KR101789082B1 - CONDUCTIVE ADHESIVE, CONDUCTIVE ADHESIVE SHEET, and WIRING DEVICE - Google Patents

Abstract

Disclosed is a conductive filler comprising a copper-based conductive filler. The conductive filler has a stable viscosity and is excellent in connection reliability and adhesion even after exposure to a high temperature and high humidity environment for a long period of time. A conductive adhesive sheet, and a wiring device with good connection reliability even in a high circuit.
(B) a thermosetting resin (A) having a carboxyl group, an epoxy resin, a copper as a main component, a curing agent, and a silane coupling agent.

Description

CONDUCTIVE ADHESIVE, CONDUCTIVE ADHESIVE SHEET, AND WIRING DEVICE [0002]

The present invention relates to a conductive adhesive, a conductive adhesive sheet, and a wiring device. More specifically, the present invention relates to a conductive adhesive which can be used in a process for mounting electronic components and the like. The present invention also relates to a conductive adhesive sheet provided with a conductive adhesive layer formed of the related conductive adhesive agent. The present invention also relates to a wiring device formed by bonding a wiring board and a reinforcing plate to each other with a bonding layer composed of a cured product of a conductive adhesive layer.

Electronic devices such as OA devices, communication devices, and mobile phones have become more sophisticated and miniaturized. Flexible printed wiring boards have curvature characteristics. For this reason, a flexible printed wiring board to which an electronic circuit is coupled is used as an internal substrate or the like arranged in a narrow and complicated space of electronic equipment. In this case, it is general to provide an electromagnetic wave shielding layer on a flexible printed wiring board (hereinafter referred to as " FPC ") for shielding an electromagnetic wave from an electromagnetic wave generated by an electronic device. In addition, due to the increase in the amount of information supplied to the recent electronic circuit and the increase in the frequency and the miniaturization of the electronic circuit, such countermeasures against electromagnetic waves become more important.

As an FPC provided with an electromagnetic wave shielding layer, Patent Document 1 and Patent Document 2 disclose an FPC in which a conductive reinforcing plate and a grand circuit are connected by a conductive adhesive layer. Specifically, a conductive reinforcing plate made of metal such as stainless steel is attached to an FPC by using a conductive adhesive, thereby electrically connecting the conductive reinforcing plate to the grand circuit. Because of this, since the electromagnetic wave shielding layer is provided in the FPC, the FPC can stably transmit the circuit signal.

With respect to the above-described conductive adhesive, excellent conductive properties including stability over time are required. Therefore, when the conductive adhesive is provided as the conductive sheet, the characteristics of the conductive filler contained in the sheet become important. As a conductive filler, a conductive sheet containing silver has been put to practical use because silver powder has excellent conductivity characteristics. However, the price of silver is higher than that of other materials such as conductive sheets and the like, and the use of silver as a conductive filler is costly. In addition, due to the surge in silver prices these days, the rise in prices of conductive sheets using silver has become a serious problem. In order to achieve a reduction in the cost of electronic devices, it is necessary to reduce the use proportion of the conductive filler in the conductive adhesive. However, when the specific gravity of the conductive filler is reduced, there arises a problem that the desired conductivity can not be maintained in the conductive adhesive.

Thus, a method of using a conductive filler having a coating layer composed of a conductive material as an alternative conductive filler at a lower cost than silver is studied. For example, the surface of copper is plated with a conductive material such as silver. However, if the coating amount of the coating layer made of a conductive material is further reduced in order to reduce the cost, the inside copper is liable to be exposed. For this reason, there is a problem that the viscosity stability of the conductive adhesive deteriorates due to elution of copper ions. Further, the conductive adhesive layer using copper and the above-described conductive filler having a large exposed surface of copper as described above, when exposed to a high temperature and high humidity environment (for example, at a temperature of 85 DEG C and a humidity of 85%) for a long time, . As a result, there has been a problem that the characteristics of the electromagnetic wave shielding layer are deteriorated and the bonding strength is deteriorated and the metal reinforcing plate is easily peeled off.

Further, when the conductive reinforcing plate is connected to the grand circuit by using the conductive adhesive, the conductive adhesive is filled in the through hole, and the conductive adhesive hardens. Thereby, the conductive reinforcing plate is fixed while electrically interconnecting the conductive reinforcing plate to the grand circuit. However, when a conductive filler containing copper as a main component is used, there is a problem that the reliability of the connection by the conductive adhesive is lowered in a place where the level difference of the through hole is high.

Japanese Patent Application Laid-Open No. 2009-218443 International Publication No. 2014/010524

Accordingly, an object of the present invention is to provide a conductive adhesive, a conductive adhesive sheet, and a wiring device using a conductive filler containing copper as a main component. In the present invention, the cost is reduced by using copper and the viscosity of the conductive adhesive is stable. Further, there is a problem that the conductive adhesive has good connection reliability and adhesion even after exposure to a high temperature and high humidity environment over a long period of time. Further, the problem is that the reliability of the connection by the conductive adhesive is good even in a circuit in which the level difference of the through hole of the grand wiring substrate is high.

As a result of intensive investigations by the present inventors, it has been found that when a conductive filler containing copper as a main component is used for a conductive adhesive, the conductive adhesive contains a thermosetting resin (A) having a carboxyl group, an epoxy resin, a curing agent and a silane coupling agent Mentioned problems can be solved and the present invention has been accomplished.

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

Further, the present invention relates to the conductive adhesive characterized in that the conductive filler (B) comprises a core composed of copper and a coating layer composed of a conductive material different from copper.

Further, the present invention relates to the conductive adhesive characterized in that the covering layer is 40 parts by mass or less based on 100 parts by mass of the core of the conductive filler (B).

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

Further, the present invention is characterized in that the thermosetting resin (A) is selected from the group consisting of a polycarbonate-based polyurethane resin, a polyester-based polyurethane resin, a polyether-based polyurethane resin and a methacrylic polyurethane thermosetting resin To the conductive adhesive agent.

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

According to another aspect of the present invention,

A reinforcing plate provided on at least one side of the wiring board,

And a conductive adhesive layer for bonding the wiring board and the reinforcing plate to each other,

And the conductive adhesive layer is formed of the conductive adhesive agent.

Wherein the reinforcing plate has conductivity,

And the wiring board further includes a ground wiring connected to the reinforcing plate.

According to the present invention having the above structure, it is possible to provide a conductive adhesive agent, a conductive adhesive sheet, and a wiring device using a conductive filler containing copper as a main component in a conductive adhesive agent. In the present invention, the viscosity of the conductive adhesive is stable while cost can be reduced by using copper. Further, even after exposure to a high temperature and high humidity environment over a long period of time, the conductive adhesive has good connection reliability and adhesion. Further, even in a circuit in which the level difference of the through hole of the grand wiring substrate is high, the reliability of connection by the conductive adhesive is good.

1 is a schematic diagram of a connection reliability test.

The conductive adhesive of the present invention includes a thermosetting resin (A) having a carboxyl group (hereinafter, also referred to as "thermosetting resin (A)"), an epoxy resin, a conductive filler, a curing agent and a silane coupling agent. The conductive adhesive agent can be used as it is to apply the adhesive agent to a desired place in the same manner as a general adhesive agent. As another application, the conductive adhesive may be applied to a substrate such as a peelable sheet to form a conductive adhesive sheet and then used to bond the members.

