JP5886957B2 - Conductive adhesive composition, conductive adhesive film, adhesion method, and circuit board - Google Patents

Description

The present invention relates to a conductive adhesive composition, a conductive adhesive film, an adhesion method, and a circuit board.

In a flexible printed wiring board, a conductive adhesive composition or a conductive adhesive film obtained by molding the conductive adhesive composition is often used. Such a conductive adhesive contains a curable resin and a conductive filler.

From the viewpoint of increasing the required physical properties in recent years, it has been demanded to improve the physical properties of such conductive adhesives. More specifically, for example, many physical properties such as heat resistance, physical strength, water resistance, moisture resistance, and electrical properties are required to be improved.

Patent Documents 1 to 3 describe a polyurethane polyurea resin and a curable polyurethane polyurea adhesive composition containing an epoxy group. In such an adhesive composition, it is necessary to further improve the above-described physical properties and at the same time sufficiently control the processing characteristics.

As a method for improving the properties such as heat resistance, physical strength, water resistance, moisture resistance, and electrical resistance, it is conceivable that the cured film has a high crosslinking density. In order to obtain a resin having a high crosslink density, it is necessary to increase the number of reaction points. From such a viewpoint, it is necessary to use an epoxy compound having a large amount of functional groups. However, an epoxy resin having a large amount of functional groups generally has a low molecular weight, and therefore has a problem that it is easy to bleed out when used as a conductive adhesive film and is difficult to handle. That is, it is necessary to bond as shown in FIG. 2, but when bleeding out, the resin flows out of the bonded portion as shown in FIG.

It is also possible to improve the above problem by using two or more types of epoxy resins in combination, with one having a relatively high molecular weight and the other having a low molecular weight. However, such a mixture of epoxy resins makes it difficult to react uniformly as a whole of the epoxy resin, and the crosslink density cannot be increased as a whole. Furthermore, when a low molecular weight epoxy compound having many epoxy groups is used, the reaction of the first epoxy group of the low molecular weight epoxy compound is the fastest, and the reaction rate gradually slows down to the second and third. Unreacted epoxy groups are likely to remain, and the crosslink density cannot be increased as much as the theoretical value. For this reason, the physical properties are lowered due to the remaining functional groups.

Cited Document 1 describes that two types of epoxy resins are used in combination. However, the selection of the resin here is not performed from the viewpoint as described above, but is for imparting flexibility by using a resin having a low softening point and a resin having a high softening point in combination. . Therefore, the examination from the viewpoint of increasing the crosslink density of the cured product as in the present invention has not been made, and is not intended to solve the above-described problems.

Further, as in Patent Document 4, an electromagnetic wave shielding ability can be imparted to the reinforcing plate by bonding the conductive reinforcing plate with a conductive adhesive and electrically connecting the ground layer and the reinforcing plate. It has been broken.
An example of such a circuit board is shown in FIG. In such applications, the above-described improvements in various physical properties and workability are particularly required.

JP 2010-143981 A International Publication No. 2007/032463 JP 2007-189091 A JP 2005-317946 A

In view of the above, the present invention can increase the crosslink density and improve the physical properties of the adhesive layer after curing, and also has a conductive adhesive composition and conductive adhesive having excellent properties in processing performance. The object is to provide a film.

The present invention provides a bisphenol type epoxy resin (A) having two or more epoxy groups per molecule and solid at room temperature,
A novolac epoxy resin (B) having two or more epoxy groups per molecule and solid at room temperature,
In the conductive adhesive composition containing the resin (C) having a carboxyl group and the conductive filler (D),
The resin (C) having a carboxyl group contains at least one selected from the group consisting of a carboxyl group-containing polyurethane resin (C-1) and a carboxyl group-containing polyacrylic resin (C-2). It is a conductive adhesive composition.

The ratio of the bisphenol type epoxy resin (A) to the novolac type epoxy resin (B) is preferably a weight ratio of 85:15 to 99: 1.
The bisphenol type epoxy resin (A) preferably has an epoxy equivalent of 800 to 10,000.
The novolac epoxy resin (B) preferably has an epoxy equivalent of 90 to 300.

The conductive filler (D) is preferably at least one selected from the group consisting of silver powder, silver-coated copper powder, and copper powder.
The conductive filler (D) preferably has an average particle size of 3 to 50 μm.
The conductive adhesive composition of the present invention does not contain a curing agent other than the bisphenol type epoxy resin (A), the novolac type epoxy resin (B), and the resin (C) having a carboxyl group. It is also an adhesive composition.

Moreover, this invention is also a conductive adhesive film which laminated | stacked the conductive adhesive layer using the conductive adhesive composition mentioned above, and the protective layer.
In this case, the conductive adhesive composition preferably has a thickness of 15 to 100 μm.

In addition, the present invention is also a conductive adhesive film characterized in that a peel strength when thermocompression bonding is performed after a week has elapsed after temporary bonding with a press machine is 10 N / cm or more.

This invention has the electroconductive adhesive film obtained by the process (1) and the process (1) which temporarily adheres the electroconductive adhesive film mentioned above on the to-be-adhered base material (X) which is an electroconductive reinforcement board or a flexible substrate. It is also an adhesion method consisting of a step (2) in which a substrate to be adhered (X) is overlaid with a substrate to be adhered (Y) which is a flexible substrate or a conductive reinforcing plate, and is hot pressed.

The present invention is a circuit board having at least a portion where a flexible substrate, a conductive adhesive layer, and a conductive reinforcing plate are laminated in this order, and the conductive adhesive layer is formed by the conductive adhesive film described above. It is also a circuit board characterized by being made.
It is preferable that the circuit board has a surface other than the reinforcing plate on the surface of the flexible substrate covered with an electromagnetic wave shielding film.

The conductive adhesive composition of the present invention has excellent performance in heat resistance, physical strength, water resistance, moisture resistance, electrical properties, and at the same time, bleed-out of components in the film after the pressing process, etc. It has the property of not producing. Moreover, even when it is used for attaching a substrate having a step, suitable adhesion can be performed. Furthermore, even after storing for a long time after temporary bonding, good bonding performance can be maintained in the bonding step by hot pressing.

It is a schematic diagram which shows the peel strength measuring method of an Example. It is an example of the connection resistance measurement test piece of an Example. It is a schematic diagram which shows the mode of the resin flow of an Example. It is an example of the circuit board obtained using the conductive adhesive of this invention.

