JP2006028521A - Addhesive for circuit connection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive for circuit connection with which the connection resistance increases by the internal stress based on thermal expansion coefficient difference, the detachment of the adhesive, and the distortion of chips and substrates are suppressed. <P>SOLUTION: This circuit connection adhesive is a heating adhesion adhesive which connects two circuit electrodes facing each other, by heating and pressing them, electrically in the pressing direction. In the adhesive, rubber particles whose average particle size is not more than 10 μm are dispersed. The adhesive contains a reactive resin which is cured with heat and a sulfonium salt as a latent hardener. The starting temperature of heat release of the adhesive by DSC(differential scanning calorimetry) is not lower than 60°C. The temperature at which 80% of the curing reaction of the adhesive finishes is not higher than 260°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an adhesive for circuit connection used for connecting circuit boards to each other or an electronic component such as an IC chip and a wiring board.

When electrically connecting circuit boards to each other or an electronic component such as an IC chip and a circuit board, an adhesive or an anisotropic conductive adhesive in which conductive particles are dispersed is used. That is, by placing these adhesives between the electrodes facing each other and connecting the electrodes by heating and pressurization, electrical connection can be made by providing conductivity in the pressurization direction. For example, Patent Document 1 proposes an adhesive for circuit connection based on an epoxy resin.
Japanese Patent Laid-Open No. 3-16147

  However, adhesives that use conventional adhesives based on epoxy resin are connected at the connecting part due to internal stress based on the difference in thermal expansion coefficient of the connection board when reliability tests such as thermal shock test and PCT test are performed. There is a problem that resistance increases and peeling of the adhesive occurs. Moreover, when mounting a chip | tip directly on a board | substrate via an adhesive agent, the flexible wiring board which uses a polymer film, such as a printed circuit board using a FR4 base material etc. as a connection board, a polyimide, polyester, or a glass substrate If used, warpage of the chip and the substrate is likely to occur due to internal stress based on the difference in thermal expansion coefficient from the chip after connection. The present invention provides an adhesive for circuit connection in which an increase in connection resistance of a connection part due to internal stress based on a difference in thermal expansion coefficient, peeling of an adhesive, and occurrence of warpage of a chip or a substrate are suppressed.

  The adhesive for circuit connection of the present invention is a heat-adhesive adhesive that electrically connects the electrodes in the pressing direction by heating and pressing the facing circuit electrodes, and the adhesive has at least an average. Reactive resin in which rubber particles having a particle size of 10 μm or less are dispersed and cured by heat, and a sulfonium salt as a latent curing agent, the starting temperature of heat generation by DSC (differential scanning calorimetry) of the adhesive is 60 ° C. The temperature at which 80% of the curing reaction is completed is 260 ° C. or less. DSC is based on the zero position method in which the amount of heat is supplied or removed so that the temperature difference from a standard sample that does not generate heat or endotherm is constantly canceled within the measurement temperature range. It can be measured using it. The reaction of the adhesive is an exothermic reaction, and when the temperature of the sample is increased at a constant rate of temperature increase, the sample reacts to generate heat. The calorific value is output to a chart, the area surrounded by the calorific curve and the base line is obtained with the baseline as a reference, and this is defined as the calorific value. Measurement is performed at a temperature increase rate of 10 ° C./min from room temperature to about 300 ° C., and the above-described calorific value is obtained. Some of these are performed automatically, and can be easily performed by using them. The temperature at which 80% of the curing reaction is completed can be obtained from the area of the calorific value.

  As the reactive resin, a resin comprising at least an epoxy resin and a latent curing agent is preferably used. Further, 0.2 to 30% by volume of conductive particles can be dispersed in these adhesives.

