WO2015068611A1 - Electroconductive adhesive, electroconductive adhesive sheet, wiring device, and method for manufacturing wiring device - Google Patents

Abstract

　This electroconductive adhesive includes a thermosetting resin (A) having a carboxyl group, an epoxy resin (B), an elastomer (C) having a reactive functional group, an electroconductive filler (D), and a curing agent (E). Through this configuration, an electroconductive adhesive is obtained which, after curing, has heat resistance that is maintained at the solder reflow temperature, while the electroconductive adhesive is suitable for temporary bonding and has excellent punching workability. The electroconductive adhesive preferably includes 3-200 parts by weight of the elastomer (C) having a reactive functional group with respect to 100 parts by weight of the thermosetting resin (A) having a carboxyl group.

Description

Conductive adhesive, conductive adhesive sheet, wiring device, and manufacturing method of wiring device

The present invention relates to a conductive adhesive, a conductive adhesive sheet, a wiring device, and a method for manufacturing a wiring device. Specifically, the present invention can be used in a process of mounting an electronic component or the like, and has a conductive adhesive having excellent heat resistance after curing, and a conductive adhesive layer formed from the conductive adhesive. And a wiring device formed by bonding a wiring board and a reinforcing plate with a bonding layer formed of a cured product of a conductive adhesive layer, and a method for manufacturing such a wiring device.

・ ・ ・ The performance and miniaturization of electronic devices such as OA devices, communication devices, and mobile phones are progressing. The flexible printed wiring board has a bendable characteristic. For this reason, the flexible printed wiring board is used as an internal substrate or the like disposed in a narrow and complicated space of an electronic device by incorporating an electronic circuit. In this case, an electromagnetic wave shielding layer is generally provided on a flexible printed wiring board (hereinafter referred to as “FPC”) in order to shield the electronic circuit from the generated electromagnetic waves. However, due to the recent increase in frequency due to the increase in the amount of information supplied to electronic circuits and the miniaturization of electronic circuits, countermeasures against electromagnetic waves are becoming more important.

As an FPC provided with an electromagnetic wave shielding layer, Patent Document 1 discloses an FPC in which a conductive reinforcing plate and a ground circuit are connected by a conductive adhesive layer. Specifically, a conductive reinforcing plate using a metal such as stainless steel is attached to the FPC using a conductive adhesive, thereby electrically connecting the conductive reinforcing plate to the ground circuit. Thereby, since electromagnetic wave shielding property is obtained, FPC can transmit a circuit signal stably.

On the other hand, in the electronic component mounting process, for example, solder bonding such as solder reflow is widely used. In this solder reflow, after electronic parts are mounted at a predetermined position on a printed wiring board on which a solder portion has been formed in advance by printing or coating, the printed wiring board is put together with the electronic parts at about 230 to 280 ° C. by infrared reflow or the like. Heat. Thereby, the solder is melted and the electronic component is joined to the printed wiring board. When a conductive adhesive is used for bonding with an FPC or the like, the cured product of the conductive adhesive is also exposed to the high temperature environment as described above in the solder reflow. For this reason, high heat resistance is calculated | required also in the hardened | cured material of a conductive adhesive (refer patent document 2).

JP 2005-317946 A JP 2008-108625 A

For example, the conductive adhesive is prepared by temporarily attaching a FPC and a conductive reinforcing plate by lamination or the like (also referred to as “temporary sticking”) to produce a laminate, and then heating the laminate to a high temperature (eg, 150 to 180 ° C.). ) To cure the conductive adhesive (hereinafter also referred to as “main curing”). In this case, since the conventional conductive adhesive has low adhesion strength (temporary sticking suitability) in the temporary sticking state, the conductive reinforcing plate is misaligned with respect to the FPC until the main curing step, or the FPC There was a problem of dropping out.

In addition, when a conventional conductive adhesive is used, if the laminate (FPC with a conductive reinforcing plate) is punched into a predetermined shape after temporary attachment, the conductive reinforcing plate may fall off the FPC due to an impact at that time. There was also a problem that the laminate could not be punched into a desired shape (low punching workability).

Therefore, an object of the present invention is to provide a conductive adhesive having high post-curing heat resistance that can withstand the solder reflow temperature as well as excellent temporary sticking and punching workability.

The conductive adhesive of the present invention comprises a thermosetting resin (A) having a carboxyl group, an epoxy resin (B), an elastomer (C) having a reactive functional group, a conductive filler (D), and curing. And an agent (E).

According to the conductive adhesive of the present invention having the above-described configuration, excellent temporary sticking suitability can be obtained by including an elastomer (C) having a reactive functional group (hereinafter referred to as “elastomer (C)”). Further, by including the elastomer (C), the conductive adhesive layer formed from the conductive adhesive has an appropriate elongation rate, and excellent punching workability is obtained. Furthermore, the conductive adhesive layer after hardening can maintain favorable heat resistance because the reactive functional group of the elastomer (C) is involved in the crosslinking reaction.

Therefore, according to the present invention, it is possible to provide a conductive adhesive having high post-curing heat resistance that can withstand the solder reflow temperature as well as excellent temporary sticking and punching workability.

The conductive adhesive of the present invention includes a thermosetting resin (A) having a carboxyl group (hereinafter referred to as “thermosetting resin (A)”), an epoxy resin (B), an elastomer (C), and a conductive material. A filler (D) and a curing agent (E) are included. The conductive adhesive of the present invention can be used as it is by applying it to a desired place in the same manner as a general adhesive to bond members together. In addition, it is also preferable that the conductive adhesive is used for bonding members after being coated on a base material such as a peelable sheet to form a conductive adhesive sheet.

As a method for curing the conductive adhesive, for example, when the sheet is formed into a sheet, the curing agent (E) is cured and reacted with the thermosetting resin (A) and the elastomer (C), and the conductive adhesive is used. In a final curing step, the epoxy resin (B) is further subjected to a curing reaction with the thermosetting resin (A) and the elastomer (C), thereby achieving high heat resistance that can withstand the solder reflow temperature. The hardening method which makes it the hardening state which has, or the hardening method which carries out hardening reaction of the hardening | curing agent (E) and an epoxy resin (B) with a thermosetting resin (A) and an elastomer (C) at this hardening process is mentioned. In addition, it cannot be overemphasized that other hardening methods can be employ | adopted arbitrarily for the hardening method of a conductive adhesive.

