JP2006335910A - Anisotropically conductive adhesive sheet and fine connecting structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropically conductive adhesive sheet excellent in low connection resistance, high reliability for insulation and fine circuit connecting property. <P>SOLUTION: The anisotropically conductive adhesive sheet is composed of at least a curing agent, a curable insulating resin, conductive particles and insulating particles. In the anisotropically conductive adhesive sheet, ≥90% conductive particles and ≥90% insulating particles each exists in a region within the range of 2.0 times of average particle diameter of conductive particles in the thickness direction from the one side surface of the anisotropically conductive adhesive sheet and ≥90% conductive particles exist without coming into contact with other conductive particles and average particle interval between adjacent conductive particles is ≥0.5 time and ≤5 times of average particle diameter of the conductive particles and average particle diameter of the insulating particles is smaller than that of the conductive particles. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an anisotropic conductive adhesive sheet excellent in fine circuit connectivity and a connection structure.

  So far, with regard to anisotropic conductive adhesive sheets for connecting microcircuits, various conductive particles and anisotropic conductive adhesive configurations have been studied in order to improve connectivity and prevent short circuits. . For example, a method of blending insulating particles having a thermal expansion coefficient equivalent to that of the conductive particles (see Patent Document 1), and a method of attaching the insulating particles to the surface of the conductive particles to prevent a short circuit (see Patent Document 2) Alternatively, a method of covering the surface of conductive particles with an electrically insulating resin (see Patent Document 3), a method of stacking a layer containing conductive particles and a layer not containing conductive particles, and preventing a short circuit between adjacent circuits (patent References 4 and 5), the terminal circuit is covered with a photosensitive resin, the part other than the connection part is selectively cured to eliminate the adhesiveness, the conductive particles are attached to the adhesive part, and then the adhesive resin is used. A method of covering and preventing a short circuit between adjacent terminal circuits (see Patent Document 6) is well known.

  However, in the prior art such as blending insulating particles, it is necessary to prevent the short circuit due to the aggregation of the conductive particles in the inter-terminal direction and to ensure insulation, so it is necessary to blend many insulating particles. . On the other hand, in order to ensure connectivity during crimping, the insulating particles must be removed from the connecting portion, so there is a limit to blending a large number of insulating particles to ensure sufficient insulation. In the case of circuit connection, it was not possible to satisfy both the insulation and the number of connected particles. Further, even in the prior art such as short circuit prevention by the adhesive configuration, in the case of the fine circuit connection, insulation and electrical connectivity cannot be satisfied at the same time.

JP-A-6-349339 Japanese Patent No. 28958872 Japanese Patent Publication No. 7-99644 JP-A-6-45024 JP 2003-49152 A Japanese Patent No. 3165477

  The present invention provides an anisotropic conductive adhesive sheet that realizes good electrical connectivity without impairing insulation between adjacent circuits of a fine circuit, a method for producing the same, and a finely connected structure using the same. The purpose is to do.

  As a result of intensive studies to solve the above problems, the present inventors have found that the conductive particles are present in a certain range without contacting with a certain proportion or more of the conductive particles. By using an anisotropic conductive adhesive sheet characterized by the presence of insulating particles having a specific average particle diameter in the existing region in the thickness direction of the conductive particles, the above problem can be solved. I found it.

  That is, one aspect of the present invention is an anisotropic conductive adhesive sheet comprising at least a curing agent, a curable insulating resin, conductive particles, and insulating particles, in the thickness direction from one surface of the anisotropic conductive adhesive sheet. In addition, 90% or more of the number of conductive particles, 90% or more of the number of insulating particles are present in a region within 2.0 times the average particle size of the conductive particles, and 90% or more of the conductive particles are other The average particle spacing between the adjacent conductive particles is 0.5 to 5 times the average particle size of the conductive particles, and the average particle of the insulating particles An anisotropic conductive adhesive sheet having a diameter smaller than the average particle diameter of conductive particles.

In the anisotropic conductive adhesive sheet, the average particle diameter of the conductive particles is 1 to 8 μm, the average particle interval between adjacent conductive particles is 20 μm or less, and the thickness of the anisotropic conductive adhesive sheet is Is preferably 1.5 times or more and 40 μm or less of the average particle spacing. The conductive particles are at least one conductive particle selected from the group consisting of resin particles coated with noble metal, metal particles coated with noble metal, metal particles, alloy particles coated with noble metal, and alloy particles. Is preferred. Further, the average particle size of the insulating particles is preferably 0.05 times or more and 0.9 times or less than the average particle size of the conductive particles, and the number of insulating particles is 0.5 to 20 times the number of conductive particles. A range is preferable.
The glass transition temperature of the insulating particles is preferably made of a resin having a temperature of 25 ° C or higher and 150 ° C or lower.

In the second aspect of the present invention, an adhesive layer is provided on a biaxially stretchable film to form a laminate, and conductive particles having an average particle diameter of 1 to 8 μm are adhered onto the laminate, thereby forming a conductive particle-adhered film. The conductive particle-adhering film is biaxially stretched and held so that the average particle spacing between the conductive particles is 0.5 to 5 times the average particle size of the conductive particles. After spraying the insulating particles to adhere the insulating particles between the conductive particles, the conductive particles and the insulating particles are transferred to an adhesive sheet containing at least a curing agent and a curable insulating resin. It is the manufacturing method of one anisotropic conductive adhesive sheet of this invention characterized by including the process of producing an adhesive sheet.
In the method for producing the anisotropic conductive adhesive sheet, it is preferable that the biaxially stretchable film is a long film and the adhesive sheet is a long adhesive sheet.

The third aspect of the present invention is a connection method in which an electronic circuit component having a fine connection terminal and a circuit board are electrically connected by one anisotropic conductive adhesive sheet of the present invention, wherein the height of the fine connection terminal is close to the conductive layer. 3 to 15 times the average particle spacing of the conductive particles and 40 μm or less, the spacing between the fine connection terminals is 1 to 10 times the average particle spacing and 40 μm or less, and the pitch of the fine connection terminals is 3 times the average particle spacing. The connection method is characterized by being 30 times and 80 μm or less.
A fourth aspect of the present invention is a finely connected structure characterized by including an electronic circuit component and a circuit board connected by the third connection method of the present invention.

