JP2007224112A - Anisotropic conductive adhesive sheet and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropic conductive adhesive sheet which realizes good electric connectability without deteriorating an insulating property between the adjacent circuits of fine circuits. <P>SOLUTION: This anisotropic conductive adhesive sheet comprising at least a curing agent, a curable insulating resin and conductive particles is characterized by the following characteristics. A conductive particle group A whose narrowest inter-particle distance is 0 to 0.5 times the average particle diameter of the conductive particles occupy 5 to 60% of the total conductive particles, and a conductive particle group B whose narrowest inter-particle distance is 1.0 to 5 times occupy 40 to 95%. ≥95% of the total conductive particles exist in a region of ≤1.5 times the average particle diameter of the conductive particles in the thickness direction from one side surface of the anisotropic conductive adhesive sheet. The thickness of the anisotropic conductive adhesive sheet is in a range from 2 times the average particle diameter of the conductive particles to 40 μm. <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 forming a dense region of conductive particles in a main part using a photosensitive resin (see Patent Document 1), a method of regularly arranging conductive particles using a release liner having regularly arranged concave portions ( Patent Document 2) or an anisotropic conductive film that suppresses secondary aggregation by dispersing conductive particles at a constant flow rate and monodisperse on the surface of an insulating adhesive formed on a separator that runs at a constant speed. Are known (see Patent Document 3), a method of laminating a layer containing conductive particles and a layer not containing conductive particles to prevent a short circuit between adjacent circuits (see Patent Documents 4 and 5), and the like.

  However, in order to ensure the conductive particles in the connection portion, in the conventional technology such as forming a dense region of a plurality of conductive particles, it is difficult to mass-produce a large number of fine dense regions, and the connection portion Due to the difficulty of aligning the dense area and the dense area, it has not been put into practical use. In addition, attempts to balance connectivity and insulation by a method of monodispersing conductive particles, a method of laminating a layer containing conductive particles and a layer not containing conductive particles, etc., increase the conductive particles in the connection portion. Therefore, since the number of conductive particles is increased also in other originally insulating portions, it is not possible to satisfy both of sufficient insulation and connectivity.

JP 11-121072 A JP-T-2002-519473 JP 2000-149677 A Japanese Patent Laid-Open No. 06-45024 JP 2003-49152 A

  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 conductive particles having a specific inter-particle distance exist in a specific ratio, and the conductive particles are anisotropic. It has been found that the above problems can be solved by using an anisotropic conductive adhesive sheet characterized by being present in a specific region of the conductive adhesive sheet.

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 narrowest interparticle distance between the conductive particles is 0 to 0 of the average particle size of the conductive particles. The conductive particles A which are 0.5 times occupy 5 to 60% of the total number of conductive particles, and the narrowest interparticle distance between the conductive particles is 1.0 to 1.0 of the average particle diameter of the conductive particles. The conductive particle B which is 5 times occupies 40 to 95% of the total number of the conductive particles, and 1.5 times the average particle size of the conductive particles along the thickness direction from one side surface of the anisotropic conductive adhesive sheet. The anisotropic conductivity is characterized in that 95% or more of the total number of conductive particles is present in the area within and the thickness of the anisotropic conductive adhesive sheet is not less than twice the average particle size of the conductive particles and not more than 40 μm. Adhesive sheet.
(2) 90% or more of the electroconductive particle which exists in the said electroconductive particle group A consists of 2-4 particle groups, The anisotropically conductive adhesive sheet as described in (1) characterized by the above-mentioned.
(3) 50% or more of the conductive particles present in the conductive particle group A are composed of three particle groups, and the centers of the respective particles form a substantially equilateral triangle. The anisotropic conductive adhesive sheet according to 1 or 2.
(4) The conductive particles are at least one selected from the group consisting of metal-coated resin particles, noble metal-coated metal particles, metal particles, noble metal-coated alloy particles and alloy particles, and an average particle diameter thereof The anisotropic conductive adhesive sheet according to any one of claims (1) to (3), wherein is 2 to 8 µm.
(5) A pressure sensitive adhesive layer having a height of 0.1 to 3 times the average particle size of the conductive particles is provided on a biaxially stretchable film to form a laminate, and the top of the laminate A conductive particle-attached film is prepared by attaching conductive particles having an average particle diameter of 2 to 8 μm to the film, and the conductive particle-attached film is biaxially stretched and held so that the stretch ratio is 1 to 5 times And a step of transferring the conductive particles to an adhesive sheet comprising at least a curing agent and a curable insulating resin after being biaxially stretched and held. The manufacturing method of the anisotropically conductive adhesive sheet in any one.
(6) 2 in which the laminate has a particle size 0.1 to 3 times the average particle size of the conductive particles, and a microgel containing the pressure-sensitive adhesive component is dispersed in the pressure-sensitive adhesive component It obtains by laminating | stacking on the film which can be axially stretched, The manufacturing method of the anisotropically conductive adhesive sheet as described in (5) characterized by the above-mentioned.
(7) The method for producing an anisotropic conductive adhesive sheet according to (5) or (6), wherein the biaxially stretchable film is a long film, and the adhesive sheet is a long adhesive sheet.
(8) In a method of electrically connecting an electronic circuit component having a fine connection terminal and a circuit board having a corresponding circuit with an anisotropic conductive adhesive sheet, the area of the connection portion of the electronic circuit board is conductive. An electronic circuit component having a range of 100 to 1000 times the area of a circle whose diameter is the average particle diameter of the particles, and the shortest distance between the connection terminals being four or more times the average particle diameter, A connection method comprising: electrically connecting a circuit board having a circuit corresponding thereto using the anisotropic conductive adhesive sheet according to any one of (1) to (4).
(9) A fine connection structure connected by the connection method according to (8).

