JP2007161793A - Anisotropically conductive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropically conductive adhesive sheet that has low connection resistance, high insulation resistance, and excellent fine electric circuit connectability. <P>SOLUTION: The anisotropically conductive adhesive sheet comprises at least a hardening agent, a curable insulating resin and conductive particles, wherein the average particle size of the conductive particles is 2 to 8 μm and more than 90% of the conductive particles are composed the conductive particles having a shortest distance of 0.1 to 2μ from the surface of one side of the anisotropically conductive adhesive sheet to the surface of the conductive particle. The conductive particles are preferably arranged so that the average interval between adjacent conductive particles may be 0.5 to 5 times of the average particle size of the conductive particle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

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) , A method of coating the surface of conductive particles with an electrically insulating resin (see Patent Document 3), a method of laminating a layer including conductive particles and a layer not including conductive particles, and preventing a short circuit between adjacent circuits (Patent Document) 4, 5), a method of blending ion scavenger particles to prevent short-circuiting due to ion migration from an electrode made of a material that is easily ionized (see Patent Documents 6 and 7), and a method of arranging single particles on one side surface (Patent Document 8) and the like are known.
In conventional techniques such as laminating a layer containing conductive particles and a layer not containing conductive particles to prevent a short circuit between adjacent circuits, the number of conductive particles on the circuit terminal surface side is increased, whereby the circuit terminals and connection terminals It is possible to increase the number of conductive particles sandwiched between them. However, when the circuit terminal and the connection terminal come close to each other due to the positional deviation of the circuit terminal, the amount of conductive particles that are in contact with the circuit terminal and not sandwiched between the circuit terminal and the connection terminal increases. Therefore, there is a risk of short circuit between the circuit terminal and the connection terminal. On the other hand, in the case of the method of coating the surface of the conductive particles with an electrically insulating resin, it has not been possible to satisfy both sufficient insulation and connectivity.

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. 3035579 Japanese Patent No. 3633422 International Publication No. 2005/054388 Pamphlet

  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-mentioned problems, the present inventor found that conductive particles having a specific average particle diameter exist within a specific range, and that the conductive particles are specified. It has been found that the above-mentioned problems can be solved by using an anisotropic conductive adhesive sheet characterized by being present without contacting with a proportion or more of the conductive particles.
That is, the present invention is as described below.

(1) An anisotropic conductive adhesive sheet comprising at least a curing agent, a curable insulating resin, and conductive particles, wherein the conductive particles have an average particle diameter of 2 to 8 μm, and the anisotropic conductive adhesive sheet An anisotropic conductive adhesive sheet, wherein the conductive particles having the shortest distance from the surface on one side to the surface of the conductive particles in the range of 0.1 μm to 2 μm are 90% or more of the number of conductive particles.
(2) The anisotropic conductive adhesive sheet according to (1), wherein 95% or more of the number of conductive particles is present without being in contact with other conductive particles.
(3) (1) or (2), characterized in that the average particle spacing between adjacent conductive particles is arranged to be 0.5 to 5 times the average particle size of the conductive particles An anisotropic conductive adhesive sheet as described in 1.
(4) Two layers of adhesive layers having different film thicknesses each consisting of at least a curing agent and a curable resin, and anisotropic conductive adhesive sheets made of conductive particles, wherein the conductive particles are two layers of the adhesive layer. Any one of (1) to (3), wherein the conductive particle portion present at the interface and contained in the thin adhesive layer is 1/50 to 4/5 of the average particle diameter of the conductive particles An anisotropic conductive adhesive sheet according to claim 1.
(5) The anisotropic conductive adhesive sheet according to (4), wherein an elastic modulus of the thin adhesive layer is higher than an elastic modulus of the thick adhesive layer.
(6) The anisotropic conductive adhesive sheet according to (4) or (5), wherein a curing reaction rate of the thin adhesive layer is higher than a curing reaction rate of the thick adhesive layer.
(7) An adhesive layer is provided on a biaxially stretchable film to form a laminate, and conductive particles having an average particle diameter of 2 to 8 μm are adhered onto the laminate to produce 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 diameter of the conductive particles. The conductive particles are transferred to an adhesive sheet containing at least a curing agent and a curable insulating resin on the support, and the biaxially stretchable film is peeled off, and then the conductive particles. The anisotropic conductivity according to any one of (1) to (6), including a step of laminating an adhesive layer made of at least a curing agent and a curable insulating resin on the surface to which the material is transferred. Manufacturing method of adhesive sheet.
(8) An adhesive layer composed of at least a curing agent and a curable resin is provided on a biaxially stretchable film to form a laminate, and conductive particles having an average particle diameter of 2 to 8 μm are adhered onto the laminate. The conductive particle-attached film is biaxially formed so that the average particle interval between the conductive particles is 0.5 to 5 times the average particle size of the conductive particles. After stretching and holding, and biaxially stretching and holding, the conductive particles and the pressure-sensitive adhesive layer are provided on an adhesive sheet containing at least a curing agent and a curable insulating resin on the surface where the conductive particles are present. The method for producing an anisotropic conductive adhesive sheet according to any one of (1) to (6), comprising a step of transferring and laminating.
(9) In the anisotropic conductive adhesive sheet according to any one of (1) to (6), the surface with the shortest distance from the conductive particles to the one-side surface is arranged on the circuit board surface having a relatively low wiring height. And a method of manufacturing a connection structure, wherein the circuit board and the electronic component are connected by thermocompression bonding of an electronic component having a relatively high wiring height.
(10) A contact structure produced by the method according to (9).

