JP2009299079A - Connecting member for circuit, and circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connecting member for a circuit which is used for connection of an electronic component to a circuit board, is capable of relaxing a stress on a circuit connection boundary surface, and shows remarkably enhanced reliability without causing increase of connection resistance and separation of an adhesive agent in the connection part even after a reliability test, and to provide a circuit board showing excellent reliability. <P>SOLUTION: The connecting member for the circuit electrically connecting circuit electrodes in a pressing direction to each other by heating and pressing the electrodes facing to each other includes an adhesive composition composed of an epoxy resin (A) in which there is dispersed an acrylic rubber particle obtained by polymerizing a (meth)acrylate-based monomer, having a diameter of 0.02 to 1 μm and occupying not less than 70 vol% of the whole rubber particles, a latent curing agent (B) for the epoxy resin, and a conductive particle (C) having an average particle diameter of 1 to 18 μm as essential components. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a circuit connecting member and a circuit board used for connecting circuit boards to each other or electronic components such as an IC chip and a circuit board.

  An anisotropic conductive adhesive in which an adhesive or conductive particles are dispersed is used when the circuit boards are electrically connected to each other or the connection between the IC chip or electronic component and the circuit board. That is, these adhesives are arranged between electrodes, and after 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 by 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. In particular, when a chip is directly mounted on a substrate via an adhesive, if a printed circuit board using an FR-4 base material or a flexible wiring board based on polyimide or polyester is used as a connection substrate, the chip after connection and Warpage of the chip and the substrate is likely to occur due to internal stress based on the difference in thermal expansion coefficient. The present invention provides a circuit connection member that is used for connection between circuit boards or an electronic component such as an IC chip and a circuit board, and enables excellent connection reliability, and a circuit board excellent in connection reliability.

The circuit connection member of the present invention is a circuit connection member that electrically connects the electrodes in the pressing direction by heating and pressurizing the circuit electrodes facing each other, and the circuit connection member is (A). An epoxy resin in which acrylic rubber particles are dispersed, having a diameter of 0.02 to 1 micron obtained by polymerizing a (meth) acrylic acid ester monomer, and 70% by volume or more of the total rubber particles;
(B) an epoxy resin latent curing agent, and (C) conductive particles having an average particle diameter of 1 to 18 microns,
It contains the adhesive composition which uses as an essential component.

  Moreover, in said circuit connection member, a phenoxy resin can be contained in the adhesive composition, and the weight average molecular weight of the phenoxy resin is preferably 20,000 to 60,000. The content of the conductive particles having an average particle diameter of 1 to 18 microns is preferably 0.1 to 20 parts by volume with respect to 100 parts by volume of the adhesive composition. The shape of the circuit connection member can be a film, and the area after connection of the circuit connection member can be 2.0 to 5.0 times the area before connection. .

  The circuit board of the present invention has a first circuit member having a first connection terminal and a second circuit member having a second connection terminal, the first connection terminal and the second connection terminal being opposed to each other. The circuit connection member is interposed between the first connection terminal and the second connection terminal arranged opposite to each other, and the first connection terminal and the second connection terminal arranged opposite to each other are heated and pressurized. An electrically connected circuit board, wherein the circuit connection member is the circuit connection member of the present invention.

The connection member for a circuit of the present invention is used for connection of an IC chip and a printed circuit board, or connection of an IC chip and a flexible wiring board. Latent curing of epoxy resin (B) epoxy resin in which rubber particles having a diameter of 0.02 to 1 micron are dispersed. And an adhesive composition containing (C) a phenoxy resin as essential components.

  As described above, according to the circuit connection member and the circuit board of the present invention, the stress at the circuit connection interface can be relieved, and there is no increase in connection resistance or peeling of the adhesive even after the reliability test, and the connection Reliability is greatly improved.

The epoxy resin used in the present invention is a bisphenol type epoxy resin derived from epichlorohydrin and bisphenol A, F, AD or the like, an epoxy novolac resin derived from epichlorohydrin and phenol novolak or cresol novolac, or a naphthalene having a skeleton containing a naphthalene ring. Various epoxy compounds having two or more glycidyl groups in one molecule such as epoxy resin, glycidylamine, glycidyl ester, biphenyl, alicyclic, etc. can be used alone or in admixture of two or more. is there. 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 of the present invention have a diameter of 0.02 to 1 micron and are dispersed in an epoxy resin. The rubber particles can be uniformly dispersed in the epoxy resin as primary particles. The rubber particles having a diameter of 0.02 to 1 micron are preferably 70% by volume or more, more preferably 90% by volume or more of the total rubber particles. The epoxy resin (A) in which rubber particles having a diameter of 0.02 to 1 micron are dispersed can be obtained by directly mixing and dehydrating a rubber emulsion with the epoxy resin.