  The anisotropic conductive adhesive sheet and fine connection structure of the present invention have good insulation characteristics between adjacent connection terminals, and have good electrical connectivity and connection reliability between connected connection terminals. That is, conductive particles are arranged within a specific thickness range from the surface of one side of the anisotropic conductive adhesive sheet by arranging conductive particles having a narrow interparticle distance and other single particles at a specific ratio. By doing this, the number of conductive particles in the connection portion is ensured and the connectivity is maintained, and a short circuit at the time of pressure bonding is prevented. Good connection reliability can be ensured by forming a conductive particle dense portion composed of a plurality of conductive particles in the connection portion.

Hereinafter, the present invention will be specifically described.
First, the conductive particles in the connection structure 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 size of the conductive particles is preferably 2 to 8 μm, and more preferably 2 to 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.

In the present specification, the conductive particles are divided into the following three.
(1) Particle A: Conductive particles having the narrowest interparticle distance between the conductive particles being 0 to 0.5 times the average particle size
(2) Particle B: conductive particles having the narrowest interparticle distance between the conductive particles 1 to 5 times the average particle diameter
(3) Other particles: conductive particles that are neither of the above particles A and particles B In the present invention, the particles A having the narrowest interparticle distance of the conductive particles being 0 to 0.5 times the average particle size The particle B, which is 5 to 60% of the total number of conductive particles and the narrowest interparticle distance is 1 to 5 times the average particle diameter, is 40 to 95% of the total number of conductive particles. From the viewpoint of insulation, the narrowest interparticle distance of the particles A is preferably 0.01 times or more, and preferably 0.5 times or less, and 0.3 times or less from the viewpoint of connectivity. It is more preferable. Further, from the viewpoint of insulation, 90% or more, preferably 100% of the particles A are preferably composed of 2 to 4 particle groups. Moreover, from the balance of insulation and connectivity, it is preferable that 50% or more of the particles A are particle groups composed of three particles, and the centers of the particle groups form a substantially equilateral triangle. The reason why the ratio of the particles A is 5 to 60% of the total number of conductive particles is that 5% or more is preferable from the viewpoint of connectivity and 60% or less is preferable from the viewpoint of insulation. Moreover, it is more preferable that it is 10 to 40% from the balance of connectivity and insulation.
The proportion of the above (3) other particles is preferably 0 to 20%, more preferably 0 to 5% of the total number of conductive particles. The narrowest particle interval between the conductive particles of other particles is preferably 0.5 to 1.0 times the average particle size, and more preferably 0.8 to 1.0 times.

The narrowest interparticle distance of the particle B, which is a single particle, is 1 to 5 times the average particle diameter of the conductive particles, but is preferably 1 or more from the viewpoint of insulating properties, From the viewpoint, it is preferably 5 times or less. The proportion of the particles B is 40 to 95%, but is preferably 40% or more from the viewpoint of insulation, and preferably 95% or less from the viewpoint of connectivity. The dispersion of the average interparticle distance, which is the average value of the interparticle distance between the particles B, is preferably smaller, and the standard deviation thereof is preferably 20% or less of the average interparticle distance, and preferably 10% or less. More preferred.
In the present invention, the “conductive particles having the narrowest inter-particle distance of the conductive particles being 1.0 to 5 times the average particle size of the conductive particles” may be referred to as “single particles” or “single particles”. .

