JP4958417B2 - Conductive particle transfer sheet and connection structure - Google Patents

Description

The present invention relates to a conductive particle transfer sheet and a connection structure excellent in circuit connectivity.

  Until now, regarding the method for connecting the connection terminals of the electronic components, various connection methods have been studied in order to improve connectivity and prevent short circuit. For example, a method using an anisotropic conductive film, a joining method by forming a eutectic between metal surfaces of connection terminals, and the like are known. Among them, for fine circuit connection, a method using an anisotropic conductive film that can reduce the effect of height variation between terminals is common, but short-circuiting due to conductive particles between adjacent terminals is likely to occur. There was a problem.

  Therefore, studies have been made to dispose conductive particles only in the connection terminal portion. For example, a method of arranging conductive particles on a terminal through a mask in which corresponding openings are formed (see Patent Document 1), a pressure-sensitive adhesive layer is formed on a transparent film, and the conductive particles are attached to the back surface. A method in which the conductive particles are selectively peeled off by irradiating laser light, and the peeled conductive particles are transferred and arranged on the electrode (see Patent Document 2), or a photo having a pattern similar to that of the connection terminal The UV adhesive tape with UV-curing adhesive coated on the mask is in close contact with the UV adhesive tape to irradiate UV through the mask to form an adhesive part with the same pattern as the connection terminal on the UV adhesive tape, and conductive A method of disposing conductive particles, forming a conductive particle transfer tape, and transferring the conductive particles to the connection terminals (see Patent Document 3), through a mask in which openings are formed in a predetermined pattern And a method (see Patent Documents 4, 5 and 6) to the conductive particles transferred arranged in the adhesive layer is formed transfer plate on are known.

  However, in the prior art such as arranging conductive particles on the terminals, there is a limit in the manufacturing process to arrange the conductive particles on a large number of connection terminals, and it is possible to achieve both short-circuiting and connection with adjacent terminals. Was not satisfactory. Further, in the method in which the conductive particles are arranged in advance on the transfer sheet, when the pattern is fine, there is a limit to disposing the conductive particles by forming fine and many patterns. When the pattern is enlarged to form a dense region of conductive particles, the number of conductive particles transferred onto the connection terminal may be too large, and both short-circuit prevention and connection with the adjacent terminal can be satisfied. It was not a thing.

JP 7-6799 A JP-A-10-70151 Japanese Patent Laid-Open No. 10-321678 Japanese Patent No. 3256331 JP-A-11-135553 Japanese Patent Laid-Open No. 10-215065

  The present invention relates to a conductive particle transfer sheet that realizes good electrical connectivity without impairing insulation between adjacent circuits of a fine circuit, a method for producing the same, a method for producing a connection structure using the same, and the same An object of the present invention is to provide a connection structure using the.

As a result of intensive studies to solve the above problems, the present inventor is characterized in that conductive particles are arranged at a specific conductive particle interval on a support on which an adhesive layer is formed. It has been found that the above problems can be solved by using the conductive particle transfer sheet.
That is, the present invention is as follows.

(1) A conductive particle transfer sheet for transferring conductive particles to a connection surface of a connection terminal, the support, the adhesive layer formed on the surface of the support, and the conductivity adhered to the surface of the adhesive layer A conductive particle transfer sheet in which conductive particles are arranged so that the average particle interval between adjacent conductive particles is 0.3 to 5 times the average particle size of the conductive particles. The conductive particles are transferred only in contact with the connection surface of the first connection terminal, and then the connection surface of the first connection terminal transferred by the conductive particles is connected to the connection surface of the second connection terminal. A method for manufacturing a connection structure.
(2) When transferring the conductive particles by bringing the conductive particle transfer sheet into close contact with only the connection surface of the first connection terminal, an adhesive layer is formed on the connection surface in advance to transfer the conductive particles. (1) The manufacturing method of the connection structure according to (1).
(3) When connecting the connection surface of the first connection terminal to which the conductive particles have been transferred to the connection surface of the second connection terminal, the connection is made via an insulating adhesive sheet (1) The manufacturing method of the connection structure as described in (2).
(4) A connection structure manufactured by the method for manufacturing a connection structure according to any one of (1) to (3).