The present invention is described in detail below.
The conductive adhesive composition of the present invention has two or more epoxy groups per molecule, bisphenol type epoxy resin (A) that is solid at room temperature, and two or more epoxy groups per molecule, A novolac epoxy resin (B) that is solid at room temperature, a resin (C) having a carboxyl group and a conductive filler (D), and the resin (C) having a carboxyl group is a carboxyl group-containing polyurethane resin (C- It contains at least one selected from the group consisting of 1) and a carboxyl group-containing polyacrylic resin (C-2). Such an adhesive layer formed by the conductive adhesive composition of the present invention has a uniform crosslink density after curing and a high crosslink density. As a result, an adhesive layer having excellent properties in moisture resistance, water resistance, heat resistance, physical strength, electrical properties, and the like can be formed. Further, it has excellent processing characteristics without causing problems such as bleeding out during processing. Furthermore, even after storing for a long time after temporary bonding, good bonding performance can be maintained in the bonding step by hot pressing.

(Bisphenol type epoxy resin (A) and novolak type epoxy resin (B))
The epoxy resin (A) used in the present invention is a bisphenol type epoxy resin that has two or more epoxy groups per molecule and is solid at room temperature. Being solid at room temperature means a solid state having no fluidity in a solvent-free state at 25 ° C. If the adhesive layer is made only of a novolac type epoxy resin, there is a problem in that the adhesion and film forming property are not sufficient, and therefore the bisphenol type epoxy resin (A) is essential. Moreover, in order to make workability favorable, it is necessary to use a solid thing at normal temperature.

Such bisphenol type epoxy resin (A) is not particularly limited, and examples thereof include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, tetrabromobisphenol A type epoxy resin and the like. These epoxy resins can be used individually by 1 type or in combination of 2 or more types. Among these, it is preferable to use a bisphenol A type epoxy resin or a bisphenol F type epoxy resin from the viewpoint of high adhesion and heat resistance.

As said bisphenol-type epoxy resin (A), it is preferable to use what has an epoxy equivalent of 800-10000. This is preferable in that the adhesion with the reinforcing plate is further improved. The lower limit of the epoxy equivalent is more preferably 1000, and still more preferably 1500. The upper limit of the epoxy equivalent is more preferably 5000, and still more preferably 3000.

Commercially available epoxy resins that can be used as the bisphenol type epoxy resin (A) include EPICLON 4050, 7050, HM-091, HM-101 (trade name, manufactured by DIC Corporation), jER1003F, 1004, 1004AF, 1004FS, 1005F, 1006FS, 1007, 1007FS, 1009, 1009F, 1010, 1055, 1256, 4250, 4275, 4004P, 4005P, 4007P, 4010P (trade names, manufactured by Mitsubishi Chemical Corporation) can be exemplified.

The novolac type epoxy resin (B) is a novolac type epoxy resin having two or more epoxy groups per molecule and solid at room temperature. Although novolac epoxy resin has high epoxy resin density, it has good miscibility with other epoxy resins and has little reactivity difference between epoxy groups. High crosslink density can be achieved uniformly.
The novolak type epoxy resin is not particularly limited, and examples thereof include a cresol novolak type epoxy resin, a phenol novolak type epoxy resin, an α-naphthol novolak type epoxy resin, and a brominated phenol novolak type epoxy resin. Among these, it is preferable to use a phenol novolac type epoxy resin or a cresol novolac type epoxy resin from the viewpoint of high adhesion and heat resistance.

As for the said novolak-type epoxy resin (B), it is especially preferable that epoxy equivalent is 90-300. As a result, the effect of increasing the heat resistance of the resin is obtained. The lower limit of the epoxy equivalent is more preferably 150, and even more preferably 170. The upper limit of the epoxy equivalent is more preferably 250, and still more preferably 230.

Commercially available epoxy resins that can be used as the novolac type epoxy resin (B) as described above include EPICLONN-660, N-665, N-670, N-673, N-680, N-695, N- 655-EXP-S, N-662-EXP-S, N-665-EXP, N-665-EXP-S, N-672-EXP, N-670-EXP-S, N-685-EXP, N- 673-80M, N-680-75M, N-690-75M, N-740, N-770, N-775, N-740-80M, N-770-70M, N-865, N-865-80M ( (Trade name, manufactured by DIC Corporation) jER152, 154, 157S70 (trade name, manufactured by Mitsubishi Chemical Corporation) YDPN-638, YDCN-700, YDCN-700-2, YDCN- 00-3, YDCN-700-5, YDCN-700-7, YDCN-700-10, YDCN-704, YDCN-700-A (trade name, manufactured by Nippon Steel Chemical Co., Ltd.), and the like can be given.

The conductive adhesive layer of the conductive adhesive composition of the present invention contains the bisphenol type epoxy resin (A) and the novolac type epoxy resin (B) in a ratio of 85:15 to 99: 1 by weight. It is preferable. By setting it as the said ratio, the adhesive force to a reinforcement board is ensured and the heat resistance which can endure the reflow process at the time of component mounting can be provided. Further, if the ratio of the bisphenol type epoxy resin (A) is larger than 99: 1 in the above ratio, it is not preferable in that it may not be able to endure the reflow process at the time of component mounting, and it is not preferable than 85:15. When the ratio of the type epoxy resin (B) is increased, it is not preferable in terms of a decrease in adhesion to an adherend (Ni-SUS, SUS, gold plating electrode, polyimide resin, etc.).

In addition, the epoxy equivalent in this specification is a value measured by potentiometric titration.

(Resin having a carboxyl group (C))
The conductive adhesive composition of the present invention may further contain at least one selected from the group consisting of a carboxyl group-containing polyurethane resin (C-1) and a carboxyl group-containing polyacrylic resin (C-2). preferable.
That is, since the curing is performed by a reaction between a carboxyl group and an epoxy group, preferable performance can be obtained in terms of improving heat resistance and improving adhesion to an adherend.
Moreover, although a carboxyl group may have at the terminal of a chain | strand or it may have as a side chain, it is preferable to have as a side chain.

(Polyurethane resin having carboxyl group (C-1))
The polyurethane resin (C-1) having a carboxyl group will be described below.
The polyurethane resin (C-1) having a carboxyl group is a resin containing a carboxyl group in the molecule. The polyol compound (1) having a carboxyl group, the polyol (2), and a short-chain diol compound (if necessary) It is obtained by reacting 3), if necessary, a polyamine compound (4) and a polyisocyanate compound (5). In such a reaction, a polyurethane resin (C-1) having a carboxyl group can be suitably obtained by using a polyol compound (1) having a carboxyl group.

In the present specification, “polyurethane” means a general term for polyurethane and polyurethane-urea. The “polyurethane” may be a product obtained by reacting an amine component as necessary. In addition, the “active hydrogen-containing group” in the present specification means a functional group having active hydrogen having reactivity with an isocyanate group. Specific examples of such “active hydrogen-containing group” include a hydroxyl group, a mercapto group, a carboxyl group, and an amino group.