  The anisotropic conductive adhesive sheet and the fine connection structure of the present invention have good insulation characteristics between adjacent connection terminals and good electrical connectivity between connected connection terminals. That is, the conductive particles are arranged at specific intervals in the in-plane direction of the anisotropic conductive adhesive sheet that requires insulation, the insulating particles are arranged within the intervals, and the insulating particles are arranged in the direction of the connection surface. By not being present, it is possible to prevent a short circuit during crimping and to ensure good connectivity.

Hereinafter, the present invention will be specifically described.
First, the conductive particles in the anisotropic conductive adhesive sheet of the present invention will be described.
As the conductive particles, it is preferable to use at least one selected from resin particles coated with noble metal, metal particles coated with noble metal, metal particles, alloy particles coated with noble metal, and alloy particles.
As the resin particles coated with the noble metal, it is preferable to use those obtained by coating spherical particles such as polystyrene, benzoguanamine, and polymethyl methacrylate with nickel and gold in this order.

Resin particles coated with a noble metal can be formed using softer resin particles according to the hardness of the fine connection terminal (bump) to be connected.
When the bump hardness to be connected is less than 50 Hv in terms of Vickers hardness, it is preferable to use flexible resin particles such as polymethacrylate resin. Moreover, when bump hardness is 50 Hv or more, it is preferable to use hard resin particles, such as a benzoguanamine resin.

  As the metal particles coated with the noble metal, it is preferable to use a metal particle such as nickel or copper coated with a noble metal such as gold, palladium or rhodium on the outermost layer. As a coating method, a thin film forming method such as a vapor deposition method or a sputtering method, a coating method using a dry blend method, a wet method such as an electroless plating method or an electrolytic plating method can be used. From the viewpoint of mass productivity, the electroless plating method is preferable.

  As the metal particles, those selected from metals such as silver, copper and nickel are preferably used. The alloy particles preferably have a melting point of 150 ° C. or more and 500 ° C. or less, and more preferably low melting point alloy particles having a melting point of 150 ° C. or more and 350 ° C. or less. When the melting point is 500 ° C. or less, a metal bond can be formed between the connection terminals, which is preferable from the viewpoint of connection reliability. Moreover, it is preferable that melting | fusing point is 150 degreeC or more from a viewpoint of heat-resistant connection reliability.

  As the alloy particles coated with the noble metal, for example, alloy particles composed of two or more kinds selected from gold, silver, copper, nickel, tin, zinc, bismuth, indium, etc. are coated with the noble metal using the above method or the like. Can be used.

  As the alloy particles, for example, alloy particles composed of two or more selected from gold, silver, copper, nickel, tin, zinc, bismuth, indium and the like are preferable. When alloy particles having a melting point of 150 ° C. or higher and 500 ° C. or lower are used, it is preferable to coat the particle surface with a flux or the like in advance. It is preferable to use a so-called flux because the surface oxides can be removed. As the flux, fatty acids such as abietic acid can be used.

  The ratio of the average particle size to the maximum particle size of the conductive particles is preferably 2 or less, and more preferably 1.5 or less. The particle size distribution of the conductive particles is preferably narrower, and the geometric standard deviation of the particle size distribution of the conductive particles is preferably 1.2 to 2.5, and preferably 1.2 to 1.4. Is particularly preferred. When the geometric standard deviation is the above value, the variation in particle size is reduced. Usually, when a certain gap exists between two terminals to be connected, it is considered that the conductive particles function more effectively as the particle diameters become uniform.

  The geometric standard deviation of the particle size distribution is a value obtained by dividing the σ value of the particle size distribution (particle size value of 84.13% cumulative) by the particle size value of 50% cumulative. When the particle size distribution (logarithm) is set on the horizontal axis of the particle size distribution graph and the cumulative value (%, cumulative number ratio, logarithm) is set on the vertical axis, the particle size distribution is almost linear, and the particle size distribution is lognormal distribution. Follow. The cumulative value indicates the number ratio of particles having a certain particle size or less with respect to the total number of particles, and is expressed in%. The sharpness of the particle size distribution is expressed by the ratio of σ (the cumulative particle size value of 84.13%) and the average particle size (the cumulative particle size value of 50%). The σ value is an actual measurement value or a read value from the plot value of the graph.

  The average particle size and particle size distribution can be measured using a known method and apparatus, and a wet particle size distribution meter, a laser particle size distribution meter, or the like can be used. Alternatively, the average particle size and particle size distribution may be calculated by observing the particles with an electron microscope or the like. The average particle size and particle size distribution of the present invention can be determined by a laser particle size distribution meter.

  The average particle diameter of the conductive particles is preferably 1 to 8 μm, and more preferably 2 to 6 μm. The thickness is preferably 8 μm or less from the viewpoint of insulation, and is preferably less than 1 μm from the viewpoint of electrical connectivity, and is not easily affected by variations in height of connection terminals and the like.

  As the insulating particles in the anisotropic conductive adhesive sheet of the present invention, any particles can be used as long as sufficient insulating properties are possible. For example, thermoplastic resin particles such as acrylic resin, styrene resin, acrylic-styrene copolymer resin, resin particles such as benzoguanamine resin and phenol resin, thermosetting resin particles such as solid epoxy resin, silicon oxide, titanium oxide, etc. Ceramic particles or the like can be used. A thermoplastic resin is preferred because it is easy to ensure the connectivity during crimping. A resin having a glass transition temperature of 25 ° C. or higher and 150 ° C. or lower is particularly preferable from the viewpoint of securing connectivity during pressure connection. As the shape, spherical particles are preferable. As a method for measuring the glass transition temperature, a known method can be used. Specifically, it can be measured using a TMA-50 thermomechanical analyzer (manufactured by Shimadzu Corporation) at a temperature rising rate of 10 ° C./min.