  The conductive particle transfer sheet and the fine connection structure of the present invention have good insulation characteristics between adjacent electrode terminals and allow good electrical connectivity between connected connection terminals. That is, by using the conductive particle transfer sheet of the present invention, the conductive particles can be arranged at a specific interval only on the connection surface of the first connection terminal. Next, by electrically connecting the first connection terminal and the corresponding second connection terminal via the conductive particles, while ensuring the insulation between the adjacent terminals, in the direction of the connection surface, There is little variation in the number of conductive particles, and stable connection can be obtained by arranging them uniformly.

Hereinafter, the present invention will be specifically described.
First, the conductive particles in the conductive particle transfer sheet of the present invention will be described.
The conductive particles are preferably one or more selected from metal-coated resin particles, metal-coated metal particles, metal particles, metal-coated alloy particles, and alloy particles.

The metal-coated resin particles are preferably metal-coated on spherical particles such as polystyrene, benzoguanamine, and polymethyl methacrylate.
In the case of forming a bond by interdiffusion of metal with the electrode terminal, for example, one coated with one or more metals or alloys selected from tin, zinc, silver, copper, indium, bismuth, etc. is used. be able to. In the case of connection by contact, precious metal coating is preferable, and nickel and gold coated in this order are preferably used.
Resin particles coated with metal using more flexible resin particles can be formed 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 metal, it is preferable to use metal particles such as nickel and copper as the core. In the case of forming a bond with the connection terminal by mutual diffusion of metal, for example, one coated with one or more metals or alloys selected from tin, zinc, silver, copper, indium, bismuth, etc. is used. be able to. In the case of connection by contact, precious metal coating is preferable, and it is preferable to use a precious metal such as gold, palladium or rhodium coated 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 metal-coated alloy particles, for example, alloy particles composed of two or more kinds selected from gold, silver, copper, nickel, tin, zinc, bismuth, indium, etc., which are metal-coated 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 average particle size of the conductive particles is preferably 1 to 50 μm, and more preferably 2 to 30 μm. The thickness is preferably 50 μm or less from the viewpoint of insulation, and is preferably less than 1 μm from the viewpoint of electrical connectivity, and is not easily affected by variations in height of connection terminals and the like.
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 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.

Next, the conductive particle transfer sheet of the present invention will be described.
The conductive particle transfer sheet of the present invention comprises a support, an adhesive layer and conductive particles. The conductive particle transfer sheet is for connection terminal connection. That is, when the conductive particle transfer sheet electrically connects the corresponding connection terminals to each other via the conductive particles in order to connect the connection terminals of the first electronic component and the connection terminal of the second electronic component. It is a sheet used for. The conductive particle transfer sheet is used by transferring conductive particles to the connection surface of the connection terminal.

A known resin film can be used as the support used in the conductive particle transfer sheet of the present invention. For example, a polypropylene film and the like can be mentioned. Among them, it is preferable to use a biaxially stretchable film. The biaxially stretchable film will be described later.
The thickness of the support is preferably from 10 μm to 200 μm, and more preferably from 50 μm to 100 μm. 10 μm or more is preferable from the viewpoint of mechanical connection strength, and 200 μm or less is preferable from the viewpoint of ensuring smoothness during transfer of conductive particles.

An adhesive such as non-crosslinkable acrylic-modified natural rubber can be used for the adhesive layer in the conductive particle transfer sheet of the present invention. A preferable pressure-sensitive adhesive in the case of producing a conductive particle transfer sheet by biaxially stretching the support will be described later.
The thickness of the pressure-sensitive adhesive layer in the conductive particle transfer sheet of the present invention is preferably in the range of 0.05 to 0.7 times the average particle size of the conductive particles. It is preferably 0.05 times or more from the viewpoint of holding conductive particles, and preferably 0.7 times or less from the viewpoint of ease of transfer.

In the conductive particle transfer sheet of the present invention, the conductive particles are arranged so that the average particle interval between adjacent conductive particles is 0.3 to 5 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.