  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, conductive particles having a specific average particle diameter are arranged in the in-plane direction of the anisotropic conductive adhesive sheet that requires insulation, and the shortest distance from one side surface of the anisotropic conductive adhesive sheet to the conductive particle surface By preventing the short circuit at the time of crimping by keeping within a specific range, good insulation is ensured by maintaining a predetermined interval between the connection substrate wiring other than the connection part and the conductive particles I can do it.

Hereinafter, the present invention will be specifically described.
The conductive particles in the anisotropic conductive adhesive sheet of the present invention are 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. It is preferable to use more than one species. 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 of the conductive particles is a value obtained by dividing the σ value of the particle size distribution (the 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 of the conductive particles can be measured using a known method and apparatus, and a wet particle size distribution meter, a laser type particle size distribution meter and 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 size of the conductive particles is preferably 2 to 8 μm, more preferably 2 to 5 μm, and most preferably 2.5 to 3.5 μm. The thickness is preferably 8 μm or less from the viewpoint of insulation, is less susceptible to variations in height of connection terminals and the like, and is preferably 2 μm or more from the viewpoint of electrical connectivity.

The anisotropic conductive adhesive sheet of the present invention has a conductive adhesive ratio of 90% or more, more preferably 95% or more, still more preferably 98%, most preferably 100% of the number of conductive particles (total number of conductive particles). The shortest distance from one surface of the sheet to the surface of the conductive particles is 0.1 μm to 2 μm. From the viewpoint of ensuring insulation, it is preferably 0.1 μm or more, and from the viewpoint of securing the number of conductive particles at the time of connection, it is preferably 2 μm or less. More preferably, it is 0.2 μm to 1 μm. 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 0.05 μm or less, and particularly preferably 0.01 μm or less.
In the present specification, conductive particles that exist without being in contact with other conductive particles may be referred to as “single particles”.

In the present invention, it is preferable that 95% or more of the number of conductive particles is present without contact with other conductive particles, more preferably 98% or more, and further preferably 100% is present without contact. It is preferable.
In the anisotropic conductive adhesive sheet of the present invention, the average particle interval between adjacent conductive particles is preferably 0.5 to 5 times the average particle size of the conductive particles. More preferably, the average particle size is 20 μm or less and 1.5 to 3 times the average particle size of the conductive particles.