In the present invention, the thermosetting resin (A) is a thermosetting resin that can be used for conductive adhesives and can exhibit excellent heat resistance after curing. Therefore, the thermosetting resin (A) needs to contain a carboxyl group as a reactive functional group. Specifically, as the thermosetting resin (A), for example, a resin obtained by introducing a carboxyl group into a urethane resin, a urethane urea resin, an epoxy ester resin, an acrylic resin, a phenol resin, or the like is preferable. Among these, the thermosetting resin (A) was obtained by introducing a carboxyl group into a urethane urea resin, an epoxy ester resin, and an acrylic resin in terms of heat resistance and workability after curing. A resin is more preferable.

The acid value of the thermosetting resin (A) is preferably 3 to 25 mgKOH / g, more preferably 7 to 20 mgKOH / g. When the acid value is 3 mgKOH / g or more, the crosslinking efficiency (reaction efficiency) with the epoxy resin (B) increases, and the heat resistance after curing of the conductive adhesive is further improved. Moreover, the adhesive strength with respect to the member (especially the conductive reinforcement board mentioned later) to which a conductive adhesive is joined as an acid value is 25 mgKOH / g or less improves more.

The weight average molecular weight (Mw) of the thermosetting resin (A) is preferably 5,000 to 300,000. When the weight average molecular weight is 5,000 or more, the heat resistance after curing of the conductive adhesive is further improved. Moreover, the viscosity of a conductive adhesive falls that a weight average molecular weight is 300,000 or less, and it becomes easier to handle.

Hereinafter, a method for synthesizing a polyurethane urea resin will be described as an example of the thermosetting resin (A). However, it goes without saying that the thermosetting resin (A) is not interpreted as being limited to the polyurethane urea resin.

The polyurethane urea resin may be a polyurethane urea resin having a carboxyl group. Such a polyurethane urea resin is prepared by first reacting a diol compound (a) having a carboxyl group, a polyol compound (b) having no carboxyl group, and an organic diisocyanate (c) to obtain a urethane having a carboxyl group and an isocyanate group. Obtained through a first step of obtaining a prepolymer (d) and then a second step of reacting the obtained urethane prepolymer (d) having a carboxyl group and an isocyanate group with the polyamino compound (e). be able to. In the second step, a reaction terminator can be used as necessary.

Examples of the diol compound (a) having a carboxyl group include dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, dimethylolalkanoic acid such as dimethylolpentanoic acid, dihydroxysuccinic acid, and dihydroxybenzoic acid. . Among these, dimethylolpropionic acid and dimethylolbutanoic acid are preferable as the diol compound (a) having a carboxyl group. This is because the reactivity and solubility are particularly high.

Examples of the polyol compound (b) having no carboxyl group include various polyols generally known as a polyol component constituting a polyurethane resin. Examples of such polyols include polyether polyol, polyester polyol, polycarbonate polyol, polybutadiene glycol, and the like. In addition, these polyols can be used individually or in combination of 2 or more types.

Examples of the polyether polyol include homopolymers or copolymers such as ethylene oxide, propylene oxide, and tetrahydrofuran.

Examples of the polyester polyol include 1) polyester polyol obtained by dehydration condensation of saturated or unsaturated low-molecular diols and dicarboxylic acids and / or their anhydrides, and 2) ring-opening polymerization of cyclic ester compounds. And polyester polyols obtained in this way.

Examples of saturated or unsaturated low molecular weight diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, and pentane. Examples thereof include diol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, dipropylene glycol, and dimer diol.

On the other hand, examples of dicarboxylic acids include adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Etc.

As the polycarbonate polyol, for example, 1) a reaction product of a diol or bisphenol and a carbonate ester, and 2) a reaction product obtained by reacting diol or bisphenol with phosgene in the presence of an alkali can be used. . Examples of the carbonate ester include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, and the like.

Examples of the diol include ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, 3 , 3'-dimethylol heptane, polyoxyethylene glycol, polyoxypropylene glycol, propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1 , 9-nonanediol, neopentyl glycol, octanediol, butylethylpentanediol, 2-ethyl-1,3-hexanediol, cyclohexanediol, 3,9-bis (1,1-dimethyl-2-hydroxyethyl, , 2,8,10- tetraoxospiro [5.5] undecane.

Examples of the bisphenol include bisphenols to which alkylene oxides such as bisphenol A, bisphenol F, ethylene oxide, and propylene oxide are added.
Among these polyols, as the polyol compound (b) having no carboxyl group, a polyester polyol is preferable, and a polyester diol is more preferable.

The number average molecular weight (Mn) of the polyol compound (b) having no carboxyl group is usually preferably from 500 to 8,000, and more preferably from 1,000 to 5,000. When the Mn of the polyol compound (b) having no carboxyl group is 500 or more, an appropriate number of urethane bonds can be introduced into the polyurethane polyurea resin, and thus a conductive adhesive having high adhesive strength can be easily obtained. . In addition, when the Mn of the polyol compound (b) having no carboxyl group is 8,000 or less, the distance between the urethane bonds tends to be appropriate, and a conductive adhesive having excellent heat resistance after curing is obtained. It becomes easy to obtain.

As the organic diisocyanate (c), aromatic diisocyanate, aliphatic diisocyanate, alicyclic diisocyanate and the like are preferable.
Examples of the aromatic diisocyanate include 1,5-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 4,4′-benzyl isocyanate, dialkyldiphenylmethane diisocyanate, and tetraalkyldiphenylmethane. Examples thereof include diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate and the like.

Examples of the aliphatic diisocyanate include butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate.

Examples of the alicyclic diisocyanate include cyclohexane-1,4-diisocyanate, isophorone diisocyanate, norbornane diisocyanate methyl, bis (4-isocyanatocyclohexyl) methane, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexane diisocyanate. Etc.

In addition, these diisocyanates can be used alone or in combination of two or more. Among these, as the organic diisocyanate (c), isophorone diisocyanate is preferable.

The reaction conditions in the first step are not particularly limited as long as the components (a) to (c) are blended so that the amount of isocyanate groups is excessive with respect to the amount of hydroxyl groups. Specifically, the equivalent ratio of isocyanate group / hydroxyl group is preferably 1.05 / 1 to 3/1, and more preferably 1.2 / 1 to 2/1. Further, the reaction temperature is suitably set within a range of preferably 20 to 150 ° C., more preferably within a range of 60 to 120 ° C.

The polyamino compound (e) used in the second step is used as a chain extender. Specific examples of the polyamino compound (e) include, for example, ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane-4,4′-diamine, norbornanediamine, 2- (2-amino Ethylamino) ethanol, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxypropylethylenediamine and the like. Among these, as a polyamino compound (e), isophorone diamine is preferable.