The average particle spacing between adjacent conductive particles is determined as follows.
First, a photograph of the conductive particle transfer sheet of the present invention is taken with an optical microscope from the surface side where the conductive particles are present. Next, arbitrary 20 conductive particles are selected, the distance from the 6 conductive particles closest to the respective conductive particles is measured, the average value of the whole is obtained, and the average particle interval is obtained. . At the same time, the standard deviation of the particle interval can be obtained.
The average particle interval is 0.3 to 5 times the average particle size of the conductive particles. Preferably, they are 0.5 times or more and 3 times or less, More preferably, they are 1 time or more and 3 times or less. From the viewpoint of preventing protrusion of particles during transfer of conductive particles, the average particle diameter is preferably 0.3 times or more, and from the viewpoint of securing the number of conductive particles transferred, it is preferably 5 times or less of the average particle diameter.
As for the standard deviation of the particle spacing, the conductive particles may be present with a standard deviation of the average particle spacing of 0.3 times or less, more preferably 0.1 times or less of the average particle spacing of the conductive particles. preferable.

Next, the manufacturing method of the electroconductive particle transfer sheet in this invention is demonstrated.
As a method for producing the conductive particle transfer sheet of the present invention, the conductive particles are on the adhesive layer so that the average particle spacing between adjacent conductive particles is 0.3 to 5 times the average particle size of the conductive particles. As long as it can be arranged in a well-known manner, a known method can be used.

  As a method for producing the conductive particle transfer sheet of the present invention, a biaxially stretchable film is used as a support, and a laminate is formed by providing an adhesive layer on the biaxially stretchable film. A conductive particle adhesion film is prepared by adhering conductive particles on the conductive particle adhesion film, and the average particle interval between adjacent conductive particles is 0.3 times the average particle diameter of the conductive particles. It is preferable to include a step of biaxial stretching and holding so as to be ˜5 times.

  As the biaxially stretchable film, a known resin film or the like can be used. A polyethylene resin, a polypropylene resin, a polyester resin, a polyvinyl butyral resin, a polyvinyl alcohol resin, a polyvinylidene chloride resin or the like can be used alone or as a copolymer. Or 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. A film having a shrinkage ratio of 10% or less after stretching is preferred.

  As the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer, a known one can be used, but when biaxial stretching is performed while heating, it is preferable to use a non-thermal crosslinkable pressure-sensitive adhesive. Specifically, natural rubber latex adhesive, synthetic rubber latex adhesive, synthetic resin emulsion adhesive, silicone adhesive, ethylene-vinyl acetate copolymer adhesive, acrylic adhesive, etc. Or they can be used in combination. Further, it is preferable to use an acrylic pressure-sensitive adhesive that can be reduced in viscosity by ultraviolet irradiation.

  The thickness of the adhesive layer is preferably in the range of 1/50 to 10 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 when the conductive particles are attached and stretched, the thickness of the adhesive layer is preferably 1/50 or more of the average particle diameter of the conductive particles, and the particle transfer to the conductive particle transfer sheet after stretching In view of the above, 10 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 preparing a conductive particle-attached film by attaching conductive particles on the laminate, it is preferable to prepare a film in which conductive particles are arranged (closely packed) in a single layer with almost no gap. 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.

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

As a method for biaxially stretching the obtained conductive particle-adhered film, a known method can be used, but it is preferable to use a biaxial stretching apparatus from the viewpoint of uniform dispersion arrangement. From the viewpoint of particle spacing, the degree of stretching is preferably 30% 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.

  It is preferable to hold the conductive particle transfer film after stretching so that the conductive particle spacing does not change. Examples of the holding method include a method in which the conductive particle transfer film is bonded and fixed to a metal or resin frame, a method in which the conductive particle transfer film is bonded and fixed to a support plate made of glass or metal having good smoothness, and the like. .

Next, the conductive particle transfer sheet is brought into close contact with the connection surface of the first connection terminal to transfer the conductive particles, and then the connection surface of the first connection terminal to which the conductive particles are transferred is used as the second connection terminal. A method for manufacturing a connection structure connected to the connection surface will be described.
As a method for transferring the conductive particles by using the conductive particle transfer sheet of the present invention to adhere to the connection surface of the first connection terminal, the conductive particle transfer sheet is fixed on a smooth plate, and the conductive particles are transferred. A method of transferring by connecting the connection terminals to the conductive particles on the transfer sheet is preferable. Examples of the transfer method include the following methods.