The ratio of the particle A and the particle B in the present invention is obtained 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, an arbitrary area including 300 conductive particles is selected in the field of view of the photograph, and for each of the conductive particles, a particle A (the narrowest interparticle distance is 0 to 0.5 of the average particle diameter). Times) and particle B (the narrowest interparticle distance is 1 to 5 times the average particle diameter), and the number of each is measured.

Next, the anisotropic conductive adhesive sheet of the present invention will be described.
In the anisotropic conductive adhesive sheet of the present invention, 95% or more of the total number of conductive particles, more preferably 100%, the average particle diameter of the conductive particles is 1 along the thickness direction from one surface of the conductive adhesive sheet. It is preferable that it exists in the area within 5 times. 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.
The anisotropic conductive adhesive sheet of the present invention preferably has a structure in which conductive particles are arranged and embedded in an adhesive sheet made of at least a curing agent and a curable insulating resin.

  The film thickness of the anisotropic conductive adhesive sheet is preferably 2 times or more and 40 μm or less, more preferably 3 times or more and 30 μm or less of the average particle diameter of the conductive particles. It is preferably 2 times or more from the viewpoint of aggregation due to resin flow at the time of connection, and when it is 40 μm or less, it is preferable that it is not easily affected by the flow of conductive particles at the connection portion due to resin flow.

The anisotropic conductive adhesive sheet of this invention is illustrated.
As the curable insulating resin used for the anisotropic conductive adhesive sheet, 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 addition to the curing agent and the curable insulating resin, a thermoplastic resin or the like may be blended in the anisotropic conductive adhesive sheet. 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 40 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.

Next, the manufacturing method of the anisotropic conductive adhesive sheet in the present invention will be illustrated.
As a method for producing the anisotropic conductive adhesive sheet, a pressure-sensitive adhesive layer having a convex portion having a height 0.1 to 3 times the average particle diameter of conductive particles on a biaxially stretchable film or sheet. The conductive particles are formed, and the conductive particles are arranged in a single layer, and then stretched to disperse the conductive particles, and the conductive particles are maintained in the stretched state at least with the curing agent and the curable material. It is preferable to transfer to an adhesive sheet made of an insulating resin. Even when the conductive particles adhered to the convex portions are stretched, the distance between the particles is difficult to spread, which is preferable. The height of the convex portion is preferably 0.1 to 3 times the average particle size of the conductive particles, more preferably 0.2 to 2 times, and still more preferably 0.4. Double to 1 time. A known method can be used as a method of forming the predetermined convex portion on the adhesive layer.

As a method for forming a laminate of a pressure-sensitive adhesive layer having a height of 0.1 to 3 times the average particle size of the conductive particles and a biaxially stretchable film, the average of the conductive particles as the height A pressure-sensitive adhesive layer is formed by dispersing a microgel of a pressure-sensitive adhesive component having a particle size of 0.1 to 3 times the particle size in the pressure-sensitive adhesive component and applying it to a biaxially stretchable film. It is preferable. In the case of a microgel, since the microgel is flexible, the conductive particles adhered to the convex portions made of them are difficult to spread the distance between the particles after biaxial stretching, and the influence of the height is also affected by biaxial stretching. Since it is hard to receive, it is preferable. The size of the microgel is preferably 0.1 to 3 times the average particle size of the conductive particles, more preferably 0.2 to 2 times, and still more preferably 0.4 to 1 time. . The number of convex portions formed by the microgel is 0.5 to 30% of the number (calculated value from the average particle diameter of the conductive particles) when the adhesive layer is filled with the conductive particles most closely. It is preferable that the number is 1 to 20%, more preferably 2 to 15%. It is preferable that the distance between them is at least twice the average particle diameter of the conductive particles. As a method of forming a convex part, it can produce by adjusting the density | concentration of a microgel dispersion liquid and apply | coating.
As a method for dispersing the microgel, a suspension solution is prepared by adding a solvent in which the adhesive is difficult to dissolve to the adhesive solution, and the resulting solution is filtered to obtain a microgel-containing solution having a predetermined size, or For example, a method of preparing a microgel-containing solution having a predetermined size by centrifuging the suspension can be used. It is also possible to use a method of mixing fine particles insoluble in the pressure-sensitive adhesive solution, a method of adding fine particles to a biaxially stretchable film, forming a convex portion, and forming a pressure-sensitive adhesive layer thereon. .