The polyol compound (1) containing a carboxyl group is a compound containing at least one carboxyl group and two or more hydroxyl groups. Specific examples include dimethylolalkanoic acid such as dimethylolpropanoic acid and dimethylolbutanoic acid; alkylene oxide low-mole adduct of dimethylolalkanoic acid (number average molecular weight of less than 500 by terminal functional group determination); dimethylolalkanoic acid ε-caprolactone low molar adduct (number average molecular weight less than 500 by terminal functional group determination); half ester derived from acid anhydride of dimethylol alkanoic acid and glycerin; hydroxyl group of dimethylol alkanoic acid and unsaturated bond And a compound obtained by subjecting a monomer having a free radical reaction to a monomer having a carboxyl group and an unsaturated bond. Of these, dimethylolpropanoic acid and dimethylolalkanoic acid such as dimethylolbutanoic acid are preferred from the viewpoints of availability, ease of adjustment of acid value, and the like. The content of the polyol compound (1) in the polyurethane resin (C-1) is such that the resulting polyurethane resin (C-1) is crosslinked with the epoxy to improve heat resistance, durability, flexibility, and adhesion. It is set from the viewpoint of both. More specifically, the content of the polyol compound (1) in the reaction component is preferably set to an amount such that the resulting polyurethane resin (C-1) has an acid value of 3 to 100 mgKOH / g.

The polyol (2) is a component having two or more hydroxyl groups, and those having a number average molecular weight of 500 to 3000 can be preferably used. In addition, the said polyol (2) points out only what does not correspond to the said polyol compound (1).

The polyol (2) is not particularly limited, and a conventionally known polyol used for urethane synthesis can be used. Specific examples of the polyol (2) include polyester polyol, polyether polyol, polycarbonate polyol, and other polyols.

Polyester polyols include aliphatic dicarboxylic acids (eg succinic acid, adipic acid, sebacic acid, glutaric acid, azelaic acid etc.) and / or aromatic dicarboxylic acids (eg isophthalic acid, terephthalic acid etc.), low Molecular weight glycol (for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, neopentyl glycol, 1,4-bishydroxymethylcyclohexane, etc. ), And those obtained by condensation polymerization.

  Specific examples of such polyester polyols include polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyneopentyl adipate diol, polyethylene / butylene adipate diol, polyneopentyl / hexyl adipate diol, poly-3- Examples thereof include methylpentane adipate diol, polybutylene isophthalate diol, polycaprolactone diol, and poly-3-methylvalerolactone diol.

Specific examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and random / block copolymers thereof.
Specific examples of the polycarbonate polyol include polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyneopentyl carbonate diol, polyhexamethylene carbonate diol, poly (1,4-cyclohexanedimethylene carbonate) diol, and random / Examples thereof include a block copolymer.

Specific examples of other polyols include dimer diol, polybutadiene polyol and its hydrogenated product, polyisoprene polyol and its hydrogenated product, acrylic polyol, epoxy polyol, polyether ester polyol, siloxane-modified polyol, α, ω-polymethyl Examples thereof include methacrylate diol and α, ω-polybutyl methacrylate diol.

The number average molecular weight (Mn, based on terminal functional group determination) of the polyol (2) is not particularly limited, but is preferably 500 to 3,000. If the number average molecular weight (Mn) of the polyol (2) is more than 3,000, the cohesive force of urethane bonds is hardly expressed and the mechanical properties tend to be lowered. In addition, a crystalline polyol having a number average molecular weight of more than 3,000 may cause a whitening phenomenon when formed into a film. In addition, a polyol (2) can be used individually by 1 type or in combination of 2 or more types.

In addition, as a reaction component for obtaining a polyurethane resin (C-1), it is also preferable to use a short-chain diol component (3) and a polyamine component (4) as needed as needed. This makes it easy to control the hardness and viscosity of the polyurethane resin. Specific examples of the short-chain diol component (3) include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, neopentyl glycol, and the like. Aliphatic glycol and its alkylene oxide low molar adduct (number average molecular weight less than 500 by terminal functional group determination); 1,4-bishydroxymethylcyclohexane, 2-methyl-1,1-cyclohexanedimethanol and other alicyclic glycols And its alkylene oxide low molar adduct (number average molecular weight less than 500, same as above); aromatic glycol such as xylylene glycol and its alkylene oxide low mole adduct (number average molecular weight less than 500, same as above); bisphenol A, thiobisphenol, Sulfonbispheno Bisphenols and alkylene oxide low molar adducts such as Le (number average molecular weight of less than 500, supra); and alkyl dialkanolamine such as alkyl diethanolamine C1~C18 can be mentioned.

Specific examples of the polyamine compound (4) include aliphatic diamine compounds such as methylene diamine, ethylene diamine, trimethylene diamine, hexamethylene diamine, and octamethylene diamine; phenylene diamine and 3,3′-dichloro. Aromatic diamine compounds such as -4,4'-diaminodiphenylmethane, 4,4'-methylenebis (phenylamine), 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone; cyclopentyldiamine, cyclohexyldiamine, 4 And alicyclic diamine compounds such as 1,4′-diaminodicyclohexylmethane, 1,4-diaminocyclohexane and isophoronediamine. Furthermore, hydrazines such as hydrazine, carbodihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, phthalic acid dihydrazide can be used as the diamine compound (4). Examples of long-chain ones include long-chain alkylene diamines, polyoxyalkylene diamines, terminal amine polyamides, and siloxane-modified polyamines. These polyamine compounds (4) can be used singly or in combination of two or more.

As the polyisocyanate compound (5), a conventionally known polyisocyanate used in the production of polyurethane can be used. Specific examples of the polyisocyanate (5) include toluene-2,4-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene. Diisocyanate, 4-butoxy-1,3-phenylene diisocyanate, 2,4-diisocyanate diphenyl ether, 4,4′-methylenebis (phenylene isocyanate) (MDI), durylene diisocyanate, tolidine diisocyanate, xylylene diisocyanate (XDI), 1, Aromatic diisocyanates such as 5-naphthalene diisocyanate, benzidine diisocyanate, o-nitrobenzidine diisocyanate, 4,4′-diisocyanate dibenzyl; methylene diisocyanate Aliphatic diisocyanates such as 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decamethylene diisocyanate; 1,4-cyclohexylene diisocyanate, 4,4-methylenebis (cyclohexyl isocyanate), 1 , 5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate, hydrogenated MDI, hydrogenated XDI, and other alicyclic diisocyanates; obtained by reacting these diisocyanates with low molecular weight polyols or polyamines so that the ends are isocyanates. Examples include polyurethane prepolymers. From the viewpoint of obtaining a polymer composition having excellent weather resistance, aliphatic diisocyanates and alicyclic diisocyanates are preferred.

Active hydrogen groups (however, (1) such as the polyol compound (1) having the carboxyl group, the polyol (2), the short-chain diol compound (3) as necessary, and the polyamine compound (4) as necessary. It is preferable that the equivalent ratio with the isocyanate group of the polyisocyanate compound (5) is 0.5 to 1.5. By setting it within the above range, it is preferable in that a urethane having high heat resistance and high mechanical strength can be obtained.