  The average particle size of the insulating particles is smaller than the average particle size of the conductive particles and smaller than the conductive particle interval, but may be 0.05 to 0.9 times the average particle size of the conductive particles. preferable. From the viewpoint of insulation, it is preferably 0.05 times or more, and from the viewpoint of connectivity, it is preferably smaller than the average particle diameter of the conductive particles. The number of insulating particles is preferably in the range of 0.5 to 20 times the number of conductive particles, and more preferably in the range of 1 to 5 times. 0.5 times or more is preferable from the viewpoint of ensuring insulation, and 20 times or less is preferable from the viewpoint of adhesiveness.

  In the anisotropic conductive adhesive sheet of the present invention, there are portions having insulating particles between the conductive particles in the surface direction, and there are no insulating particles above and below the conductive particles in the connecting direction. There is no need to eliminate the insulating particles on the connection surface, and it is possible to effectively provide insulation with a smaller amount of insulating particles compared to a structure in which the insulating particles are uniformly mixed.

  In addition, the usual production method often employs a method in which insulating particles are preliminarily mixed in an insulating adhesive solution, but in this case, the influence of the solvent cannot be ignored, and the insulating particles in the insulating adhesive solution cannot be ignored. Resins that can be used as insulating particles have been limited due to concerns such as particle swelling, gelation, and aggregation. In the method for producing an anisotropic conductive adhesive sheet of the present invention, a method of transferring insulating particles in a dry manner to an insulating adhesive sheet that already contains no solvent is also possible. Therefore, there is no limitation on the material resin of the insulating particles that can be used for the solvent, and the effect can be exhibited.

Next, the anisotropic conductive adhesive sheet of the present invention will be described.
The anisotropic conductive adhesive sheet of the present invention has 90% or more of the number of conductive particles in a region within 2.0 times the average particle diameter of the conductive particles along the thickness direction from one surface of the conductive adhesive sheet. Existing. Preferably, 95% or more is present.
Also, in the insulating particles, 90% or more of the number of insulating particles is present in a region within 2.0 times the average particle diameter of the conductive particles along the thickness direction from the one side surface of the conductive adhesive sheet. Preferably, 95% or more is present.

  In the anisotropic conductive adhesive sheet of the present invention, the average particle interval between adjacent conductive particles is 0.5 to 5 times the average particle size of the conductive particles. Preferably, it is 20 μm or less and 1.5 to 3 times the average particle size. From the viewpoint of preventing particle aggregation due to particle flow at the time of connection and ensuring insulation, the average particle diameter is preferably 0.5 times or more, and from the viewpoint of fine connection, it is preferably 5 times or less of the average particle diameter.

In the present invention, the adjacent conductive particles are selected from arbitrary conductive particles and refer to six conductive particles closest to the conductive particles. The average particle spacing between adjacent conductive particles is as follows.
First, the photograph which expanded the anisotropically conductive adhesive sheet of this invention with the optical microscope from the surface side in which electroconductive particle exists is image | photographed. Next, arbitrary 20 conductive particles are selected, the distance from the 6 conductive particles closest to the respective conductive particles is measured, the average value of the whole is obtained, and the average particle interval is obtained. . The location of the insulating particles can be read from the enlarged photograph in the same manner as described above.

  The thickness of the anisotropic conductive adhesive sheet is preferably 1.5 times or more and 40 μm or less, more preferably 2 times or more and 40 μm or less of the above average particle interval. From the viewpoint of mechanical connection strength, the average particle spacing is preferably 1.5 times or more, and from the viewpoint of preventing reduction in the number of connected particles due to particle flow during connection, it is preferably 40 μm or less.

The blending amount of the conductive particles in the anisotropic conductive adhesive sheet is preferably 0.5 parts by mass to 20 parts by mass with respect to 100 parts by mass of the components including the curing agent and the curable insulating resin. 1 to 10 parts by mass is particularly preferable. 20 parts by mass or less is preferable from the viewpoint of insulation, and 0.5 parts by mass or more is preferable from the viewpoint of electrical connectivity.
In the anisotropic conductive adhesive sheet of the present invention, some or all of the conductive particles and insulating particles may be exposed from one side surface of the anisotropic conductive adhesive sheet.

  In the anisotropic conductive adhesive sheet of the present invention, the position where the conductive particles are present relative to the thickness direction of the anisotropic conductive adhesive sheet can be measured by a laser microscope capable of measuring the displacement in the focal direction. it can. At the same time, it is also possible to measure the number of conductive particles that exist without contacting other conductive particles. When the displacement in the focal direction is measured using the laser microscope, the displacement measurement resolution is preferably 0.1 μm or less, and particularly preferably 0.01 μm or less.

Next, the manufacturing method of the anisotropically conductive adhesive sheet in which the electroconductive particle in this invention exists without contacting with other electroconductive particle is demonstrated.
In the present invention, “the conductive particles are present without being in contact with other conductive particles” means that the conductive particles are present independently without being aggregated. Hereinafter, the expressions “exist alone” and “single particle” may be used in this sense. In the present invention, 90% or more of the conductive particles are present without being in contact with other conductive particles, but 95% or more are present without being in contact with other conductive particles. preferable.

  As a method for producing the anisotropic conductive adhesive sheet of the present invention, an adhesive layer is formed on a biaxially stretchable film or sheet, conductive particles are arranged in a single layer thereon, and they are stretched. A method in which the conductive particles are dispersed and arranged, the insulating particles are dispersed in a stretched state, and the conductive particles and the insulating particles are transferred to an adhesive sheet made of at least a curing agent and a curable insulating resin. preferable.

  As the biaxially stretchable film, a known resin film or the like can be used, but a polyethylene resin, a polypropylene resin, a polyester resin, a polyvinyl butyral resin, a polyvinyl alcohol resin, a polyvinylidene chloride resin alone or a copolymer, etc. Alternatively, it is preferable to use a flexible and stretchable resin film such as a rubber sheet such as nitrile rubber, butadiene rubber, or silicone rubber. Polypropylene resin and polyester resin are particularly preferable. The shrinkage after stretching is preferably 10% or less.