  In the present invention, a mixture (C) of a rubber emulsion and an epoxy resin can be used. In this case, the diameter of the rubber particles dispersed in the rubber emulsion is preferably 0.02 to 1 micron. The rubber particles having a diameter of 0.02 to 1 micron are preferably 70% by volume or more, more preferably 90% by volume or more of the total rubber particles.

  The rubber emulsion of the present invention is an aqueous dispersion of rubber obtained from emulsion polymerization, suspension polymerization or solution polymerization, and examples thereof include acrylic emulsion, SBR, NBR, etc., alone or in combination of two or more. In particular, an acrylic rubber emulsion having a glass transition temperature of room temperature or lower, which is obtained by emulsion polymerization of a (meth) acrylic acid ester monomer, is preferred. The particle diameter of the rubber particles is preferably about 0.02 to 1 micron, but more preferably 0.1 to 0.6 micron from the viewpoint of cured properties and workability when an epoxy resin composition is formed. The rubber particles having such a particle size are preferably 70% by volume or more, and more preferably 90% by volume or more of the total rubber particles.

  The epoxy resin composition obtained by mixing and dehydrating the rubber emulsion and the epoxy resin in the present invention is obtained by directly mixing the rubber emulsion with the epoxy resin and removing water while stirring under normal pressure or reduced pressure. It is done. At this time, if the water is removed and further treated with a high-pressure homogenizer, the viscosity of the epoxy resin composition is lowered, and the workability at the time of producing the adhesive composition is improved. The amount of rubber particles dispersed in the epoxy resin composition is preferably 1 to 60 parts by weight, more preferably 2 to 30 parts by weight with respect to 100 parts by weight of the epoxy resin.

  Examples of latent curing agents for epoxy resins include imidazole series, hydrazide series, boron trifluoride-amine complexes, sulfonium salts, amine imides, diaminomaleonitrile, melamine and derivatives thereof, polyamine salts, dicyandiamide, and their modified products. These can be used alone or as a mixture of two or more. These are anionic or cationic polymerizable catalyst-type curing agents, which are preferable because they are easy to obtain fast curability and require less chemical equivalent considerations. As the curing agent, other polyaddition types such as polyamines, polymercaptans, polyphenols, and acid anhydrides, and the combined use with the catalyst-type curing agent can be used.

  As an anionic polymerization type catalyst-type curing agent, an epoxy resin blended with tertiary amines or imidazoles can be cured by heating at a medium temperature of about 160 to 200 ° C. for several tens of seconds to several hours. (Pot life) is relatively long. As the cationic polymerization type catalyst-type curing agent, a photosensitive onium salt that cures the resin by energy ray irradiation, for example, an aromatic diazonium salt, an aromatic sulfonium salt, or the like is mainly used. In addition to irradiation with energy rays, aliphatic sulfonium salts and the like are also activated by heating to cure the epoxy resin. This type of curing agent is preferred because it has the property of fast curing.

  It is preferable to use these hardeners coated with a polymer material such as polyurethane or polyester, a metal thin film such as Ni or Cu, and an inorganic material such as calcium silicate so that the pot life can be extended. .

  In the adhesive composition obtained above, as usual additives, for example, fillers, softeners, accelerators, anti-aging agents, colorants, flame retardants, thixotropic agents, coupling agents and phenol resins, Curing agents such as melamine resins and isocyanates can also be contained.

  The phenoxy resin used in the present invention will be described. The phenoxy resin corresponds to a high molecular weight epoxy resin having a weight average molecular weight of 10,000 or more determined by high performance liquid chromatography (HPLC), and there are other types such as bisphenol A type, AD type, and AF type as well as the epoxy resin. is there. Since these are similar in structure to epoxy resins, they have good compatibility and also have good adhesive properties. The higher the molecular weight, the easier the film-forming property is obtained, and the melt viscosity that affects the fluidity during connection can be set in a wide range. The weight average molecular weight is preferably 10,000 to 80,000 in view of melt viscosity and compatibility with other resins, and more preferably 20,000 to 60,000 phenoxy resin. When these resins contain polar groups such as hydroxyl groups and carboxyl groups, the compatibility with the epoxy resin is improved, and a film having a uniform appearance and characteristics can be obtained, and the reaction at the time of curing is accelerated. It is also preferable from the viewpoint of obtaining curing. As a compounding quantity, it is preferable to set it as 20 to 80 weight% with respect to the whole resin component from the point of acceleration | stimulation of film formation property or hardening reaction. Further, a styrene resin, an acrylic resin, or the like may be appropriately mixed for adjusting the melt viscosity.

