 Pa · s or more.   The anisotropic conductive adhesive film according to claim 1 or 2, wherein the insulating adhesive is a thermosetting epoxy resin adhesive using a latent curing agent.   The anisotropic conductive adhesive film according to claim 1, wherein the conductive particles have an average particle size of 0.5 μm or more and less than 10 μm.   The stretchable sheet in which conductive particles are fixed in a single layer by an adhesive is stretched, and then laminated with a binder resin on the conductive particle side, and the conductive particles are embedded in the binder resin. 4. The method for producing an anisotropic conductive adhesive film according to any one of 4 above.