1. A method in which a connection terminal is pressed onto a conductive particle transfer sheet and is mechanically bitten. In this case, it can be used in combination with a method of previously forming an adhesive layer on the connection surface of the connection terminal. The combination is preferable because transfer can be performed at a lower temperature and a lower pressure.
As the adhesive layer, thermoplastic, thermosetting, photocurable, and photothermosetting adhesives and adhesives can be used, but from the viewpoint of transfer, it is preferably made of a curable component.
The load is preferably in the range of 0.1 g to 10 g, more preferably in the range of 0.3 g to 5 g, per particle to be transferred.
The temperature is preferably in the range of 30 ° C. to 200 ° C., more preferably 50 ° C. to 150 ° C.

2. A method in which a connection terminal is brought into contact with conductive particles while being pressed and transferred by applying ultrasonic vibration. The ultrasonic vibration application time is preferably in the range of 0.1 to 5 seconds, more preferably in the range of 0.2 to 1 second.

3. A method in which an electrode terminal is brought into contact with conductive particles and heated to a temperature at which the metal on the surface of the connection terminal and the metal on the surface of the conductive particle mutually diffuse to form a metal bond and transfer.
In this case, it is preferable to select a metal or alloy that relatively easily diffuses, and the metal or alloy on the surface of the conductive particles preferably has a melting point of 500 ° C. or lower, preferably 300 ° C. or lower. In order to reduce the influence of the metal oxide, it is preferable to apply a flux component on the connection terminals in advance. When transferring the conductive particles after applying the flux component, it is preferable to wash the flux component after transferring the conductive particles.

  When the conductive particles are transferred to the connection terminal using the conductive particle transfer sheet of the present invention, the sum of the projected areas of the transferred conductive particles with respect to the area of the connection surface of the connection terminal is 1% to 70%. It is preferably in the range, more preferably in the range of 10% to 60%. The sum of the projected areas is preferably 1% or more from the viewpoint of connectivity, and when the connection terminals are connected to the substrate, the sum of the projected areas is 70% from the viewpoint of a decrease in insulation due to protrusion of transfer particles. The following is preferable. The sum of the projected areas of the transferred conductive particles can be measured by taking a photograph of the connecting terminal portion to which the particles have been transferred using a laser microscope or the like, and performing image processing.

The average particle spacing of the transferred conductive particles is preferably in the range of 0.3 to 5 times the average particle size of the conductive particles. The standard deviation of the number of conductive particles transferred to each connection terminal is preferably 0.2 times or less, more preferably 0.1 times or less of the average number of transfer particles.
As a material for the connection terminal used in the connection structure of the present invention, a known material can be used. As an example, a metal surface such as gold, a gold alloy, or copper is coated with nickel and gold in this order.

As a method for producing a connection structure, the connection surface of the first connection terminal transferred by the conductive particles is connected to the connection surface of the second connection terminal using the conductive particle transfer sheet of the present invention. This method can be used. For example, the method of crimping with the corresponding terminal, the method of connecting with the corresponding terminal by ultrasonic vibration, the metal on the surface of the conductive particles by heating, the metal and the connection terminal surface metal corresponding to each other is diffused between each other A method or the like can be used.
When the corresponding connection terminal is a metal type, an ultrasonic vibration method or an interdiffusion method between metals can be used, and when the corresponding connection terminal is a metal oxide type, a crimping method can be used. When connecting using a crimping method or an ultrasonic method, it is preferable to seal a portion other than the connecting portion with a curable resin or the like.

As a method of sealing, it can seal using an insulating adhesive sheet or an adhesive agent.
In connecting the connection surface of the first connection terminal to which the conductive particles are transferred and the connection surface of the second connection terminal, it is a preferable embodiment of the present case to connect via the insulating adhesive sheet. In this case, the curable resin can be cured by heating at the time of connection. Further, after the connection, the thermosetting resin can be cured by heating. In the case of the interdiffusion method between metals, after connection, it can be sealed using a low-viscosity liquid sealing resin.

