JP6508078B2 - Conductive adhesive, conductive adhesive sheet, and wiring device - Google Patents

Description

  The present invention relates to a conductive adhesive, a conductive adhesive sheet, and a wiring device. Specifically, a conductive adhesive that can be used in a process of mounting electronic components and the like, a conductive adhesive sheet provided with a conductive adhesive layer formed from the conductive adhesive, a wiring board and a reinforcing plate The present invention relates to a wiring device formed by bonding with a bonding layer composed of a cured product of a conductive adhesive layer.

  Further advances in performance and miniaturization of electronic devices such as OA devices, communication devices, and mobile phones are in progress. Flexible printed wiring boards have bendable characteristics. For this reason, the flexible printed wiring board is used as an internal board etc. which are arrange | positioned in the narrow and complex space of an electronic device by incorporating an electronic circuit. In this case, in order to shield the electronic circuit from the generated electromagnetic waves, it is general to provide an electromagnetic shielding layer on a flexible printed wiring board (hereinafter referred to as "FPC"). However, due to the increase in frequency due to the increase in the amount of information supplied to electronic circuits in recent years and the miniaturization of electronic circuits, measures against electromagnetic waves are further increasing in importance.

  Patent Document 1 and Patent Document 2 disclose an FPC in which a conductive reinforcing plate and a ground circuit are connected by a conductive adhesive layer as an FPC provided with an electromagnetic wave shielding layer. Specifically, the conductive reinforcing plate is electrically interconnected with the ground circuit by attaching a conductive reinforcing plate using a metal such as stainless steel to the FPC using a conductive adhesive. Thereby, since electromagnetic wave shielding property is obtained, FPC can transmit a circuit signal stably.

  The above-mentioned conductive adhesive is required to have excellent conductive properties including stability over time, and the properties of the conductive filler contained in the sheet become important. As a conductive filler, since silver powder is excellent in a conductive characteristic, the conductive sheet etc. which contain silver powder until now are utilized. However, the price of silver powder is expensive and expensive as compared with resins and other materials used for conductive sheets and the like. Moreover, with the recent increase in silver price, price increase of conductive sheets and the like using silver powder has become a serious problem. In order to achieve lower prices for electronic devices, it is necessary to reduce the use ratio of the conductive filler, but when the use ratio of the conductive filler is reduced, the desired conductivity can not be maintained. Face the problem of

  Therefore, a method using a conductive filler having a coating layer made of a conductive material plated with a conductive material such as silver on a surface of copper as a low cost alternative conductive filler of silver is studied. However, if the coating amount of the coating layer made of a conductive material is reduced for further cost reduction, there is a problem that the copper inside is easily exposed and the viscosity stability of the conductive adhesive is deteriorated due to the elution of copper ions. There is. In addition, the conductive adhesive layer using the conductive filler having copper and the above-described exposed surface of copper as described above is oxidized by copper when exposed to a high temperature and high humidity environment (for example, 85 ° C. 85%) for a long time There is a problem that the conductivity is deteriorated to deteriorate the shield characteristics, or the adhesive strength is deteriorated to make the metal reinforcing plate easily peeled off.

  In addition, when connecting the conductive reinforcing plate to the ground circuit using the conductive adhesive, the conductive reinforcing plate is fixed and grounded at the same time as the conductive reinforcing plate is fixed by embedding and curing the conductive adhesive in the through holes. In the case of using a conductive filler containing copper as a main component, there is a problem that the connection reliability is low when the through hole has a large step.

JP, 2009-218443, A International Publication No. 2014/010524

  Therefore, it is an object of the present invention to use a conductive filler based on copper and to reduce the cost, yet the viscosity of the conductive adhesive is stable, even after being exposed to a moist heat environment for a long period of time An object of the present invention is to provide a conductive adhesive, a conductive adhesive sheet, and a wiring device having good connection reliability and adhesiveness, and having good connection reliability even in a circuit having a high level difference in ground wiring board through holes. I assume.

  As a result of intensive studies by the present inventors, when using a conductive filler containing copper as a main component, a thermosetting resin (A) having a carboxyl group, an epoxy resin, a curing agent, and a silane coupling agent are used. By using the electroconductive adhesive to contain, it discovered that the above-mentioned subject could be solved, and came to this invention.

  That is, the present invention is characterized by containing a thermosetting resin (A) having a carboxyl group, an epoxy resin, a conductive filler (B) containing copper as a main component, a curing agent, and a silane coupling agent. It relates to a conductive adhesive.

  The present invention also relates to the conductive adhesive, wherein the conductive filler (B) comprises a core made of copper and a coating layer made of a conductive material different from copper.

  The present invention also relates to the conductive adhesive, wherein the coating layer is 40 parts by weight or less with respect to 100 parts by weight of the core of the conductive filler (B).

  Further, the present invention is characterized in that the silane coupling agent is at least one selected from the group consisting of a vinyl based silane coupling agent, an epoxy based silane coupling agent, and an amino based silane coupling agent. It relates to a conductive adhesive.

  Furthermore, the present invention is characterized in that the thermosetting resin (A) is selected from the group consisting of polycarbonate polyurethane resins, polyester polyurethane resins, polyether polyurethane resins, and methacrylic polyurethane thermosetting resins. The present invention relates to the conductive adhesive.

  The present invention also relates to a conductive adhesive sheet comprising a conductive adhesive layer formed of the conductive adhesive on a peelable sheet.

Further, the present invention provides a wiring board including signal wiring,
A reinforcing plate provided on at least one surface side of the wiring board;
A wiring device comprising a conductive adhesive layer for bonding the wiring board and the reinforcing plate,
The wiring device is characterized in that the conductive adhesive layer is formed of the conductive adhesive.

The reinforcing plate has conductivity.
The wiring device further includes a ground wiring connected to the reinforcing plate.

  According to the present invention of the above configuration, it is possible to reduce the cost while using the conductive filler whose main component is copper, while the viscosity of the conductive adhesive is stable and after being exposed to a moist heat environment for a long time To provide a conductive adhesive, a conductive adhesive sheet, and a wiring device having good connection reliability and adhesiveness, and having good connection reliability even in a circuit having a high level difference in ground wiring board through holes. It becomes possible.

It is a schematic diagram of a connection reliability test.

  The conductive adhesive of the present invention comprises a thermosetting resin (A) having a carboxyl group (hereinafter sometimes referred to as "thermosetting resin (A)"), an epoxy resin, a conductive filler, and curing. Agent and a silane coupling agent. The conductive adhesive can be applied as it is to a desired place as in a general adhesive and used to bond the members together. In addition, it is also preferable to use a conductive adhesive for bonding members after forming a conductive adhesive sheet by coating it on a base material such as a peelable sheet.