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. Moreover, the average particle | grain space | interval of the adjacent electroconductive particles in this invention is calculated | required 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, and the average value of the whole is obtained to obtain the average particle interval. . The variation in the average particle spacing of the conductive particles is preferably small, and the standard deviation thereof is preferably 10% or less of the average particle spacing.

The anisotropic conductive adhesive sheet of the present invention has a structure of two adhesive layers each composed of at least a curing agent and a curable resin, and has a structure in which conductive particles are arranged and laminated on the interface between them. Is preferred.
In the case of laminating two adhesive sheets, the conductive particle portion contained in the thin adhesive layer is preferably in the range of 1/50 to 4/5 of the average particle diameter of the conductive particles. Is more preferably in the range of 3/5. From the viewpoint of aggregation due to resin flow at the time of connection, the conductive particles are preferably present at the interface between the two layers, and in the range of 1/50 to 4/5, it is preferable that the resin flow is hardly affected.

  Of the two adhesive layers to be laminated, the elastic modulus of the thin adhesive layer is preferably higher than the elastic modulus of the adhesive sheet of the thick adhesive layer. In this case, the movement of the conductive particles due to the resin flow at the time of connection hardly occurs, and the connection reliability of the connection structure is good, which is preferable. The elastic modulus of each adhesive layer is measured by, for example, the Tensilon method or the Vibron method, etc., by preparing a sheet of each adhesive layer, sufficiently curing this sheet at the connection condition temperature. can do. The elastic modulus at 25 ° C. of each adhesive sheet is preferably 0.5 GPa or more and 5 GPa or less in any measurement method, and more preferably in the range of 1 to 4 GPa.

Furthermore, it is preferable that, among the two adhesive layers to be laminated, the curing reaction rate of the thin adhesive layer is higher than the curing reaction rate of the thick adhesive layer. In this case, the connection reliability of the connection structure is good and preferable. The curing reaction rate of each adhesive layer can be measured by preparing a sheet of each adhesive layer and using this sheet. For example, a sheet of an adhesive layer is sandwiched between two sheets having good releasability such as a fluororesin sheet, and the test is performed by heating at a temperature equal to or lower than a normal connection temperature (for example, 80% temperature) and a normal connection condition. A sheet is produced. Using these sheets, the curing reaction rate can be calculated by measuring the consumption rate of the functional group by microscopic IR before and after the treatment, or by calculating the reaction heat amount ratio using a differential scanning calorimeter. As a specific method for calculating the curing reaction rate, for example, when an epoxy resin is used, the adhesive layer is formed into a sheet, the sheet is subjected to IR measurement, and the epoxy group absorption strength (914 cm ⁻¹ ) / methyl group absorption. The ratio (strength ratio) of the strength (2922 cm ⁻¹ ) was calculated, and the ratio of the strength ratio before and after heating was calculated in the same manner for the curing rate measurement sample that was cured by applying heat to the sheet. The rate is calculated, and the curing reaction rate is obtained by subtracting the epoxy group residual rate from 100%.

As a method of laminating the adhesive sheet, a known method can be used.
However, in order to maintain a distance of usually 0.1 μm to 2.0 μm, it is necessary to laminate an adhesive sheet having a film thickness close to that distance, and such an extremely thin sheet is skillfully laminated, and It is not easy to control the distance. For example, when a thin adhesive sheet is prepared in advance and laminated, the bite into the sheet to be transferred first is shallow and exposed, and the conductive particles are sufficiently cut into the thin adhesive sheet to be laminated. The distance to the surface can be controlled to 0.1 μm to 2.0 μm. In addition, a resin solution composed of at least a curing agent, a curable resin, and a solvent is applied on an adhesive sheet in which conductive particles are embedded in advance to a predetermined depth using a coating apparatus such as a die coater, a blade coater, or a comma coater. Then, a method of drying the solvent and forming an adhesive layer having a predetermined thickness can be used.
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.

  In the anisotropic conductive adhesive sheet of the present invention, a thermoplastic resin or the like may be blended 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 and 300 degrees C or less.