  As the curable insulating resin used for the insulating adhesive sheet or adhesive, thermosetting resin, photocurable resin, light and thermosetting resin, electron beam curable resin, and 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 for the insulating adhesive sheet or adhesive 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 insulating adhesive sheet or adhesive. 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 in the insulating resin are phenoxy resin, polyvinyl acetal resin, polyvinyl butyral resin, alkylated cellulose resin, polyester resin, acrylic resin, styrene resin, urethane resin, polyethylene terephthalate resin, etc. One or two or more resins may be combined. 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.

Insulating adhesive sheets or adhesives may contain additives in 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 present invention also relates to a connection structure connected by a connection terminal having conductivity transferred by a conductive particle transfer sheet.
The material of the substrate having the connection terminals constituting the connection structure of the present invention may be an organic substrate or an inorganic substrate. As the organic substrate, a polyimide film substrate, a polyamide film substrate, a polyethersulfone film substrate, a rigid substrate obtained by impregnating a glass cloth with an epoxy resin, a rigid substrate obtained by impregnating a glass cloth with a bismaleimide-triazine resin, or the like may be used. it can. As the inorganic substrate, a silicon substrate, a glass substrate, an alumina substrate, an aluminum nitride substrate, or the like can be used. The wiring material of the wiring board is inorganic wiring materials such as indium tin oxide and indium zinc oxide, metal wiring materials such as gold-plated copper, chromium-copper, aluminum and gold bumps, and metal materials such as aluminum and chromium indium tin oxide. A composite wiring material covering an inorganic wiring material such as an object can be used.

Applications for applying the conductive particle transfer sheet of the present invention or 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, and electroluminescence display devices. It can also be used for mounting electronic components such as LSIs of these devices, wiring board connection parts of other devices, and mounting electronic components such as LSIs. Among the display devices, it is preferably used for plasma display devices and electroluminescence display devices that require reliability.
Next, the present invention will be described with reference to examples and comparative examples.

[Example 1]
On a non-stretched polypropylene film with a thickness of 90 μm, a graft copolymer adhesive of nitrile rubber latex-methyl methacrylate as an adhesive layer is applied to a thickness of 4 μm, and gold with an average particle size of 3.0 μm as conductive particles. The plated plastic 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 film was fixed using 10 chucks in the vertical and horizontal directions using a biaxial stretching device (X6H-S manufactured by Toyo Seiki, pantograph type corner stretch type biaxial stretching device), and preheated at 135 ° C. for 120 seconds. Thereafter, the film was stretched and fixed by 200% at a speed of 10% / second. Then, it fixed using the 15 cm square glass plate (thickness 5mm) which apply | coated the adhesive agent to 1 cm of outer periphery, and obtained the electroconductive particle transfer sheet.
As a result of randomly selecting 20 of the conductive particles of the obtained conductive particle transfer sheet and observing them using a laser microscope (Keyence Corporation, VK9500, shape measurement resolution 0.01 μm), the average particle spacing is It was 11.2 μm, which was 3.7 times the average particle size.
When the thickness of the adhesive layer was measured with a stylus-type film thickness meter, it was 1 μm, which was 0.33 times the average particle diameter of the conductive particles.

[Example 2]
The same nitrile rubber latex-methyl methacrylate graft copolymer adhesive as in Example 1 was applied to a thickness of 3 μm on an unstretched polypropylene film having a thickness of 100 μm. A conductive particle-adhered film was obtained in which gold-plated plastic particles were applied in a single layer with almost no gap by the same method as in Example 1.
This film was fixed by stretching 120% in the longitudinal and lateral directions using a biaxial stretching apparatus in the same manner as in Example 1. Thereafter, an adhesive was applied to the outer periphery of 1 cm and fixed to a plastic plate (square, 15 cm square, thickness 5 mm) cut through the inside to obtain a conductive particle transfer sheet.
As a result of randomly selecting 20 of the conductive particles of the obtained conductive particle transfer sheet and observing them using a laser microscope (Keyence Corporation, VK9500, shape measurement resolution 0.01 μm), the average particle spacing is It was 8.49 μm, which was 1.7 times the average particle size.
When the thickness of the adhesive layer was measured with a stylus type film thickness meter, it was 0.7 μm, which was 0.14 times the average particle diameter of the conductive particles.