Moreover, you may have a blocking group in the terminal part. That is, it may be formed by forming an isocyanate terminal by reacting with an excess of an isocyanate group, and blocking the terminal by reacting the isocyanate terminal with a monofunctional group compound.

(Method for producing polyurethane resin (C-1))
The polyurethane resin (C-1) can be produced by a conventionally known method for producing polyurethane. Specifically, first, in the presence or absence of an organic solvent containing no active hydrogen in the molecule, a polyol compound (1) containing a carboxyl group, a polyol (2), and a chain extender as necessary. The reaction component (for example, prepolymer) is obtained by reacting a short-chain diol compound (3) used as needed, a reaction component comprising a polyamine compound (4) and, if necessary, a polyisocyanate (5). In general, the reaction component may be a blended composition in which a prepolymer having a terminal isocyanate group is formed. Moreover, what is necessary is just to make it react until it becomes theoretical isocyanate% by 20-150 degreeC normally by the one shot method or a multistage method, Preferably it is 60-110 degreeC.

The obtained reaction product (prepolymer) may be chain-extended so as to have a desired molecular weight by reacting the polyamine compound (4), if necessary. Further, the total active hydrogen-containing group of the polyol compound (1), polyol (2), short chain diol compound (3), and polyamine compound (4) containing a carboxyl group (excluding the carboxyl group of the compound (1)). And the isocyanate group (2) of the polyisocyanate compound (5) are preferably reacted at an equivalent ratio of 0.5 to 1.5.

The polyurethane resin (C-1) obtained as described above has a weight average molecular weight (Mw) of 1,000 to 1,000,000, which means that the polyurethane has flexibility, adhesion, heat resistance, and coating. It is preferable because properties such as performance are more effectively exhibited. In the present specification, “weight average molecular weight (Mw)” and “number average molecular weight (Mn)” mean values in terms of polystyrene measured by gel permeation chromatography (GPC) unless otherwise specified. .

  In the present invention, a catalyst can be used as necessary in the urethane synthesis. For example, salts of metals and organic and inorganic acids such as dibutyltin laurate, dioctyltin laurate, stannous octoate, zinc octylate, tetra-n-butyl titanate, and organic amine derivatives such as organometallic derivatives, triethylamine, diaza Bicycloundecene catalysts and the like can be mentioned.

  The polyurethane resin (C-1) may be synthesized without using a solvent or may be synthesized with an organic solvent. As the organic solvent, an organic solvent inert to the isocyanate group or an organic solvent less active than the reaction component with respect to the isocyanate group can be used. Specific examples of organic solvents include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; toluene, xylene, swazole (trade name, manufactured by Cosmo Oil Co., Ltd.), Solvesso (trade name, manufactured by Exxon Chemical Co., Ltd.) Aromatic hydrocarbon solvents such as n-hexane; Alcohol solvents such as methanol, ethanol and isopropyl alcohol; Ether solvents such as dioxane and tetrahydrofuran; Ethyl acetate, butyl acetate and isobutyl acetate Ester solvents such as ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, 3-methyl-3-methoxybutyl acetate, ethyl-3-ethoxypropionate, etc. Ether-based solvents; dimethylformamide, amide solvents such as dimethylacetamide; lactams solvents such as N- methyl-2-pyrrolidone and the like.

  In the urethane synthesis, when an isocyanate group remains at the end of the polymer, it is also preferable to perform a termination reaction of the isocyanate group. The termination reaction of the isocyanate group can be performed using a compound having reactivity with the isocyanate group. As such a compound, a monofunctional compound such as monoalcohol or monoamine; a compound having two kinds of functional groups having different reactivity with respect to isocyanate can be used. Specific examples of such compounds include monoalcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol; monoethylamine, n-propylamine, diethylamine And monoamines such as di-n-propylamine and di-n-butylamine; alkanolamines such as monoethanolamine and diethanolamine. Of these, alkanolamine is preferable because of easy control of the reaction.

(Acrylic resin (C-2))
The acrylic resin (C-2) that can be used in the present invention is a resin containing a carboxyl group in the molecule and causes a crosslinking reaction with the epoxy resin. This acrylic resin (C-2) is obtained by polymerizing a polymerizable monomer (6) having a carboxyl group and another polymerizable monomer (7) by a usual polymerization method such as radical polymerization, cationic polymerization, and anionic polymerization. Can be obtained.

  Examples of the polymerizable monomer (6) having a carboxyl group include acrylic acid, methacrylic acid, and an acrylic ester having a carboxyl group, such as 2-acryloyloxyethyl-succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, 2 -Acryloyloxyethyl-phthalic acid, methacrylic acid ester having a carboxyl group, such as 2-methacryloyloxyethyl-succinic acid, 2-methacryloyloxyethyl hexahydrophthalic acid, 2-methacryloyloxyethyl-phthalic acid, etc. Of these, acrylic acid and methacrylic acid are preferable from the viewpoint of reactivity and availability (hereinafter, “acryl” and “methacryl” are also referred to as “(meth) acryl”). ).

  As the other polymerizable monomer (7), various monomers can be used, and a (meth) acrylic acid monomer is preferable. Specific examples of such (meth) acrylic acid monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, Isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, amyl (meth) acrylate, isoamyl (meth) acrylate, heptyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl ( (Meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate, dodecyl (meth) acryl , Tridecyl (meth) acrylate, n-lauryl (meth) acrylate, n-stearyl (meth) acrylate, isostearyl (meth) acrylate, dicyclopentanyl (meth) acrylate, isobornyl (meth) acrylate, phenoxyethyl ( And (meth) acrylate, N- (meth) acryloyloxyethyl hexahydrophthalimide, and the like. In addition, as the other polymerizable monomer (7), a styrene monomer or an acrylonitrile monomer can also be used. These monomers can be used individually by 1 type or in combination of 2 or more types.

  The acrylic resin (C-2) has a higher cross-linking point and higher heat resistance as the acid value is higher. However, the conductive adhesive composition obtained by using an acrylic resin (C-2) having an acid value that is too high as a component is too hard, and the flexibility is lowered, and the carboxyl group cannot be completely reacted with an epoxy or the like and is durable. Tend to decrease. For this reason, it is preferable that the acid value of acrylic resin (C-2) is 3-100 mgKOH / g.