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.

The thickness of the anisotropic conductive adhesive sheet is preferably 10 μm or more and 30 μm or less, and more preferably 15 μm or more and 25 μm or less. From the viewpoint of mechanical connection strength, it is preferably 10 μm or more, and from the viewpoint of preventing a decrease in the number of connected particles due to particle flow during connection, it is preferably 30 μm or less.
When the anisotropic conductive adhesive sheet is composed of two adhesive layers, the thickness of the two layers is one thin and the other thick, but the thick adhesive layer has a thickness of 5 to 29.8 μm. The film thickness is preferably 0.1 μm or more and less than 5 μm.

Next, an example of a method for producing an anisotropic conductive film in which 95% or more of the number of conductive particles in the present invention exists without contacting with other conductive particles will be described.
As the method for producing the anisotropic conductive film, an adhesive layer is formed on a biaxially stretchable film or sheet, conductive particles are arranged in a single layer on the film, and the conductive particles are stretched. The conductive particles are dispersed and arranged, and the conductive particles are transferred to a thick adhesive layer composed of at least a curing agent and a curable insulating resin while maintaining the stretched state, and then on the conductive particle transfer surface side. It is preferable to laminate a thin adhesive layer made of at least a curing agent and a curable insulating resin.
In addition, by using a thin adhesive layer made of at least a curing agent and a curable insulating resin as the adhesive layer, the thin adhesive layer to which the conductive particles are attached is transferred and laminated together with the conductive particles to the thick adhesive layer. It is also preferable to do.

  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. When an adhesive sheet made of at least a curing agent and a curable insulating resin is used as the adhesive layer, it is preferable to use a polyethylene resin, silicone rubber, or the like because it is preferably stretched at a lower temperature. In this case, in order to facilitate the transfer of the adhesive sheet, it is preferable to perform a peeling treatment on the film in advance.

  As a method for arranging and fixing conductive particles on a biaxially stretchable film, a known method can be used. For example, a method in which an adhesive layer containing at least a thermoplastic resin is formed on the biaxially stretchable film, conductive particles are brought into contact therewith and adhered, and a single layer is arranged 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, an adhesive is formed on the biaxially stretchable film to form an adhesive layer, and conductive particles are adhered thereon, and if necessary, the adhesion is repeated several times and arranged in a single layer. be able to.

  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 500% 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.

  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-based adhesives, synthetic rubber-based adhesives, synthetic resin emulsion-based adhesives, silicone-based adhesives, ethylene-vinyl acetate copolymer adhesives, and the like can be used alone or in combination. . From the viewpoint of conductive particle retention before stretching, uniformity of conductive particle dispersion during stretching, and transferability of conductive particles after stretching, a pressure-sensitive adhesive obtained by graft polymerization of a natural rubber-based pressure-sensitive adhesive with acrylate is particularly preferable. Furthermore, it is preferable to heat-process for 1 minute to 5 minutes below extending | stretching temperature before extending | stretching from the point of the uniformity at the time of heating extending | stretching.

  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, a bar coater, or a spray coat 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 that the conductive particles are arranged in a single layer with almost no gap (dense packing). 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 film after stretching, it is preferably 1 time or less.

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

The electronic circuit components constituting the connection structure of the present invention include wiring board connection applications for display devices such as liquid crystal display devices, plasma display devices, electroluminescence display devices, and electronic device mounting applications such as LSIs for these devices, and others. Can be used for mounting electronic circuit parts such as wiring board connection parts of LSIs and 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.