[Example 3]
In the same manner as in Example 1, gold-plated copper particles having an average particle diameter of 3.2 μm were applied as conductive particles to an unstretched polypropylene film having a thickness of 100 μm coated with 3 μm of an ethylene-vinyl acetate copolymer adhesive. A conductive particle adhesion film coated with a single layer with almost no gap was obtained.
This film was fixed by stretching 150% in the longitudinal and lateral directions using a biaxial stretching apparatus in the same manner as in Example 1. Thereafter, an adhesive was applied to the outer periphery of 1 cm and fixed to a plastic plate (square, 15 cm square, thickness 5 mm) cut through the inside to obtain a conductive particle transfer sheet.
As a result of randomly selecting 20 of the conductive particles of the obtained conductive particle transfer sheet and observing them with a laser microscope (VK9500, manufactured by Keyence Corporation, shape measurement resolution 0.01 μm), The average particle spacing was 6.72 μm, which was 2.11 times the average particle size.
When the thickness of the adhesive layer was measured with a stylus type film thickness meter, it was 0.49 μm, which was 0.15 times the average particle diameter of the conductive particles.

[Comparative Example 1]
An average particle size of 3.0 μm as conductive particles is applied to a non-stretched polypropylene film having a thickness of 10 μm and a 0.5 μm thick nitrile rubber latex-methyl methacrylate graft copolymer adhesive as an adhesive layer. A single layer of gold-plated plastic particles was applied 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. Thereafter, excess particles were scraped off with a scrubber made of soft rubber, and then fixed using a 15 cm square glass plate (thickness 5 mm) coated with an adhesive on the outer periphery 1 cm to obtain a conductive particle transfer sheet. Since the conductive particles are densely packed, it is difficult to measure the average particle spacing.
Table 1 shows a summary of the average particle diameter of the conductive particles and other numerical values for the conductive particle transfer sheets of the above Examples and Comparative Examples.

The test results of connecting the connection terminals using the conductive particle transfer sheets of Examples and Comparative Examples will be described below. First, test methods and the like are shown below.
(Insulating adhesive sheet)
Acetic acid is 34 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), 29 g of bisphenol A type epoxy resin (epoxy equivalent 190, 25 ° C. viscosity, 14000 mPa · S), 0.4 g of γ-glycidoxypropyltrimethoxysilane. Dissolve in a mixed solvent of ethyl-toluene (mixing ratio 1: 1) to obtain a 50% solid content solution.
A liquid epoxy resin containing a microcapsule-type latent imidazole curing agent (average particle diameter of microcapsule 5 μm, active temperature 125 ° C.) 37 g is mixed and dispersed in the 50% solid content solution. Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film (base film), air-dried at 60 degreeC for 15 minute (s), and the film-form insulating adhesive sheet with a film thickness of 18 micrometers was obtained.

(Connection resistance measurement method)
After an oxide film is formed on the entire surface of a silicon piece (thickness 0.5 mm) of 1.6 mm × 15.1 mm in length and width, an aluminum thin film (1000 mm) having a width of 74.5 μm and a length of 120 μm is 40 μm inside from the outer side. 175 pieces are formed on the long side and 16 pieces are formed on the short side, respectively, so as to have an interval of 1 μm. In order to form two gold bumps (thickness: 15 μm) each having a width of 25 μm and a length of 80 μm on the aluminum thin film at intervals of 15 μm, the inner side of each gold bump is placed 7.5 μm inside by 10 μm laterally. Then, a polyimide protective film is formed on the entire surface other than the opening by a conventional method except for leaving the opening having a length of 85 μm. Thereafter, the gold bump is formed to obtain a test chip.
A connection pad (1500 mm) of indium tin oxide film (1500 mm) so that gold bumps on the 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. 66 μm wide and 120 μm long). Each time 20 gold bumps are connected, a lead wire of an indium zinc oxide thin film is formed on the connection pad, and an aluminum-titanium thin film (titanium 1%, 3000 mm) is formed on the lead wire. To do.