  As a method of curing the conductive adhesive, for example, when forming the conductive adhesive into a sheet, the curing agent is cured with the thermosetting resin (A) to make the conductive adhesive into a so-called semi-cured state. In the main curing step, the epoxy resin is subjected to curing reaction between the thermosetting resin (A) and the silane coupling agent to obtain a cured state having a high heat resistance that can withstand the solder reflow temperature, or In the main curing step, there is a curing method in which a curing agent and an epoxy resin are cured and reacted with the thermosetting resin (A). Needless to say, any other curing method can be adopted as the method of curing the conductive adhesive.

<Thermosetting resin (A) having a carboxyl group>
In the present invention, the thermosetting resin is a thermosetting resin that can be used in the application of the conductive adhesive 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, for example, a resin obtained by introducing a carboxyl group into a polyurethane resin, a polyester resin, an acrylic resin, a polyamide resin, a phenol resin, etc. may be used. Can. Among these, polyurethane-based thermosetting resins are preferable from the viewpoint of moisture heat resistance after curing and level difference followability. In particular, polycarbonate-based polyurethane resins, polyester-based polyurethane resins, polyether-based polyurethane resins, and methacrylic polyurethane resins are preferable because they are excellent in connection reliability and adhesion after a wet heat resistance test.

  The acid value of the thermosetting resin (A) is preferably 1 to 100 mg KOH / g, and more preferably 3 to 50 mg KOH / g. When the acid value is 1 mg KOH / g or more, the crosslinking efficiency (reaction efficiency) with the epoxy resin is enhanced, and the resistance value and adhesion after wet heat aging of the conductive adhesive are further improved. Moreover, the viscosity stability of a conductive adhesive improves more that an acid value is 100 mgKOH / g or less.

  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 step following property of the conductive adhesive is improved, and the connection reliability is further improved. Moreover, the viscosity of a conductive adhesive falls that a weight average molecular weight is 300,000 or less, and handling becomes easier.

  Hereinafter, a method of synthesizing a polyurethane-based thermosetting resin will be described as one 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-based thermosetting resin.

  The polyurethane-based thermosetting resin may be a polyurethane-based thermosetting resin having a carboxyl group. The polyurethane-based thermosetting resin is prepared by first reacting a diol compound (a) having a carboxyl group, a polyol compound (b) not having a carboxyl group, and an organic diisocyanate (c) to form a carboxyl group and an isocyanate group. A first step of obtaining a urethane prepolymer (d) having the following, and a second step of reacting the obtained urethane prepolymer (d) having a carboxyl group and an isocyanate group with a polyamino compound (e). You can get through. In the second step, a reaction terminator may be used, if 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, dihydroxybenzoic acid and the like. . Among these, as the diol compound (a) having a carboxyl group, dimethylol propionic acid and dimethylol butanoic acid are preferable. These are because the reactivity and solubility are particularly high.

  As a polyol compound (b) which does not have a carboxyl group, the various polyols generally known as a polyol component which comprises a polyurethane resin are mentioned. Examples of such polyols include polyether polyols, polyester polyols, polycarbonate polyols, 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 polyols include homopolymers or copolymers of ethylene oxide, propylene oxide, tetrahydrofuran and the like.

As the polyester polyol, for example, 1) a polyester polyol obtained by dehydration condensation of a saturated or unsaturated low molecular weight diol and a dicarboxylic acid and / or an anhydride thereof, 2) ring-opening polymerization of a cyclic ester compound And polyester polyols etc. obtained.
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, pentane Diol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, dipropylene glycol, dimer diol and the like can be mentioned.
On the other hand, as dicarboxylic acids, for example, 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, sebacic acid Etc.

As the polycarbonate polyol, for example, 1) a reaction product of a diol or a bisphenol and a carbonic ester, 2) a reaction product obtained by reacting phosgene with a diol or a bisphenol in the presence of an alkali can be used. . Examples of the carbonate include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate and the like.
Also, as the diol, for example, ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, 3 1,3'-dimethylolheptane, 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 , 2,8,10-tetraoxo spiro [5.5] undecane etc. are mentioned.
Further, examples of the bisphenol include bisphenol A, bisphenol F, and bisphenols to which an alkylene oxide such as ethylene oxide or propylene oxide is added.
Among these polyols, as a polyol compound (b) which does not have a carboxyl group, polyester polyol is preferable and polyester diol is more preferable.

  The number average molecular weight (Mn) of the polyol compound (b) not having a carboxyl group is usually preferably 500 to 8,000, and more preferably 1,000 to 5,000. When the Mn of the polyol compound (b) not having a carboxyl group is 500 or more, an appropriate number of urethane bonds can be introduced into the polyurethane polyurea resin, which makes it easy to obtain a conductive adhesive having high adhesive strength. . 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 the conductive adhesive having excellent heat resistance after curing It becomes easy to get.

As the organic diisocyanate (c), aromatic diisocyanate, aliphatic diisocyanate, alicyclic diisocyanate and the like are preferable.
Examples of the aromatic diisocyanate include 1,5-naphthyl diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-benzylisocyanate, dialkyldiphenylmethane diisocyanate, and tetraalkyldiphenylmethane. Diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate and the like can be mentioned.

  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 (isocyanatemethyl) cyclohexane, methylcyclohexane diisocyanate Etc.

  In addition, these diisocyanates can be used individually or in combination of 2 or more types. Among these, as organic diisocyanate (c), isophorone diisocyanate is preferable.

  The reaction conditions of the first step are not particularly limited, as long as the components (a) to (c) may be blended so that the amount of isocyanate groups is excessive 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. Moreover, reaction temperature is suitably set within the range of preferably 20 to 150 ° C., more preferably within the 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, norbornane diamine, 2- (2-amino) Ethylamino) ethanol, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxypropylethylenediamine and the like can be mentioned. Among these, as the 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, alcohols such as ethanol and isopropyl alcohol, and the like. Be

The reaction condition of the second step is that the equivalent of amino group is preferably 0.5 to 1.3, where one equivalent of the free isocyanate group present at both ends of the urethane prepolymer (d) is used. And 0.8 to 1.05 are more preferable. The molecular weight of a polyurethane-type thermosetting resin can be enlarged more that the equivalent of an amino group is 0.5 or more. In addition, when the equivalent weight of the amino group is 1.3 or less, the storage stability may be lowered depending on the storage condition of the conductive adhesive.
When an amine (for example, dialkylamines or dialkanolamines) is used as a reaction terminator, the amino group equivalent is an amino group of the polyamino compound (e) and an amino group of the reaction terminator. It is the total equivalent.

  The weight average molecular weight of the polyurethane thermosetting resin is preferably 5,000 to 200,000. The heat resistance after hardening of a conductive adhesive improves more that a weight average molecular weight is 5,000 or more. 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 the polyurethane-based thermosetting resin, for example, it is appropriately selected from ester solvents, ketone solvents, glycol ether solvents, aliphatic solvents, aromatic solvents, alcohol solvents, carbonate solvents, water, etc. Solvents can be used. In addition, these solvents can be used individually or in combination of 2 or more types.

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

  Examples of the ketone-based solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, diacetone alcohol, isophorone, cyclohexanenon and the like.