(Connection structure manufacturing method)
After forming an oxide film on the entire surface of a silicon piece (thickness 0.5 mm) of 1.6 mm × 15.1 mm in length and width, aluminum thin films (1000 mm) of 77 μm in width and 120 μm in length are placed at intervals of 23 μm, 40 μm inside. 140 pieces are formed on the long side and 14 pieces are formed on the short side. Further, a similar aluminum thin film is formed in the same pattern so that the gap and the position of the aluminum thin film are shifted from the pattern by 25 μm on the inner side of 30 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 25 μm, a width of 10 μm inside 7.5 μm from the outer peripheral portion of each gold bump placement location. Then, a protective film of silicon oxide is formed on the entire surface other than the opening by a conventional method except for leaving the opening having a length of 60 μm. Thereafter, the gold bump is formed to obtain a test chip.
Connection pad of indium tin oxide film (1500 mm) so that gold bumps on the outer aluminum thin film are connected to a gold bump on the adjacent aluminum thin film on a non-alkali glass having a thickness of 0.7 mm so as to be paired with each other. (Width 77 μm, length 100 μm). Each time 20 gold bumps are connected, an indium tin oxide thin film lead wire is formed on the connection pad (this lead wire serves as a connection resistance measurement portion).

  In addition, a connection pad (25 μm wide, 100 μm long) of an indium tin oxide film (1500 mm) is formed in such a positional relationship that the gold bumps on the outer aluminum thin film are connected to different sides. Lead wires (15 μm wide, indium tin oxide film) are formed from the connection pads through the corresponding bumps on the inner side, and indium tin oxide thin film connection wires are formed so that 10 bumps can be connected. Connect. Further, connection pads are formed in a similar manner so that the inner 10 bumps are paired with them, and connection wirings are formed between the outer bumps to form a comb pattern. A lead wire of an indium tin oxide thin film is formed on each connection wire (this lead wire becomes an insulation resistance measurement part).

An aluminum-titanium thin film (titanium 1%, 3000 mm) is formed on each lead wiring to form a connection substrate. A 2.5 mm wide pressure-bonding head is provided by temporarily stretching the side of the anisotropic conductive adhesive sheet having a width of 2 mm and a length of 17 mm where the conductive particles are present so that the connection pads are all covered on the connection substrate. After pressing 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 positions of the connection pads and the gold bumps are aligned, and pressure bonding with 2.0 MPa is performed at 200 ° C. for 10 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.
In addition, the resistance between the paired lead wires is measured to obtain an insulation resistance value.

  While maintaining this insulation resistance test substrate at 60 ° C. and 90% relative humidity, a DC voltage of 25 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 ◯.

[Example 1]
35 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000) and 34 g of bisphenol A type epoxy resin (epoxy equivalent 240, semi-solid) are dissolved in a mixed solvent of ethyl acetate-toluene (mixing ratio 1: 1) to obtain a solid. A 50% min solution was obtained. A liquid epoxy resin containing a microcapsule type latent imidazole curing agent (average size of microcapsules 5 μm, active temperature 125 ° C.) 31 g was 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 the film-like adhesive sheet A with a film thickness of 15 micrometers was obtained.

  35 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), 34 g of naphthalene type epoxy resin (epoxy equivalent 136, semi-solid), 0.06 g of γ-glycidoxypropyltrimethoxysilane, mixed solvent of ethyl acetate-toluene (Mixing ratio 1: 1) was dissolved to obtain a 50% solid content solution. A liquid epoxy resin containing a microcapsule type latent imidazole curing agent (average size of microcapsules 5 μm, active temperature 125 ° C.) 31 g was 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 the film-form adhesive sheet B with a film thickness of 3 micrometers was obtained.