Examples of the reaction terminator usable in the second step include dialkylamines such as di-n-butylamine, dialkanolamines such as diethanolamine, and alcohols such as ethanol and isopropyl alcohol. It is done.

The reaction conditions of the second step are preferably such that the equivalent of amino group is 0.5 to 1.3 when the free isocyanate groups present at both ends of the urethane prepolymer (d) are defined as 1 equivalent. 0.8 to 1.05 is more preferable. When the amino group equivalent is 0.5 or more, the molecular weight of the polyurethane urea resin can be increased. Further, when the amino group equivalent is 1.3 or less, the storage stability of the conductive adhesive may be lowered depending on the conditions during storage of the conductive adhesive.

In addition, when using amines (for example, dialkylamines and dialkanolamines) as a reaction terminator, the equivalent of the amino group is the same as the amino group of the polyamino compound (e) and the amino group of the reaction terminator. The total equivalent.

The weight average molecular weight of the polyurethane urea resin is preferably 5,000 to 200,000. When the weight average molecular weight is 5,000 or more, the heat resistance after curing of the conductive adhesive is further improved. Moreover, the viscosity of a conductive adhesive falls that a weight average molecular weight is 200,000 or less, and it becomes easier to handle.

For the synthesis of polyurethane urea resin, for example, a solvent appropriately selected from ester solvents, ketone solvents, glycol ether solvents, aliphatic solvents, aromatic solvents, alcohol solvents, carbonate solvents, water, etc. is used. can do. In addition, these solvents can be used individually or in combination of 2 or more types.

Examples of the ester solvent include ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, and ethyl lactate.

Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, diacetone alcohol, isophorone, and cyclohexanenone.

Examples of the glycol ether solvent include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether or acetic esters of these monoethers, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether. Examples thereof include butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and acetates of these monoethers.

Examples of the aliphatic solvent include n-heptane, n-hexane, cyclohexane, methylcyclohexane, ethylcyclohexane and the like.

Examples of the aromatic solvent include toluene and xylene.

Examples of the alcohol solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and cyclohexanol.

Examples of the carbonate solvent include dimethyl carbonate, ethyl methyl carbonate, di-n-butyl carbonate and the like.

In the present invention, the epoxy resin (B) is a compound having two or more epoxy groups in one molecule. The property of the epoxy resin (B) may be liquid or solid.
As the epoxy resin (B), for example, glycidyl ether type epoxy resin, glycidyl amine type epoxy resin, glycidyl ester type epoxy resin, cycloaliphatic (alicyclic type) epoxy resin and the like are preferable.

Examples of the glycidyl ether type epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AD type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, α-naphthol novolak. Type epoxy resin, bisphenol A type novolak type epoxy resin, dicyclopentadiene type epoxy resin, tetrabromobisphenol A type epoxy resin, brominated phenol novolac type epoxy resin, tris (glycidyloxyphenyl) methane, tetrakis (glycidyloxyphenyl) ethane Etc.

Examples of the glycidylamine-type epoxy resin include tetraglycidyldiaminodiphenylmethane, triglycidylparaaminophenol, triglycidylmetaaminophenol, tetraglycidylmetaxylylenediamine, and the like.

Examples of the glycidyl ester type epoxy resin include diglycidyl phthalate, diglycidyl hexahydrophthalate, diglycidyl tetrahydrophthalate, and the like.

Examples of the cycloaliphatic (alicyclic) epoxy resin include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate, bis (epoxycyclohexyl) adipate, and the like.
Among these, as the epoxy resin (B), bisphenol A type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, tris (glycidyloxyphenyl) methane, and tetrakis (glycidyloxyphenyl) ethane are preferable. By using these epoxy resins, the adhesive strength of the conductive adhesive and the heat resistance after curing are further improved.

The blending amount of the epoxy resin (B) in the conductive adhesive is preferably 3 to 200 parts by weight with respect to 100 parts by weight of the thermosetting resin (A), and 5 to 100 parts by weight. Is more preferably 5 to 40 parts by weight. By adding 3 to 200 parts by weight of the epoxy resin (B) to 100 parts by weight of the thermosetting resin (A), a conductive adhesive having higher heat resistance after curing and higher adhesive strength can be obtained. can get.

In the present invention, the elastomer (C) is an elastomer having a reactive functional group. Here, the elastomer may be an elastic body, but is preferably a block copolymer. As such an elastomer, for example, a styrene elastomer, an ethylene elastomer, a urethane elastomer, a polyamide elastomer and a styrene acrylic elastomer are preferable. The reactive functional group may be a functional group that can react with at least one of the epoxy resin (B) and the curing agent (E). Specifically, as the reactive functional group, for example, a carboxyl group, an amino group, a hydroxyl group and the like are preferable.

Examples of the styrene elastomer include a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a styrene-butadiene-isoprene-styrene block copolymer, and a styrene-butadiene-isoprene-styrene block copolymer. Examples thereof include polymers or hydrogenated products thereof.
Examples of the ethylene elastomer include an ethylene-vinyl acetate copolymer, an ethylene-methacrylic acid ester copolymer, an ethylene-acrylic acid ester copolymer, and an amorphous polyalphaolefin copolymer.
These elastomers can have a carboxyl group by carboxy modification.

Examples of the urethane elastomer include a urethane-urea block copolymer, a urethane-ester block copolymer, a urethane-amide block copolymer, and the like.
Examples of the polyamide-based elastomer include polyether ester-amide block copolymers, polyester-amide block copolymers, and the like.
Examples of the styrene acrylic elastomer include styrene acrylonitrile copolymer and styrene methacrylic acid.

The elastomer (C) preferably has a durometer D hardness of 25 to 40. When the durometer D hardness is within this range, it is possible to further improve the temporary sticking suitability and punching workability of the conductive adhesive. The durometer D hardness can be measured by a test method based on JIS K 7115: 1999.

The storage modulus at 25 ° C. of the elastomer (C) is preferably 5 to 55 MPa, and more preferably 10 to 50 MPa. If the storage elastic modulus is within the above range, the appropriateness of temporary attachment of the conductive adhesive and the heat resistance after curing are further improved.

When the elastomer (C) has an acid value, the value is preferably 3 to 8 mgKOH / g.

The blending amount of the elastomer (C) in the conductive adhesive is preferably 3 to 200 parts by weight and preferably 5 to 100 parts by weight with respect to 100 parts by weight of the thermosetting resin (A). More preferred. By blending 3 to 200 parts by weight of the elastomer (C) with 100 parts by weight of the thermosetting resin (A), it is possible to further improve the temporary sticking suitability and punching processability of the conductive adhesive.