If an ester of (meth) acrylic acid and a long-chain alcohol is used as the polymerizable monomer, the glass transition point (Tg) of the resulting acrylic resin (C-2) tends to decrease. When such an acrylic resin (C-2) having a low glass transition point (Tg) is used, a conductive adhesive composition excellent in flexibility and adhesion can be obtained. On the other hand, when an ester of (meth) acrylic acid and a short-chain alcohol, (meth) acrylic acid, styrene, or acrylonitrile is used as the polymerizable monomer, the glass transition point (Tg) of the resulting acrylic resin (C-2). ) Tend to increase. When such an acrylic resin (C-2) having a high glass transition point (Tg) is used, a conductive adhesive composition having excellent heat resistance and durability can be obtained. That is, by selecting the kind and ratio of the polymerization component so that the glass transition point (Tg) of the acrylic resin (C-2) becomes an appropriate numerical value, the flexibility, adhesion, heat resistance, and durability are improved. Can be obtained. Specifically, it is preferable to use two or more kinds of (meth) acrylic acid monomers as the double bond-containing component. Moreover, it is preferable that the glass transition point (Tg) of acrylic resin (C-2) is -20-30 degreeC. When the glass transition point (Tg) of the acrylic resin (C-2) is more than 30 ° C., flexibility and adhesion tend to be lowered. On the other hand, when the glass transition point (Tg) of the acrylic resin (C-2) is less than −20 ° C., heat resistance and durability tend to be lowered.

(Method for producing acrylic resin (C-2))
The acrylic resin (C-2) is a conventional polymerization monomer (6) having a carboxyl group and other polymerizable monomer (7) such as emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization. It can be obtained by polymerizing by a known polymerization method. For example, in solution polymerization, a polymerization component may be polymerized in an appropriate solvent in the presence of a polymerization initiator.

The kind of solvent used in the solution polymerization is not particularly limited as long as it does not adversely affect the polymerization reaction. Specific examples of the solvent include water; methanol, ethanol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, n-pentyl alcohol, ethyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, ethylene Alcohol solvents such as glycol, propylene glycol and diethylene glycol; aliphatic hydrocarbon solvents such as petroleum ether, hexane and heptane; aromatic hydrocarbon solvents such as benzene, toluene and xylene; diethyl ether, dibutyl ether and tetrahydrofuran (THF), ether solvents such as dioxane; methyl ethyl ketone, 2-pentanone, 3-pentanone, 2-heptanone, 3-heptanone, 2-octa Ketone solvents such as ethyl, cyclohexanone, cyclopentanone and methyl isobutyl ketone; ester solvents such as ethyl acetate, propyl acetate and butyl acetate; N, N-dimethylformamide (DMF), N, N-dimethylacetamide, N- Examples include amide solvents such as methylpyrrolidone (NMP).
The amount of solvent used is appropriately determined depending on the conditions of the polymerization reaction. Usually, it is about 0.1 to 100 times, preferably about 0.2 to 20 times by mass ratio to the polymerization component. In addition, these solvents can be used individually by 1 type or in combination of 2 or more types.

Conventional polymerization initiators can be used. Specific examples of the polymerization initiator include peroxides such as benzoyl peroxide, dibutyl peroxide and cumene hydroperoxide; azo polymerization such as azobisisobutyronitrile and azobis (2,4-dimethylvaleronitrile). Mention may be made of initiators. These polymerization initiators can be used singly or in combination of two or more. Although the usage-amount of a polymerization initiator is not specifically limited, Usually, it is about 0.1-10 mass% with respect to a polymerization component.

The temperature of the polymerization reaction is appropriately set depending on the reaction conditions. Usually, the temperature may be any temperature from room temperature (25 ° C.) to the boiling point of the solvent used. Moreover, in order to adjust the polymerization degree of the obtained acrylic resin (C-2), a chain transfer agent such as mercaptans or a polymerization inhibitor such as hydroquinone may be added to the polymerization reaction system.

The weight average molecular weight (Mw) of the acrylic resin (C-2) thus obtained is 1 in order to satisfy various performances such as adhesion, heat resistance, durability, compatibility, and coating performance. It is preferable that it is 1,000-1,500,000, and it is further more preferable that it is 5,000-1,000,000.

(Mixing ratio of epoxy resin and carboxyl group-containing resin)
In the present invention, the mixing ratio of the mixture of the bisphenol type epoxy resin (A) and the novolac type epoxy resin (B) to the polyurethane resin (C-1) and the acrylic resin (C-2) is 70:30 to 30. : 70 is preferable. By setting it within the above-mentioned range, it is preferable in terms of facilitating imparting film formability and adjusting heat resistance.

(Other ingredients)
In the conductive adhesive composition of the present invention, it is preferable not to add components involved in the curing reaction other than the above-described (A), (B) and (C). That is, it is preferable not to contain an epoxy curing agent that is usually used in combination with an epoxy compound.

The conductive adhesive composition of the present invention can be particularly suitably used for adhesion between a substrate and a conductive reinforcing material in a flexible wiring board. When used for such applications, it is preferable not to contain the epoxy curing agent described above.

Such applications will be described in detail separately below, but after temporary bonding, bonding by hot pressing is performed, but for the convenience of the manufacturing process, after temporary bonding, the time until hot pressing is long. May be stored for a period (more than a week). In such a case, when the curing reaction is started by heating by temporary bonding and the curing reaction rapidly progresses during storage, sufficient bonding strength may not be obtained in the bonding process by hot pressing.

On the other hand, by not blending the above epoxy curing agent, such a problem does not occur, and even if it is subjected to a bonding process by hot pressing after being stored for a long time after temporary bonding, the peel after passing through the bonding process The strength is preferable in that good adhesive performance of 10 N / cm or more can be maintained.

In addition, the hardening | curing agent with which it is preferable not to mix | blend in this invention is used in order to accelerate | stimulate reaction of a polyurethane resin and an epoxy resin, or reaction of epoxy resins. Examples of such curing agents include isocyanate compounds, hydroxyl group-containing compounds, carbodiimide compounds, oxazoline compounds, silanol compounds, aziridine compounds, acid anhydride compounds, tertiary amine compounds, phosphine compounds, imidazole compounds, It is not limited to this. Note that the curing agent may be added as long as the peel strength after the bonding step by the hot press, which is a feature of the present invention, satisfies the condition of 10 N / cm or more. As such a compounding quantity, the range of 0.1 weight% or less can be mentioned with respect to the total amount of (A)-(C) component, for example.

(Conductive filler (D))
The conductive adhesive composition of the present invention contains a conductive filler (D). The conductive filler (D) is not particularly limited, and for example, a metal filler, a metal-coated resin filler, a carbon filler, and a mixture thereof can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. These metal powders are electrolyzed, atomized, and reduced. Can be created by law.
In particular, in order to make it easy to obtain contact between the fillers, it is preferable that the average particle diameter of the conductive filler is 3 to 50 μm. In addition, examples of the shape of the conductive filler include a spherical shape, a flake shape, a dendritic shape, and a fibrous shape.
The conductive filler (D) is preferably at least one selected from the group consisting of silver powder, silver-coated copper powder, and copper powder from the viewpoint of connection resistance and cost.
The conductive filler (D) is preferably contained in a proportion of 40 to 90% by weight with respect to the total amount of the conductive adhesive composition.

In addition, the conductive adhesive composition includes a silane coupling agent, an antioxidant, a pigment, a dye, a tackifier resin, a plasticizer, an ultraviolet absorber, an antifoaming agent, and a leveling as long as the solder reflow resistance is not deteriorated. Conditioners, fillers, flame retardants, etc. may be added.