After peeling off each of the adhesive sheets A and B from the polyethylene terephthalate film, a cured film was prepared by heating and curing at 180 ° C. for 2 hours, a strip sample having a width of 5 mm and a length of 70 mm was prepared, a distance between chucks of 50 mm, and a tensile speed. The tensile elastic modulus was measured under the condition of 10 mm / min. As a result, the elastic modulus of the adhesive sheet A was 2.2 GPa, and the elastic modulus of the adhesive sheet B was 2.6 GPa.
Also, each of the adhesive sheets A and B is peeled off from the polyethylene terephthalate film, sandwiched between Teflon (registered trademark) film (25 μm thickness), and pressure-pressed at 2.0 MPa for 10 seconds at 160 ° C. to obtain a reaction hardening rate measurement sample. . IR measurement of each reaction hardening rate measurement sample was performed.
In advance, IR measurement is performed on the adhesive sheets A and B before heating, and the ratio of epoxy group absorption strength (914 cm ⁻¹ ) / methyl group absorption strength (2922 cm ⁻¹ ) is calculated. It calculates similarly about a hardening rate measurement sample. The ratio of the strength ratio before and after heating is calculated, and the residual ratio of epoxy groups is calculated. The epoxy reaction rate is subtracted from 100% to obtain the curing reaction rate. The curing reaction rate of the adhesive sheet A was 56%, and the curing reaction rate of the adhesive sheet B was 65%.

Gold-plated plastic particles with an average particle size of 3.0 μm (conductivity) obtained by applying a natural rubber-methyl methacrylate graft copolymer adhesive 6 μm thick as an adhesive layer on an unstretched polypropylene film with a thickness of 100 μm The particles were applied in a single layer with almost no gap. 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 conductive particle adhesion film was heat-treated at 100 ° C. for 3 minutes in a dryer.

This film was fixed using 10 chucks vertically and horizontally using a biaxial stretching device (X6H-S manufactured by Toyo Seiki, pantograph type corner stretch type biaxial stretching device), preheated at 130 ° C. for 120 seconds, Thereafter, the film was stretched and fixed by 100% at a speed of 5% / second. Then, after laminating the adhesive sheet A on the stretched film, the polypropylene film was peeled off. As a result of observing this adhesive sheet with a laser microscope, the average amount of protrusion of 100 conductive particles was 1.5 μm. Thereafter, the adhesive sheet B was laminated to obtain an anisotropic conductive adhesive sheet.
As a result of laser microscope observation, 99% of 100 conductive particles were single particles. The average particle spacing was 4.21 μm. 100% of 100 conductive particles were separated from the surface of the anisotropic conductive adhesive sheet by 0.1 μm or more and 2 μm or less.

[Example 2]
In the same manner as in Example 1, an adhesive sheet A was produced.
30 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), 34 g of naphthalene type epoxy resin (epoxy equivalent 136, semi-solid), 0.06 g of γ-glycidoxypropyltrimethoxysilane are dissolved in ethyl acetate and solid Make a 50% min solution. A liquid epoxy resin containing a microcapsule-type latent imidazole curing agent (average particle diameter of microcapsules 5 μm, active temperature 125 ° C.) 36 g was mixed and dispersed in the 50% solid content solution. Then, it apply | coated on the 80-micrometer-thick unstretched polyethylene film, air-dried at 40 degreeC for 15 minute (s), and the film-form adhesive sheet C with a film thickness of 5 micrometers was obtained. On this adhesive sheet C, gold-plated plastic particles (conductive particles) with an average particle size of 3.0 μm were applied in a single layer with almost no gap. 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 50 ° C. for 120 seconds, Thereafter, the film was stretched and fixed by 120% at a speed of 5% / second.
Thereafter, the adhesive sheet A was laminated on the stretched film, and then the polyethylene film was peeled off to obtain an anisotropic conductive film.
As a result of laser microscope observation, 98% of 100 conductive particles were single particles. Further, the average particle interval was 4.51 μm. 100% of 100 conductive particles were separated from the surface of the anisotropic conductive adhesive sheet by 0.1 μm or more and 2 μm or less.
In the same manner as in Example 1, the tensile elastic modulus was measured. As a result, the elastic modulus of the adhesive sheet C was 2.7 GPa.