In the method of curing the conductive adhesive, for example, when forming the conductive adhesive in the form of a sheet, first, the conductive adhesive is cured in a semi-cured state by curing the thermosetting resin (A) using a curing agent. Thereafter, in the final curing step, the thermosetting resin (A) and the silane coupling agent are cured and reacted with each other using an epoxy resin, thereby curing the conductive adhesive. In such a cured state, the conductive adhesive has high heat resistance capable of withstanding the solder reflow temperature. Another curing method includes a curing method in which the curing agent and the epoxy resin are cured together with the thermosetting resin (A) in the main curing step. Needless to say, other curing methods can be optionally employed as the curing method of 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 for a conductive adhesive. Further, it is a thermosetting resin capable of exhibiting 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 and a phenol resin can be used. Among them, a polyurethane-based thermosetting resin is preferable from the viewpoints of moisture resistance and heat resistance after curing and step-following ability. Particularly, the polycarbonate-based polyurethane resin, the polyester-based polyurethane resin, the polyether-based polyurethane resin, and the methacrylic-based polyurethane resin are excellent in connection reliability and excellent in adhesiveness after resistance to high temperature and high humidity environments It is good because.

The acid value of the thermosetting resin (A) is preferably 1 to 100 mgKOH / g, more preferably 3 to 50 mgKOH / g. When the acid value is 1 mgKOH / g or more, the crosslinking efficiency (reaction efficiency) between the thermosetting resin (A) and the epoxy resin is increased. Therefore, after a long time exposure in a high temperature and high humidity environment, the resistance value and adhesive force of the conductive adhesive agent are further improved. When the acid value is 100 mgKOH / g or less, the viscosity stability of the conductive adhesive is further improved.

The weight average molecular weight (Mw) of the thermosetting resin (A) is preferably 5,000 to 300,000. If the weight average molecular weight is 5,000 or more, the step following property of the conductive adhesive improves and the connection reliability is further improved. When the weight average molecular weight is 300,000 or less, the viscosity of the conductive adhesive decreases, and handling of the conductive adhesive becomes easier.

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

The polyurethane-based thermosetting resin may be a polyurethane-based thermosetting resin having a carboxyl group. To obtain such a polyurethane-based thermosetting resin, a diol compound (a) having a carboxyl group, a polyol compound (b) having no carboxyl group, and an organic diisocyanate (c) are reacted. Then, a urethane prepolymer (d) having a carboxyl group and an isocyanate group is obtained. The urethane prepolymer (d) having a carboxyl group and an isocyanate group obtained after the first step is reacted with the polyamino compound (e). The polyurethane-based thermosetting resin can be obtained through the second step described above. In the second step, a reaction terminator may be used if necessary.

Examples of the diol compound (a) having a carboxyl group include dimethylolalkanoic acids such as dimethylol acetic acid, dimethylol propionic acid, dimethylol butanoic acid, and dimethylol pentanoic acid; Dihydroxysuccinic acid; And dihydroxybenzoic acid. Among them, dimethylol propionic acid and dimethylol butanoic acid are preferable as the diol compound (a) having a carboxyl group. They are particularly reactive and highly soluble.

As the polyol compound (b) having no carboxyl group, various polyols are mentioned. Generally, such polyols are known as polyol components constituting polyurethane resins. Examples of such polyols include polyether polyols, polyester polyols, polycarbonate polyols, polybutadiene glycols, and the like. These polyols may be used alone or in combination of two or more.

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

Examples of the polyester polyol include 1) a polyester polyol obtained by dehydration condensation of 1) a low-molecular diol of a saturated or unsaturated group, and an anhydride of a dicarboxylic acid or a dicarboxylic acid, 2) ) Polyester polyol obtained by ring-opening polymerization of an ester compound.

Examples of the saturated or unsaturated low molecular diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, Methyl-1,5-pentane diol, hexane diol, octane diol, 1,4-butylene diol, diethylene glycol triethylene glycol, dipropylene glycol, dimer diol and the like.

Examples of the dicarboxylic acids include adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, gluconic acid, pimelic acid, suberic acid, azelaic acid, Respectively.

Examples of the polycarbonate polyol include 1) a reaction product of a diol or a bisphenol and a carbonic ester, and 2) a reaction product obtained by reacting a diol or a bisphenol with phosgene in the presence of an alkali.

Examples of the carbonic ester include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, and the like.

Examples of diols include ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 3-methyl-1,5-pentanediol, Diol, 3,3'-dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,3-hexanediol, cyclohexanediol, 3,9-bis (1,1-dimethyl-2-hydroxyphenyl) Ethyl, 2,2,8,10-tetraoxospiro (5.5) undecane, and the like.

As the bisphenol, for example, bisphenol A and bisphenol F are mentioned. And bisphenols to which alkylene oxide such as 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, more preferably from 1,000 to 5,000. When the Mn of the polyol compound (b) having no carboxyl group is 500 or more, it is possible to introduce an appropriate number of urethane bonds into the polyurethane polyurea resin. Therefore, it is easy to obtain a conductive adhesive having a high adhesive strength. 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 become appropriate. For this reason, it is easy to obtain a conductive adhesive excellent in heat resistance after curing.

As the organic (organic) diisocyanate (c), aromatic diisocyanate, aliphatic diisocyanate and alicyclic diisocyanate are preferable.

Examples of the aromatic diisocyanate include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-benzylisocyanate, di Alkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, trilenediisocyanate, 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, norbornene diisocyanate methyl, bis (4-isocyanatocyclohexyl) methane, 1,3- Methyl) cyclohexane, methylcyclohexane diisocyanate, and the like.

These diisocyanates may be used alone or in combination of two or more. Of these, isophorone diisocyanate is preferable as the organic diisocyanate (c).

As the reaction condition of the first step, the amount of the isocyanate group is made excessive with respect to the amount of the hydroxyl group. All the components (a) to (c) need only be blended to satisfy this condition. There are no particular restrictions on the reaction conditions of the first step. Specifically, the equivalence ratio of isocyanate group / hydroxyl group is preferably 1.05 / 1 to 3/1, more preferably 1.2 / 1 to 2/1. The reaction temperature is suitably set within a range of preferably 20 to 150 占 폚, more preferably within a range of 60 to 120 占 폚.

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, aliphatic diamines such as ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane- Norbornene diamine, 2- (2-aminoethylamino) ethanol, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di- . Among them, isophoronediamine is preferable as the polyamino compound (e).

Examples of the reaction terminator that can be used in the second step include, for example, Dialkylamines such as di-n-butylamine, dialkanolamines such as diethanolamine; Alcohols such as ethanol and isopropyl alcohol, and the like.

As the reaction conditions of the second step, the equivalents of the amino groups are as follows. When a free isocyanate group is present at both ends of the urethane prepolymer (d), it is 1 equivalent. In this case, the equivalent of the amino group is preferably 0.5 to 1.3, more preferably 0.8 to 1.05. When the equivalent of the amino group is 0.5 or more, the molecular weight of the polyurethane-based thermosetting resin can be further increased. When the equivalent of the amino group is 1.3 or less, the storage stability may deteriorate depending on the conditions and the like at the time of preservation of the conductive adhesive.