  As the conductive particles, there are metal particles such as Au, Ag, Ni, Cu, and solder, carbon, etc., and these and non-conductive glass, ceramics, plastics, etc. formed by coating the above-mentioned conductive layer. Good. In the case of using plastic as a core or hot-melt metal particles, it is preferable because it has deformability by heating and pressurization, so that the contact area with the electrode is increased at the time of connection and reliability is improved. The conductive particles are properly used depending on the application in a wide range of 0.1 to 30% by volume with respect to 100 volumes of the adhesive component. In order to prevent an adjacent circuit from being short-circuited by excessive conductive particles, the content is more preferably 0.1 to 10% by volume.

  The adhesive composition of the present invention is particularly useful as a one-component adhesive, particularly as a film adhesive for bonding liquid crystal panels and semiconductor chips. In this case, for example, the adhesive composition obtained above is liquefied as a dispersion or the like in the case of a solvent or emulsion, and formed on a peelable substrate such as a release paper, or the above-mentioned compounding in a substrate such as a nonwoven fabric The solution may be impregnated to form on a peelable substrate, dried at a temperature lower than the activation temperature of the curing agent, and the solvent or dispersion may be removed. At this time, the solvent to be used is preferably an aromatic hydrocarbon-based and oxygen-containing mixed solvent in order to improve the solubility of the material. Here, the SP value of the oxygen-containing solvent is preferably in the range of 8.1 to 10.7 in terms of protecting the latent curing agent, and acetates are more preferable. The boiling point of the solvent can be 150 ° C. or less. When the boiling point exceeds 150 ° C., a high temperature is required for drying, and since the temperature is close to the activation temperature of the latent curing agent, the potential is lowered, and at a low temperature, the workability during drying is lowered. For this reason, the boiling point is preferably 60 to 150 ° C, more preferably 70 to 130 ° C.

The ratio of the area after connection of the adhesive and the area before connection is measured by the following means. That is, an adhesive having a thickness of 50 μm and a size of 5 mm square is sandwiched between two glass plates having a thickness of 1.1 mm and a size of 15 mm square. This is heated and pressurized by a thermocompression bonding machine under the conditions of a heating temperature of 180 ° C., a pressure of 18 kgf / cm ² , and a pressure time of 20 seconds, heating, adhesive area (A) before pressing, and heating, By measuring the pressure-sensitive adhesive area (B) using an image processing apparatus, the ratio (B / A) of the area after connection of the adhesive and the area before connection can be determined. When the ratio of the area after connection of the adhesive to the area before connection (B / A) is less than 2.0, the exclusion of the molten adhesive between the connection electrodes or between the connection electrodes and the conductive particle interface decreases, It becomes difficult to ensure electrical continuity between the connection electrodes or between the connection electrodes and the conductive particles. On the other hand, if the ratio of the area after connection of the adhesive to the area before connection (B / A) exceeds 5.0, the fluidity of the adhesive at the time of connection is too high and bubbles are likely to be formed, resulting in reliability. Tend to decrease.

  In the case of a film adhesive, the adhesive layer can be multilayered. For example, an anisotropic conductive film filled with conductive particles for imparting anisotropic conductivity and an adhesive film filled with conductive particles and a two-layer anisotropic conductive film laminated with an adhesive layer not filled with conductive particles An anisotropic conductive film having a three-layer structure in which an adhesive layer not filled with conductive particles is laminated on both sides can be used. Since these multilayered anisotropic conductive films can efficiently capture conductive particles on the connection electrodes, they are advantageous for narrow pitch connection. In consideration of the adhesiveness with the circuit member, the circuit members 1 and 2 can be laminated by laminating an adhesive film having excellent adhesiveness.

  As circuit members used in the circuit board of the present invention, electronic components such as active elements such as semiconductor chips, transistors, diodes and thyristors, passive elements such as capacitors, resistors and coils, printed boards, polyimide and polyester as base materials Examples thereof include a flexible wiring board and a glass substrate on which an ITO circuit is formed. On the electrode pad of the semiconductor chip or substrate, the tip of the bump or gold wire formed by plating is melted with a torch or the like to form a gold ball, and after the ball is pressure-bonded on the electrode pad, the wire is cut. Protruding electrodes such as wire bumps obtained in this way can be provided and used as connection terminals. The circuit member is usually provided with a large number of connection terminals (or a single connection terminal in some cases), and at least one set of the circuit members is disposed so that at least a part of the connection terminals provided on the circuit members are opposed to each other. Then, an adhesive is interposed between the connection terminals arranged opposite to each other, and the connection terminals arranged opposite to each other by heating and pressing are electrically connected to form a circuit board. By heating and pressurizing at least one set of circuit members, the connection terminals arranged opposite to each other are electrically connected by direct contact or via conductive particles.