(Conductive adhesive composition)
The conductive adhesive composition of the present invention is obtained by reacting the above-described components to obtain a conductive adhesive composition, which is then applied onto a substrate to form a coating film, thereby forming a conductive adhesive. It is used as an agent. When a conductive adhesive composition is applied onto a substrate to form a coating film, the conductive adhesive composition is dissolved or dispersed in a solvent. The manufacturing method etc. which use for a drying process and form a coating film according to it can be employ | adopted accordingly.

(Conductive adhesive film)
The conductive adhesive film of the present invention can be produced by coating a release film with a conductive adhesive. The coating method is not particularly limited, and a known device such as a coating device represented by die coating, lip coating, or comma coating can be used. Moreover, you may use for a drying process as needed, after coating a mold release film with a conductive adhesive. The drying conditions in this case may be set to optimum conditions from the viewpoint of productivity.

As the release film, use is made of a base film such as polyethylene terephthalate or polyethylene naphthalate coated with a silicon-based or non-silicon-based release agent on the surface on which the conductive adhesive layer is formed. be able to. In addition, the thickness of a release film is not specifically limited, It determines suitably considering the ease of use.

The thickness of the conductive adhesive layer formed on the release film is preferably 15 to 100 μm. If it is thinner than 15 μm, the embedding property becomes insufficient, and if it is thicker than 100 μm, it is disadvantageous in cost and cannot meet the demand for thinning. Such a thickness is preferable in that it can be deformed into a shape that fills the concave portion by appropriately flowing when the substrate has irregularities, and can be bonded with good adhesion.

(Adhesion method)
Next, the usage method of the electroconductive adhesive film of this invention is demonstrated. The conductive adhesive film is not particularly limited in its application, but is used, for example, to bond a reinforcing plate to a circuit board. In particular, when the reinforcing plate is conductive, it is used not only for bonding the metal reinforcing plate but also for electrically connecting the ground electrode in the circuit board body and the metal reinforcing plate. .

The material of the circuit board main body may be any material as long as it has insulating properties and can form an insulating layer, and a typical example thereof is polyimide resin.

A metal plate is preferably used as the conductive reinforcing plate, and a stainless plate, an iron plate, a copper plate, an aluminum plate, or the like can be used as the metal plate. Among these, it is more preferable to use a stainless steel plate. By using a stainless steel plate, it has sufficient strength to support electronic components even with a thin plate thickness. The thickness of the conductive reinforcing plate is not particularly limited, but is preferably 0.025 to 2 mm, and more preferably 0.1 to 0.5 mm. If the conductive reinforcing plate is within this range, it can be easily built into a small device and has sufficient strength to support the mounted electronic component.
In addition, as an electronic component here, chip components, such as a resistor and a capacitor | condenser, can be mentioned besides a connector and IC.

In the bonding method of the present invention, the conductive adhesion obtained by the step (1) and the step (1) of temporarily bonding the above-described conductive adhesive film onto the adherend substrate (X) which is a reinforcing plate or a flexible substrate. This is a bonding method comprising a step (2) in which a substrate to be bonded (X) having a film is overlapped with a substrate to be bonded (Y) which is a flexible substrate or a reinforcing plate and hot pressed.

The conductive adhesive film described above can be suitably used particularly for bonding the flexible substrate and the reinforcing plate in the flexible circuit substrate. That is, as described in the cited document 4, a conductive metal plate or the like is used as a reinforcing plate, and this is adhered to a flexible circuit board with a conductive adhesive composition, whereby an electromagnetic wave generated by the reinforcing plate. Obtaining shielding ability is done.

With such a technique, the conductive adhesive film of the present invention has a particularly excellent effect in that good adhesive performance is obtained when the reinforcing plate is bonded. That is, since the curing reaction proceeds slowly when stored for a certain period after temporary bonding, the bonding performance does not deteriorate when performing main bonding by hot pressing.

In the bonding method of the present invention, first, a conductive adhesive film is temporarily bonded onto the adherend substrate (X). The adherend substrate (X) may be either a reinforcing plate, a flexible substrate or a reinforcing plate, but is preferably a reinforcing plate. Temporary bonding is not particularly limited in terms of conditions, and it is sufficient that the conductive adhesive film is fixed on the substrate to be bonded and bonded without slipping, but it is not point bonding but surface bonding. It is preferable to do. That is, it is preferable to temporarily bond the entire bonding surface.

Temporary bonding can be performed with a press, and examples of bonding conditions include temperature: 120 ° C., time: 5 seconds, and pressure: 0.5 MPa.

The adherend substrate (X) to which the conductive adhesive film has been temporarily bonded in the step (1) described above may be immediately used for the step (2), or for one week before being used for the step (2). The above may be stored. The conductive adhesive composition of the present invention is preferable in this respect because the adhesive performance does not deteriorate even after partially cured.

In the step (2), the release film on the conductive adhesive film is peeled off from the adherend base material (X) having the conductive adhesive film obtained in the step (1), and the adhesive base is a flexible substrate or a reinforcing plate. This is a process of stacking materials (Y) and hot pressing. Note that one of the adherend substrate (X) and the adherend substrate (Y) is a reinforcing plate and the other is a flexible substrate.

Hot press can be performed on normal conditions, for example, 1-5 Mpa, 140-190 degreeC, 15-90 minutes.

(Circuit board)
The circuit board of the present invention is a circuit board having at least a portion where a flexible substrate, a conductive adhesive composition, and a conductive reinforcing plate are laminated in this order. Such a circuit board may be bonded by the above-described bonding method, or may be obtained by other bonding methods. A schematic diagram of such a circuit board is shown in FIG. In FIG. 4, the circuit board and the reinforcing plate are bonded by the conductive adhesive composition of the present invention and are also electrically connected.

In the circuit board, the conductive reinforcing plate is preferably present only in a part of the circuit board. That is, it is preferable that the portion having the electronic component has a reinforcing plate.

In the circuit board of the present invention, it is preferable that at least a part of the surface other than the reinforcing plate as described above is covered with an electromagnetic wave shielding film. That is, the electromagnetic wave shielding film may cover only a part of the surface other than the reinforcing plate, or may cover the entire surface other than the reinforcing plate. In this case, the electromagnetic wave shielding film may overlap with at least a part of the reinforcing plate. This is preferable in that good electromagnetic shielding performance can be obtained over the entire circuit board. The electromagnetic wave shielding film is not particularly limited, but those having an insulating layer / isotropic conductive adhesive layer or those having an insulating layer / metal layer / anisotropic conductive adhesive layer are preferred.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.