  According to the adhesive for circuit connection of the present invention, since the rubber particles are dispersed in the adhesive, it can absorb internal stress generated in reliability tests such as thermal shock and PCT test, and can be connected even after the reliability test. There is no increase in connection resistance or peeling of the adhesive at the portion, and connection reliability is improved. Further, since the warpage of the substrate is reduced when the chip is mounted on the LCD panel, adverse effects on the display quality can be suppressed. Therefore, the adhesive for circuit connection of the present invention is for electrically connecting the LCD panel and TAB, TAB and printed circuit board, LCD panel and IC chip, and IC chip and printed circuit board only in the pressurizing direction at the time of connection. Preferably used.

  The present invention is an adhesive comprising a reactive resin that is cured by heat in which rubber particles having an average particle size of 10 μm or less, preferably 5 μm or less are dispersed. The reactivity of the adhesive can be measured by DSC (temperature increase rate: 10 ° C./min). As a reactive resin, the heat generation start temperature at DSC is 60 ° C. or more and 80% of the curing reaction is completed. A resin whose temperature is 260 ° C. or lower is used. Examples of reactive resins include a mixture of an epoxy resin and an imidazole series, a hydrazide series, a boron trifluoride-amine complex, a sulfonium salt, an amine imide, a polyamine salt, a dicyandiamide, and other radical curing resins. A mixture of peroxides is used.

Epoxy resins used in the present invention include bisphenol-type epoxy resins derived from epichlorohydrin and bisphenol A, F, AD, etc., epoxy novolac resins derived from epichlorohydrin and phenol novolac or cresol novolac, and skeletons containing a naphthalene ring. It is possible to use various epoxy compounds having two or more glycidyl groups in one molecule such as naphthalene type epoxy resin, glycidylamine, glycidyl ether, biphenyl, alicyclic, etc. Is possible. For these epoxy resins, it is preferable to use a high-purity product in which impurity ions (Na ⁺ , Cl ^−, etc.), hydrolyzable chlorine and the like are reduced to 300 ppm or less, in order to prevent electron migration.

  The rubber particles dispersed in the reactive resin are not particularly limited as long as the glass particles have a glass transition temperature of 25 ° C. or lower, but butadiene rubber, acrylic rubber, styrene-butadiene styrene rubber, acrylonitrile-butadiene rubber, silicone A rubber or the like can be used, and those having an average particle size of 0.1 to 10 μm are used, and rubber particles in which the particles having an average particle size or less occupy 80% or more of the particle size distribution are particularly preferable, more preferably 0. . Those having a size of 1 to 5 μm are used. Further, when the surface of the fine particles is treated with a coupling agent, it is more preferable because dispersibility with respect to the reactive resin is improved. Among the rubber particles, the silicone rubber particles can be used as effective rubber particles because they are excellent in solvent resistance and dispersibility. Silicone rubber particles can be hydrolyzed and polycondensed by adding a silane compound and methyltrialkoxysilane and / or a partially hydrolyzed condensate thereof to an aqueous alcohol solution adjusted to pH> 9 with a basic substance such as caustic soda or ammonia. It can be obtained by copolymerization of organosiloxane. In addition, silicone fine particles containing a functional group such as a hydroxyl group, an epoxy group, a ketimine, a carboxyl group, or a mercapto group at the molecular terminal or inner molecular chain are preferable because dispersibility in a reactive resin is improved. The storage elastic modulus at room temperature of the rubber particles used in the present invention is 0. 1 to 100 MPa is preferable, and 1 to 30 MPa is more preferable for reducing dispersibility of rubber particles and interfacial stress at the time of connection.

  Moreover, in order to make film formation easier, adhesives can also contain thermoplastic resins such as phenoxy resin, polyester resin, and polyamide resin. These film-forming polymers are effective in relieving stress when the reactive resin is cured. In particular, when the film-forming polymer has a functional group such as a hydroxyl group, the adhesiveness is improved, which is more preferable.

  For film formation, an adhesive composition composed of at least epoxy resin, rubber particles, and latent curing agent is liquefied by dissolving or dispersing in an organic solvent, and applied to a peelable substrate, and the temperature is below the activation temperature of the curing agent. By removing the solvent. The solvent used at this time is preferably an aromatic hydrocarbon-based and oxygen-containing mixed solvent because the solubility of the material is improved.