Further, the adhesive sheet C was peeled off from the polyethylene film, sandwiched between Teflon (registered trademark) films (25 μm thickness), and pressure-bonded to 2.0 MPa at 160 ° C. for 10 seconds to obtain a curing rate measurement sample. IR measurement of each hardening rate measurement sample was performed.
The IR measurement of the adhesive sheet C before heating is performed in advance, and the ratio of epoxy group absorption strength (914 cm ⁻¹ ) / methyl group absorption strength (2922 cm ⁻¹ ) is calculated. It calculated similarly about the hardening rate measurement sample. The ratio of the strength ratio before and after heating was calculated to calculate the epoxy residual ratio. The epoxy residual rate is subtracted from 100% to obtain the curing reaction rate. The curing reaction rate of the adhesive sheet was 62%.

[Example 3]
An adhesive sheet D, which is the same as the adhesive sheet A of Example 1 except that the film thickness is 16 μm, is prepared, and a conductive particle-attached stretched sheet is prepared in the same manner as in Example 1, and then laminated, and conductive An adhesive sheet E to which the conductive particles were transferred was prepared.
39 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), 34 g of naphthalene type epoxy resin (epoxy equivalent 136, semi-solid), 0.06 g of γ-glycidoxypropyltrimethoxysilane, mixed solvent of ethyl acetate-toluene (Mixing ratio 5: 1) was dissolved to obtain a 30% solid content solution. Varnish A was obtained by blending and dispersing in 27 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.) and 30% solid content solution. Thereafter, varnish A is applied to the conductive particle transfer surface side of the adhesive sheet E to which the conductive particles have been transferred with a die coater, and blown and dried at 50 ° C. for 15 minutes to obtain an anisotropic conductive adhesive sheet having a total film thickness of 18 μm. Obtained.
Separately, varnish A was applied onto a polyethylene terephthalate film (50 μm) and air-dried at 50 ° C. for 15 minutes to prepare an adhesive sheet F having a thickness of 5 μm. The tensile elastic modulus of this film was measured in the same manner as in Example 1. As a result, the elastic modulus of the adhesive sheet F was 2.4 GPa. Further, the curing reaction rate calculated in the same manner as in Example 1 was 65%.
As a result of observing the anisotropic conductive adhesive sheet with a laser microscope, 98% of 100 conductive particles were single particles. Further, the average particle interval was 4.32 μm. The average distance from the anisotropic conductive adhesive sheet surface was 0.9 μm, and 100% of 100 conductive particles were separated from the anisotropic conductive adhesive sheet surface by 0.1 μm or more and 2 μm or less.

[Comparative Example 1]
44 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, 25 ° C. viscosity, 14000 mPa · S), 0.3 g of γ-glycidoxypropyltrimethoxysilane It was dissolved in a mixed solvent of ethyl-toluene (mixing ratio 1: 1) to obtain a 50% solid content solution.
30 g of a liquid epoxy resin containing a microcapsule-type latent imidazole curing agent (average size of microcapsules 5 μm, active temperature 125 ° C.) and 4.0 g of gold-plated plastic particles having an average particle size of 3.0 μm are mixed with 50% solid content. Formulated and dispersed 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 25-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, 85% of 100 conductive particles measured were single particles.

[Comparative Example 2]
In the adhesive sheet A of Example 1, the same adhesive sheet G was obtained except that the film thickness was 20 μm.
Gold-plated plastic particles with an average particle size of 8.0 μm (conductive) coated on a non-stretched polypropylene film with a thickness of 100 μm and a 6 μm thick natural rubber-methyl methacrylate graft copolymer adhesive as an adhesive layer The particles were applied in a single layer with almost no gap. 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 conductive particle adhesion film was heat-treated at 100 ° C. for 3 minutes in a dryer.
This film was fixed using 10 chucks vertically and horizontally using a biaxial stretching device (X6H-S manufactured by Toyo Seiki, pantograph type corner stretch type biaxial stretching device), preheated at 130 ° C. for 120 seconds, Thereafter, the film was stretched and fixed by 50% at a speed of 5% / second. Then, after laminating the adhesive sheet G on the stretched film, the polypropylene film was peeled off to obtain an anisotropic conductive adhesive sheet. As a result of laser microscope observation, 99% of 100 conductive particles were single particles. The average particle spacing was 4.55 μm. 100% of 100 conductive particles were exposed from the surface of the anisotropic conductive adhesive sheet.
Using the anisotropic conductive film thus obtained, a connection structure was obtained by pressure bonding in the same manner as in the connection resistance measurement method at a connection temperature of 200 ° C.
Table 1 shows connection resistance values and insulation test results of the connection structures of Examples and Comparative Examples. As is clear from Table 1, the anisotropic conductive adhesive sheet of the present invention exhibits very excellent insulation reliability.