  As a method for dispersing and fixing conductive particles on a biaxially stretchable film, a known method can be used. For example, a method in which a pressure-sensitive adhesive layer containing at least a thermoplastic resin is formed on the biaxially stretchable film, and conductive particles are brought into contact with and adhered to the film, and placed in a single layer by applying a load with a rubber roll or the like. Can be taken. In this case, a method of repeating the adhesion-roll operation several times is preferable for filling without gaps. In the case of spherical conductive particles, since the closest packing is the most stable structure, it can be filled relatively easily. Alternatively, a method of applying a pressure-sensitive adhesive on the biaxially stretchable film to form an adhesive layer, attaching conductive particles thereon, repeating the attachment several times if necessary, and dispersing and arranging in a single layer, etc. Can be used.

  As a method for stretching a biaxially stretchable film in which conductive particles are arranged in a single layer, a known method can be used, but a biaxial stretching device is preferably used from the viewpoint of uniform dispersion alignment. From the viewpoint of particle spacing, the degree of stretching is preferably 50% or more and 400% or less, and more preferably 100% or more and 300% or less. In addition, 100% stretching means that the length of the portion stretched along the stretching direction is 100% of the length before stretching. The stretching direction is arbitrary, but biaxial stretching with a stretching angle of 90 ° is preferable, and simultaneous stretching is preferable. In the case of biaxial stretching, the degree of stretching in each direction may be the same or different.

As the biaxial stretching apparatus, a simultaneous biaxial continuous stretching apparatus is preferable.
As the simultaneous biaxial continuous stretching apparatus, a known one can be used, but a tenter type stretching machine that continuously stretches by fixing the long side with a chuck fitting and simultaneously stretching the distance in the vertical and horizontal directions is preferable. As a method for adjusting the degree of stretching, a screw method or a pantograph method can be used, but a pantograph method is more preferable from the viewpoint of accuracy of adjustment. When stretching while heating, it is preferable to provide a preheating zone before the stretched portion and a heat setting zone behind the stretched portion.

  The anisotropic conductive adhesive sheet of the present invention may be a single-layer sheet comprising at least a curing agent, a curable insulating resin, and conductive particles, and further does not include conductive particles in the sheet. It may be a multilayer sheet in which resin sheets containing an insulating resin are laminated.

  As the curable insulating resin used for the anisotropic conductive adhesive sheet of the present invention, a thermosetting resin, a photocurable resin, light and thermosetting resin, an electron beam curable resin, or the like can be used. In view of ease of handling, it is preferable to use a thermosetting insulating resin. As the thermosetting resin, an epoxy resin, an acrylic resin, or the like can be used, and an epoxy resin is particularly preferable.

  The epoxy resin is a compound having two or more epoxy groups in one molecule, and is preferably a compound having a glycidyl ether group, a glycidyl ester group or an alicyclic epoxy group, or a compound obtained by epoxidizing a double bond in the molecule. . Specifically, bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthalene type epoxy resin, novolac phenol type epoxy resin, or modified epoxy resins thereof can be used.

  The curing agent used in the present invention may be any one that can cure the curable insulating resin. When a thermosetting resin is used as the curable insulating resin, a resin that can be cured by reacting with the thermosetting resin at 100 ° C. or higher is preferable. In the case of an epoxy resin, a latent curing agent is preferable from the viewpoint of storage stability. For example, an imidazole curing agent, a capsule type imidazole curing agent, a cationic curing agent, a radical curing agent, a Lewis acid curing agent. An agent, an amine imide curing agent, a polyamine salt curing agent, a hydrazide curing agent, and the like can be used. From the viewpoint of storage stability and low-temperature reactivity, capsule-type imidazole curing agents are preferred.

  The anisotropic conductive adhesive sheet of the present invention may contain a thermoplastic resin or the like in addition to the curing agent and the curable insulating resin. By blending a thermoplastic resin, it can be easily formed into a sheet. In this case, the blending amount is preferably 200 parts by mass or less, particularly preferably 100 parts by mass or less, based on 100 parts by mass of the components including the curing agent and the curable insulating resin.

  Thermoplastic resins that can be blended with the curable insulating resin of the present invention include phenoxy resin, polyvinyl acetal resin, polyvinyl butyral resin, alkylated cellulose resin, polyester resin, acrylic resin, styrene resin, urethane resin, polyethylene terephthalate resin, etc. There may be a combination of one or more resins selected from them. Among these resins, a resin having a polar group such as a hydroxyl group or a carboxyl group is preferable from the viewpoint of adhesive strength. Moreover, it is preferable that a thermoplastic resin contains 1 or more types of thermoplastic resins whose glass transition temperature is 80 degreeC or more.

  In the anisotropic conductive adhesive sheet of the present invention, an additive may be blended with the above components. In order to improve the adhesion between the anisotropic conductive adhesive sheet and the adherend, a coupling agent can be blended as an additive. As the coupling agent, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent, or the like can be used, and a silane coupling agent is preferable. Examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-mercaptotrimethoxysilane, γ-aminopropyltrimethoxysilane, β-aminoethyl-γ- Aminopropyltrimethoxysilane, γ-ureidopropyltrimethoxysilane, and the like can be used.

  The blending amount of the coupling agent is preferably 0.01 parts by mass to 1 part by mass with respect to 100 parts by mass of the components including the curing agent and the curable insulating resin. 0.01 mass part or more is preferable from a viewpoint of adhesive improvement, and 1 mass part or less is preferable from a reliability viewpoint.

  Furthermore, an ion scavenger can be blended as an additive in order to prevent a decrease in insulation due to an ionic component in the anisotropic conductive adhesive sheet during moisture absorption. As the ion scavenger, an organic ion exchanger, an inorganic ion exchanger, an inorganic ion adsorbent, and the like can be used, but an inorganic ion exchanger excellent in heat resistance is preferable.

  As the inorganic ion exchanger, zirconium compounds, zirconium bismuth compounds, antimony bismuth compounds, and magnesium aluminum compounds can be used. There are positive ion type, negative ion type, and both ion types as ion types to be exchanged, but metal ions (positive ions) that cause direct ion migration, increase electrical conductivity, and cause generation of metal ions. Both anions are preferred because both anions can be exchanged.