The elastomer (C) preferably has a glass transition temperature (hereinafter referred to as “Tg”) of −70 to 0 ° C., more preferably −65 to −5 ° C., and −60 to −10 ° C. More preferably it is. When the Tg is −70 ° C. or higher, the cured conductive adhesive is further improved in heat resistance at the solder reflow temperature. In addition, when Tg is 0 ° C. or less, the suitability for temporary attachment of the conductive adhesive is further improved.

The amount of the reactive functional group of the elastomer (C) is preferably 2 to 5 g / eq. It becomes easy to maintain the heat resistance after hardening of a conductive adhesive because the quantity of a reactive functional group is the said range.

In addition, as the elastomer (C), a polyamide-based elastomer is more preferable. Moreover, if it is a range which does not impair the heat resistance of a conductive adhesive, the elastomer which does not have a reactive functional group can be used together with an elastomer (C).

In the present invention, the conductive filler (D) has a function of imparting conductivity to the conductive adhesive. Specifically, as the conductive filler (D), for example, conductive metal particles made of a metal such as gold, silver, copper, lead, zinc, iron and nickel or an alloy thereof, and composite particles of the conductive metal Etc. Examples of the composite particles include silver-coated copper particles, silver-coated nickel particles, gold-coated copper particles, and gold-coated nickel particles.

Examples of the shape of the conductive filler (D) include a spherical shape, a flake shape, a disc shape, a dendritic shape, a needle shape, and an indefinite shape. The average particle size of the conductive filler (D) is preferably 1 to 50 μm. When the shape of the conductive filler (D) is spherical, the average particle size (average particle diameter) of the conductive filler (D) is an enlarged image of the conductive filler (D) by a scanning electron microscope (for example, This is a numerical value obtained by selecting about 10 to 20 particles from an average of 1,000 to 10,000 times and averaging the diameters of the particles.

In addition, when the length in the longitudinal direction of the spherical conductive filler (D) and the length in the short direction are greatly different, the length in the longitudinal direction is used to determine the average particle size of the conductive filler (D) (average (Particle diameter) is calculated. Furthermore, when the conductive filler (D) has a shape other than a spherical shape, the average particle size of the conductive filler (D) is calculated using the maximum length of the conductive filler (D).

The blending amount of the conductive filler (D) in the conductive adhesive is preferably 200 to 1,000 parts by weight, preferably 300 to 600 parts by weight with respect to 100 parts by weight of the thermosetting resin (A). It is more preferable that By blending 200 to 1,000 parts by weight of conductive filler (D) with 100 parts by weight of thermosetting resin (A), the conductivity of the conductive adhesive and the film strength of the conductive adhesive layer Will be improved.

In the present invention, the curing agent (E) has a function of making the conductive adhesive layer semi-cured by a crosslinking reaction when the conductive adhesive is formed into a sheet shape to obtain a conductive adhesive layer. , It may not have such a function, and may have a function of undergoing a crosslinking reaction during the main curing. As the curing agent (E), for example, an isocyanate curing agent, an amine curing agent, an aziridine curing agent, an imidazole curing agent and the like are preferable.

Examples of isocyanate curing agents include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate, 1,5-naphthalene diisocyanate, tetramethylxylylene diisocyanate, trimethylhexamethylene diisocyanate. Etc.

Examples of amine curing agents include diethylenetriamine, triethylenetetramine, methylene bis (2-chloroaniline), methylene bis (2-methyl-6-methylaniline), 1,5-naphthalene diisocyanate, n-butylbenzyl phthalic acid, and the like. Can be mentioned.

Examples of aziridine curing agents include trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, N, N′-diphenylmethane-4,4 ′. -Bis (1-aziridinecarboxamide), N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) and the like.

Examples of the imidazole curing agent include 2-methylimidazole, 2-heptadecylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate and the like.

The blending amount of the curing agent (E) in the conductive adhesive is preferably 0.3 to 20 parts by weight with respect to 100 parts by weight of the thermosetting resin (A), and 1 to 15 parts by weight. More preferably. By blending 0.3 to 20 parts by weight of the curing agent (E) with 100 parts by weight of the thermosetting resin (A), it is possible to make the conductive adhesive layer after semi-curing difficult to flow. Therefore, it becomes easy to suppress blocking of the conductive adhesive layer.

The conductive adhesive of the present invention preferably further contains an inorganic filler (F). By including the inorganic filler (F), the heat resistance after curing of the conductive adhesive is further improved.
Examples of the inorganic filler (F) include silica, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, titanium oxide, zinc oxide, antimony trioxide, magnesium oxide, talc, montmorolinite, kaolin and bentonite. Inorganic compounds such as Among these, as the inorganic filler (F), hydrophobic silica obtained by reacting a silanol group on the silica surface with a halogenated silane is preferable. By using hydrophobic silica, the water content of the conductive adhesive can be reduced. In the present invention, the inorganic filler (F) is different from the conductive filler (D).

The average particle size (average particle diameter) of the inorganic filler (F) is preferably 0.5 to 10 μm, and more preferably 0.7 to 8 μm. When the average particle size of the inorganic filler is 0.5 to 10 μm, the punching processability can be further improved. The average particle size of the inorganic filler (F) can also be specified by the same method as that for the conductive filler (D).

When the conductive adhesive contains an inorganic filler (F), the blending amount of the inorganic filler (F) in the conductive adhesive is 7 to 50 parts by weight with respect to 100 parts by weight of the thermosetting resin (A). The amount is preferably 15 to 40 parts by weight. By adding 7 to 50 parts by weight of the inorganic filler (F) to 100 parts by weight of the thermosetting resin (A), the conductive adhesive (conductive adhesive layer) S (stress) -S ( Since the elongation by the strain) curve can be within an appropriate range, the punching workability can be further improved.

The conductive adhesive of the present invention preferably further contains a silane coupling agent (G).
When the alkoxysilyl group of the silane coupling agent (G) undergoes a crosslinking reaction, the cured conductive adhesive can further improve the heat resistance at the solder reflow temperature. As a result, even at the solder reflow temperature, foaming and the like hardly occur in the cured product of the conductive adhesive layer.
As the silane coupling agent (G), for example, vinyl silane coupling agents, epoxy silane coupling agents, amino silane coupling agents, isocyanate silane coupling agents and the like are preferable.

Examples of the vinyl silane coupling agent include vinyl trimethoxysilane and vinyl triethoxysilane.