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

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

  Examples of the aromatic solvents include toluene and xylene.

  As said alcohol solvent, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, cyclohexanol etc. are mentioned, for example.

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

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

  As a glycidyl ether type epoxy resin, for example, 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 novolac Epoxy resin, bisphenol A novolac epoxy resin, dicyclopentadiene epoxy resin, tetrabromobisphenol A epoxy resin, brominated phenol novolac epoxy resin, tris (glycidyloxyphenyl) methane, tetrakis (glycidyloxyphenyl) ethane Etc.

  Examples of the glycidyl amine type epoxy resin include tetraglycidyldiaminodiphenylmethane, triglycidyl paraaminophenol, triglycidyl metaaminophenol, tetraglycidyl metaxylylene diamine and the like.

  As said glycidyl ester type epoxy resin, a diglycidyl phthalate, a diglycidyl hexahydro phthalate, a diglycidyl tetrahydro phthalate etc. are mentioned, for example.

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

  The compounding amount of the epoxy resin in the conductive adhesive is preferably 3 to 200 parts by weight, and more preferably 5 to 100 parts by weight with respect to 100 parts by weight of the thermosetting resin (A). And 5 to 40 parts by weight. By blending 3 to 200 parts by weight of the epoxy resin with 100 parts by weight of the thermosetting resin (A), a conductive adhesive having higher connection reliability after a wet heat aging and adhesion can be obtained.

<Conductive filler (B)>
The conductive filler (B) of the present invention is a conductive filler containing copper as a main component. The conductive filler has a function of imparting conductivity to the conductive adhesive. The conductive filler (B) may contain copper as a main component, and may be an alloy with another element. Other alloying elements include zinc, manganese, iron, lead, phosphorus, silver, nickel, silica, tin, aluminum, beryllium and titanium.
The conductive filler (B) can also use composite fine particles having a coating layer in which the main component copper is a core and the surface of the core is coated with a conductive material. Here, copper serving as a core may be pure copper or copper alloyed with the above-described elements. The covering layer may be a material having conductivity, and preferably a conductive metal or a conductive polymer. Conductive metals include, for example, gold, platinum, silver, nickel, manganese, and indium, and alloys thereof. The conductive polymer may, for example, be polyaniline or polyacetylene. Among these, silver is preferable in terms of cost and conductivity.

The coating layer is preferably 40 parts by weight or less, more preferably 20 parts by weight or less, and more preferably 10 parts by weight or less, with respect to 100 parts by weight of the core of the conductive filler. By reducing the coating layer to 40 parts by weight or less, the cost of the conductive adhesive can be reduced.
The conductive adhesive of the present invention is capable of achieving such cost reduction, and the viscosity stability of the conductive adhesive is good even when the coating amount of the conductive material is small, and the high temperature and high humidity environment Even when exposed to the lower side for a long time, it is possible to obtain a conductive sheet which is excellent in conductivity and excellent in shield characteristics and adhesion strength to a metal reinforcing plate.

The shape of the conductive filler may be any shape as long as desired conductivity can be obtained, and the shape is not limited. Specifically, for example, a spherical shape, a flake shape, a leaf shape, a dendritic shape, a plate shape, a needle shape, a rod shape, and a grape shape are preferable.
The conductive fillers may be used alone or in combination of two or more.

1-100 micrometers is preferable and, as for the average particle diameter of a conductive filler, 3-50 micrometers is more preferable. Connection reliability and viscosity stability can be both highly compatible by the average particle diameter being in a predetermined range. Furthermore, from a viewpoint of suppressing sedimentation of a conductive filler, less than 12 micrometers is preferred. The average particle size can be determined by a laser diffraction / scattering particle size distribution measuring apparatus. Here, the average particle size is a particle size having a cumulative value of 50% in the particle size cumulative distribution.
In addition to the above method, about 10 to about 20 particles are selected from a magnified image (for example, 1,000 to 10,000 times) of the conductive filler by a scanning electron microscope, and the average diameter is measured. Particle size can also be measured. When the length in the longitudinal direction of the conductive filler and the length in the lateral direction are significantly different, the length in the longitudinal direction is used to calculate the average particle diameter of the conductive filler. Furthermore, when the conductive filler is in a shape other than spherical, the average particle size of the conductive filler is calculated using the maximum length of the conductive filler.

  In the conductive filler (B), in the case of coating the core, the coating layer of the conductive material only needs to cover at least a part of the core containing copper as a main component, but more excellent conductive properties The higher the coverage, the better. From the viewpoint of maintaining good conductivity, the average coverage by the coating layer is preferably 60% or more, more preferably 70% or more, and still more preferably 80% or more. In addition, the average coverage in this specification says the value calculated | required by the measurement of the powder by ESCA mentioned later.

  The compounding amount of the conductive filler (B) in the conductive adhesive is preferably 200 to 1,000 parts by weight, and 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 the conductive filler (B) with respect to 100 parts by weight of the thermosetting resin (A), the conductivity of the conductive adhesive and the film strength of the conductive adhesive layer Improve more.

  The conductive adhesive of the present invention can also use a conductive filler other than the conductive filler (B). Conductive fillers other than the conductive filler (B) include, for example, gold, platinum, silver, nickel, manganese, and indium, and alloys thereof.

<Hardening agent>
In the present invention, the curing agent has a function of bringing the conductive adhesive layer into a semi-cured state by a crosslinking reaction when forming the conductive adhesive into a sheet to obtain the conductive adhesive layer, And may have a function of causing a crosslinking reaction during main curing. As the curing agent, for example, an isocyanate-based curing agent, an amine-based curing agent, an aziridine-based curing agent, an imidazole-based curing agent and the like are preferable. When the thermosetting resin and the epoxy resin described later and the silane coupling agent have unsaturated bonds, peroxide curing agents and azo curing agents are preferred.

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

  Examples of amine curing agents include diethylenetriamine, triethylenetetramine, methylenebis (2-chloroaniline), methylenebis (2-methyl-6-methylaniline), 1,5-naphthalenediisocyanate, n-butylbenzylphthalic acid and the like. It can be mentioned.

  As an aziridine type curing agent, for example, trimethylolpropane-tri-β-aziridinyl propionate, tetramethylolmethane-tri-β-aziridinyl propionate, N, N′-diphenylmethane-4,4 ′ And -bis (1-aziridinecarboxamide), N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide), and the like.

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

  Examples of the peroxide curing agent include cumene hydroperoxide, t-butylperoxy-2-ethylhexanoate and the like.

Examples of the azo curing agent include 2,2′-azobisisobutyl nitrile, 2,2′-azobis (2,4-dimethyl valeronitrile) and the like.
The compounding amount of the curing agent in the conductive adhesive is preferably 0.3 to 20 parts by weight, and 1 to 15 parts by weight with respect to 100 parts by weight of the thermosetting resin (A). More preferable. By blending 0.3 to 20 parts by weight of the curing agent with respect to 100 parts by weight of the thermosetting resin (A), the conductive adhesive layer after being semi-cured can be made less likely to flow, so that it is possible to conduct electricity. It becomes easy to suppress blocking of the adhesive layer.