(1) <Synthesis of polyurethane resin (C-1)>
[Synthesis Example c1: Carboxyl group-containing polyurethane (urethane urea)]
A reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen blowing tube, and a manhole was prepared. After replacing the inside of the reaction vessel with nitrogen gas, 6.0 g of dimethylolpropionic acid (DMPA), polyhexamethylene carbonate diol (trade name “Placcel CD220”, manufactured by Daicel Corporation, number average molecular weight 2000 by terminal functional group determination, 2000 ) 100 g and 59.0 g of dimethylformamide (DMF). Next, 31.9 g of hexamethylene diisocyanate (HDI) (NCO group is twice equivalent to OH group) is added, and the reaction is carried out at 90 ° C. until the NCO group of the resin reaches 4.0% of the theoretical value. A prepolymer solution was obtained. To the obtained urethane prepolymer solution, 298.5 g of DMF was added and cooled to 40 ° C., and then 16.1 g of isophoronediamine (IPDA) was added dropwise to react with the NCO group of the urethane prepolymer. Stir until absorption at 2,270 cm −1 due to the free isocyanate group disappears as measured by infrared absorption spectrum analysis, acid value is 16.4 mg KOH / g, number average molecular weight (Mn) is 50,000, weight A DMF solution (solid content concentration 30%) of polyurethane resin (c1) having an average molecular weight (Mw) of 105,000 was obtained.

[Synthesis Example c2: Polycarboxylate-containing polyurethane (no urea bond)]
A reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen blowing tube, and a manhole was prepared. After replacing the inside of the reaction vessel with nitrogen gas, DMPA 6.0 g, 1,4-butanediol 6.0 g, Plaxel CD220 100 g, and DMF 139.1 g were charged. Next, 27.1 g of HDI (NCO group equivalent to OH group) was added, and the mixture was stirred at 90 ° C. until 2,270 cm −1 absorption due to free isocyanate groups disappeared as measured by infrared absorption spectrum analysis. DMF solution (solid content) of polyurethane resin (c2) having an acid value of 18.1 mgKOH / g, a number average molecular weight (Mn) of 52,000, and a weight average molecular weight (Mw) of 112,000. A concentration of 30%) was obtained. It was confirmed by infrared absorption spectrum that the polyurethane resin (c2) did not have a urea bond.

[Synthesis Example c3: Polycarboxylate-containing polyurethane (with urea bond)]
A reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen blowing tube, and a manhole was prepared. After replacing the inside of the reaction vessel with nitrogen gas, 6.0 g of DMPA, 100 g of Plaxel CD220, and 70.8 g of DMF were charged. Next, 42.1 g of isophorone diisocyanate (IPDI) (2 times equivalent of NCO group to OH group) was added, and the reaction was carried out at 90 ° C. until the NCO group of the resin reached 3.6% of the theoretical value. A polymer solution was obtained. After adding 312.3 g of DMF to the obtained urethane prepolymer solution and cooling to 40 ° C., 16.1 g of IPDA was added dropwise to react with the NCO group of the urethane prepolymer. Stir until 2,270 cm-1 absorption due to free isocyanate groups disappears, as determined by infrared absorption spectrum analysis, acid value is 15.3 mg KOH / g, number average molecular weight (Mn) is 50,000, weight A DMF solution (solid content concentration 30%) of polyurethane resin (c3) having an average molecular weight (Mw) of 102,000 was obtained.

[Comparative Synthesis Example c4: No carboxyl group]
A reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen blowing tube, and a manhole was prepared. After the inside of the reaction vessel was replaced with nitrogen gas, 4.0 g of 1,4-butanediol, 100 g of CD220, and 58.2 g of DMF were charged. Next, 31.7 g of HDI (NCO group was 2 times equivalent to OH group) was added, and the reaction was carried out at 90 ° C. until the NCO group of the resin reached 4.1% of the theoretical value to obtain a urethane prepolymer solution. . After adding 295.8 g of DMF to the obtained urethane prepolymer solution and cooling to 40 ° C., 16.0 g of IPDA was added dropwise to react with the NCO group of the urethane prepolymer. Stir until absorption at 2,270 cm −1 due to free isocyanate groups disappears, as determined by infrared absorption spectrum analysis, and do not contain carboxyl groups, number average molecular weight (Mn) is 52,000, weight average molecular weight ( A DMF solution (solid content concentration 30%) of polyurethane resin (c4) having a Mw of 109,000 was obtained.

(2) <Synthesis of acrylic resin (C-2)>
[Synthesis Example c5: Acrylic Resin Containing Carboxyl Group]
A reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen blowing tube, and a manhole was prepared. After replacing the inside of the reaction vessel with nitrogen gas, 100 g of methyl ethyl ketone (MEK) was charged and heated to 80 ° C. in a nitrogen atmosphere. A mixture of 5 g of methyl methacrylate, 65 g of 2-ethylhexyl methacrylate, 25 g of n-lauryl methacrylate, 5 g of methacrylic acid and 2 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was prepared. 1/3 of the mixture was added into the reaction vessel, and the rest was dropped into the reaction vessel with a dropping funnel over 1 hour. After dropping, the reaction is allowed to proceed for 6 hours, and the acid value is 32.5 mgKOH / g, the weight average molecular weight (Mw) is 29,000, the number average molecular weight (Mn) is 10,000, and the calculated value of Tg is A solution (solid content concentration 50%) of acrylic resin (c5) at −18.5 ° C. was obtained.

[Comparative Synthesis Example c6: No carboxyl group]
A reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen blowing tube, and a manhole was prepared. After replacing the inside of the reaction vessel with nitrogen gas, 100 g of methyl ethyl ketone (MEK) was charged and heated to 80 ° C. in a nitrogen atmosphere. A mixture of 10 g of methyl methacrylate, 65 g of 2-ethylhexyl methacrylate, 25 g of n-lauryl methacrylate, and 2 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was prepared. 1/3 of the mixture was added into the reaction vessel, and the rest was dropped into the reaction vessel with a dropping funnel over 1 hour. An acrylic resin having a weight average molecular weight (Mw) of 35,000, a number average molecular weight (Mn) of 14,000, and a calculated Tg of −19.1 ° C. A solution of (c6) (solid content concentration 50%) was obtained.

(Example film sample manufacturing method)
The manufacturing method of the electroconductive adhesive film of each Example, each reference example, and each comparative example is demonstrated. Each material is blended to create a predetermined paste. This was hand-coated using a doctor blade (plate-like spatula) on a polyethylene terephthalate film subjected to a mold release treatment, and dried at 100 ° C. for 3 minutes to produce a conductive adhesive film. The doctor blade is appropriately selected from 1 mil to 5 mil depending on the thickness of the conductive adhesive film to be produced. Note that 1 mil = 1/1000 inch = 25.4 μm. In each example, each reference example, and each comparative example, each conductive adhesive film was prepared so that the thickness of the conductive adhesive film was a predetermined thickness. The thickness of the conductive adhesive film is measured with a micrometer.