Examples of epoxy silane coupling agents include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3- Examples thereof include glycidoxypropylmethyldiethoxysilane and 3-glycidoxypropyltriethoxysilane.

Examples of amino-based silane coupling agents include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, and 3-aminopropyltrimethoxysilane. Examples include methoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, and N-phenyl-3-aminopropyltrimethoxysilane.

Examples of the isocyanate-based silane coupling agent include 3-isocyanatopropyltriethoxysilane.

When a conductive adhesive contains a silane coupling agent (G), the compounding quantity of the silane coupling agent (G) in a conductive adhesive is 0 with respect to 100 weight part of thermosetting resins (A). The amount is preferably 5 to 25 parts by weight, and more preferably 0.75 to 15 parts by weight. By blending 0.5 to 25 parts by weight of the silane coupling agent (G) with 100 parts by weight of the thermosetting resin (A), the heat resistance of the conductive adhesive after curing is further improved.

In the conductive adhesive of the present invention, heat stabilizers, pigments, dyes, tackifying resins, plasticizers, ultraviolet absorbers, antifoaming agents, leveling regulators and the like can be blended as other optional components. For example, when a heat stabilizer is blended, decomposition of the resin can be suppressed, so that the heat resistance after curing of the conductive adhesive can be further improved. Specifically, the heat stabilizer is preferably a hindered phenol compound, a phosphorus compound, a lactone compound, a hydroxylamine compound, a sulfur compound, or the like, and more preferably a hindered phenol compound.

The conductive adhesive of the present invention comprises 3 to 50% by weight of thermosetting resin (A) and 3 to 50% by weight of epoxy resin with respect to 100% by weight of the total of components (A) to (E). (B), 0.5 to 30% by weight of elastomer (C), 40 to 80% by weight of conductive filler (D), and 0.02 to 5% by weight of curing agent (E). Is also preferable.

The conductive adhesive sheet of the present invention is a sheet comprising a peelable sheet and a conductive adhesive layer provided on one surface side of the peelable sheet. The conductive adhesive layer is formed, for example, by applying a conductive adhesive on a peelable sheet, and is preferably in a semi-cured state. The conductive adhesive layer of the conductive adhesive sheet is, for example, temporarily bonded to a reinforcing plate (conductive reinforcing plate) and then fully cured by high-temperature heating so that it can withstand high adhesive strength and solder reflow temperature. Is obtained.

The gel fraction of the semi-cured conductive adhesive layer is preferably 60 to 95%, more preferably 65 to 90%. When the gel fraction is in this range, the cohesive force of the conductive adhesive layer is increased, and the temporary sticking suitability and punching workability are further improved. Moreover, in this invention, a sheet is synonymous with a film and a tape. Moreover, since a semi-hardened state means that an epoxy resin is an unreacted state, there is no intention to exclude the case where the gel fraction of a conductive adhesive layer is 0%.

The conductive adhesive layer is formed on the release surface of the release sheet, for example, knife coat, die coat, lip coat, roll coat, curtain coat, bar coat, gravure coat, flexo coat, dip coat, spray coat, spin coat, etc. In this method, the conductive adhesive is applied to form a coating film, and the coating film is usually heated at a temperature of 40 to 150 ° C.

The thickness of the conductive adhesive layer is preferably 5 to 500 μm, and more preferably 10 to 100 μm.
The conductive adhesive layer can be easily handled by attaching a peelable sheet to the surface.

The conductive adhesive sheet of the present invention uses the conductive adhesive layer, for example, temporarily laminates a wiring board and a reinforcing board to produce a laminated body (wiring board with a reinforcing board), and then punches the laminated body In many cases, it is processed into a desired shape by processing. In this case, since the semi-cured conductive adhesive layer has a predetermined elongation rate, the laminate exhibits even better punchability. Specifically, the elongation percentage of the conductive adhesive layer calculated from the SS curve (stress-strain curve) at 25 ° C. is preferably 50 to 300%. When the elongation percentage is 50% or more, the conductive adhesive layer is easily deformed so as to relieve external stress at the time of punching the laminated body, and thus is difficult to break. Moreover, it becomes difficult to produce the punching defect in a laminated body because elongation rate is 300% or less.

Further, the conductive adhesive sheet of the present invention can produce the wiring device of the present invention using the conductive adhesive layer. This wiring device is composed of a wiring board provided with signal wiring, a reinforcing board provided on one side of the wiring board, and a cured product of a conductive adhesive layer, and joins the wiring board and the reinforcing board. A bonding layer.

Such a wiring device is, for example, by temporarily bonding a wiring board and a conductive reinforcing plate via a semi-cured conductive adhesive layer to form a laminated body, and then heating the laminated body at a high temperature, It can be obtained by forming a bonding layer by fully curing the conductive adhesive layer. A bonding layer (cured product of the electric adhesive layer) having excellent adhesive strength and heat resistance is obtained by the main curing.

In addition, the heating temperature in the main curing is preferably 130 to 210 ° C., and more preferably 140 to 200 ° C. The laminate can be pressurized during the heating, and the pressure is preferably 0.2 to 12 MPa, and more preferably 0.3 to 10 MPa.

The wiring board includes an insulating substrate, a signal wiring provided on the insulating substrate, and an insulating layer provided on the insulating substrate so as to cover the signal wiring. Usually, in a wiring device, the insulating layer of a wiring board and a reinforcement board are joined by a joining layer.

Further, it is preferable that the wiring board further includes a ground wiring in addition to the signal wiring. By using a conductive reinforcing plate (conductive reinforcing plate) as a reinforcing plate and making an electrical connection with the ground wiring, this conductive reinforcing plate can function as a shield layer (electromagnetic wave shield layer). it can. As a constituent material of the conductive reinforcing plate, a conductive metal and its alloy are preferable. Specific examples of the constituent material of the conductive reinforcing plate include, for example, slenless and aluminum.

In addition, as a method for obtaining the electrical connection, a through hole is formed in the insulating layer and a conductive adhesive is filled in the through hole, or the conductive adhesive layer is formed by thermocompression bonding during the main curing. The method of making it flow and filling in a through-hole etc. is mentioned.

The wiring board is preferably a flexible printed wiring board (FPC). When the wiring board is FPC, the constituent material of the insulating substrate and the insulating layer is preferably a heat-resistant resin material such as polyimide or liquid crystal polymer. On the other hand, when the wiring board is a rigid wiring board, glass epoxy is preferable as a constituent material of the insulating substrate and the insulating layer (insulating base material). By forming the insulating substrate and the insulating layer with such a material, the insulating substrate and the insulating layer exhibit high heat resistance.