  In the adhesive for circuit connection of the present invention, conductive particles can be mixed and dispersed for the purpose of positively imparting anisotropic conductivity in order to absorb variations in the height of the bumps of the chip and the substrate electrodes. In the present invention, the conductive particles are, for example, metal particles such as Au, Ag, Cu, and solder, and a polymer spherical core material such as polystyrene provided with a conductive layer such as Ni, Cu, Au, and solder. More preferred. Furthermore, a surface layer of Sn, Au, solder or the like can be formed on the surface of the conductive particles. The particle size needs to be smaller than the minimum distance between the electrodes of the substrate. When there is a variation in the height of the electrodes, it is preferably larger than the variation in height, and preferably from 1 to 10 μm. The amount of conductive particles dispersed in the adhesive is 0.1 to 30% by volume, preferably 0.2 to 15% by volume.

  An inorganic filler can be mixed and dispersed in the adhesive for circuit connection of the present invention. The inorganic filler is not particularly limited, and examples thereof include powders such as fused silica, crystalline silica, calcium silicate, alumina, and calcium carbonate. The blending amount of the inorganic filler is preferably 10 to 200 parts by weight with respect to 100 parts by weight of the adhesive composition. The larger the blending amount, the more effective it is to reduce the thermal expansion coefficient. If the blending amount is small, the thermal expansion coefficient cannot be sufficiently lowered. For these reasons, 20 to 90 parts by weight are more preferable. The average particle size is preferably 3 microns or less for the purpose of preventing poor conduction at the connection. Further, it is desirable to use a spherical filler for the purpose of preventing a decrease in resin fluidity at the time of connection and damage to the passivation film of the chip. The inorganic filler can be mixed and dispersed together with the conductive particles or in a layer in which the conductive particles are not used. The calorific value based on the curing reaction of the adhesive can be determined by DSC (temperature increase rate: 10 ° C./min). In the adhesive for circuit connection of the present invention, the compounding amount of the reactive resin, rubber particles, film forming material, etc. is adjusted so that the calorific value is 50 to 140 J / g. Furthermore, a preferable calorific value is 60 to 100 J / g. When the heat generation amount of the adhesive exceeds 140 J / g, the internal stress increases due to an increase in the curing shrinkage force and elastic modulus of the adhesive, and when the circuits are connected to each other, the circuit boards are warped, and the connection reliability is reduced. This causes a problem that deteriorates the characteristics of electronic components. On the other hand, if the calorific value is less than 50 J / g, the adhesive is not sufficiently hardened, which causes a problem that the adhesiveness and connection reliability are lowered. Further, the temperature at which 80% of the curing reaction is completed is set to 260 ° C. or less, and the upper limit of the curability of the adhesive and the connection temperature is secured.