Example 1
From bisphenol A and epichlorohydrin, 60 g of bisphenol A type phenoxy resin (average molecular weight 30000) was prepared by a general method, and this was prepared by weight ratio of toluene (boiling point 110.6 ° C., SP value 8.90) / ethyl acetate (boiling point 77). .1 ° C., SP value 9.10) = dissolved in a mixed solvent of 50/50 to obtain a bisphenol A phenoxy resin solution having a solid content of 30% by weight. Bisphenol A type of 20 parts by weight and 80 parts by weight of an acrylic rubber emulsion obtained by emulsion polymerization of 80 parts by weight of ethyl acrylate, 10 parts by weight of methyl methacrylate and 10 parts by weight of glycidyl methacrylate together with an emulsifier which is a terminal alkyl group-containing polymer. The epoxy resin was mixed and stirred, heated to remove water, and then treated with a high-pressure homogenizer to obtain a liquid epoxy resin in which acrylic rubber particles having a diameter of 0.3 microns were primarily dispersed. 30 parts by weight of this acrylic rubber particle-dispersed liquid epoxy resin was mixed with the above bisphenol type A phenoxy resin solution (resin part: 30 parts by weight) having a solid content of 30% by weight. Next, a latent hardener, Novacure 3941 HPS (a microcapsule type hardener having an average particle size of 5 μm having an imidazole modified as a core and polyurethane coated on the surface thereof, was placed in a liquid bisphenol F type epoxy resin. 40 parts of a master batch type curing agent formed by dispersion, an active temperature of 125 ° C., a product name manufactured by Asahi Kasei Kogyo Co., Ltd., and a nickel layer with a thickness of 0.2 μm on the surface of conductive particles (polystyrene-based particles) Furthermore, a gold layer having a thickness of 0.02 μm is provided on the outside of the nickel layer to produce conductive particles having an average particle diameter of 5 μm and a specific gravity of 2.5) (to 100 parts by volume of the adhesive composition). In contrast, the mixture was dispersed and applied to a fluororesin film having a thickness of 80 μm using a coating apparatus, and the thickness of the adhesive layer was 50 μm by drying with hot air at 75 ° C. for 10 minutes. To obtain a circuit connecting member.

(Circuit connection) Using the circuit connection member described above, a chip (10 mm × 10 mm) with a gold bump (area: 80 μm × 80 μm, height: 15 μm), Ni / Au with a line width of 50 μm, a pitch of 100 μm, and a thickness of 18 μm A flexible circuit board (FPC) having a plated copper circuit was connected as shown below. A circuit connection member (12 mm × 12 mm) was attached to a Ni / Au plated Cu circuit printed circuit board at 80 ° C. and 10 kgf / cm ² , then the fluororesin film was peeled off, and the chip bumps and Ni / Au plated Cu circuit FPC Was aligned. Next, the main connection was made by heating and pressing from above the chip under the conditions of 170 ° C., 30 g / bump, and 20 seconds. The connection resistance after this connection is a maximum of 6 mΩ per bump, an average of 2 mΩ, and an insulation resistance of 10 ⁸ Ω or more. These values are from the thermal shock test at −55 to 125 ° C., 1000 cycle treatment, PCT test (121 No change even after 10 seconds of immersion in a solder bath at 260 ° C. for 200 hours at 2 ° C., and good connection reliability was exhibited.