<Silane coupling agent>
In the present invention, the crosslinking reaction of the alkoxysilyl group of the silane coupling agent causes the silane coupling agent to crosslink, thereby increasing the crosslink density of the coating after curing and improving the heat and moisture resistance of the conductive adhesive. As a result, even after the heat and humidity resistance test, the increase in resistance value is suppressed, and the adhesion is less likely to be reduced.
As a silane coupling agent, For example, a vinyl type silane coupling agent, an epoxy type silane coupling agent, an amino type silane coupling agent, a vinyl type silane coupling agent, a methacryl type coupling agent, a thiol type coupling agent, an isocyanate Preferred are silane coupling agents and the like.
Particularly preferably, when the silane coupling agent is a vinyl based silane coupling agent, an epoxy based silane coupling agent, or an amino based silane coupling agent, the viscosity stability of the conductive adhesive is excellent.

  As a vinyl type silane coupling agent, vinyl trimethoxysilane, vinyl triethoxysilane, etc. are mentioned, for example.

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

  As an amino type silane coupling agent, for example, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltrile. Examples thereof include methoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, and N-phenyl-3-aminopropyltrimethoxysilane.

  As a vinyl type silane coupling agent, vinyl trimethoxysilane, vinyl triethoxysilane, etc. are mentioned, for example.

  Examples of the methacrylic silane coupling agent include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane and the like.

  As a thiol system silane coupling agent, 3-mercapto propyl methyl dimethoxysilane, 3-mercapto propyl trimethoxysilane, etc. are mentioned, for example.

  As an isocyanate type silane coupling agent, 3-isocyanate propyl triethoxysilane etc. are mentioned, for example.

  The compounding amount of the silane coupling agent in the conductive adhesive is preferably 0.1 to 25 parts by weight, and 0.5 to 15 parts by weight with respect to 100 parts by weight of the thermosetting resin (A). It is more preferable that By blending 0.5 to 25 parts by weight of the silane coupling agent with respect to 100 parts by weight of the thermosetting resin (A), the heat resistance after curing of the conductive adhesive is further improved.

<Inorganic filler>
The conductive adhesive of the present invention preferably further contains an inorganic filler. By including the inorganic filler, the moisture and heat resistance and the punching processability of the conductive adhesive are further improved.
As the inorganic filler, for example, inorganic materials such as silica, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, titanium oxide, zinc oxide, antimony trioxide, magnesium oxide, talc, montmorillonite, kaolin, bentonite and the like Compounds are mentioned. Among these, as the inorganic filler, hydrophobic silica obtained by reacting a silanol group on the surface of silica with a halogenated silane is preferable. By using hydrophobic silica, the moisture content of the conductive adhesive can be reduced. In the present invention, the inorganic filler is different from the conductive filler.

  The average particle size (average particle size D50) of the inorganic filler is preferably 0.01 to 10 μm, and more preferably 0.05 to 8 μm. Punching processability can be further improved by the average particle diameter of the inorganic filler being 0.01 to 10 μm. The average particle size of the inorganic filler can also be specified by the same method as the conductive filler.

  In the conductive adhesive of the present invention, a heat resistant stabilizer, a pigment, a dye, a tackifier resin, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling regulator, and the like can be blended as other optional components. For example, when the heat resistant stabilizer is blended, the decomposition of the resin can be suppressed, so that the heat resistance after curing of the conductive adhesive can be further improved. Specifically, as the heat resistant stabilizer, hindered phenol compounds, phosphorus compounds, lactone compounds, hydroxylamine compounds, sulfur compounds and the like are preferable, and hindered phenol compounds are more preferable.

  The conductive adhesive can be made by mixing and stirring the materials described above. Stirring can use well-known stirring apparatuses, such as a disper mat | matte and a homogenizer, for example.

<Method of manufacturing conductive adhesive sheet>
The conductive adhesive sheet of the present invention is a sheet comprising a peelable sheet and a conductive adhesive layer provided on one 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 attached to a reinforcing plate (conductive reinforcing plate), and then main curing is performed by high temperature heating, whereby high connection reliability and heat and humidity resistance can be obtained.

  The conductive adhesive layer is, for example, a knife coat, a die coat, a lip coat, a roll coat, a curtain coat, a bar coat, a gravure coat, a flexo coat, a dip coat, a spray coat, a spin coat, etc. on the release surface of the release sheet. After the conductive adhesive is applied to form a coating film by the method described above, the coating film can be generally formed by heating the coating film 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 is easy to handle by bonding a peelable sheet to the surface thereof.

  The conductive adhesive sheet of the present invention is prepared by temporarily sticking the conductive adhesive onto a reinforcing plate to produce a laminate (conductive adhesive sheet with a reinforcing plate), and processing the laminate into a desired shape by punching. There are many. In this case, the conductive adhesive layer in the semi-cured state has a predetermined elongation rate, and the laminate exhibits better punching processability.

<Wiring device>
A wiring device according to the present invention comprises a wiring board having signal wiring, a reinforcing board provided on at least one surface of the wiring board, and the conductive adhesive according to the present invention for bonding the wiring board and the reinforcing board And a conductive adhesive layer formed by
Such a wiring device is, for example, temporarily laminating a wiring board and a conductive reinforcing plate via a semi-cured conductive adhesive layer to form a laminate, and then heating the laminate at a high temperature, It can be obtained by forming the bonding layer by fully curing the conductive adhesive layer. The main curing provides a bonding layer (cured product of the conductive adhesive layer) having excellent adhesive strength and heat resistance.

Moreover, it is preferable that it is 130-210 degreeC, and, as for the heating temperature in this curing | hardening, it is more preferable that it is 140-200 degreeC. While the laminate can be pressurized during heating, 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 the wiring device, the insulating layer and the reinforcing plate of the wiring board are bonded by the bonding layer.

In addition to the signal wiring, the wiring board preferably further includes a ground wiring. Using a conductive reinforcing plate (conductive reinforcing plate) as a reinforcing plate to electrically connect with the ground wiring to make the conductive reinforcing plate function as a shield layer (electromagnetic wave shielding 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, stainless steel, aluminum and the like.
In addition, as a method of taking the electrical connection, a method of forming a through hole in the insulating layer, and filling a conductive adhesive in the through hole, a conductive adhesive layer by thermocompression bonding at the time of main curing The method of making it flow and filling in a through-hole etc. are mentioned.