The wiring device of the present invention described above can be used for a touch panel type liquid crystal display or the like, or a mobile phone, a smartphone, a tablet terminal or the like incorporating them. In addition, the conductive adhesive and the conductive adhesive sheet of the present invention can be used for production of a wiring device, and can be used for various applications that require electrical conductivity. Note that the signal wiring and the ground wiring included in the wiring board may form a circuit having a desired function.

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
In the examples, “part” represents “part by weight” and “%” represents “% by weight”. “Mn” represents the number average molecular weight, and “Mw” represents the weight average molecular weight.

<Measurement method of weight average molecular weight>
The weight average molecular weight is a numerical value in terms of polystyrene determined by GPC (gel permeation chromatography) measurement. The measurement conditions are as follows.
Equipment: Shodex GPC System-21 (manufactured by Showa Denko)
Column: 1 Shodex KF-802 (Showa Denko), 1 Shodex KF-803L (Showa Denko) and 1 Shodex KF-805L (Showa Denko) connected in series Connected column Solvent: Tetrahydrofuran Flow rate: 1.0 mL / min
Temperature: 40 ° C
Sample concentration: 0.2%
Sample injection volume: 100 μL

[Synthesis Example 1]
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 195.0 parts of polyoxytetramethylene glycol of Mn2,029, 6.70 parts of dimethylolbutanoic acid, and isophorone diisocyanate 40 8 parts and 70.0 parts of toluene were charged. Next, these were reacted at 90 ° C. for 4 hours under a nitrogen atmosphere to obtain a reaction solution, and then 250 parts of toluene was added to the reaction solution. This obtained the solution containing the urethane prepolymer which has an isocyanate group of Mw22,000.

Next, 6.11 parts of isophoronediamine, 0.59 parts of di-n-butylamine, 112.5 parts of 2-propanol, and 184.5 parts of toluene were mixed to obtain a mixed solution. Next, 506.3 parts of a solution containing the obtained urethane prepolymer having an isocyanate group was added to the mixed solution, and these were reacted at 85 ° C. for 4 hours. As a result, a solution (nonvolatile content: 25%) containing polyurethane urea resin A-1 having an Mw of 105,000 and an acid value of 10.2 mgKOH / g was obtained.

[Synthesis Example 2]
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dripping device, and a nitrogen introduction tube was reacted with terephthalic acid, adipic acid and 3-methyl-1,5-pentanediol to obtain Mn2,040. 195.2 parts of polyester polyol, 6.67 parts of dimethylol butanoic acid, 40.7 parts of isophorone diisocyanate, and 70.0 parts of toluene were charged. Next, these were reacted at 90 ° C. for 4 hours under a nitrogen atmosphere to obtain a reaction solution, and then 250 parts of toluene was added to the reaction solution to prepare a solution containing a urethane prepolymer having an isocyanate group of Mw 21,000. Obtained.

Next, 6.08 parts of isophoronediamine, 0.59 parts of di-n-butylamine, 112.5 parts of 2-propanol, and 184.5 parts of toluene were mixed to obtain a mixed solution. Next, 506.3 parts of a solution containing the obtained urethane prepolymer having an isocyanate group was added to the mixed solution, and these were reacted at 85 ° C. for 4 hours. As a result, a solution (nonvolatile content: 25%) containing polyurethane urea resin A-2 having an Mw of 110,000 and an acid value of 10.1 mgKOH / g was obtained.

[Synthesis Example 3]
In a four-necked flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, an inlet tube, and a thermometer, 173.5 g of Priol 1009 (hydrogenated dimer acid made by CRODA) as a polybasic acid compound and preamine as a polyamine compound 107.4 (Dimeramine manufactured by CRODA) 157.9 g was added and stirred until the temperature of heat generation became constant to obtain a mixed solution. After confirming that the temperature was stable, the mixture was heated until the temperature reached 110 ° C., and the start of the dehydration reaction was confirmed.

Next, the mixture was heated until the temperature reached 120 ° C. over 30 minutes. Thereafter, the mixed solution was heated at a speed at which the temperature increased by 10 ° C. in 30 minutes. After the temperature reached 230 ° C., the reaction was continued for 3 hours while maintaining the temperature at 230 ° C. Then, after maintaining the state which pressure-reduced the inside of a 4-neck flask to the vacuum of about 2 kPa for 1 hour, the liquid mixture was cooled. Next, an antioxidant was added to the mixed solution to obtain a polyamide resin elastomer C-1 having an Mw of 124,000, an acid value of 4 mgKOH / g, and a glass transition temperature of −58 ° C.

[Synthesis Example 4]
In a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, inlet tube and thermometer, 60.60 g of sebacic acid as a polybasic acid compound, 40.86 g of isophoronediamine as a polyamine compound, and 50 g of ion-exchanged water And stirred until the temperature of heat generation became constant, to obtain a mixed solution. After the temperature was stabilized, heating of the mixed solution was started and it was confirmed that water was removed. Thereafter, the mixture was heated until the temperature reached 110 ° C., and the start of the dehydration reaction was confirmed.

Next, the mixture was heated until the temperature reached 120 ° C. over 30 minutes. Thereafter, the mixed solution was heated at a speed at which the temperature increased by 10 ° C. in 30 minutes. After the temperature reached 230 ° C., the reaction was continued for 3 hours while maintaining the temperature at 230 ° C. Then, after maintaining the state which pressure-reduced the inside of a 4-neck flask to the vacuum of about 2 kPa for 1 hour, the liquid mixture was cooled.

After the temperature of the mixed solution dropped to 150 ° C., 38.92 g of polytetramethylene ether glycol of Mn650 and 0.14 g of tetrabutyl orthotitanate were further added to the mixed solution. Next, the mixture was heated again until the temperature reached 230 ° C., and the reaction was allowed to proceed by maintaining the inside of the four-necked flask under a vacuum of about 2 kPa for 1 hour and further under a vacuum of about 1 kPa for 2 to 3 hours. . Finally, an antioxidant was added to the mixed solution to obtain a polyamide resin elastomer C-2 having an Mw of 85,000, an acid value of 3.5 mgKOH / g, and a glass transition temperature of −58 ° C.