Example 1 50 g of phenoxy resin (Union Carbide, PKHC) was dissolved in 115 g of ethyl acetate to obtain a 30 wt% solution. Silicone fine particles were added to an aqueous alcohol solution having a pH of 12 stirred at 300 rpm with methyltrimethoxysilane at 20 ° C., hydrolyzed and condensed to obtain spherical fine particles having a storage elastic modulus of 8 MPa at 25 ° C. and an average particle size of 2 μm. 45 g of phenoxy resin, 30 g of silicone fine particles, 20 g of liquid epoxy (epoxy equivalent 185, manufactured by Asahi Kasei Kogyo Co., Ltd., Novacure HX-3941), bisphenol A type epoxy (epoxy equivalent 180) 5 g) was blended, and 6 vol% of conductive particles having an Au layer formed on the surface of a polystyrene core (diameter: 5 μm) were dispersed to obtain a film coating solution. Next, this solution was applied to a PET (polyethylene terephthalate) film having a surface treated with a thickness of 50 μm using a coating device, and dried with hot air at 70 ° C. for 10 minutes to form a film with an adhesive layer thickness of 45 μm. An agent was obtained. This adhesive was measured and measured by DSC. As a result, the reaction start temperature was 90 ° C., the reaction end temperature was 190 ° C., and the calorific value was 90 J / g. Next, using the produced film adhesive, a chip (10 × 10 mm, thickness: 500 μm) with gold bumps (area: 80 × 80 μm, space 30 μm, height: 15 μm, number of bumps 288) and chip electrodes are used. Connections of Ni / Au plated Cu circuit printed circuit boards with corresponding circuit electrodes were made as follows. After a film adhesive (12 × 12 mm) was applied to a Ni / Au plated Cu circuit printed circuit board (electrode height: 20 μm, thickness: 0.8 mm) at 80 ° C. and 1.0 MPa (10 kgf / cm ² ), The separator was peeled off, and the bumps of the chip and the Ni / Au plated Cu circuit printed board (thickness: 0.8 mm) were aligned. Next, the main connection was performed by heating and pressing from above the chip under the conditions of 180 ° C., 75 g / bump, and 20 seconds. The warp of the chip after this connection was 3.1 μm (a warp convex on the chip side). In addition, the connection resistance after this connection is 15 mΩ at the maximum per banff, the average is ⁸ mΩ, and the insulation resistance is 10 ⁸ Ω or more. These values are the thermal shock test at −55 to 125 ° C., 1000 cycle treatment, PCT test (121 ° C., 0.2 MPa (2 atm)) No change even after 10 seconds of immersion in a solder bath at 260 ° C. for 200 hours, showing good connection reliability.

Example 2 50 g of phenoxy resin (Union Carbide, PKHC) was dissolved in 115 g of ethyl acetate to obtain a 30 wt% solution. Silicone fine particles were added to a pH 12 alcohol aqueous solution stirred at 300 rpm at 20 ° C., and hydrolyzed and condensed to obtain spherical fine particles having a storage elastic modulus of 8 MPa at 25 ° C. and an average particle size of 2 μm. 45 g of phenoxy resin, 30 g of silicone fine particles, 20 g of liquid epoxy (epoxy equivalent 185, manufactured by Asahi Kasei Kogyo Co., Ltd., Novacure HX-3941), bisphenol A type epoxy (epoxy equivalent 180) 5 g) was blended, and 10 volume% of conductive particles having an Au layer formed on the surface of a polystyrene core (diameter: 3 μm) were blended and dispersed to obtain a film coating solution. Next, this solution was applied to a PET film having a surface of 50 μm on one side using a coating apparatus, and dried with hot air at 70 ° C. for 10 minutes to obtain a film adhesive a having an adhesive layer thickness of 10 μm. It was. Next, in the preparation of the film coating solution, a film coating solution prepared by the same method except that the conductive particles on which the Au layer was formed was not dispersed was applied to a PET film having a surface treated on one side having a thickness of 50 μm. It apply | coated using the coating apparatus and the film adhesive b whose thickness of an adhesive bond layer is 15 micrometers was obtained by hot-air drying at 70 degreeC for 10 minutes. Furthermore, while heating the obtained film adhesives a and b at 40 ° C., a two-layer anisotropic conductive film laminated with a roll laminator was produced. This adhesive was measured by DSC. As a result, the reaction start temperature was 90 ° C., the reaction end temperature was 200 ° C., and the calorific value was 85 J / g. Next, using the produced anisotropic conductive film, a chip (1.7 × 17 mm, thickness: 500 μm) with a gold bump (area: 50 × 50 μm, space 20 μm, height: 15 μm, number of bumps 362) and an ITO circuit The attached glass substrate (thickness: 1.1 mm) was connected as shown below. An anisotropic conductive film (2 × 20 mm) was attached to a glass substrate with an ITO circuit at 80 ° C. and 1 MPa (10 kgf / cm ² ), and then the separator was peeled off to align the chip bump and the glass substrate with the ITO circuit. went. Next, the main connection was performed by heating and pressing from above the chip under the conditions of 190 ° C., 40 g / buff, and 10 seconds. The chip warpage after this connection was 2.5 μm. In addition, the connection resistance is 80 mΩ at the maximum per banff, 30 mΩ on average, and the insulation resistance is 10 ⁸ Ω or more. These values are 1000 cycles of thermal shock tests at −40 to 100 ° C., high temperature and high humidity (85 (° C., 85% RH, 1000 h) No change was observed after the test, and good connection reliability was exhibited.