  The wiring board is preferably a flexible printed wiring board (FPC). When the wiring board is an FPC, heat-resistant resin materials such as polyimide and liquid crystal polymer are preferable as the insulating substrate and the insulating constituent material. 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 materials, 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 liquid crystal display or the like or a mobile phone, a smart phone, a tablet terminal or the like incorporating the same. Further, the conductive adhesive and the conductive adhesive sheet of the present invention can be used in the manufacture of wiring devices and can be used in various applications where conductivity is required. As preferable examples, a conductive adhesive layer for an electromagnetic wave shield sheet, an anisotropic conductive sheet, an antistatic sheet, a sheet for ground connection, a thermally conductive sheet, a conductive sheet for a jumper circuit and the like can be mentioned. Note that the signal wiring and the ground wiring of the wiring board may form a circuit having a desired function.

EXAMPLES The present invention will next be described in more detail by way of examples, which should not be construed as limiting the invention thereto.
In addition, "part" shall represent "weight part" and "%" shall represent "weight%." Moreover, "Mn" represents a number average molecular weight and "Mw" represents a weight average molecular weight.

  The acid value of the resin, the glass transition temperature (Tg) of the resin, the weight average molecular weight of the resin, the coverage of the coating layer of the conductive filler, and the average particle diameter of the conductive filler were measured by the following methods.

<Measurement of acid number>
1 g of a thermosetting resin was dissolved in 40 ml of methyl ethyl ketone, and an automatic titrator "AT-510" manufactured by Kyoto Electronics Industries, Ltd. was connected to "APB-510-20B" manufactured by the same company as a burette. Potentiometric titration was performed using a 0.1 mol / L ethanolic KOH solution as a titration reagent, and the mg number of KOH per 1 g of resin was calculated.

<Glass transition temperature (Tg)>
The measurement of Tg was measured by differential scanning calorimetry ("DSC-1" manufactured by METTLER TOLEDO).

<Method of measuring weight average molecular weight (Mw)>
The weight average molecular weight (Mw) is a value in terms of polystyrene calculated by GPC (gel permeation chromatography) measurement. The measurement conditions are as follows.
Device: Shodex GPC System-21 (made by Showa Denko)
Column: One Shodex KF-802 (made by Showa Denko) and one Shodex
Connection column in which KF-803L (made by Showa Denko) and 1 Shodex KF-805L (made by Showa Denko) are connected in series Solvent: tetrahydrofuran Flow rate: 1.0 mL / min
Temperature: 40 ° C
Sample concentration: 0.2%
Sample injection volume: 100 μL

<Method of measuring coverage of coating layer of conductive filler>
As a method of measuring the coverage of the coating layer of the conductive filler, the coverage of silver in the case where the coating layer is silver with respect to the core made of copper is shown as an example.
AXIS-HS (Shimadzu Corporation / Kratos), X-ray source: Dual (Mg) 15 kV, 10 mA Pass energy 80 eV, Step: 0.1 eV / Step, Speed: 120 seconds / element, Dell: 300, number of integrations: The mass concentration of silver and copper was determined from the peak areas of Ag3d: 2 and Cu2P: 1 under the conditions of 8, and the ratio of mass concentration of silver was taken as the coverage.
The coverage of the coating layer of the conductive filler was measured by X-ray photoelectron spectroscopy (ESCA). The conductive filler measurement using copper for the core and silver for the coating layer will be described as an example. First, a double-sided pressure-sensitive adhesive tape was attached to a dedicated pedestal, the conductive filler was uniformly attached, and the excess was removed with air to obtain a measurement sample. The measurement sample was measured at three different places under the following conditions.
Device: AXIS-HS (Shimadzu Corporation / Kratos)
Vacuum level in sample chamber: 1 x 10 ^-8 Torr or less X-ray source: Dual (Mg) 15 kV, 5 mA Pass energy 80 eV
Step: 0.1 eV / Step
Speed: 120 seconds / Element Dell: 300, accumulated number of times: 5
Photoelectron take-off angle: 90 degrees with respect to the sample surface Binding energy: C1s main peak shift corrected to 284.6 eV Cu (2p) peak area: 926 to 936 eV
Ag (3d) peak region: 376 to 362 eV
The peak appearing in the above peak area is subjected to smoothing treatment, a baseline is drawn by the linear method, the atomic concentration of silver and copper "Atomic Conc" is determined, and the average value of the three values calculated by the following formula is conducted. It was the coverage of the filler.
Coverage = [atomic concentration of silver] / ([atomic concentration of copper] + [atomic concentration of silver]) × 100
When the covering layer is nickel, the peak region is Ni (2p): 848 to 870 eV.

<Method of measuring D50 average particle diameter of conductive filler>
The D50 average particle size was measured using a laser diffraction / scattering particle size distribution analyzer LS13320 (manufactured by Beckman Coulter, Inc.), and the conductive filler was measured with a tornado dry powder sample module. The refractive index was set to 1.6.

  The materials used in the examples are shown below.

<Thermosetting resin>
(Thermosetting resin 1)
Synthesis Example 1: Synthesis of Polycarbonate-Based Polyurethane
In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, nitrogen introducing pipe, 194 parts of a polycarbonate-based diol "Dacel Co., Ltd., Plaxel CD 220", 7 parts of dimethylol butanoic acid, 42 parts of isophorone diisocyanate, and toluene 70 parts were charged and reacted at 90 ° C. for 3 hours under nitrogen atmosphere. To this, 250 parts of toluene was added to obtain a solution of a urethane prepolymer having an isocyanate group at the end. Next, 506 parts of the solution of the obtained urethane prepolymer is added to a mixture of 6 parts of isophorone diamine, 0.6 parts of di-n-butylamine, 113 parts of 2-pronol, and 185 parts of toluene, and 70 ° C. The reaction was carried out for 3 hours to obtain a solution of a polycarbonate-based polyurethane resin having Mw = 50000, Tg of 3 ° C. and acid value of 7 mg KOH / g. Toluene and 2-propanol were added to this to obtain a thermosetting resin 1 (polycarbonate polyurethane resin) solution having a solid content of 30%.

(Thermosetting resin 2)
Synthesis Example 2: Synthesis of Polyester-Based Polyurethane
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introducing pipe, 195 parts of polyester-based diol "Kuraray Co., Ltd., P-2011", 7 parts of dimethylol butanoic acid, 40 parts of isophorone diisocyanate, And 70 parts of toluene were charged and reacted at 90.degree. C. for 3 hours under a nitrogen atmosphere. To this, 250 parts of toluene was added to obtain a solution of a urethane prepolymer having an isocyanate group at the end. Next, 506 parts of the solution of the obtained urethane prepolymer is added to a mixture of 6 parts of isophorone diamine, 0.6 parts of di-n-butylamine, 113 parts of 2-pronol, and 185 parts of toluene, and 70 ° C. The reaction was carried out for 3 hours to obtain a polyurethane-based thermosetting resin solution having a Mw of 43,000, a Tg of -5.degree. C. and an acid value of 10 mg KOH / g. Toluene and 2-propanol were added to this, and the thermosetting resin 2 (polyester type polyurethane resin) solution which is solid content 30% was obtained.