Example 2
From bisphenol A and epichlorohydrin, 60 g of bisphenol A type phenoxy resin (average molecular weight 30000) was prepared by a general method, and this was prepared by weight ratio of toluene (boiling point 110.6 ° C., SP value 8.90) / ethyl acetate (boiling point 77). .1 ° C., SP value 9.10) = dissolved in a mixed solvent of 50/50 to obtain a bisphenol A phenoxy resin solution having a solid content of 30% by weight. Bisphenol A type of 20 parts by weight and 80 parts by weight of an acrylic rubber emulsion obtained by emulsion polymerization of 80 parts by weight of ethyl acrylate, 10 parts by weight of methyl methacrylate and 10 parts by weight of glycidyl methacrylate together with an emulsifier which is a terminal alkyl group-containing polymer. The epoxy resin was mixed and stirred, heated to remove water, and then treated with a high-pressure homogenizer to obtain a liquid epoxy resin in which acrylic rubber particles having a diameter of 0.3 microns were primarily dispersed. 30 parts by weight of this acrylic rubber particle-dispersed liquid epoxy resin was mixed with the above bisphenol type A phenoxy resin solution (resin part: 30 parts by weight) having a solid content of 30% by weight. Next, a latent hardener, Novacure 3941HPS (a microcapsule type hardener having an average particle size of 5 μm, the surface of which is coated with polyurethane and having a modified imidazole as a core, is added to the liquid bisphenol F type epoxy resin. 40 parts of a master batch type curing agent formed by dispersion, an active temperature of 125 ° C., a product name manufactured by Asahi Kasei Kogyo Co., Ltd., and a nickel layer with a thickness of 0.2 μm on the surface of conductive particles (polystyrene-based particles) Furthermore, a gold layer having a thickness of 0.02 μm is provided on the outside of the nickel layer to produce conductive particles having an average particle diameter of 5 μm and a specific gravity of 2.5) (to 100 parts by volume of the adhesive composition). In contrast, the mixture was dispersed and applied to a fluororesin film having a thickness of 80 μm using a coating apparatus, and the thickness of the adhesive layer was 25 μm by drying with hot air at 75 ° C. for 10 minutes. It was obtained of the adhesive film a. Next, the film coating solution prepared in the same manner as in the preparation of the film coating solution was applied to a fluororesin film having a thickness of 80 μm except that the conductive particles were not dispersed, and 75 ° C. for 10 minutes. The dried adhesive film b having a thickness of 25 μm was produced.

(Circuit connection) Using the circuit connection member described above, a chip (10 mm × 10 mm) with a gold bump (area: 80 μm × 80 μm, height: 15 μm), Ni / Au with a line width of 50 μm, a pitch of 100 μm, and a thickness of 18 μm A flexible circuit board (FPC) having a plated copper circuit was connected as shown below. After bonding the adhesive film b side of the circuit connection member (12 mm × 12 mm) to the Ni / Au plated Cu circuit printed circuit board at 80 ° C. and 10 kgf / cm ² , the fluororesin film was peeled off, and the chip bump and Ni / Au plating Cu circuit FPC was aligned. Next, the main connection was made by heating and pressing from above the chip under the conditions of 170 ° C., 30 g / bump, and 20 seconds. The connection resistance after this connection is a maximum of 4 mΩ per bump, an average of 2 mΩ, and an insulation resistance of 10 ⁸ Ω or more. These values are from the thermal shock test at −55 to 125 ° C., 1000 cycle treatment, the PCT test (121 No change even after 10 seconds of immersion in a solder bath at 260 ° C. for 200 hours at 2 ° C., and good connection reliability was exhibited.

Claims (7)

A circuit connection member for electrically connecting the electrodes in the pressurizing direction by heating and pressurizing circuit electrodes facing each other, wherein the circuit connection member is composed of (A) (meth) acrylic acid ester monomer An epoxy resin having acrylic rubber particles dispersed therein having a diameter of 0.02 to 1 micron obtained by polymerization and 70% by volume or more of the total rubber particles;
(B) an epoxy resin latent curing agent, and (C) conductive particles having an average particle diameter of 1 to 18 microns,
The circuit connection member characterized by containing the adhesive composition which contains as an essential component.   The circuit connection member according to claim 1, wherein the adhesive composition contains a phenoxy resin.   The connection member for a circuit according to claim 2, wherein the phenoxy resin has a weight average molecular weight of 20,000 to 60,000.   The circuit connection member according to claim 1, wherein the content of the conductive particles is 0.1 to 20 parts by volume with respect to 100 parts by volume of the adhesive composition.   The connection member for a circuit according to any one of claims 1 to 4, wherein the shape is a film shape.   The circuit connection member according to any one of claims 1 to 5, wherein an area of the circuit connection member after connection is 2.0 to 5.0 times that of an area before connection.   A first circuit member having a first connection terminal and a second circuit member having a second connection terminal are disposed so that the first connection terminal and the second connection terminal are opposed to each other, and the opposed arrangement is performed. A circuit in which a circuit connection member is interposed between the first connection terminal and the second connection terminal, and the first connection terminal and the second connection terminal that are arranged to face each other by heating and pressurizing are electrically connected. It is a board, Comprising: The said circuit connection member is a circuit connection member as described in any one of Claims 1-6, The circuit board characterized by the above-mentioned.