(Comparative example 1) The comparative test with respect to Example 1 was done using anisotropic conductive film FC-110A (The Hitachi Chemical Co., Ltd. make, film thickness: 45 micrometers). The DSC measurement of this adhesive had a reaction start temperature of 90 ° C., a reaction end temperature of 206 ° C., and a heat generation amount of 200 J / g. Next, using the above film adhesive, a chip (10 × 10 mm, thickness: 500 μm) with gold bumps (area: 80 × 80 μm, space 30 μm, height: 15 μm, number of bumps 288) and Ni / Au plating Connection of the Cu circuit printed circuit board was performed as shown below. A film adhesive (12 × 12 mm) was attached to a Ni / Au plated Cu circuit printed circuit board (electrode height: 20 μm, thickness: 0.8 mm) at 80 ° C. and 1 MPa (10 kgf / cm ² ), and then a separator was attached. The chip bumps and the Ni / Au plated Cu circuit printed circuit board were aligned. Next, the main connection was performed by heating and pressing from above the chip under the conditions of 190 ° C., 75 g / bump, and 10 seconds. The warp of the chip after this connection was 7.2 μm (a warp convex on the chip side). The connection resistance after this connection was 20 mΩ at the maximum per bump, 10 mΩ on average, and the insulation resistance was 10 ⁸ Ω or more, but the connection resistance was 1000 cycles of thermal shock test at −55 to 125 ° C., PCT In addition to the increase in the test (121 ° C., 2 MPa (2 atm)) for 200 hours and immersion in a solder bath at 260 ° C. for 10 seconds, some connection failures occurred.

(Comparative Example 2) A comparative test for Example 2 was performed using an anisotropic conductive film AC-8401 (manufactured by Hitachi Chemical Co., Ltd., film thickness: 23 microns). The DSC measurement of this adhesive had a reaction start temperature of 90 ° C., a reaction end temperature of 205 ° C., and a heat generation amount of 200 J / g. Next, using this anisotropic conductive film, a chip (1.7 × 17 mm, thickness: 500 μm) with gold bumps (area: 50 × 50 μm, space 20 μm, height: 15 μm, Banff number 362) and an ITO circuit are provided. The glass substrate (thickness: 1.1 mm) was connected as shown below. An anisotropic conductive film (2 × 20 mm) was attached to a glass substrate with lTO circuit at 80 ° C. and 1 MPa (10 kgf / cm ² ), and then the separator was peeled off to align the chip bump and the glass substrate with ITO circuit. went. Next, the main connection was performed by heating and pressing from above the chip under the conditions of 190 ° C., 40 g / bump, and 10 seconds. The chip warpage after this connection was 8.2 μm, which was larger than that of Example 2.

Claims (3)

  In a heat-adhesive adhesive in which circuit electrodes facing each other are heated and pressed to electrically connect the electrodes in the pressing direction, rubber particles having an average particle size of 10 μm or less are dispersed in the adhesive. , A reactive resin that cures by heat, and a sulfonium salt as a latent curing agent, the DSC (Differential Scanning Thermal Analysis) heat generation start temperature of the adhesive is 60 ° C. or more, and 80% of the curing reaction An adhesive for circuit connection, characterized in that the finishing temperature is 260 ° C. or lower.   The adhesive for circuit connection according to claim 1, wherein the reactive resin comprises an epoxy resin and a latent curing agent. The adhesive for circuit connection according to claim 1, wherein 0.2 to 30% by volume of conductive particles are further dispersed in the adhesive.