(Thermosetting resin 3)
Synthesis Example 3: Synthesis of Polyether-Based Polyurethane
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introducing pipe, 196 parts of polyether-based diol "PTG-2000sn manufactured by Hodogaya Kogyo Co., Ltd.", 6 parts of dimethylol butanoic acid, isophorone diisocyanate 41 Parts and 70 parts of toluene were charged and reacted at 90 ° C. for 3 hours under a nitrogen atmosphere. To this, 250 parts of toluene was added to obtain a solution of a urethane prepolymer having an isocyanate group at the end. Next, 506 parts of the solution of the obtained urethane prepolymer is added to a mixture of 6 parts of isophorone diamine, 0.6 parts of di-n-butylamine, 113 parts of 2-pronol, and 185 parts of toluene, and 70 ° C. The reaction was carried out for 3 hours to obtain a solution of polyether polyurethane resin having Mw = 70,000, Tg of -10.degree. C. and acid value of 15 mg KOH / g. Toluene and 2-propanol were added to this to obtain a thermosetting resin 3 (polyether polyurethane resin) solution having a solid content of 30%.

(Thermosetting resin 4)
Synthesis Example 4 Synthesis of Vinyl-Based Polyurethane
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, a nitrogen introducing pipe, a polybutadiene-based diol "Nihon Soda Co., Ltd. G-2000" 196 parts, 6 parts dimethylol butanoic acid, 41 parts isophorone diisocyanate And 70 parts of toluene were charged and reacted at 90 ° C. for 3 hours under a nitrogen atmosphere. To this, 250 parts of toluene was added to obtain a solution of a urethane prepolymer having an isocyanate group at the end. Next, 506 parts of the solution of the obtained urethane prepolymer is added to a mixture of 6 parts of isophorone diamine, 0.6 parts of di-n-butylamine, 113 parts of 2-pronol, and 185 parts of toluene, and 70 ° C. The reaction was carried out for 3 hours to obtain a solution of a polybutadiene-based polyurethane resin having a Mw of 30,000, a Tg of 5 ° C. and an acid value of 13 mg KOH / g. Toluene and 2-propanol were added to this to obtain a thermosetting resin 4 (polybutadiene-based polyurethane resin) solution having a solid content of 30%.

(Thermosetting resin 5)
Synthesis Example 5 Synthesis of Polyester
In a flask equipped with a stirrer, thermometer, nitrogen gas inlet tube and reflux dehydrating apparatus, 184.4 parts of dimethyl terephthalate, 94.8 parts of neopentyl glycol, 94.2 parts of ethylene glycol, 2-methyl-1, 3 54.7 parts of propanediol and 0.035 parts of zinc acetate were charged. Stirring is started when the raw materials are melted by heating and stirring becomes possible, and the temperature is gradually raised from 170 ° C. to 220 ° C. over 3 hours while removing distilled methanol out of the reaction system under normal pressure, 220 ° C. Hold for 1 hour. Once the internal temperature is cooled to 170 ° C, 92.6 parts of adipic acid, 65.8 parts of isophthalic acid, and 113.6 parts of 1,4-cyclohexanedicarboxylic acid are added, and distilled water is removed from the reaction system under normal pressure. The temperature was raised to 240 ° C. over 3 hours while maintaining the temperature at 240 ° C., and the reaction was continued until the acid value of the product reached 15 mg KOH / g. Next, the apparatus is replaced with a vacuum decompression apparatus, 0.06 parts of tetrabutyl titanate is added, and the reaction is continued at a temperature of 240 ° C. under a reduced pressure of 2 Torr for 6 hours, and then taken out in a container made of polytetrafluoroethylene resin. The The number average molecular weight of this resin was 18,000, and the glass transition temperature was 27 ° C. Subsequently, 100 parts of toluene was added to and dissolved in 100 parts of the obtained polyester resin. Subsequently, 5 parts of ethylene glycol bis trimellitate dianhydride was added to each flask and reacted at a temperature of 100 ° C. for 5 hours to obtain a polyester resin solution having Mw = 50000 and an acid value of 19 mg KOH / g. Toluene was added and diluted to this, and the solid content obtained the thermosetting resin 5 (polyester resin which has a carboxyl group) solution which is 30%.

(Thermosetting resin 6)
Synthesis Example 6: Synthesis of Polyamide
In a flask equipped with a stirrer and a reflux dehydrator, 100 parts by weight of dimer acid as a dicarboxylic acid component, 7.62 parts by weight of butanediamine as a diamine component, and 7.44 parts by weight of piperazine were charged. The temperature was raised to 230 ° C. at an internal temperature of 25 ° C. to 115 ° C./hour, the reaction was continued at that temperature for 6 hours, and then cooling was performed to obtain a thermosetting resin 6 (polyamide resin). The acid value of the polyamide resin was 4 (mg KOH / g), and the weight average molecular weight was 66000.

<Other resin>
(Other resin 1)
Synthesis Example 7: Synthesis of carboxylic acid-less-polyester polyurethane
Mn = 981 obtained from adipic acid and 3-methyl-1,5-pentanediol and 1,6-hexane carbonate diol in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen introducing pipe Then, 432 parts of diol, 137 parts of isophorone diisocyanate, and 40 parts of toluene were charged, and reacted at 90 ° C. for 3 hours under a nitrogen atmosphere. To this, 300 parts of toluene was added to obtain a solution of a urethane prepolymer having an isocyanate group at an end. Next, 818 parts of the solution of the obtained urethane prepolymer is added to a mixture of 25 parts of isophorone diamine, 3 parts of di-n-butylamine, 342 parts of 2-propanol and 576 parts of toluene, and 3 The mixture was reacted for time to obtain a solution of polyester-based urethane resin having Mw = 100000 and an acid value of 0 mg KOH / g. To this, 144 parts of toluene and 72 parts of 2-propanol were added to obtain another resin 1 (polyester-based urethane resin) solution having a solid content of 30%.

Properties of the synthesized thermosetting resin and other resins are summarized in Table 1.

<Conductive filler>
The conductive fillers used in the examples are described below.

The materials used other than the thermosetting resin and the conductive filler are as follows.
Epoxy resin 1: Bisphenol A type epoxy having an epoxy equivalent weight of 190 g / eq ("ADECAResin EP-4100", manufactured by ADEKA)
Epoxy resin 2: A trifunctional reactive epoxy of 150 g / eq of epoxy equivalent ("ED-505", manufactured by ADEKA)
Hardener 1: Trimethylolpropane-tri-β-aziridinyl propionate Hardener 2: Cumene hydroperoxide
Epoxy-based silane coupling agent: 3-glycidoxypropyltrimethoxysilane amine-based silane coupling agent: n-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane vinyl-based silane coupling agent: vinyltriethoxysilane Methacrylic silane coupling agent: 3-methacryloxypropylmethyldiethoxysilane thiol based silane coupling agent: 3-mercaptopropyltrimethoxysilane Inorganic filler 1: commercially available hydrophobic silica having an average particle diameter of 1.2 μm inorganic filler 2: average Commercially available ultrafine particle talc of 3.8 μm in particle diameter

Example 1
100 parts of thermosetting resin 1 (polycarbonate-based polyurethane resin) (solid content), 30 parts of epoxy resin 2, 350 parts of conductive filler 5, 2 parts of curing agent 1, epoxy-based silane coupling agent 3 parts and 3 parts in a container, mixed solvent of toluene: isopropyl alcohol (weight ratio 2: 1) is added so that nonvolatile content concentration becomes 45% by weight, and a conductive adhesive is obtained by stirring with a disper for 10 minutes. The
The conductive adhesive was applied to a peelable sheet using a doctor blade so as to have a dry thickness of 60 μm, and dried at 100 ° C. for 2 minutes to obtain a conductive adhesive sheet.