When an amine (for example, dialkylamines or dialkolamines) is used as the reaction terminator, the equivalent amount of the amino group is the total equivalent of the amino group of the polyamino compound (e) and the amino group of the reaction terminator.

The weight average molecular weight of the polyurethane-based thermosetting resin is preferably 5,000 to 200,000. When the weight average molecular weight is 5,000 or more, the heat resistance of the conductive adhesive after curing is further improved. When the weight average molecular weight is 200,000 or less, the viscosity of the conductive adhesive agent is lowered and handling becomes easier.

For the synthesis of the polyurethane-based thermosetting resin, for example, a solvent appropriately selected from ester solvents, ketone solvents, glycol ether solvents, aliphatic solvents, aromatic solvents, alcohol solvents, carbonate solvents and water can be used have. These solvents may be used alone or in combination of two or more.

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

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

Examples of the glycol ether-based solvent include: Ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether and acetic acid esters of monoethers thereof; Diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether and acetic acid esters of these monoethers; .

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

Examples of the aromatic solvents include toluene, xylene, and the like.

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

As the carbonate-based solvent, for example, dimethyl carbonate, ethylmethyl carbonate, di-n-butyl carbonate and the like can be mentioned.

&Lt; 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 glycidylamine type epoxy resin, a glycidyl ester type epoxy resin, and a cyclic aliphatic (alicyclic) epoxy resin are preferably used.

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 novolak type epoxy resin, phenol novolak type epoxy resin, bisphenol A novolak type epoxy resin, dicyclopentadiene type epoxy resin, tetrabromo bisphenol A type epoxy resin, brominated phenol novolak type epoxy resin, tris (glycidyloxyphenyl) epoxy resin, Methane, tetrakis (glycidyloxyphenyl) ethane, and the like.

Examples of the glycidylamine type epoxy resin include tetraglycidyldiaminodiphenylmethane, triglycidylparaaminophenyl, triglycidylmethaminophenol, tetraglycidylmethoxyldiamine, and the like.

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

Examples of the cyclic aliphatic (alicyclic) epoxy resin include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate and bis (epoxycyclohexyl) adipate.

Among them, bisphenol A type epoxy resin, cresol novolak type epoxy resin, phenol novolak type epoxy resin, tris (glycidyloxyphenyl) methane, and tetrakis (glycidyloxyphenyl) ethane are preferable as the epoxy resin Do. By using these epoxy resins, the resistance value and adhesive force of the conductive adhesive agent after the exposure for a long time under a high temperature and high humidity environment are further improved.

The blending amount of the epoxy resin in the conductive adhesive is preferably 3 to 200 parts by mass, more preferably 5 to 100 parts by mass, and more preferably 5 to 40 parts by mass with respect to 100 parts by mass of the thermosetting resin (A). By mixing an epoxy resin in an amount of 3 to 200 parts by mass based on 100 parts by mass of the thermosetting resin (A), a conductive adhesive having higher connection reliability and adhesive force can be obtained even after prolonged exposure under a high temperature and high humidity environment.

&Lt; 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 its main component. The conductive filler (B) may be an alloy of copper and other elements. Other alloying elements include zinc, manganese, iron, lead, phosphorus, nickel, silica, tin, aluminum, beryllium, and titanium.

The conductive filler (B) may be a composite fine particle having copper as a main component and a core. And a composite fine particle having a coating layer formed by coating the surface of the core with a conductive material may be used. Here, the metal to be a nucleus may be pure copper, or an alloy of copper and the above-described elements. The conductive material of the coating layer may be a conductive material. The related material is preferably a conductive metal or a conductive polymer. The conductive metal includes, for example, gold, platinum, silver, nickel, manganese, and indium, and alloys thereof. Examples of the conductive polymer include polyaniline, polyacetylene, and the like. Of these, silver is preferable in terms of price and conductivity.

The coating layer is preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and more preferably 10 parts by mass or less, based on 100 parts by mass of the conductive filler core. By reducing the coating layer to 40 parts by mass or less, the cost of the conductive adhesive agent can be reduced.

With the conductive adhesive of the present invention, such a cost reduction is not only possible but also the viscosity stability of the conductive adhesive is good even when the amount of the conductive material covered with the conductive adhesive is small. In addition, even when the conductive adhesive is exposed for a long time under a high temperature and high humidity environment, the conductivity of the conductive adhesive is good. In addition, a conductive sheet having excellent shielding characteristics and adhesion strength to a metal reinforcing plate can be produced with a conductive adhesive.

The shape of the conductive filler is not limited as long as desired conductivity is obtained. Specific examples of the shape of the conductive filler include spherical shape, flake shape, leaf shape, tree shape, plate shape, needle shape, bar shape A rod shape, and a grape shape are preferable.

The conductive filler may be used alone or in combination of two or more kinds.

The average particle diameter of the conductive filler is preferably 1 to 100 mu m, more preferably 3 to 50 mu m. Since the average particle diameter is within a predetermined range, connection reliability and viscosity stability of the conductive adhesive can be highly compatible. In addition, from the viewpoint of suppressing sedimentation of the conductive filler in the conductive adhesive, the average particle diameter is preferably less than 12 mu m. The average particle diameter can be obtained by a laser diffraction / scattering method particle size distribution measuring apparatus. Here, the average particle diameter is a particle diameter at which the cumulative value in the cumulative distribution of particle diameters is 50%.

In addition to the above methods, about 10 to 20 particles are selected in an enlarged image (for example, 1,000 to 10,000 times) of the conductive filler obtained by a scanning electron microscope, and the diameter of the particles The average particle diameter can also be measured by measuring. When the length in the longitudinal direction of the conductive filler and the length in the short direction are significantly different, the average particle diameter of the conductive filler is calculated using the length in the longitudinal direction. In addition, when the conductive filler has 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 case of covering the core in the conductive filler (B), the coating layer of the conductive material may cover at least a part of the core composed mainly of copper. In order to obtain more excellent conductive properties, it is preferable that the covering ratio is higher. From the viewpoint of maintaining the conductive property well, the average covering ratio of the coating layer is preferably 60% or more, more preferably 70% or more, and more preferably 80% or more. The average covering ratio in the present specification refers to a value obtained by measuring a powder by ESCA described later.

The amount of the conductive filler (B) in the conductive adhesive is preferably 200 to 1,000 parts by mass, more preferably 300 to 600 parts by mass, per 100 parts by mass of the thermosetting resin (A). By adding the conductive filler (B) in an amount of 200 to 1,000 parts by mass based on 100 parts by mass of the thermosetting resin (A), the conductivity of the conductive adhesive agent and the film strength of the conductive adhesive agent layer are further improved.

The conductive adhesive of the present invention may be used in combination with a conductive filler other than the conductive filler (B). Examples of the conductive filler other than the conductive filler (B) include gold, platinum, silver, nickel, manganese, indium and the like, and alloys thereof.