The test chip was placed on a glass substrate coated with the adhesive listed in Table 1 with a thickness of 1 μm so that the bumps contacted, and the adhesive was transferred onto the bumps by applying a load of 0.1 MPa for 2 seconds. Thereafter, a conductive particle transfer sheet is placed on the glass substrate, the chip is placed on the conductive particle surface, and the conductive particles are transferred onto the bumps by applying pressure of 1 MPa at 40 ° C. for 3 seconds. Chip. An insulating adhesive sheet having a width of 2 mm and a length of 17 mm is temporarily stretched on the connection evaluation board so as to cover all the connection pads, and a pressure bonding head having a width of 2.5 mm is used. After pressurizing for 3 seconds, the polyethylene terephthalate base film is peeled off. Then, a conductive particle transfer test chip is placed so that the positions of the connection pads and the gold bumps are matched, and pressure bonding with pressure is performed at 210 ° C. for 5 seconds at 2.0 MPa. After the crimping, the resistance value between the lead wires (daisy chain of 20 gold bumps) is measured with a four-terminal resistance meter to obtain a connection resistance value.

(Insulation resistance test method)
A connection pad (65 μm wide, 120 μm long) of an indium zinc oxide film (1500 mm) is formed on a non-alkali glass with a thickness of 0.7 mm so that the two gold bumps on the aluminum thin film are connected to each other. To do. A connection wiring of an indium zinc oxide thin film is formed so that every other five connection pads can be connected, and further, every five other connection pads can be connected so as to form a comb pattern. A connection wiring of an indium zinc oxide thin film is formed. A lead wire of an indium zinc oxide thin film is formed on each connection wire, and an aluminum-titanium thin film (titanium 1%, 3000 mm) is formed on the lead wire to obtain an insulating evaluation substrate. On the insulating evaluation substrate, an adhesive sheet having a width of 2 mm and a length of 17 mm is temporarily stretched so as to cover all the connection pads, and using a 2.5 mm width crimping head, 80 ° C., 0.3 MPa, After pressurizing for 3 seconds, the polyethylene terephthalate base film is peeled off. A conductive particle transfer test chip prepared in such a manner that the connection pads and gold bumps are aligned with each other (connection resistance value measuring method) is mounted and pressure-bonded at 200 ° C. for 10 seconds and 1.2 MPa, and an insulation resistance test is performed. A substrate is used.
A DC voltage of 100 V is applied between a pair of lead wires using a constant voltage constant current power source on this insulation resistance test substrate. The insulation resistance between these wirings is measured, and those having an insulation resistance value of 1 MΩ or less are evaluated as x, and cases where the resistance is 1 MΩ or more are evaluated as ◯.

The results are shown in Table 2. As is apparent from Table 2, the anisotropic conductive adhesive sheet of the present invention exhibits very excellent insulation reliability.
In Table 2, since Comparative Example 1 did not maintain an appropriate conductive particle interval, conductive particles were clogged between connection terminals in the pattern surface after being transferred to the connection surface.

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

It is the schematic which shows the structure of the cross section of the electroconductive particle transfer sheet of this invention. It is the schematic which shows the structure of the cross section of the connection structure of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive particle 2 Adhesive 3 Support body 4 Insulating resin and hardening agent 5 Connection terminal

Claims (4)

A conductive particle transfer sheet for transferring conductive particles to a connection surface of a connection terminal, comprising a support, an adhesive layer formed on the surface of the support, and conductive particles attached to the surface of the adhesive layer The conductive particle transfer sheet in which the conductive particles are arranged so that the average particle interval between the adjacent conductive particles is 0.3 to 5 times the average particle size of the conductive particles. The connection is characterized in that the conductive particles are transferred only in contact with the connection surfaces of the terminals, and then the connection surfaces of the first connection terminals transferred by the conductive particles are connected to the connection surfaces of the second connection terminals. Manufacturing method of structure. When transferring conductive particles by bringing the conductive particle transfer sheet into close contact with only the connection surface of the first connection terminal, an adhesive layer is formed on the connection surface in advance to transfer the conductive particles. The manufacturing method of the connection structure of Claim 1.   3. The connection according to claim 1, wherein when the connection surface of the first connection terminal to which the conductive particles are transferred is connected to the connection surface of the second connection terminal, the connection is made via an insulating adhesive sheet. Method for manufacturing the connection structure of the present invention.   The connection structure manufactured by the manufacturing method of the connection structure of any one of Claims 1-3.

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