  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.

  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 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 1.6 mm × 15.1 mm silicon piece (thickness 0.5 mm), an aluminum thin film (1000 μm) measuring 77 μm wide and 80 μm long at an inner side of 40 μm at intervals of 23 μm. 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 60 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 silicon oxide 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 40 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 60 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, 60 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 形成) is formed on each lead-out wiring, and an insulating thin film (500 Å) of silicon oxide is formed on the entire portion under the chip except for the connection pad portion.

  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.

The connection structure was subjected to a thermal cycle test at -40 ° C. (30 minutes) and 80 ° C. (30 minutes) as one cycle, taken out after 250 cycles, and measured for connection resistance after 1 hour at 25 ° C. The case where the resistance value is less than twice is marked with ◯, and the case where it is two times or more is marked with x.
Similarly, another connection structure is produced, and the resistance between the paired lead wires is measured to obtain the insulation resistance value.
While maintaining this insulation resistance test substrate at 80 ° C. and 85% 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 lowering time is less than 240 hours is indicated by x, and the case where the insulation lowering time is 240 hours or more is indicated by ◯.

[Example 1]
37 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 Dissolve in (mixing ratio 1: 1) 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.) 29 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-form adhesive sheet of 20-micrometer-thickness.

10 g of methanol was added to a pressure-sensitive adhesive solution of 10 g of a natural rubber-methyl methacrylate graft copolymer and 180 g of toluene to prepare a pressure-sensitive adhesive suspension, and then a pressure-sensitive adhesive coating solution was prepared through a 5 μm filter.
The pressure-sensitive adhesive coating solution was coated on an unstretched polypropylene film having a thickness of 100 μm, and was heat-dried at 60 ° C. for 20 minutes to prepare a pressure-sensitive adhesive laminate film having a thickness of 3 μm. When a part of the surface of the pressure-sensitive adhesive laminate was observed with an electron microscope, a maximum convex portion of 2 μm was formed. A single layer of gold-plated plastic particles (conductive particles) having an average particle size of 3.0 μm was applied to the pressure-sensitive adhesive laminate film almost without any 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 in the vertical and horizontal directions using a biaxial stretching device (X6H-S, Toyo Seiki X6H-S, pantograph type corner stretching type biaxial stretching device), preheated at 130 ° C. for 120 seconds, Thereafter, the film was stretched and fixed by 100% at a speed of 10% / second. Then, after laminating the adhesive sheet on the stretched film, it was peeled off to obtain an anisotropic conductive adhesive sheet having a thickness of 20 μm.

As a result of laser microscope observation, the number of particles having the narrowest interparticle distance in the range of 0 to 1.5 μ among the 300 conductive particles is 97 (32.3%), of which two particle groups are There were 15 sets, 30 sets, 21 sets, 63 sets of 3 particles, and 4 sets of 4 sets of 4 particles, in which the particle center formed a substantially equilateral triangle. The other particles were single particles having the narrowest interparticle distance in the range of 3 to 15 μm. (67.6%)
In addition, 100% of 100 conductive particles were present within a range of 4.5 μm from the anisotropic conductive adhesive sheet surface.

[Example 2]
4 g of methanol and 1 g of acetone are added to an adhesive solution of 10 g of a natural rubber-methyl methacrylate graft copolymer and 185 g of toluene to prepare an adhesive suspension, and then the adhesive coating solution is passed through a 5 μm filter. Produced.
The pressure-sensitive adhesive coating solution was coated on an unstretched polypropylene film having a thickness of 100 μm, and was heat-dried at 60 ° C. for 20 minutes to prepare a pressure-sensitive adhesive laminate film having a thickness of 3 μm. When a part of the surface of the pressure-sensitive adhesive laminate was observed with an electron microscope, a convex portion having a maximum of 0.5 μm was formed.
An anisotropic conductive adhesive sheet having a thickness of 20 μm was produced in the same manner as in Example 1 except that the above-mentioned pressure-sensitive adhesive laminate film was used.

As a result of laser microscope observation, among 300 conductive particles, the number of particles having the narrowest inter-particle distance in the range of 0 to 1.5 μm is 111 (37%), of which 2 particle groups are 6 sets. , 12 particles, and 3 particle groups in which the particle center forms a substantially equilateral triangle were 33 sets, 99 particles. The other particles were single particles having the narrowest interparticle distance in the range of 3 to 15 μm. (63%)
In addition, 100% of 100 conductive particles were present within a range of 4.5 μm from the anisotropic conductive adhesive sheet surface.