<Curing agent>

In the present invention, the curing agent has a function of forming a semi-cured state of the conductive adhesive layer by a cross-linking reaction when the conductive adhesive agent is formed into a sheet form to obtain the conductive adhesive layer. When the curing agent does not have such a function, the curing agent may have a function of performing a cross-linking reaction during the final curing. As the curing agent, for example, an isocyanate curing agent, an amine curing agent, an aziridine curing agent, an imidazole curing agent and the like are preferable. When the thermosetting resin and the epoxy resin described later and the silane coupling agent have an unsaturated bond, peroxide-based curing agent and azo-based curing agent are preferable as the curing agent.

Examples of the isocyanate curing agent include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, dicyclohexylmethane diisocyanate, 1,5-naphthalene diisocyanate, tetra Methyl xylene diisocyanate, trimethyl hexamethylene diisocyanate, and the like.

Examples of the amine curing agent include diethylenetriamine, triethylenetetramine, methylenebis (2-chloroaniline), methylenebis (2-methyl-6-methylaniline), 1,5-naphthalene diisocyanate, n -Butylbenzylphthalic acid, and the like.

Examples of the aziridine curing agent include trimethylolpropane-tri-? -Aziridinylpropionate, tetramethylolmethane-tri-? -Aziridinylpropionate, N, N'-diphenylmethane- 4'-bis (1-aziridine carboxamide), N, N'-hexamethylene-1,6-bis (1-aziridine carboxamide).

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

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

Examples of the azo-based curing agent include 2,2'-azobisisobutylnitrile and 2,2'-azobis (2,4-dimethylvaleronitrile).

The blending amount of the curing agent in the conductive adhesive is preferably from 0.3 to 20 parts by mass, more preferably from 1 to 15 parts by mass, per 100 parts by mass of the thermosetting resin (A). By mixing 0.3 to 20 parts by mass of the curing agent in 100 parts by mass of the thermosetting resin (A) in the conductive adhesive agent, it is possible to make the hardened conductive adhesive layer hard to flow. This makes it easier to suppress blocking of the conductive adhesive layer.

<Silane coupling agent>

In the present invention, the alkoxysilyl group of the silane coupling agent undergoes a crosslinking reaction, whereby the crosslinking density of the coating film after curing can be increased. Further, the resistance of the conductive adhesive to high temperature and high humidity environment can be improved. As a result, an increase in the resistance value of the conductive adhesive agent is suppressed even after the resistance test for a high temperature and high humidity environment. For this reason, the adhesive force of the conductive adhesive agent is less likely to deteriorate.

Examples of the silane coupling agent include vinyl silane coupling agents, epoxy silane coupling agents, amino silane coupling agents, vinyl silane coupling agents, methacrylic coupling agents, thiol coupling agents, isocyanate silane coupling agents, etc. .

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 conductive adhesive has excellent viscosity stability.

As the vinyl silane coupling agent, for example, vinyltrimethoxysilane, vinyltriethoxysilane and the like can be mentioned.

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

Examples of the amino silane coupling agent include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3- Propyl trimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N- And the like.

As the vinyl silane coupling agent, for example, vinyltrimethoxysilane, vinyltriethoxysilane and the like can be given.

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

Examples of the thiol-based silane coupling agent include 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane.

As the isocyanate-based silane coupling agent, for example, 3-isocyanatepropyltriethoxysilane and the like can be mentioned.

The blending amount of the silane coupling agent in the conductive adhesive is preferably 0.1 to 25 parts by mass, more preferably 0.5 to 15 parts by mass relative to 100 parts by mass of the thermosetting resin (A). The heat resistance of the conductive adhesive after curing of the conductive adhesive is further improved by incorporating 0.5 to 25 parts by mass of the silane coupling agent into 100 parts by mass of the thermosetting resin (A) in the conductive adhesive.

<Inorganic filler>

The conductive adhesive of the present invention preferably further contains an inorganic (inorganic) filler. By including the inorganic filler, the reliability of the conductive adhesive for high temperature and high humidity environments and the punching workability of the conductive adhesive are further improved.

Examples of the inorganic filler include inorganic compounds such as silica, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, titanium oxide, zinc oxide, antimony trioxide, magnesium oxide, talc, montmorillonite, kaolin and bentonite. Among them, hydrophobic silica obtained by reacting a silanol group on the surface of silica with a halogenated silane is preferable as the inorganic filler. By using the hydrophobic silica, the water content of the conductive adhesive agent can be reduced. In the present invention, the inorganic filler is a filler different from the conductive filler.

The average particle diameter (average particle diameter D50) of the inorganic filler is preferably 0.01 to 10 mu m, more preferably 0.05 to 8 mu m. Since the average particle diameter of the inorganic filler is 0.01 to 10 占 퐉, the punching workability can be further improved. The average particle size of the inorganic filler can also be specified by the same method as the conductive filler.

As the other optional components, a heat stabilizer, a pigment, a dye, a tackifier resin, a plasticizer, an ultraviolet absorber, a defoaming agent, a leveling regulating agent and the like can be added to the conductive adhesive of the present invention. For example, when a heat-resistant stabilizer is mixed with a conductive adhesive, decomposition of the resin (resin) can be suppressed. Therefore, the heat resistance of the conductive adhesive after curing of the conductive adhesive can be further improved. Specifically, hindered phenol compounds, phosphorus compounds, lactone compounds, hydroxylamine compounds, sulfur compounds and the like are preferable as heat-resistant stabilizers, and hindered phenol compounds are more preferable.

The conductive adhesive can be prepared by mixing and mixing the materials described so far. As the stirring means, for example, a known stirrer such as a dispermat or a homogenizer may be used.

&Lt; Method of producing conductive adhesive sheet >

The conductive adhesive sheet of the present invention is a sheet having 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 coating a conductive adhesive agent on a peelable sheet. The conductive adhesive layer is preferably semi-cured. For example, after the conductive adhesive layer of the conductive adhesive sheet is temporarily attached to a reinforcing plate (conductive reinforcing plate), the conductive adhesive layer is completely cured (thoroughly cured) by high-temperature heating. As a result, a conductive adhesive layer having high connection reliability and resistance to high temperature and high humidity environments is obtained.

In order to form the conductive adhesive layer, the release surface of the release sheet may be coated with a release coating such as knife coating, die coating, lip coating, roll coating, curtain coating, bar coating, gravure coating, A coating film is formed by applying a conductive adhesive agent by a method such as coating or spin coating. Thereafter, the conductive adhesive layer can be formed by heating the coating film at a temperature of usually 40 to 150 ° C.

The thickness of the conductive adhesive layer is preferably 5 to 500 mu m, more preferably 10 to 100 mu m.

By attaching a releasable sheet to the surface of the conductive adhesive layer, the handling of the conductive adhesive layer becomes easy.

The conductive adhesive layer of the conductive adhesive sheet of the present invention is adhered temporarily to the reinforcing plate to produce a laminate (conductive adhesive sheet with reinforcing plate). Thereafter, the conductive adhesive sheet of the present invention is often processed into a desired shape by punching the laminate. In this case, the semi-cured conductive adhesive layer has a predetermined elongation. Therefore, the laminate exhibits better punch workability.