In addition, as each component shown in Table 1, what was described in Table 2 below was used.
Moreover, the tertiary amine compound (the Mitsubishi Chemical make, brand name jER3010) was used for the hardening | curing agent.

As the conductive fillers in Table 1, the following were used.
Conductive filler D-1: Silver powder (average particle size 12 μm, manufactured by Fukuda Metal Foil Powder Co., Ltd.)
Conductive filler D-2: Silver-coated copper powder (average particle size 20 μm, manufactured by Fukuda Metal Foil Powder Co., Ltd.)
Conductive filler D-3: Silver-coated copper powder (average particle size 25 μm, manufactured by Fukuda Metal Foil Powder Co., Ltd.)

(Adhesion method)
The reinforcing plate and the conductive adhesive film are temporarily bonded by thermocompression with a press machine (temperature: 120 ° C., time: 5 seconds, pressure: 0.5 MPa), and the separator film on the conductive adhesive film is peeled off to form a flexible substrate. After temporary bonding by the temporary bonding method, thermocompression bonding is further performed with a press (temperature: 170 ° C., time: 30 minutes, pressure: 3 MPa).

(Evaluation method)
For the evaluation, peel strength, connection resistance value, reflow resistance, resin flow when thermocompression bonding is performed within 1 hour after temporary bonding and when thermocompression bonding is performed after storage for one week after temporary bonding. The reliability test was evaluated by the following method. Here, assuming a long-term storage, it was stored for one week in a room temperature-controlled at 23 ° C. and 60% RH.

(Peel strength)
The adhesion with the reinforcing plate was measured using a 90 ° peel test. Specifically, as shown in FIG. 1, the surface side of a polyimide layer in a copper clad laminate having a stainless steel plate (width 10 mm, length 100 mm), a polyimide layer and a thin film copper layer, and the conductivity of this example. After the press bonding as described in the method of using the conductive adhesive film of the above-described embodiment through the adhesive adhesive film, the copper clad laminate was pulled off in the vertical direction. If it is 10 N / cm or more, it can be used without problems.

(Connection resistance value)
Electrical evaluation was carried out on the circuit board with metal reinforcing plate prepared by the above method. Connection resistance of the circuit board with the metal reinforcing plate when the conductive adhesive film is pressed between the reinforcing plate and the flexible printed circuit board simulating the ground having a diameter of 1.0 mm in the connection portion (electrode in FIG. 2) Between). In addition, if it is 1Ω or less, shielding performance is secured.

(Reflow resistance)
Evaluation after reflow was performed. As the reflow temperature condition, a lead-free solder was assumed and a temperature profile of a maximum of 265 ° C. was set. A test piece of a circuit board with a metal reinforcing plate obtained by pressing a conductive adhesive film with a reinforcing plate was passed five times through IR reflow, and the presence or absence of swelling was observed.

(Resin flow)
The resin flow distance was measured about the circuit board with a metal reinforcement board produced by said method. When the prepared circuit board with a metal reinforcing plate was observed from the reinforcing plate side, the distance between the conductive adhesive end protruding from the bottom of the reinforcing plate and the reinforcing plate end was measured. If it is 300 micrometers or less, it can be used without a problem.

(Reliability test)
The peel test specimen prepared by the above method and the connection resistance measurement test specimen were left in a high temperature and high humidity environment (85 ° C., 85%) for 1000 hours, and then the peel strength and connection resistance were measured. .

The evaluation results are shown in Table 3 below.

From the results of Table 3, the conductive adhesive composition of the present invention has good physical properties and electrical properties. Furthermore, it has good adhesion performance even after being stored for a long time after temporary adhesion. Furthermore, good adhesion performance and electrical conductivity can be obtained even when bonded onto a substrate having a step.

The conductive adhesive composition of the present invention can be used particularly preferably in applications where a metal reinforcing plate is bonded to a flexible substrate.

1. Metal reinforcement plate (Ni-SUS)
2. Electrode (Ni-Au electroless plating treatment)
3. Resin flow4. GND (Ni-Au electroless plating treatment)
5. 5. Conductive adhesive 6. Coverlay film Copper foil layer 8. Copper clad laminate 9. Connection resistance measurement point

Claims (12)

Bisphenol type epoxy resin (A) which has two or more epoxy groups per molecule and is solid at room temperature,
A novolac epoxy resin (B) having two or more epoxy groups per molecule and solid at room temperature,
In the conductive adhesive composition containing the resin (C) having a carboxyl group and the conductive filler (D),
The resin (C) having a carboxyl group contains at least one selected from the group consisting of a carboxyl group-containing polyurethane resin (C-1) and a carboxyl group-containing polyacrylic resin (C-2) ,
A conductive adhesive composition characterized by not containing a curing agent other than the bisphenol type epoxy resin (A), the novolac type epoxy resin (B) and the resin (C) having a carboxyl group . 2. The conductive adhesive composition according to claim 1, wherein the ratio of the bisphenol type epoxy resin (A) to the novolac type epoxy resin (B) is a weight ratio of 85:15 to 99: 1. The conductive adhesive composition according to claim 1 or 2, wherein the bisphenol-type epoxy resin (A) has an epoxy equivalent of 800 to 10,000. The conductive adhesive composition according to any one of claims 1 to 3, wherein the novolac type epoxy resin (B) has an epoxy equivalent of 90 to 300. 5. The conductive adhesive composition according to claim 1, wherein the conductive filler (D) is at least one selected from the group consisting of silver powder, silver-coated copper powder, and copper powder. The conductive adhesive composition according to any one of claims 1 to 5, wherein the conductive filler (D) has an average particle diameter of 3 to 50 µm. The electroconductive adhesive film which laminated | stacked the electroconductive adhesive layer using the electroconductive adhesive composition of any one of Claims 1-6 , and the protective layer. The conductive adhesive film according to claim 7 , wherein the thickness of the conductive adhesive layer is 15 to 100 μm. 9. The conductive adhesive film according to claim 7, wherein a peel strength when thermocompression bonding is performed after one week has elapsed after temporary bonding with a press machine is 10 N / cm or more. It obtained by the process (1) and the process (1) which temporarily adhere | attach the electroconductive adhesive film of any one of Claims 7-9 on the to-be-adhered base material (X) which is an electroconductive reinforcement board or a flexible substrate. A bonding method comprising a step (2) in which a substrate to be bonded (X) having a conductive adhesive film is overlapped with a substrate to be bonded (Y) which is a flexible substrate or a conductive reinforcing plate and hot pressed. It is a circuit board which has the site | part which laminated | stacked the flexible substrate, the conductive adhesive layer, and the conductive reinforcement board in this order in part, Comprising: A conductive adhesive layer is any one of Claims 7-9. A circuit board characterized by being formed of a conductive adhesive film. The circuit board according to claim 11 , wherein a surface other than the reinforcing plate on the surface of the flexible substrate is covered with an electromagnetic wave shielding film.