[Example 1]
400 parts of a solution containing polyurethane urea resin A-1, 60 parts of bisphenol A type epoxy (“Adeka Resin EP-4100” manufactured by ADEKA) having an epoxy equivalent of 190 g / eq, and polyamide resin C-1 (glass transition) as an elastomer 75 parts of storage elastic modulus at temperatures of −58 ° C. and 25 ° C., acid value 4 mg KOH / g, tensile elastic modulus 11 MPa), 300 parts of silver-coated copper particles having an average particle diameter of 12.7 μm as a conductive filler, 3 parts of 2-methylimidazole, 25 parts of hydrophobic silica having an average particle diameter of 1.2 μm as an inorganic filler, and 3 parts of n-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane as a silane coupling agent Mixing was performed to obtain a conductive adhesive.

After applying this conductive adhesive to the peelable sheet, it was dried at 100 ° C. for 2 minutes to form a conductive adhesive layer having a thickness of 40 μm to obtain a conductive adhesive sheet. In addition, it was 80% when the gel fraction of the said conductive adhesive layer was calculated | required in accordance with the method mentioned later.

[Examples 2 to 15 and Comparative Examples 1 to 4]
A conductive adhesive and a conductive adhesive sheet were prepared in the same manner as in Example 1 except that each component and its blending amount were changed as shown in Table 1.

The abbreviations in Table 1 are as follows.
Epoxy resin B-1: Bisphenol A type epoxy having an epoxy equivalent of 190 g / eq (“ADEKA RESIN EP-4100”, manufactured by ADEKA)
Epoxy resin B-2: a trifunctional reaction type epoxy having an epoxy equivalent of 150 g / eq (“ED-505”, manufactured by ADEKA)

Elastomer C-3: Acrylic ester copolymer having a glass transition temperature of 4 ° C. and an acid value of 9 mg KOH / g (“Taisan Resin Series SG-708-6”, manufactured by Nagase ChemteX Corporation)
Elastomer C-4: Hydrogenated styrene thermoplastic elastomer having a glass transition temperature of 45 ° C. and no acid value (“Hytrel 2521”, manufactured by Toray DuPont)

Conductive filler D-1: Silver-coated copper particles having an average particle diameter of 12.7 μm Conductive filler D-2: Silver-coated copper particles having an average particle diameter of 12 μm Curing agent E-1: 2-methylimidazole Curing agent E-2: Trimethylolpropane-tri-β-aziridinylpropionate

Inorganic filler F-1: Hydrophobic silica with an average particle size of 1.2 μm Inorganic filler F-2: Ultrafine talc with an average particle size of 3.8 μm Silane coupling agent G-1: n-2- (aminoethyl) -3 -Aminopropylmethyldimethoxysilane Silane coupling agent G-2: 3-glycidoxypropyltrimethoxysilane

The Tg and storage elastic modulus of the elastomer were determined by the following method.
20 parts of elastomer, 40 parts of toluene, and 40 parts of isopropyl alcohol were blended and stirred until the elastomer was dissolved to obtain an elastomer solution. This elastomer solution was applied to a peelable sheet so that the thickness after drying was 40 μm to obtain a coating film, and then the coating film was dried. The dried coating film was cut into a size of width 10 mm × length 100 mm, and the peelable sheet was peeled off to obtain a measurement sample.

Using a dynamic elastic modulus measuring apparatus DVA-200 (made by IT Measurement & Control Co., Ltd.), deformation mode “tensile”, frequency 10 Hz, temperature rising rate 10 ° C./min, measurement temperature range −50 to 300 Measurement was performed under the condition of ° C., and the glass transition temperature and the storage elastic modulus at 25 ° C. were obtained.

The following physical properties of the obtained conductive adhesive and conductive adhesive sheet were evaluated. The results are shown in Table 2.

<Gel fraction>
A 100-mesh stainless wire mesh was cut into a width of 30 mm and a length of 100 mm, and the weight (W1) was measured. Subsequently, the conductive adhesive sheet was cut into a size of width 10 mm × length 80 mm, and then the peelable sheet was peeled off to obtain a conductive adhesive layer. The conductive adhesive layer was wrapped with the stainless steel wire mesh so as not to be seen, and used as a test piece, and its weight (W2) was measured. The prepared test piece was immersed in methyl ethyl ketone (MEK) at room temperature (25 ° C.) and left for 1 hour. Next, the test piece was taken out from the MEK, dried at 150 ° C. for 10 minutes, and then its weight (W3) was measured. And the gel fraction of the conductive adhesive layer was computed using the following formula (1).
(W3−W1) / (W2−W1) × 100 [%] (1)

<Adhesive strength>
After the conductive adhesive sheet was cut into a size of 25 mm wide × 100 mm long, the peelable sheet was peeled off to obtain a conductive adhesive layer. This conductive adhesive layer is sandwiched between a polyimide surface of a 40 μm thick copper clad laminate (“Esperflex” manufactured by Sumitomo Metal Mining Co., Ltd.) and a 200 μm thick stainless steel plate (SUS304). Formed. Thereafter, the obtained laminate was pressure-bonded under conditions of 170 ° C., 2 MPa, and 5 minutes, and then heated in an electric oven at 160 ° C. for 60 minutes. As a result, a laminate of “copper-clad laminate / cured product of conductive adhesive layer / SUS plate” was obtained. The laminate was subjected to a T peel peel test at a tensile rate of 50 mm / min in an atmosphere of 23 ° C. and a relative humidity of 50%, and the adhesive strength (N / cm) was measured.

<Solder heat resistance>
The laminate obtained in the same manner as described above was floated on molten solder at 260 ° C. for 1 minute with its SUS surface down. Thereafter, the laminate was taken out of the molten solder, the appearance of the cured product of the conductive adhesive layer was visually confirmed, and evaluated according to the following criteria. In addition, evaluation was performed about five laminated bodies.

A: In any of the five laminates, no bubbles were generated in the cured product of the conductive adhesive layer, and there was no abnormality in the adhesion state. That is, the cured product of the conductive adhesive layer has excellent solder heat resistance, and the conductive adhesive has no problem in practical use.
B: In 3 to 4 laminates, no bubbles were generated in the cured product of the conductive adhesive layer, and there was no abnormality in the adhesion state. That is, the cured product of the conductive adhesive layer is slightly inferior in solder heat resistance, but the conductive adhesive is practical.
C: Only in two or less laminates, no bubbles were generated in the cured product of the conductive adhesive layer, and there was no abnormality in the adhesion state. That is, the cured product of the conductive adhesive layer has poor solder heat resistance, and the conductive adhesive is not practical.