The average particle size of the ion scavenger to be blended is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.01 μm or more and 1 μm or less.
The compounding amount of the ion scavenger is preferably 0.01 to 3 parts by mass with respect to 100 parts by mass of the resin component. When the blending amount is less than 0.01 parts by mass, the ion trapping effect is insufficient, and 3 parts by mass or less is preferable from the viewpoint of electrical connection.

Next, the manufacturing method of the anisotropically conductive adhesive sheet of this invention is demonstrated.
First, an adhesive layer is provided on a biaxially stretchable film to form a laminate, and conductive particles having an average particle diameter of 1 to 8 μm are adhered on the laminate to produce a conductive particle-adhered film. The conductive particle-attached film is biaxially stretched and held so that the average particle interval between the conductive particles and the adjacent particles is 0.5 to 5 times and 20 μm or less the average particle size of the conductive particles. By keeping the stretched state, the insulating particles are sprayed thereon, and then the conductive particles and the insulating particles are transferred to an adhesive sheet containing at least a curing agent and a curable insulating resin. The anisotropic conductive adhesive sheet of the invention can be produced.
Preferably, the biaxially stretchable film is a long film, and the adhesive sheet is also a long adhesive sheet. In the present application, the long length means that the length is 10 m or more. If a long adhesive sheet is used, a connection structure can be produced continuously, which is efficient.

The adhesive sheet is an adhesive layer comprising a curing agent and a curable insulating resin, and this adhesive sheet is usually formed on a peelable base film (holding film). For this reason, the anisotropically conductive adhesive sheet obtained is normally formed on the peelable base film.
In the present specification, the laminate of the anisotropic conductive adhesive sheet and the base film may be referred to as an anisotropic conductive adhesive sheet.

  As the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer, a known one can be used, but when biaxial stretching is performed while heating, it is preferable to use a non-thermal crosslinkable pressure-sensitive adhesive. Specifically, natural rubber latex adhesives, synthetic rubber latex adhesives, synthetic resin emulsion adhesives, silicone adhesives, ethylene-vinyl acetate copolymer adhesives, etc. may be used alone or in combination. Can do.

  The thickness of the adhesive layer is preferably in the range of 1/50 to 3 times the average particle diameter of the conductive particles used, and more preferably in the range of 1/10 to 2 times. From the viewpoint of holding the conductive particles at the time of adhesion and stretching of the conductive particles, the thickness of the adhesive layer is preferably 1/50 or more of the average particle diameter of the conductive particles, from the viewpoint of particle transfer to the adhesive sheet after stretching. 3 times or less is preferable. As the method for forming the adhesive layer, a method in which a dispersion or solution in a solvent or water is applied and dried by a known method such as a gravure coater, a die coater, a knife coater, or a bar coater can be used. When a hot-melt type pressure-sensitive adhesive is used, it can be roll-coated without a solvent.

  In applying the conductive particles to the adhesive layer, it is preferable to dispose the conductive particles in a single layer (close packing) with almost no gap. As a method for dense packing, the above-described method of dispersing and arranging conductive particles on a biaxially stretchable film can be used. In addition, close packing means filling so that the average particle | grain space | interval between the filled particles may be 1/2 or less of an average particle diameter. More preferably, the average particle interval between the filled particles is 1/5 or less of the average particle size.

  The film thickness of the biaxially stretched film is preferably 1/10 to 1 times the total thickness of the adhesive sheet to be transferred and the base film of the adhesive sheet, and 1/5 to 1/2. It is particularly preferred that From the viewpoint of handling properties of the stretched film, it is preferably 1/10 or more, and from the viewpoint of particle transfer to the adhesive sheet after stretching, it is preferably 1 time or less.

  As a method of spraying the insulating particles while maintaining the stretched state, it is preferable that the insulating particles are subjected to charge removal treatment in order to prevent aggregation of the insulating particles due to charging.

Next, the connection method of the present invention, in which an electronic circuit component having fine connection terminals and a circuit board having a corresponding circuit are electrically connected with an anisotropic conductive adhesive sheet, will be described.
In the connection method, the height of the fine connection terminal of the electronic circuit component is 3 to 15 times the average particle interval of the conductive particles and 40 μm or less, and the interval of the fine connection terminal is 1 to 10 of the average particle interval. The pitch of the fine connection terminals is 3 to 30 times the average particle interval and 80 μm or less. The electronic circuit component and a circuit board having a corresponding circuit are electrically connected using the anisotropic conductive adhesive sheet of the present invention.

  The height of the fine connection terminal is 3 to 15 times the average particle interval of the conductive particles and 40 μm or less, and preferably 4 to 10 times. Three times or more is preferable from the viewpoint of the mechanical strength of the fine connection structure, and the conductive particles move due to the resin flow of the adhesive sheet at the time of connection, and the connectivity due to the decrease in the number of conductive particles under the fine connection terminals. From the viewpoint of reduction, it is 15 times or less and preferably 40 μm or less.

  The fine connection terminal interval is 1 to 10 times the average particle interval and 40 μm or less, preferably 1 to 10 times and 20 μm or less, more preferably 2 to 5 times and 15 μm or less. 1 times or more is preferable from the viewpoint of insulation, and 10 times or less and 40 μm or less are preferable from the viewpoint of fine connection. The pitch is 3 to 30 times the average particle interval and 80 μm or less, and preferably 5 to 20 times and 40 μm or less. It is preferably 3 times or more from the viewpoint of connectivity, and preferably 30 times or less and 80 μm or less from the viewpoint of fine connection.