<Wiring device>

A wiring device of the present invention includes a wiring board having signal wiring. The wiring device of the present invention further comprises a reinforcing plate provided on at least one surface side of the wiring board. The wiring device of the present invention further comprises a conductive adhesive layer formed of the conductive adhesive of the present invention. Here, the conductive adhesive layer bonds the wiring board and the reinforcing plate.

In order to obtain such a wiring device, for example, a laminate is formed by adhering a wiring board and a conductive reinforcing plate temporarily through a conductive adhesive layer in a semi-cured state. Thereafter, this laminate is heated at a high temperature to completely cure the conductive adhesive layer. Thus, by forming the bonding layer, such a wiring device can be obtained. By the complete curing, a bonding layer (cured product of the conductive adhesive layer) having excellent bonding strength and heat resistance is obtained.

The overheat temperature in the present curing is preferably 130 to 210 占 폚, more preferably 140 to 200 占 폚. The laminate can be pressed upon heating. The pressure is preferably 0.2 to 12 MPa, more preferably 0.3 to 10 MPa.

Further, the wiring board has an insulating substrate. The wiring board further includes a signal wiring provided on the insulating substrate. The wiring board further includes an insulating layer provided on the insulating substrate so as to cover the signal wiring. Usually, in the wiring device, the insulating layer of the wiring board and the reinforcing plate are bonded by the bonding layer.

It is also preferable that the wiring board further includes a ground wiring in addition to the signal wiring. By using a reinforcing plate (conductive reinforcing plate) having conductivity as a reinforcing plate, electrical connection is provided between the reinforcing plate and the ground wiring. Thus, the conductive reinforcing plate can function as a shielding layer (electromagnetic wave shielding layer). The constituent material of the conductive reinforcing plate is preferably at least one of a conductive metal and an alloy thereof. Specific examples of the constituent material of the conductive reinforcing plate include stainless steel, aluminum and the like.

As a method of providing the electrical connection, a method of forming a through hole in the insulating layer and filling the through hole with a conductive adhesive is cited. Further, a method of filling a part of the conductive adhesive layer in the through-hole by flowing a part of the conductive adhesive layer by hot pressing at the time of main curing can be mentioned.

It is preferable that the wiring board is a flexible printed wiring board (FPC). When the wiring board is an FPC, a resin material having heat resistance such as polyimide or liquid crystal polymer is 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 substrate). By constituting the insulating substrate and the insulating layer with these materials, the insulating substrate and the insulating layer exhibit high heat resistance.

The above-described wiring device of the present invention can be used for a touch panel type liquid crystal display or the like. Such a touch panel type liquid crystal display or the like can be used in combination with a mobile phone, a smart phone, or a tablet terminal. Further, the conductive adhesive agent and the conductive adhesive sheet of the present invention can be used in the production of a wiring device. The conductive adhesive and the conductive adhesive sheet of the present invention can be used for various other applications requiring conductivity. Suitable examples include conductive adhesive layers for electromagnetic shielding sheets, anisotropic conductive sheets, electrostatic elimination sheets, gland connecting sheets, thermally conductive sheets, conductive sheets for jumper circuits, and the like. A circuit having a desired function may be formed in the signal wiring and the ground wiring of the wiring board.

[Example]

Now, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

In addition, "part" means "mass part" and "%" means "mass%". "Mn" represents the number average molecular weight, and "Mw" represents the 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 conductive filler coating layer, and the average particle diameter of the conductive filler were measured by the following methods.

&Lt; Measurement of acid value &

1 g of the thermosetting resin was dissolved in 40 ml of methyl ethyl ketone. We used a device connected to the same company product "APB-510-20B" as a burette for Kyoto automated industrial titration device "AT-510". As a titration reagent, 0.1 mol / L of an ethanolic KOH solution was used. Potentiometric titration was carried out to calculate the number of mg of KOH per 1 g of the resin.

&Lt; Glass transition temperature (Tg) >

The Tg was measured by differential scanning calorimetry ("DSC-1" manufactured by Mettler Trade Co.).

&Lt; Measurement method of weight average molecular weight (Mw) >

The weight average molecular weight (Mw) is the polystyrene reduced value determined by GPC (Gel Permeation Chromatography) measurement. The measurement conditions are as follows.

Device: Shodex GPC System-21 (manufactured by Showa Denko)

Column: Connection column connecting one Shodex KF-802 (manufactured by Showa Denko), one Shodex KF-803L (manufactured by Showa Denko) and one Shodex KF-805L (manufactured by Showa Denko)

Solvent: tetrahydrofuran

Flow rate: 1.0 mL / min

Temperature: 40 ° C

Sample concentration: 0.2%

Sample injection amount: 100 μL

&Lt; Method for Measuring Coverage of Cover Layer of Conductive Filler >

An example of a method of measuring the covering ratio of the covering layer of the conductive filler is shown. A method of measuring the coverage of silver in a conductive filler having a core composed of copper and a coating layer composed of silver is shown.

The mass concentration of silver and copper in the conductive filler was determined. The conditions were as follows; AXIS-HS (Shimadzu Works / Kratos), X-ray source: Dual (Mg) 15kV, 10mA Pass energy 80eV, Step: 0.1 eV / Step, Speed: 120 sec / element, Dell: 300, Under these conditions, the mass concentrations of silver and copper were determined at peak areas of Ag3d: 2 and Cu2P: 1. The ratio of the mass concentration of silver was determined as the covering ratio.

The coating rate of the covering layer of the conductive filler was measured by X-ray photoelectron spectroscopy (ESCA). The measurement of the conductive filler using copper as a core and silver as a coating layer will be described as an example. First, a double-sided adhesive tape was attached to a dedicated pedestal and the conductive filler was evenly adhered. Here, the excess conductive filler was removed with air to obtain a measurement sample. The measurement samples were measured at three places while changing the location under the following conditions.

Device: AXIS-HS (Shimadzu Corporation / Kratos)

Vacuum in the sample chamber: 1 × 10 ^{- 8} Torr or less

X-ray source: Dual (Mg) 15kV, 5mA Pass energy 80eV

Step: 0.1 eV / Step

Speed: 120 seconds / Element

Dell: 300, accumulation count: 5

Optoelectronic extraction angle (extraction angle): 90 degrees relative to the sample surface

Coupling energy: C1s Shift correction of main peak to 284.6 eV

Cu (2p) peak region: 926 to 936 eV

Ag (3d) peak region: 376 to 362 eV

The peak appearing in the peak region was smoothed. The baseline was drawn with a straight line method. The atomic concentration of silver and copper "Atomic Conc" was obtained. The average value in three places of the values calculated by the following formulas was defined as the covering ratio of the conductive filler.

Coating ratio = [atomic concentration of silver] / ([atomic concentration of copper] + [atomic concentration of silver]) × 100

When the coating layer was made of nickel, the peak area was Ni (2p): 848 to 870 eV.

&Lt; Method for Measuring Average Particle Diameter of D50 of Conductive Filler >

The D50 average particle diameter was measured using a laser diffraction / scattering method particle size distribution measuring apparatus LS13320 (manufactured by Beckman Coulter). In the tornado dry powder sample module, the D50 average particle diameter of the conductive filler was measured. The refractive index was set at 1.6. The D50 average particle diameter was based on volume.