  The connection structure of the present invention exhibits low connection resistance and high insulation reliability, and is suitable as a connection structure for a high-definition display device or the like that requires fine circuit connection.

Claims (10)

  An anisotropic conductive adhesive sheet comprising at least a curing agent, a curable insulating resin, and conductive particles, wherein the conductive particles have an average particle diameter of 2 to 8 μm, from one side surface of the anisotropic conductive adhesive sheet An anisotropic conductive adhesive sheet, wherein the conductive particles having a shortest distance to the surface of the conductive particles in a range of 0.1 to 2 μm are 90% or more of the number of conductive particles.   The anisotropic conductive adhesive sheet according to claim 1, wherein 95% or more of the number of conductive particles is present without contacting with other conductive particles.   3. The anisotropy according to claim 1, wherein the particles are arranged so that an average particle interval between adjacent conductive particles is 0.5 to 5 times the average particle size of the conductive particles. Conductive adhesive sheet.   Each is an anisotropic conductive adhesive sheet composed of at least two adhesive layers having different film thicknesses each composed of at least a curing agent and a curable resin, and conductive particles, and the conductive particles are present at the interface between the two adhesive layers. The conductive particle portion contained in the adhesive layer of the thin adhesive layer is 1/50 to 4/5 of the average particle diameter of the conductive particles. An anisotropic conductive adhesive sheet according to item.   The anisotropic conductive adhesive sheet according to claim 4, wherein an elastic modulus of the thin adhesive layer is higher than an elastic modulus of the thick adhesive layer.   The anisotropic conductive adhesive sheet according to claim 4 or 5, wherein a curing reaction rate of the thin adhesive layer is higher than a curing reaction rate of the thick adhesive layer.   An adhesive layer is provided on a biaxially stretchable film to form a laminate, and conductive particles having an average particle size of 2 to 8 μm are adhered onto the laminate to produce a conductive particle-adhered film. The 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 diameter of the conductive particles, and biaxially stretched and held. Then, the conductive particles are transferred to an adhesive sheet comprising at least a curing agent and a curable insulating resin on the support, the biaxially stretchable film is peeled off, and the conductive particles are transferred. The method for producing an anisotropic conductive adhesive sheet according to claim 1, comprising a step of laminating an adhesive layer made of at least a curing agent and a curable insulating resin on the surface. .   An adhesive layer made of at least a curing agent and a curable resin is provided on a biaxially stretchable film to form a laminate, and conductive particles having an average particle diameter of 2 to 8 μm are adhered onto the laminate, thereby providing conductivity. A particle-adhering film is prepared, and the conductive particle-adhering film is biaxially stretched so that the average particle interval between the conductive particles is 0.5 to 5 times the average particle diameter of the conductive particles. After holding and biaxially stretching, the conductive particles and the pressure-sensitive adhesive layer are transferred to an adhesive sheet containing at least a curing agent and a curable insulating resin on the surface where the conductive particles exist, The manufacturing method of the anisotropically conductive adhesive sheet of any one of Claims 1-6 including the process to laminate | stack.   The surface of the shortest distance from the conductive particles to the one-side surface in the anisotropic conductive adhesive sheet according to any one of claims 1 to 6 is arranged on a circuit board surface having a relatively low wiring height, and is relatively A method of manufacturing a connection structure comprising: connecting a circuit board and an electronic component by thermocompression-bonding an electronic component having a high wiring height.   A contact structure manufactured by the method for manufacturing a connecting structure according to claim 9.