The present invention also relates to a fine connection structure connected by the fine connection method.
The material of the circuit board constituting the finely connected structure of the present invention may be an organic substrate or an inorganic substrate. As the organic substrate, a polyimide film substrate, a polyamide film substrate, a polyethersulfone film substrate, a rigid substrate obtained by impregnating a glass cloth with an epoxy resin, a rigid substrate obtained by impregnating a glass cloth with a bismaleimide-triazine resin, or the like may be used. it can. As the inorganic substrate, a silicon substrate, a glass substrate, an alumina substrate, an aluminum nitride substrate, or the like can be used. The wiring material of the wiring board is inorganic wiring materials such as indium tin oxide and indium zinc oxide, metal wiring materials such as gold-plated copper, chromium-copper, aluminum and gold bumps, and metal materials such as aluminum and chromium indium tin oxide. A composite wiring material covering an inorganic wiring material such as an object can be used.

As an application to which the anisotropic conductive adhesive sheet of the present invention is applied, or as an electronic circuit component constituting the finely connected structure of the present invention, a wiring board of a display device such as a liquid crystal display device, a plasma display device, an electroluminescence display device, etc. It can be used for connection applications, electronic component mounting applications such as LSIs for those devices, wiring board connection parts of other devices, and electronic component mounting applications such as LSIs. Among the display devices, it is preferably used for plasma display devices and electroluminescence display devices that require reliability.
Next, the present invention will be described with reference to examples and comparative examples.

[Example 1]
Acetic acid is 39 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), bisphenol A type epoxy resin (epoxy equivalent 190, viscosity at 25 ° C., 14000 mPa · S) 24 g, and 0.4 g of γ-glycidoxypropyltrimethoxysilane. Dissolve in a mixed solvent of ethyl-toluene (mixing ratio 1: 1) to obtain a 50% solid content solution.
A liquid epoxy resin containing a microcapsule-type latent imidazole curing agent (average particle diameter of microcapsule 5 μm, active temperature 125 ° C.) 37 g is mixed and dispersed in the 50% solid content solution. Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film (base film), and air-dried at 60 degreeC for 15 minute (s), and obtained the film-form adhesive sheet of 18-micrometer-thickness.

A gold-plated plastic particle having an average particle size of 3.0 μm (conductive) coated on a non-stretched polypropylene film with a thickness of 40 μm and a 5 μm thick nitrile rubber latex-methyl methacrylate graft copolymer adhesive as an adhesive layer. The single particles were applied almost without any gaps. That is, the conductive particles are prepared in a container having a thickness of several layers or more in a container larger than the film width, and the adhesive particles are pressed and adhered to the conductive particles with the application surface of the adhesive facing downward. Then, excess particles were scraped off with a scrubber made of soft rubber.
By repeating this operation twice, a conductive particle adhesion film coated with a single layer without a gap was obtained.

This film was fixed using 10 chucks vertically and horizontally using a biaxial stretching device (X6H-S manufactured by Toyo Seiki, pantograph type corner stretching type biaxial stretching device), preheated at 115 ° C. for 120 seconds, Thereafter, the film was stretched 100% and fixed at a rate of 20% / second. After fixation, spherical benzoguanamine-formaldehyde condensation resin particles (specific gravity 1.40) having an average particle diameter of 1 μm were sprayed at a rate of 1 g / m ² . Then, after laminating the adhesive sheet on the stretched film, it was peeled off to obtain an anisotropic conductive adhesive sheet.

  Among the conductive particles of the obtained anisotropic conductive adhesive sheet, 100 particles were selected at random, and a laser microscope (VK9500, manufactured by Keyence Corporation, shape measurement resolution 0.01 μm) capable of measuring displacement in the focal direction was used. The distance from the anisotropic conductive adhesive sheet surface was measured. As a result, it was found that 99% of the conductive particles were present within a range of 5 μm from the anisotropic conductive adhesive sheet surface. As a result of observation with an optical microscope, 98% of 100 conductive particles were single particles. Further, the average particle interval was 4.30 μm, which was 1.43 times the average particle size. The number of insulating particles was 4.9 times that of the conductive particles, and 97% was present within a range of 5 μm from the anisotropic conductive adhesive sheet surface.

[Example 2]
41 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), 33 g of naphthalene type epoxy resin (epoxy equivalent 136, semi-solid), 0.06 g of γ-ureidopropyltrimethoxysilane were mixed in ethyl acetate-toluene mixed solvent (mixed) To a 50% solid content solution. A liquid epoxy resin containing a microcapsule-type latent imidazole curing agent (average particle diameter of microcapsule 7 μm, active temperature 125 ° C.) 26 g is mixed and dispersed in the 50% solid content solution. Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film, and air-dried at 60 degreeC for 15 minute (s), and obtained the film-like adhesive sheet of film thickness of 17 micrometers.

Example 1 Gold-plated plastic particles having an average particle size of 3.8 μm were applied to a non-stretched polyethylene film having a thickness of 45 μm and 3 μm of the same nitrile rubber latex-methyl methacrylate graft copolymer adhesive as in Example 1 applied. A conductive particle adhesion film coated with a single layer with almost no gap was obtained by the same method as above.
The film was stretched and fixed 120% vertically and horizontally by the same method as in Example 1 except that the stretching temperature was 80 ° C. After fixing, spherical crosslinked styrene resin particles having an average particle diameter of 2 μm (specific gravity 1.05, glass transition temperature 105 ° C.) were sprayed at a rate of 1.8 g / m ² . Thereafter, the adhesive sheet was laminated on the stretched film and then peeled to obtain an anisotropic conductive adhesive sheet.

  Among the conductive particles of the obtained anisotropic conductive adhesive sheet, 100 particles were selected at random, and a laser microscope (VK9500, manufactured by Keyence Corporation, shape measurement resolution 0.01 μm) capable of measuring displacement in the focal direction was used. The distance from the anisotropic conductive adhesive sheet surface was measured. As a result, it was found that 99% of the conductive particles were present within a range of 7 μm from the anisotropic conductive adhesive sheet surface. As a result of observation with an optical microscope, 97% of 100 conductive particles were single particles. The average particle spacing was 6.46 μm, which was 1.70 times the average particle size. The number of insulating particles was 3.0 times that of the conductive particles, and 98% was present within a range of 7 μm from the surface of the anisotropic conductive adhesive sheet.