Hereinafter, the materials used in Examples are shown.

&Lt; Thermosetting resin &

(Thermosetting resin 1)

[Synthesis Example 1: Synthesis of polycarbonate-based polyurethane]

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube, 194 parts of polycarbonate-based diol "DICEL product, Fraxel CD220", 7 parts of dimethylolbutanoic acid, 42 parts of isophorone diisocyanate, and 70 parts of toluene Prepare. This was allowed to react at 90 占 폚 for 3 hours under a nitrogen atmosphere. To this was added 250 parts of toluene to obtain a solution of an urethane prepolymer having an isocyanate group at the terminal. Subsequently, 6 parts of isophorone diamine, 0.6 part of di-n-butylamine, 113 parts of 2-propanol, and 185 parts of toluene were mixed. 506 parts of the obtained urethane prepolymer solution was added. This was reacted at 70 DEG C for 3 hours to obtain a solution containing polycarbonate-based polyurethane resin having Mw = 50,000, Tg of 3 DEG C and acid value of 7 mgKOH / g. To this, toluene and 2-propanol were added to make the solid content in the solution 30%. Thus, a solution of the thermosetting resin 1 (polycarbonate-based polyurethane resin) was obtained.

(Thermosetting resin 2)

[Synthesis Example 2: Synthesis of polyester-based polyurethane]

To a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen-introducing tube, 195 parts of polyester diol "P-2011" (product of Kuraray Co., Ltd.), 7 parts of dimethylolbutanoic acid, 40 parts, and toluene 70 parts were prepared. This was reacted at 90 DEG C for 3 hours under a nitrogen atmosphere. To this was added 250 parts of toluene to obtain a urethane prepolymer solution having an isocyanate group at the terminal. Subsequently, 6 parts of isophorone diamine, 0.6 part of di-n-butylamine, 113 parts of 2-propanol, and 185 parts of toluene were mixed. 506 parts of a solution of the urethane prepolymer thus obtained was added. This was reacted at 70 DEG C for 3 hours to obtain a polyurethane thermosetting resin solution having an Mw of 43,000, a Tg of -5 DEG C and an acid value of 10 mgKOH / g. To this, toluene, 2-propanol was added to make the solids in the solution 30%. Thus, a solution of thermosetting resin 2 (polyester-based polyurethane resin) was obtained.

(Thermosetting resin 3)

[Synthesis Example 3: Synthesis of polyether-series polyurethane]

A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 196 parts of a polyether diol "PTG-2000sn" manufactured by Hodogaya Kogyo Co., Ltd., 6 parts of dimethylolbutanoic acid, 41 parts of isophorone diisocyanate, And 70 parts of toluene were prepared. This was reacted at 90 DEG C for 3 hours under a nitrogen atmosphere. To this, 250 parts of toluene was added to obtain a urethane prepolymer solution having an isocyanate group at the terminal. Subsequently, 6 parts of isophorone diamine, 0.6 part of di-n-butylamine, 113 parts of 2-propanol, and 185 parts of toluene were mixed. 506 parts of the obtained urethane prepolymer solution was added. This was reacted at 70 DEG C for 3 hours to obtain a polyether polyurethane resin solution having an Mw of 70000, a Tg of -10 DEG C and an acid value of 15 mgKOH / g. To this, toluene and 2-propanol were added to make the solid content in the solution 30%. Thus, a thermally-crystallizable resin 3 (polyether-based polyurethane resin) solution was obtained.

(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, and a nitrogen inlet tube was charged with 196 parts of polybutadiene diol "G-2000" manufactured by Nippon Soda Co., Ltd., 6 parts of dimethylolbutanoic acid, 41 parts of isophorone diisocyanate, 70 parts of toluene were prepared. This was allowed to react at 90 占 폚 under a nitrogen atmosphere for 3 hours. To this, 250 parts of toluene was added to obtain a solution of urethane prepolymer having isocyanate group at the terminal. Subsequently, 6 parts of isophorone diamine, 0.6 part of di-n-butylamine, 113 parts of 2-propanol, and 185 parts of toluene were mixed. 506 parts of the obtained urethane prepolymer solution was added. This was reacted at 70 DEG C for 3 hours to obtain a polybutadiene-based polyurethane resin solution having Mw = 30000, Tg of 5 DEG C and acid value of 13 mg KOH / g. Thereto, toluene and 2-propanol were added to make the solid content in the solution 30%. Thus, a thermosetting resin 4 (polybutadiene-based polyurethane resin) solution was obtained.

(Thermosetting resin 5)

[Synthesis Example 5: Synthesis of polyester]

184.4 parts of dimethyl terephthalate, 94.8 parts of neopentyl glycol, 94.2 parts of ethylene glycol, 54.7 parts of 2-methyl-1, 3-propanediol, and 1 part of zinc acetate 0.035 parts are prepared. The stirring of the starting material was started when the raw material could be stirred by heating and melting the raw material. Methanol was removed from the reaction system by distilling out methanol from the reaction system under atmospheric pressure. While methanol was removed, the reaction system was gradually heated from 170 占 폚 to 220 占 폚 over 3 hours. The reaction system was maintained at 220 캜 for 1 hour. The inside temperature of the flask was once 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 were added to the reaction system. Water was removed from the reaction system by allowing water to flow out of the reaction system under atmospheric pressure. The raw material was heated to 240 캜 for 3 hours while removing water. The reaction was continued until the acid value of the product in the reaction system became 15 mgKOH / g while maintaining the reaction system at 240 deg. Subsequently, the reflux dewatering apparatus was replaced with a vacuum decompression apparatus. 0.06 part of tetrabutyl titanate was added to the product. The reaction was continued for 6 hours at a temperature of 240 DEG C and a reduced pressure of two tones. Thereafter, a part of the obtained polyester resin was taken out into a container made of a polyfluoroethylene resin. The polyester resin thus obtained had a number average molecular weight of 18000 and a glass transition temperature of 27 占 폚. Subsequently, 100 parts of toluene was added to 100 parts of the obtained polyester resin to obtain a polyester resin. Then, 5 parts of ethylene glycol bistrimellitate dianhydride was added to each of the flasks. This was reacted at a temperature of 100 ° C for 5 hours to obtain a polyester resin solution having an Mw of 50,000 and an acid value of 19 mg KOH / g. To this, toluene was added and diluted to make the solid content in the solution 30%. Thus, a thermosetting resin 5 (polyester resin having a carboxyl group) solution was obtained.

(Thermosetting resin 6)

[Synthesis Example 6: Synthesis of polyamide]

In a flask equipped with a stirrer and a reflux condenser, 100 parts by mass of dimeric acid as a dicarboxylic acid component and 7.62 parts by mass of butanediamine as a diamine component were prepared. Then, 7.44 parts by mass of piperazine was prepared. The internal temperature of the flask was raised from 25 占 폚 to 230 占 폚 at a heating rate of 115 占 폚 / hour. The reaction was continued at that temperature for 6 hours and then cooled to obtain a thermosetting resin 6 (polyamide resin). The polyamide resin had an acid value of 4 (mgKOH / g) and a weight average molecular weight of 66,000.