[Examples 2 to 25 and Comparative Examples 1 to 4]
A conductive adhesive and a conductive adhesive sheet were produced in the same manner as in Example 1 except that the respective components and the blending amounts (parts by weight) thereof were changed as shown in Tables 3 to 5.
In addition, the compounding quantity of resin shown to Tables 3-5 is solid content weight.

  The following physical properties of the obtained conductive adhesive and the conductive adhesive sheet were evaluated. The results are shown in Tables 3 to 5.

<Viscosity stability of conductive adhesive>
The conductive adhesive sheet is formed by applying a conductive adhesive, but if the viscosity stabilization of the conductive adhesive is insufficient, the conductive adhesive is rapidly thickened during coating to be uniform. A conductive adhesive sheet of film thickness can not be obtained.
A conductive adhesive immediately after preparation was charged in 140 ml mayobin, and the initial viscosity at 6 rpm was measured by "VISCOMERER TVB-10M" manufactured by Toki Sangyo Co., Ltd. Thereafter, the above-mentioned mayobin was left to stand for 24 hours while being stirred by a mix rotor in a constant temperature environment of 25 ° C. The viscosity of the conductive adhesive after 24 hours was taken as the temporal viscosity, and the viscosity was measured under the same conditions as the initial condition. The thickening rate was calculated by the following equation.
Viscosity ratio (%) = viscosity over time / initial viscosity × 100
Evaluation criteria are as follows.

◎: The thickening rate is less than 110%. It is a good result.
○: The thickening rate is 110% or more and less than 130%. There is no problem in practical use.
Δ: The thickening rate is 130% or more and less than 150%. There is no problem in practical use.
X: The thickening rate is 150% or more. Not practical

<Connection reliability (step 37.5 μm)>
In order for the metal reinforcing plate to exhibit electromagnetic wave shielding properties, it is important that the metal reinforcing plate is connected to the ground circuit via the conductive adhesive layer to secure a conduction path. The conductive adhesive layer is filled and adhered from the through holes of the coverlay layer disposed on the ground circuit to ensure conductivity, but if the embedding and adhesion to the through holes are not sufficient, the electromagnetic wave shielding property is ensured. In other words, the initial connection reliability is degraded.
A conductive adhesive sheet with a width of 15 mm and a length of 20 mm, and a SUS plate of 20 mm width and a length of 20 mm (a commercially available SUS304 plate with a thickness of 0.2 mm and a nickel layer with a thickness of 2 μm formed on it) A sample was obtained by pasting with a roll laminator at 90 ° C., 3 Kgf / cm ² , 1 M / min.
A peelable film is peeled off from the sample, and the exposed surface is prepared separately. A flexible printed wiring board (not electrically connected to each other on a polyimide film 11 with a thickness of 25 μm is shown in FIG. 1 (1). A copper foil circuit 12A having a thickness of 18 μm and a copper foil circuit 12B are formed, and a cover film 13 having a through hole 14 having a thickness of 37.5 μm and a diameter of 1.2 mm is attached on the copper foil circuit 12A. The laminated wiring board was pasted with a roll laminator at 90 ° C., 3 Kgf / cm ² , 1 M / min.
Then, these were pressure-bonded under the conditions of 170 ° C., 2 MPa, and 5 minutes, and then heated for 60 minutes in an electric oven at 160 ° C. to obtain a measurement sample.
Subsequently, the connection reliability between 12A-12B shown in the top view of FIG. 1 (4) was evaluated by measuring a connection resistance value using a resistance value measuring device and a BSP probe. 1 (2) is a cross-sectional view taken along the line DD 'in FIG. 1 (1), and FIG. 1 (3) is a cross-sectional view taken along the line CC' in FIG. 1 (1). Similarly, FIG. 1 (5) is a cross-sectional view taken along the line DD 'in FIG. 1 (4), and FIG. 1 (6) is a cross-sectional view taken along the line CC' in FIG.
Evaluation criteria are as follows.

◎: The connection resistance value is less than 20 mΩ / □. It is a good result.
○: Connection resistance value is 20 mΩ / □ or more and less than 100 mΩ / □. There is no problem in practical use.
:: The connection resistance value is 100 mΩ / □ or more and less than 300 mΩ / □. There is no problem in practical use.
×: Connection resistance value is 300 mΩ / □ or more. Not practical

<Connection reliability (step 60μm)>
The connection reliability was evaluated by the same method as the connection resistance value (step 37.5 μm) and evaluation criteria except that the thickness of the cover film 13 in FIG. 1 (1) was changed to 60 μm.

<Connection reliability after moisture and heat resistance test>
Electronic components incorporating an FPC are used in various environments. If the connection reliability after heat and humidity resistance is not sufficient, for example, when used for a long time in a high temperature and high humidity environment, the electromagnetic wave shielding property is deteriorated, and the frequency characteristic of the attached signal circuit is deteriorated.
The measurement sample prepared in the test of connection reliability (step 37.5 μm) was put into an oven at 85 ° C. and 85% for 500 hours. After that, the connection reliability between 12A and 12B (the connection reliability after wet heat aging) shown in the plan view of FIG. 1 (4) is measured by measuring the resistance value using a resistance value measuring device and a BSP probe. The connection reliability over time was evaluated.
Evaluation criteria are as follows.

◎: The connection resistance value is less than 20 mΩ / □. It is a good result.
○: Connection resistance value is 20 mΩ / □ or more and less than 100 mΩ / □. There is no problem in practical use.
:: The connection resistance value is 100 mΩ / □ or more and less than 300 mΩ / □. There is no problem in practical use.
×: Connection resistance value is 300 mΩ / □ or more. Not practical

<Adhesive force after wet heat resistance test>
The conductive adhesive sheet was cut into a size of 25 mm wide × 100 mm long, and then the peelable sheet was peeled off to obtain a conductive adhesive layer. A laminate obtained by sandwiching this conductive adhesive layer between the polyimide surface of a 40 μm thick copper-clad laminate (“Esperflex”, manufactured by Sumitomo Metal Mining Co., Ltd.) and a 200 μm thick stainless plate (SUS 304) Formed. Then, after pressure bonding the obtained laminated body on 170 degreeC and 2 MPa and the conditions for 5 minutes, it heated for 60 minutes in a 160 degreeC electric oven. Thus, a laminate of “cured product of copper-clad laminate / conductive adhesive layer / SUS plate” was obtained. This laminate is put into an oven at 85 ° C. and 85% for 500 hours, and then subjected to T peel peel test at 23 ° C. and an atmosphere of 50% relative humidity at a tension rate of 50 mm / min. It was measured.