[Example 3]
10 g of phenoxy resin (glass transition temperature 45 ° C., number average molecular weight 12000), 33 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), 26 g of naphthalene type epoxy resin (epoxy equivalent 136, semi-solid), γ-glycid 0.1 g of xylpropyltriethoxysilane is dissolved in a mixed solvent of ethyl acetate-toluene (mixing ratio 1: 1) to obtain a 50% solid content solution. A liquid epoxy resin containing a microcapsule-type latent imidazole curing agent (average particle diameter of microcapsule 7 μm, active temperature 125 ° C.) 31 g is mixed and dispersed in the 50% solid content solution. Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film, and it air-dried for 15 minutes at 60 degreeC, and obtained the film-form adhesive sheet of 15-micrometer-thickness.

A gold-plated copper particle having an average particle size of 3.2 μm was applied to a non-stretched polypropylene film having a thickness of 45 μm coated with 5 μm of an ethylene-vinyl acetate copolymer adhesive by a method similar to that of Example 1 to form a single layer. The applied conductive particle adhesion film was obtained.
This film was fixed by stretching 150% in the longitudinal and lateral directions using a biaxial stretching apparatus in the same manner as in Example 1. After fixation, spherical silica particles having an average particle diameter of 1 μm (specific gravity 1.82) were sprayed at a rate of 1.7 g / m ² . Then, after laminating the adhesive sheet on the stretched film, it was peeled off to obtain an anisotropic conductive adhesive sheet.

  Among the conductive particles of the obtained anisotropic conductive adhesive sheet, 100 particles were selected at random, and a laser microscope (VK9500, manufactured by Keyence Corporation, shape measurement resolution 0.01 μm) capable of measuring displacement in the focal direction was used. The distance from the anisotropic conductive adhesive sheet surface was measured. As a result, it was found that 98% of the conductive particles were present within a range of 6 μm from the anisotropic conductive adhesive sheet surface. As a result of observation with an optical microscope, 96% of 100 conductive particles were single particles. Further, the average particle interval was 6.75 μm, which was 2.11 times the average particle size. The number of insulating particles was 12 times that of the conductive particles, and 98% was present in the range of 6 μm from the anisotropic conductive adhesive sheet surface.

[Comparative Example 1]
Acetic acid containing 37 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), 26 g of bisphenol A type epoxy resin (epoxy equivalent 190, viscosity at 25 ° C., 14000 mPa · S), 0.3 g of γ-glycidoxypropyltrimethoxysilane Dissolve in a mixed solvent of ethyl-toluene (mixing ratio 1: 1) to obtain a 50% solid content solution.
37 g of liquid epoxy resin containing microcapsule type latent imidazole curing agent (average particle size of microcapsule 5 μm, active temperature 125 ° C.) and 2.0 g of gold-plated plastic particles having an average particle size of 3.8 μm are mixed with 50% solid content. Mix and disperse in the solution.
Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film, air-dried at 60 degreeC for 15 minute (s), and the film-form anisotropic conductive adhesive sheet of 20-micrometer-thickness was obtained.
Of the conductive particles of the obtained anisotropic conductive adhesive sheet, 100 particles were randomly selected, and the distance from the anisotropic conductive adhesive sheet surface was measured using a laser displacement meter. As a result, it was found that the conductive particles exist randomly in the film thickness direction of the anisotropic conductive adhesive sheet. In addition, 78% of 100 conductive particles measured were single particles. Moreover, 1% of the particles were exposed on the surface.

[Comparative Example 2]
42 g of phenoxy resin (glass transition temperature 45 ° C., number average molecular weight 12000), 32 g of naphthalene type epoxy resin (epoxy equivalent 136, semi-solid), 0.06 g of γ-ureidopropyltrimethoxysilane, mixed solvent of ethyl acetate-toluene (mixed) To a 50% solid content solution. 26 g of a liquid epoxy resin containing a microcapsule-type latent imidazole curing agent (average particle size of microcapsule 5 μm, active temperature 125 ° C.), 6.0 g of gold-plated copper particles having an average particle size of 3.2 μm, and an average particle size of 2. 10 g of 0 μm spherical silica particles (specific gravity 1.83) are mixed and dispersed in the 50% solid content solution. Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film, air-dried at 60 degreeC for 15 minute (s), and the film-form anisotropic conductive adhesive sheet of 20-micrometer-thickness was obtained.
Of the conductive particles of the obtained anisotropic conductive adhesive sheet, 100 particles were randomly selected, and the distance from the anisotropic conductive adhesive sheet surface was measured using a laser displacement meter. As a result, it was found that the conductive particles exist randomly in the film thickness direction of the anisotropic conductive adhesive sheet. Moreover, 60% of 100 measured conductive particles were single particles.

(Connection resistance measurement method)
After an oxide film is formed on the entire surface of a silicon piece (thickness 0.5 mm) having a length and width of 1.6 mm × 15.1 mm, an aluminum thin film (1000 A) having a width of 74.5 μm and a length of 120 μm is formed on the inner side by 40 μm. 175 pieces are formed on the long side and 16 pieces are formed on the short side, respectively, so as to have an interval of 1 μm. In order to form two gold bumps (thickness: 15 μm) each having a width of 25 μm and a length of 100 μm on the aluminum thin film at intervals of 15 μm, a width of 10 μm inside 7.5 μm from the outer peripheral portion of each gold bump placement location. Then, a polyimide protective film is formed on the entire surface other than the opening by a conventional method except for leaving the opening having a length of 85 μm. Thereafter, the gold bump is formed to obtain a test chip.

  A connection pad (1400A) of indium tin oxide film (1400A) so that the gold bumps on the aluminum thin film are connected to the gold bumps on the adjacent aluminum thin film on a non-alkali glass having a thickness of 0.7 mm. 66 μm wide and 120 μm long). Each time 20 gold bumps are connected, an indium tin oxide thin film lead wiring is formed on the connection pad, and an aluminum-titanium thin film (titanium 1%, 3000 A) is formed on the lead wiring. To do. A side of the anisotropic conductive adhesive sheet having a width of 2 mm and a length of 17 mm is temporarily stretched on the connection evaluation substrate so as to cover all the connection pads, and a pressure bonding of 2.5 mm width is performed. After pressing with a head at 80 ° C., 0.3 MPa for 3 seconds, the polyethylene terephthalate base film is peeled off. A test chip is placed there so that the connection pads and the gold bumps are aligned, and pressure bonding with 5.2 MPa is performed at 220 ° C. for 5 seconds. After the crimping, the resistance value between the lead wires (daisy chain of 20 gold bumps) is measured with a four-terminal resistance meter to obtain a connection resistance value.