<Other Resins>

(Other resin 1)

[Synthesis Example 7: Synthesis of carboxylic acid-free polyester polyurethane]

Mn = 981 was prepared. The related diols were obtained from adipic acid, 3-methyl-1,5-pentanediol and 1,6-hexanecarbonyl diol. 432 parts of diol, 137 parts of isophorone diisocyanate and 40 parts of toluene were prepared in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen introduction tube. This was reacted at 90 DEG C for 3 hours under a nitrogen atmosphere. To this, 300 parts of toluene was added to obtain a urethane prepolymer solution having an isocyanate group at the terminal. Subsequently, 25 parts of isophoronediamine, 3 parts of di-n-butylamine, 342 parts of 2-propanol, and 576 parts of toluene were mixed. To this was added 818 parts of the obtained urethane prepolymer solution. This was reacted at 70 DEG C for 3 hours to obtain a polyester-based urethane resin solution having Mw = 100000 and an acid value of 0 mgKOH / g. Thereto 144 parts of toluene and 72 parts of 2-propanol were added to make the solid content in the solution 30%. Thus, another resin 1 (polyester-based urethane resin) solution was obtained.

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

[Table 1]

<Conductive filler>

The conductive filler used in the examples is shown below.

[Table 2]

The materials used in addition to the thermosetting resin and the conductive charger are as follows.

Epoxy resin 1: Bisphenol A type epoxy ("ADEKA RESIN EP-4100", product of ADEKA) having an epoxy equivalent of 190 g / eq,

Epoxy resin 2: trifunctional epoxy ("ED-505", product of ADEKA) having an epoxy equivalent of 150 g / eq,

Curing agent 1: Trimethylol propane-tri- beta -aziridinyl propionate

Curing agent 2: cumene hydroperoxide

Epoxy silane coupling agent: 3-glycidoxypropyltrimethoxysilane

Amine series silane coupling agent: n-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane

Vinyl 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 탆

Inorganic filler 2: commercially available ultrafine particle talc having an average particle diameter of 3.8 mu m

[Example 1]

, 100 parts of thermosetting resin 1 (polycarbonate polyurethane resin) (solid content), 30 parts of epoxy resin 2, 350 parts of conductive filler 5, 2 parts of curing agent (1) Prepare three parts of LINGER in a container. And a mixed solvent of toluene: isopropyl alcohol (mass ratio 2: 1) was added thereto so that the non-volatile matter concentration was 45 mass%. The mixture was stirred with a disper for 10 minutes to obtain a conductive adhesive.

A conductive adhesive agent was coated on the release sheet using a doctor blade so that the dry thickness of the conductive adhesive agent was 60 占 퐉. The conductive adhesive agent was dried at 100 DEG 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 prepared in the same manner as in Example 1, except that each component and its amount (parts by mass) were changed as shown in Tables 3 to 5.

In addition, the blending amounts of the resins shown in Tables 3 to 5 are solid mold masses.

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

<Viscosity Stability of Conductive Adhesive>

The conductive adhesive sheet is formed by applying a conductive adhesive agent. However, when the stability of the viscosity of the conductive adhesive is insufficient, the conductive adhesive may rapidly increase in viscosity during coating. In this case, a conductive adhesive sheet having a uniform film thickness can not be obtained.

The conductive adhesive immediately after preparation is prepared in a 140 ml glass bottle. "VISCOMERER TVB-10M" The initial viscosity at 6 rpm was measured with the Higashi-kiki industrial product. The vial was then placed in a constant temperature environment at 25 degrees Celsius. The conductive adhesive agent in the glass bottle was allowed to stand for 24 hours while being mixed with a mixer rotor. And the viscosity of the conductive adhesive after 24 hours was determined as a time-based viscosity. The viscosity was measured at the same conditions as the initial viscosity. The increase rate was calculated from the following equation.

Increase rate (%) = Time-elapsed viscosity / Initial viscosity x 100

The evaluation criteria are as follows.

◎ (double circle): Increase rate less than 110%. Good results.

○ (one-pile circle): Increase rate is over 110%, less than 130%. There is no practical problem.

△ (triangle): Increase rate is over 130%, less than 150%. There is no practical problem.

× (X): Increase rate is over 150%. Not practicable

&Lt; Connection reliability (step difference 37.5 m) >

In order for the metal reinforcing plate to exhibit the electromagnetic shielding property, it is important that the metal reinforcing plate is connected to the grand circuit through the conductive adhesive layer. It is also important that a conductive connection is ensured between the metal reinforcement plate and the grand circuit. Conductive connection is ensured by bonding the metal reinforcing plate with the conductive adhesive layer while filling the through hole of the cover layer provided on the grand circuit with the conductive adhesive layer. However, if the property of inserting the conductive adhesive layer into the through hole and the adhesiveness by the conductive adhesive layer are not sufficient, the electromagnetic shielding property of the metal reinforcing plate is deteriorated. That is, initial connection reliability deteriorates.

A conductive adhesive sheet having a width of 15 mm and a length of 20 mm and an SUS plate having a width of 20 mm and a length of 20 mm were overlapped. The SUS plate is formed by forming a nickel layer having a thickness of 2 탆 on the surface of a commercially available SUS 304 plate having a thickness of 0.2 mm. Using a roll laminator, a conductive adhesive sheet was stuck to the SUS plate under the conditions of 90 占 폚, 3 kgf / cm2, and 1 M / min to obtain a sample.

1 (1), and the produced flexible printed wiring board will be described. A copper foil circuit 12A and a copper foil circuit 12B having a thickness of 18 mu m and not electrically connected to each other are formed on a polyimide film 11 having a thickness of 25 mu m. A cover film 13 provided with an adhesive is laminated on the copper foil circuit 12A. The thickness of the cover film 13 is 37.5 mu m. The cover film 13 has a through hole 14 having a diameter of 1.2 mm. A peelable film was peeled from the sample. The exposed surface of the sample was affixed to the produced flexible printed wiring board using a roll laminator at 90 DEG C under the conditions of 3 Kgf / cm2 and 1 M / min.

Then, they were squeezed under the conditions of 170 DEG C and 2 MPa for 5 minutes. Thereafter, a measurement sample was obtained by heating in an electric oven at 160 DEG C for 60 minutes.

Next, the connection reliability between 12A and 12B shown in the plan view of Fig. 1 (4) was evaluated. The evaluation was made by measuring the connection resistance between 12A and 12B using a resistance meter and a BSP probe. 1 (2) is a cross-sectional view taken along the line D-D 'in FIG. 1 (1), and FIG. 1 (3) is a cross-sectional view taken along the line C-C' shown in FIG. 1 (5) is a cross-sectional view taken along the line D-D 'in FIG. 1 (4), and FIG. 1 (6) is a cross-sectional view taken along the line C-C' in FIG.

The evaluation criteria are as follows.

◎ (double circle): Connection resistance value is less than 20mΩ / □. Good results.

○ (one-fold circle): Connection resistance value is more than 20mΩ / □, less than 100mΩ / □. There is no practical problem.