<Temporary sticking properties>
The conductive adhesive sheet was cut into a size of 25 mm wide × 100 mm long, and the conductive adhesive sheet was stacked on the SUS plate so that the conductive adhesive layer was in contact with the SUS plate having a width of 30 mm × length of 150 mm. . Subsequently, after roll-laminating these, the peelable sheet was peeled off from the conductive adhesive layer to obtain a SUS plate with a conductive adhesive layer.

Separately, laminate the SUS plate with the conductive adhesive layer on the copper-clad laminate so that the conductive adhesive layer contacts the polyimide surface of the copper-clad laminate cut to a width of 30 mm and a length of 200 mm. Obtained. Thereafter, the laminate was heated and pressed for 3 seconds using a commercially available iron whose surface temperature was set to 200 ° C. Next, a T-peel peel test was performed on the laminate using a tensile tester at a pulling speed of 50 mm / min, and the adhesive strength was measured.

A: Adhesive strength is 0.5 N / cm or more. That is, the conductive adhesive is excellent in temporary sticking property and has no problem in practical use.
B: Adhesive strength is 0.3 to 0.5 N / cm. That is, the conductive adhesive is practically usable although the temporary sticking property is slightly inferior.
C: Adhesive strength is less than 0.3 N / cm. That is, the conductive adhesive is inferior in temporary sticking and is not practical.

<Surface resistance value>
The conductive adhesive sheet was cut into a size of 50 mm width × 80 mm length, and then a peelable sheet was attached to the conductive adhesive layer. This is sandwiched between two polyimide films having a thickness of 125 μm (Toray DuPont Co., Ltd. “Kapton 500H”), and lamination of “polyimide film / peelable sheet / conductive adhesive layer / peelable sheet / polyimide film” is performed. Got the body. The laminate was pressure-bonded under the conditions of 170 ° C., 2 MPa, and 5 minutes, and then heated in an electric oven at 160 ° C. for 60 minutes. About the obtained hardened | cured material of the conductive adhesive layer, the surface resistance value was measured by a four-terminal method using a resistivity meter (Mitsubishi Chemical Corporation “Lorester GP MCP-T600”).

<Flow amount>
The conductive adhesive sheet is cut to a size of 10 mm wide × 60 mm long, and the conductive adhesive layer is conductive so that it contacts a polyimide film (“Kapton 200EN” manufactured by Toray DuPont) with a thickness of 50 μm. The adhesive sheet was overlaid on the polyimide film. Thereafter, a hole having a diameter of 5 mm was penetrated in the vicinity of the center of the conductive adhesive sheet with a punch.

Next, after peeling off the peelable sheet from the conductive adhesive layer, this polyimide film with the conductive adhesive layer was thermally laminated at 100 ° C. to a separately prepared polyimide film so that the conductive adhesive layer was in contact. To obtain a laminate. Subsequently, the laminate was pressure bonded under the conditions of 170 ° C., 2.0 MPa, and 5 minutes. With respect to the laminate of “polyimide film (with holes) / cured product of conductive adhesive layer (with holes) / polyimide film” thus obtained, the holes of the cured product of the conductive adhesive layer were magnified using a magnifying glass. The amount (flow amount) of the conductive adhesive that was observed and protruded into the hole was measured.

A: The flow amount is less than 0.15 mm. That is, the conductive adhesive has a sufficiently small amount of flow and has no problem in practical use.
B: The flow amount is about 0.15 mm. That is, the conductive adhesive is practical although the flow amount is slightly larger.
C: The flow amount is more than 0.15 mm. That is, the conductive adhesive has a too large flow amount and is not practical.

<Elongation>
The conductive adhesive sheet was cut into a size of 200 mm wide × 600 mm long, and then the peelable sheet was peeled off from the conductive adhesive layer to obtain a measurement sample. A tensile test (test speed 50 mm / min) was carried out under the conditions of a temperature of 25 ° C. and a relative humidity of 50% using a small desktop tester EZ-TEST (manufactured by Shimadzu Corporation). The elongation percentage (%) of the conductive adhesive layer was calculated from the obtained SS curve (Stress-Strain curve).

The conductive adhesive of the present invention comprises a thermosetting resin (A) having a carboxyl group, an epoxy resin (B), an elastomer (C) having a reactive functional group, a conductive filler (D), and curing. Agent (E). According to this invention, the conductive adhesive layer formed from the conductive adhesive which has the heat resistance after the high curing | hardening which can be endured with solder reflow temperature with excellent temporary sticking adequacy and punching workability, and this conductive adhesive A conductive adhesive sheet, a wiring device formed by bonding a wiring board and a reinforcing plate with a bonding layer composed of a cured product of a conductive adhesive layer, and a method for manufacturing such a wiring device can be provided. . Therefore, the present invention has industrial applicability.

Claims (10)

A thermosetting resin having a carboxyl group (A);
Epoxy resin (B);
An elastomer (C) having a reactive functional group;
A conductive filler (D);
A conductive adhesive comprising a curing agent (E). The conductive adhesive comprises the elastomer (C) having 3 to 200 parts by weight of the reactive functional group with respect to 100 parts by weight of the thermosetting resin (A) having a carboxyl group. Conductive adhesive. The conductive adhesive according to claim 1, wherein the elastomer (C) having a reactive functional group has a glass transition temperature of -70 to 0 ° C. A peelable sheet;
A conductive adhesive sheet comprising a conductive adhesive layer provided on one surface side of the peelable sheet and formed from the conductive adhesive according to claim 1. The conductive adhesive sheet according to claim 4, wherein the conductive adhesive layer has a gel fraction of 60 to 95%. A wiring board with signal wiring;
A reinforcing plate provided on one side of the wiring board;
It is a joining layer which is provided between the said wiring board and the said reinforcement board, and joins these, Comprising: The joining comprised with the hardened | cured material of the conductive adhesive layer formed from the conductive adhesive of Claim 1 A wiring device comprising: a layer. The reinforcing plate has conductivity,
The wiring device according to claim 6, wherein the wiring board further includes a ground wiring connected to the reinforcing plate. The wiring device according to claim 6, wherein the wiring board is a flexible printed wiring board. It is a manufacturing method of the wiring device according to claim 6,
Preparing the wiring board, the conductive adhesive layer, and the reinforcing plate;
Laminating the wiring board and the reinforcing plate via the conductive adhesive layer to obtain a laminate;
And heating the laminated body at 130 to 210 ° C. to cure the conductive adhesive layer to form the bonding layer, thereby obtaining the wiring device. . 10. The method for manufacturing a wiring device according to claim 9, wherein in the step of heating the laminate, the laminate is pressurized at 0.2 to 12 MPa.