(Insulation resistance test method)
A connection pad (65 μm wide, 120 μm long) of an indium tin oxide film (1400 A) is formed on a non-alkali glass with a thickness of 0.7 mm so that the two gold bumps on the aluminum thin film are connected to each other. To do. A connection wiring of an indium tin oxide thin film is formed so that every other five connection pads can be connected, and a pair of them is paired to form a comb pattern so that every fifth connection pad can be connected. Then, an indium tin oxide thin film connection wiring is formed. An indium tin oxide thin film lead-out wiring is formed on each connection wiring, and an aluminum-titanium thin film (titanium 1%, 3000 A) is formed on the lead-out wiring to form an insulating evaluation substrate. On the insulating evaluation substrate, an anisotropic conductive adhesive sheet having a width of 2 mm and a length of 17 mm is temporarily stretched so as to cover all the connection pads, and a pressure head having a width of 2.5 mm is used. After pressurizing at 0.3 MPa for 3 seconds, the polyethylene terephthalate base film is peeled off. Then, a test chip is mounted so that the position of the connection pad and the gold bump is matched, and pressure bonding is performed at 2.4 MPa for 10 seconds at 180 ° C. to obtain an insulation resistance test substrate.

While maintaining this insulation resistance test substrate at 85 ° C. and 85% relative humidity, a DC voltage of 30 V is applied between the pair of lead wires using a constant voltage constant current power source. The insulation resistance between the wires is measured every 5 minutes, the time until the insulation resistance value becomes 10 MΩ or less is measured, and the value is defined as the insulation decrease time. The case where the insulation decrease time is less than 240 hours is indicated as x, and the case where the insulation decrease time is 240 hours or more is indicated as ◯.
The results are shown in Table 1. As is clear from Table 1, the anisotropic conductive adhesive sheet of the present invention exhibits very excellent insulation reliability.

  The anisotropic conductive adhesive sheet of the present invention exhibits low connection resistance and high insulation reliability, and is suitable as a connection material for bare chip connection materials that require fine circuit connection and high-definition display devices.

It is the schematic which shows the structure of the cross section of the anisotropically conductive adhesive sheet of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hardener and curable insulating resin 2 Insulating particle 3 Noble metal coating 4 Resin particle 5 Conductive particle

Claims (10)

  An anisotropic conductive adhesive sheet comprising at least a curing agent, a curable insulating resin, conductive particles, and insulating particles, the average particle of the conductive particles along the thickness direction from one side surface of the anisotropic conductive adhesive sheet 90% or more of the number of conductive particles and 90% or more of the number of insulating particles are present in a region within 2.0 times the diameter, and 90% or more of the conductive particles are not in contact with other conductive particles. The average particle spacing between adjacent conductive particles is 0.5 to 5 times the average particle size of the conductive particles, and the average particle size of the insulating particles is the average particle of the conductive particles. An anisotropic conductive adhesive sheet characterized by being smaller in diameter.   The average particle diameter of the conductive particles is 1 to 8 μm, the average particle interval between adjacent conductive particles is 20 μm or less, and the thickness of the anisotropic conductive adhesive sheet is 1.5 times the average particle interval. The anisotropic conductive adhesive sheet according to claim 1, wherein the anisotropic conductive adhesive sheet is 40 μm or less.   The conductive particles are at least one conductive particle selected from the group consisting of noble metal-coated resin particles, noble metal-coated metal particles, metal particles, noble metal-coated alloy particles, and alloy particles. The anisotropic conductive adhesive sheet according to claim 1 or 2.   The anisotropic conductive adhesive according to any one of claims 1 to 3, wherein the average particle size of the insulating particles is 0.05 to 0.9 times the average particle size of the conductive particles. Sheet.   The anisotropic conductive adhesive sheet according to any one of claims 1 to 4, wherein the number of insulating particles is in the range of 0.5 to 20 times the number of conductive particles.   The anisotropic conductive adhesive sheet according to claim 1, wherein the insulating particles are made of a resin having a glass transition temperature of 25 ° C. or higher and 150 ° C. or lower.   An adhesive layer is provided on a biaxially stretchable film to form a laminate, and conductive particles having an average particle diameter of 1 to 8 μm are adhered onto the laminate to produce a conductive particle-adhered film. Conductive particle adhesion film is biaxially stretched and held so that the average particle spacing between the conductive particles is 0.5 to 5 times the average particle size of the conductive particles, and the biaxially stretched and held conductive After spraying the insulating particles on the conductive particle-adhering film to adhere the insulating particles between the conductive particles, the conductive particles and the adhesive particles comprising at least a curing agent and a curable insulating resin are provided on the adhesive sheet. The method for producing an anisotropic conductive adhesive sheet according to claim 1, further comprising a step of producing an adhesive sheet by transferring insulating particles.   The method for producing an anisotropic conductive adhesive sheet according to claim 7, wherein the biaxially stretchable film is a long film, and the adhesive sheet is a long adhesive sheet.   In the connection method which electrically connects the electronic circuit component which has a fine connection terminal, and a circuit board with the anisotropic conductive adhesive sheet of any one of Claims 1-6, the height of a fine connection terminal is proximity 3 to 15 times and 40 μm or less of the average particle interval of the conductive particles to be performed, the interval of the fine connection terminals is 1 to 10 times and 40 μm or less of the average particle interval, and the pitch of the fine connection terminals is the average particle interval 3 to 30 times and 80 μm or less.   A fine connection structure comprising an electronic circuit component and a circuit board connected by the method according to claim 9.

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