△ (triangle): Connection resistance value is more than 100mΩ / □, less than 300mΩ / □. There is no practical problem.

× (X table): Connection resistance value is 300 mΩ / □ or more. Not practicable

&Lt; Connection reliability (step difference 60 m) >

The connection reliability was evaluated by a method such as < connection reliability (step difference 37.5 mu m) > and evaluation criteria, except that the thickness of the cover film 13 of Fig. 1 (1) was changed to 60 mu m.

&Lt; Connection reliability after immunity test for high temperature and high humidity environment >

An electronic component in which an FPC is assembled is used under various environments. For this reason, if the connection reliability is insufficient after being exposed for a long time under a high temperature and high humidity environment, for example, when used for a long time in a high temperature and high humidity environment, electromagnetic shielding properties are deteriorated. As a result, the frequency characteristics of the signal circuit to which the metal reinforcing plate is attached deteriorate.

The test sample prepared in the test of &quot; Connection reliability (step 37.5 탆) &quot; was placed in an oven at 85 캜 and 85% humidity, and left for 500 hours. Thereafter, the connection reliability (the connection reliability after being exposed for a long time under a high temperature and high humidity environment) between 12A and 12B shown in the plan view of Fig. 1 (4) was evaluated. The evaluation was made by measuring the resistance value using a resistance value measuring device and a BSP probe.

The evaluation criteria are as follows.

◎ (double circle): Connection resistance value is less than 20mΩ / □. Good results.

○ (one-fold circle): Connection resistance value is more than 20mΩ / □, less than 100mΩ / □. There is no practical problem.

△ (triangle): Connection resistance value is more than 100mΩ / □, less than 300mΩ / □. There is no practical problem.

× (X table): Connection resistance value is over 300mΩ / □, practically impossible.

&Lt; Adhesion after Immunity Test for High Temperature and High Humidity Environment >

The conductive adhesive sheet was cut into a size of 25 mm wide × 100 mm long. Thereafter, the peelable sheet was peeled from the cut conductive adhesive sheet to obtain a conductive adhesive layer. This conductive adhesive layer was sandwiched between a polyimide surface of a copper-clad laminate (copper clad laminate) ("Esper Flex", Sumitomo Metal Mining Co., Ltd.) having a thickness of 40 μm and a stainless steel plate (SUS304) having a thickness of 200 μm to form a laminate did. The laminate thus obtained was pressed at 170 DEG C under a pressure of 2 MPa for 5 minutes. The laminate was then heated in an electric oven at 160 DEG C for 60 minutes. Thus, a layered product of the "copper clad laminate / cured product of electrically conductive adhesive layer / SUS plate" was obtained. This laminate was placed in an oven at a temperature of 85 캜 and a humidity of 85%, and left for 500 hours. Thereafter, the T peel peel test was conducted at a tensile rate of 50 mm / min under an atmosphere of 23 ° C and a relative humidity of 50% to measure the adhesive strength (N / cm) of the laminate.

◎ (double circle): Adhesive strength is 10N / cm or more. Good results.

○ (one-ply circle): Adhesive strength less than 10 N / cm, more than 7 N / cm. There is no practical problem.

△ (triangle): Adhesive strength less than 7 N / cm, 4 N / cm or more. There is no practical problem.

X (X table): Adhesive strength less than 4 N / cm. Not practicable.

<Punching workability>

The conductive adhesive sheets obtained in Examples and Comparative Examples were overlapped with SUS plates. The SUS plate is formed by forming a 2 占 퐉 -thick nickel layer on the surface of a commercially available SUS304 plate having a thickness of 0.2 mm. Using a roll laminator under the conditions of 90 占 폚, 3 kgf / cm2 and 1 M / min, to obtain a sample.

This sample was cut into a size of 10 mm x 30 mm with a punching machine to obtain 100 pieces. The number of defective parts was evaluated as follows. Also, a defective product is a piece in the following state after the sample is processed in the form of a mold. Partially unformed. The SUS plate and the conductive adhesive layer are peeled off; There is a distortion in the shape of the end portion of the conductive adhesive layer that has been punched out.

◎ (double circle) ... Less than 10%

○ (one-ply circle) ... 10% to less than 15%

△ (triangle) ... 15% to less than 25%

× (X table) ... 25% or more

[Table 3]

[Table 4]

[Table 5]

In the conductive adhesive of the embodiment, a conductive filler containing copper as a main component is used. From the results shown in Tables 3 to 5, it was confirmed that the conductive adhesive of the examples can reduce the cost and the viscosity of the conductive adhesive is stable. Similarly, it was confirmed that the conductive adhesive of Examples had good connection reliability and adhesion even after exposure to a high temperature and high humidity environment over a long period of time. Likewise, it was confirmed that the conductive adhesive of the embodiment can provide a conductive adhesive layer having a good connection reliability even in a circuit in which the level difference of the through hole in the grand wiring substrate is high. It was confirmed that it is possible to provide a wiring device having a conductive adhesive layer having good connection reliability despite the high level difference of the through hole in the grand wiring substrate by using the conductive adhesive of the embodiment.

11; Polyimide film
12A, 12B; Copper circuit
13; Cover film
14; Through hole
15a; Metal reinforcing plate
15b; The conductive adhesive layer

Claims (8)

In a conductive adhesive containing a thermosetting resin (A) having a carboxyl group, an epoxy resin, a conductive filler (B) containing copper, a curing agent, and a silane coupling agent,
Wherein the conductive filler (B) comprises a core composed of copper and a coating layer made of a conductive material different from copper,
The covering layer is 5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the core; or
The covering ratio is 90% or more,
The thermosetting resin (A) having a carboxyl group is obtained by reacting a diol compound (a) having a carboxyl group, a polyol compound (b) having no carboxyl group and an organic diisocyanate (c) Thermosetting resin,
The diol compound (a) having a carboxyl group is at least one selected from dimethylol alkanoic acid, dihydroxysuccinic acid, and dihydroxybenzoic acid,
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 methacrylic-based polyurethane resin,
A conductive adhesive satisfying at least one of the following conditions (I) and (II):
<I>
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 weight of a silane coupling agent is blended with 100 parts by weight of the thermosetting resin (A).
<II>
The epoxy resin is a trifunctional epoxy or tetrafunctional epoxy,
3 to 10 parts by weight of a silane coupling agent is blended with 100 parts by weight of the thermosetting resin (A). The method according to claim 1,
The conductive adhesive further comprises an inorganic filler. 3. The method according to claim 1 or 2,
And the above condition (II) is satisfied. The method of claim 3,
Wherein 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. 3. The method according to claim 1 or 2,
And satisfies the above condition (I). The conductive adhesive sheet according to any one of claims 1 to 3, further comprising a conductive adhesive layer formed on the releasable sheet with the conductive adhesive agent. A wiring board having signal wiring,
A reinforcing plate provided on at least one surface side of the wiring board,
And a conductive adhesive layer for bonding the wiring board and the reinforcing plate to each other, wherein the conductive adhesive layer is formed of the conductive adhesive according to claim 1 or 2. 8. The method of claim 7,
Wherein the reinforcing plate has conductivity,
Wherein the wiring board further comprises a ground wiring connected to the reinforcing plate.

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