◎: Adhesive strength is 10 N / cm or more. It is a good result.
○: Adhesive strength is less than 10 N / cm, 7 N / cm or more. There is no problem in practical use.
Δ: Adhesive strength less than 7 N / cm, 4 N / cm or more. There is no problem in practical use.
X: Adhesive strength is less than 4 N / cm. Not practical.

<Punching processability>
The conductive adhesive sheets obtained in Examples and Comparative Examples and a SUS plate (a commercially available SUS304 plate having a thickness of 0.2 mm on which a nickel layer having a thickness of 2 μm is formed) are overlapped, and 90 using a roll laminator A sample was obtained by sticking under the conditions of 3 ° C., 3 Kgf / cm 2 and 1 M / min.
This sample was punched out into a size of 10 mm × 30 mm with a 100-piece punching machine, and the number of defective products was evaluated as follows. Defective products are those that are not partially removed after being processed into a die-cut shape, those in which the SUS plate and the conductive adhesive layer are peeled off, and those at the end where the conductive adhesive layer is punched out. It is something whose shape is distortion.

・ ・ ・ ... less than 10% ○ ... 10% or more and less than 15% 10 ... 15% or more and less than 25% × ... 25% or more

  From the results of Tables 3 to 5, it is possible to reduce the cost even when using a conductive filler containing copper as a main component by the conductive adhesive of the example, but the viscosity of the conductive adhesive is stable. A conductive adhesive layer having good connection reliability and adhesiveness even after being exposed to a moist and heat environment for a long time, and good connection reliability even in a circuit having a high level difference in the through holes of the ground wiring substrate, and a wiring device It could be confirmed that it could be provided.

11 polyimide film 12A, 12B copper foil circuit 13 cover film 14 through hole 15a metal reinforcing plate 15b conductive adhesive layer

Claims (9)

A thermosetting resin (A) having a carboxyl group, an epoxy resin, a conductive filler (B) containing copper as a main component, a curing agent, and a silane coupling agent,
The thermosetting resin (A) having a carboxyl group is a polyurethane thermosetting resin having an acid value of 1 mg KOH / g or more,
The diol compound having a carboxyl group, wherein the polyurethane-based thermosetting resin is at least one selected from the group consisting of a polycarbonate-based polyurethane resin, a polyester-based polyurethane resin, a polyether-based polyurethane resin, and a polybutadiene-based polyurethane resin It is obtained by reacting a), a polyol compound (b) having no carboxyl group, and an organic diisocyanate (c),
The diol compound (a) having a carboxyl group is at least one of dimethylolalkanoic acid, dihydroxysuccinic acid and dihydroxybenzoic acid,
The conductive filler (B) has a core made of copper and a coating layer made of silver, and at least one of the following is satisfied:
The coating layer is 5 parts by mass or more with respect to 100 parts by mass of the core; or the coverage is 90% or more.
1 to 15 parts by mass of a silane coupling agent is blended with 100 parts by mass of the thermosetting resin (A),
A conductive adhesive characterized by A thermosetting resin (A) having a carboxyl group, an epoxy resin, a conductive filler (B) containing copper as a main component, a curing agent, and a silane coupling agent,
The thermosetting resin (A) having a carboxyl group is a polyurethane thermosetting resin having an acid value of 1 mg KOH / g or more,
The diol compound having a carboxyl group, wherein the polyurethane-based thermosetting resin is at least one selected from the group consisting of a polycarbonate-based polyurethane resin, a polyester-based polyurethane resin, a polyether-based polyurethane resin, and a polybutadiene-based polyurethane resin It is obtained by reacting a), a polyol compound (b) having no carboxyl group, and an organic diisocyanate (c),
The diol compound (a) having a carboxyl group is at least one of dimethylolalkanoic acid, dihydroxysuccinic acid and dihydroxybenzoic acid,
The conductive filler (B) has a core made of copper and a covering layer made of a conductive material different from copper, and at least one of the following is satisfied:
The coating layer is 5 parts by mass or more with respect to 100 parts by mass of the core; or the coverage is 90% or more.
The silane coupling agent is at least one selected from the group consisting of a vinyl based silane coupling agent, an epoxy based silane coupling agent, and an amino based silane coupling agent,
1 to 3 parts by mass of a silane coupling agent is blended with 100 parts by mass of the thermosetting resin (A),
A conductive adhesive characterized by Before Kishirube conductive material is silver,
The conductive adhesive according to claim 2 . A thermosetting resin (A) having a carboxyl group, an epoxy resin, a conductive filler (B) containing copper as a main component, a curing agent, and a silane coupling agent,
The thermosetting resin (A) having a carboxyl group is a polyurethane thermosetting resin having an acid value of 1 mg KOH / g or more,
The diol compound having a carboxyl group, wherein the polyurethane-based thermosetting resin is at least one selected from the group consisting of a polycarbonate-based polyurethane resin, a polyester-based polyurethane resin, a polyether-based polyurethane resin, and a polybutadiene-based polyurethane resin It is obtained by reacting a), a polyol compound (b) having no carboxyl group, and an organic diisocyanate (c),
The diol compound (a) having a carboxyl group is at least one of dimethylolalkanoic acid, dihydroxysuccinic acid and dihydroxybenzoic acid,
The epoxy resin is a compound having three or more epoxy groups in one molecule,
The conductive filler (B) has a core made of copper and a covering layer made of a conductive material different from copper,
3 to 10 parts by mass of a silane coupling agent is blended with 100 parts by mass of the thermosetting resin (A),
A conductive adhesive characterized by With the previous Kishirube conductive material is silver, satisfy at least one of the following;
The coating layer is 3 parts by mass or more with respect to 100 parts by mass of the core; or the coverage is 84% or more.
The conductive adhesive according to claim 4. The conductive adhesive according to any one of claims 1 to 5 , wherein the coating layer is 40 parts by weight or less with respect to 100 parts by weight of the core of the conductive filler (B). A conductive adhesive sheet comprising a conductive adhesive layer formed of the conductive adhesive according to any one of claims 1 to 6 on a peelable sheet. A wiring board provided with signal wiring;
A reinforcing plate provided on at least one surface side of the wiring board;
A wiring device comprising a conductive adhesive layer for bonding the wiring board and the reinforcing plate,
A wiring device characterized in that the conductive adhesive layer is formed of the conductive adhesive according to any one of claims 1 to 6 . The reinforcing plate has conductivity.
The wiring device according to claim 8 , wherein the wiring board further comprises a ground wiring connected to the reinforcing plate.