[Comparative Example 1]
3 g of gold-plated plastic particles (3 μm) were put in a polyethylene bag, shaken for 5 minutes, and then dispersed on the grounded stainless steel plate from above 10 cm. Thereafter, in the same manner as in Example 1, it was laminated on an adhesive sheet to produce an anisotropic conductive adhesive sheet having a thickness of 20 μm.
As a result of laser microscope observation, among 300 conductive particles, the number of particles having the narrowest inter-particle distance in the range of 0 to 1.5 μm is 14 (4.6%), of which 3 particle groups are 1 There were 1 set, 5 particles, and 5 particle groups, and 1 particle group and 6 particles groups. There were 236 particles (78.7%) having the narrowest interparticle distance in the range of 3 to 15 μm, and the other interparticle distance was more than 15 μm. 50 (16.7%)
In addition, 100% of 100 conductive particles were present within a range of 4.5 μm from the anisotropic conductive adhesive sheet surface.
Using the anisotropic conductive adhesive sheet 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 apparent from Table 1, the anisotropic conductive adhesive sheet of the present invention exhibits very excellent insulation reliability and connection 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 (9)

  An anisotropic conductive adhesive sheet comprising at least a curing agent, a curable insulating resin and conductive particles, wherein the narrowest interparticle distance between the conductive particles is 0 to 0.5 of the average particle size of the conductive particles. Double conductive particles A occupy 5 to 60% of the total number of conductive particles, and the narrowest interparticle distance between the conductive particles is 1.0 to 5 times the average particle diameter of the conductive particles A certain conductive particle B occupies 40 to 95% of the total number of conductive particles, and the region within 1.5 times the average particle size of the conductive particles along the thickness direction from one surface of the anisotropic conductive adhesive sheet An anisotropic conductive adhesive sheet characterized in that 95% or more of the total number of conductive particles is present therein, and the thickness of the anisotropic conductive adhesive sheet is not less than twice the average particle diameter of the conductive particles and not more than 40 μm. .   The anisotropic conductive adhesive sheet according to claim 1, wherein 90% or more of the conductive particles present in the conductive particle group A are composed of 2 to 4 particle groups.   3. The conductive particles present in the conductive particle group A are 50% or more of three particle groups, and the center of each particle forms a substantially equilateral triangle. An anisotropic conductive adhesive sheet as described in 1.   The conductive particles are at least one selected from the group consisting of metal-coated resin particles, noble metal-coated metal particles, metal particles, noble metal-coated alloy particles and alloy particles, and the average particle size is 2 to 2 It is 8 micrometers, The anisotropically conductive adhesive sheet as described in any one of Claims 1-3 characterized by the above-mentioned.   On the biaxially stretchable film, a pressure-sensitive adhesive layer having a height of 0.1 to 3 times the average particle size of the conductive particles is provided to form a laminate, and the average particle is formed on the laminate. A conductive particle-attached film is prepared by attaching conductive particles having a diameter of 2 to 8 μm, and the conductive particle-attached film is biaxially stretched and held so that the stretch ratio is 1 to 5 times. 5. The method according to claim 1, further comprising a step of transferring the conductive particles to an adhesive sheet comprising at least a curing agent and a curable insulating resin after being axially stretched and held. The manufacturing method of the anisotropically conductive adhesive sheet of description.   The laminate has a particle size of 0.1 to 3 times the average particle size of the conductive particles and can be biaxially stretched with a microgel containing an adhesive component dispersed in the adhesive component The method for producing an anisotropic conductive adhesive sheet according to claim 5, wherein the anisotropic conductive adhesive sheet is obtained by laminating on a transparent film.   The method for producing an anisotropic conductive adhesive sheet according to claim 5 or 6, wherein the biaxially stretchable film is a long film, and the adhesive sheet is a long adhesive sheet.   In the method of electrically connecting an electronic circuit component having a fine connection terminal and a circuit board having a corresponding circuit with an anisotropic conductive adhesive sheet, the area of the connection portion of the electronic circuit board is an average of conductive particles An electronic circuit component that is in the range of 100 to 1000 times the area of a circle having a particle diameter as a diameter, and whose shortest distance between connection terminals is at least 4 times the average particle diameter, and the electronic circuit board and the corresponding electronic circuit board The circuit board which has a circuit is electrically connected using the anisotropic conductive adhesive sheet as described in any one of Claims 1-4, The connection method characterized by the above-mentioned.   A fine connection structure connected by the connection method according to claim 8.