TW201900810A - Conductive adhesive - Google Patents

Abstract

This conductive adhesive contains: an acrylic resin having a weight-average molecular weight of 500,000-1,000,000 and an epoxy group; a thermosetting resin having a glass transition temperature of 0-50 DEG C; a number-average molecular weight of 10,000-50,000, and a functional group reactive with an epoxy group; and a conductive filler. The ratio of the acrylic resin with respect to the sum of the acrylic resin and the thermosetting resin is 15-95 mass%.

Description

Conductive adhesive

The present disclosure relates to a conductive adhesive.

BACKGROUND OF THE INVENTION Conductive adhesives are often used in flexible printed wiring boards. For example, a metal plate for reinforcement made of stainless steel can be attached to a flexible printed wiring board. By using a conductive adhesive when attaching a metal reinforcement plate, the metal plate for reinforcement can be used as a shield against electromagnetic waves. Shielding function. In this case, it is required for the conductive adhesive to firmly bond the insulating film (covering layer) provided on the surface of the flexible printed wiring board and the metal reinforcing plate, and at the same time ensure that it is exposed from the opening provided on the insulating film. The ground circuit is well conducted.

In recent years, with the miniaturization of electrical equipment, it is required to embed a conductive adhesive in a minute opening to ensure conductivity. Therefore, the improvement of the embedding property of the conductive adhesive has been studied (for example, refer to Patent Document 1).

Prior Art Literature Patent Literature Patent Literature 1: International Publication No. 2014/010524

SUMMARY OF THE INVENTION Problems to be Solved by the Invention However, the conductive adhesive is required not only for embedding property but also for adhesiveness. Specifically, the adhesion between the polyimide and the conductive adhesive used for the flexible printed wiring board and the adhesion between the gold plating layer and the conductive adhesive provided on the surface of the ground circuit are required.

The subject of the present disclosure is to be able to realize a conductive adhesive having both embedding and adhesion properties.

Means for Solving the Problems The conductive adhesive of the present disclosure includes: an acrylic resin having a weight average molecular weight of 500,000 to 1 million and having an epoxy group; and a thermosetting resin having a glass transition temperature of 5 ° C to 100 ° C, a number average molecular weight of 10,000 to 50,000, and a functional group that reacts with epoxy groups; and conductive fillers; and acrylic resins are more thermosetting than acrylic resins. The ratio of the total resin amount is 15 mass% or more and 95 mass% or less.

In one aspect of the conductive adhesive of the present disclosure, the glass transition temperature of the acrylic resin may be set to 0 ° C or higher and 50 ° C or lower.

In one aspect of the conductive adhesive of the present disclosure, the thermosetting resin may be a urethane-modified polyester resin.

In one aspect of the conductive adhesive of the present disclosure, the epoxy equivalent of the acrylic resin may be 1000 g / eq or more and 10,000 g / eq or less.

In one aspect of the conductive adhesive of the present disclosure, the acid value of the thermosetting resin may be 5 mgKOH / g or more and 50 mgKOH / g or less.

Advantageous Effects of Invention According to the conductive adhesive of the present disclosure, it is possible to have both embedding property and adhesion property.

The conductive adhesive for carrying out the aspect of the invention includes an acrylic resin (A) having an epoxy group, a thermosetting resin (B) having a functional group capable of reacting with an epoxy group, and a conductive filler ( C). The weight average molecular weight (Mw) of the acrylic resin (A) is 500,000 or more and 1 million or less. The glass transition temperature of the thermosetting resin (B) is 5 ° C to 100 ° C, and the number average molecular weight (Mn) is 10,000 to 50,000. The ratio of the acrylic resin (A) to the total amount of the acrylic resin (A) and the thermosetting resin (B) is 15% by mass or more and 95% by mass or less.

Acrylic resin (A) The acrylic resin in the present disclosure is a polymer containing alkyl acrylate or alkyl methacrylate as a main component. Hereinafter, acrylate and methacrylate are collectively referred to as (meth) acrylate. The (meth) acrylic acid alkyl ester is not particularly limited, and may be, for example, a (meth) acrylic acid ester having a linear or branched alkyl group having about 1 to 18 carbon atoms. Specifically, it can be methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, tertiary butyl (meth) acrylate, amyl (meth) acrylate, (meth) Hexyl acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, isodecyl (meth) acrylate Esters, lauryl (meth) acrylate, and stearyl (meth) acrylate. These alkyl (meth) acrylates may be used alone or in combination of two or more.

The acrylic resin of the present disclosure has an epoxy group. The epoxy group can be obtained by polymerizing an acrylic resin by adding an alkyl (meth) acrylate to a polymerizable monomer having an epoxy group. The polymerizable monomer having an epoxy group can be, for example, a (meth) acrylate having an epoxy group such as glycidyl (meth) acrylate. It can also be obtained by polymerizing an acrylic resin by adding a polymerizable (meth) acrylate oligomer having an epoxy group. It can also be obtained by polymerizing an acrylic resin by adding another polymerizable monomer or oligomer having an epoxy group.

The acrylic resin of the present disclosure may contain other monomer components. Other monomer components include, for example: aromatic vinyl compounds, (meth) acrylic acid, β-carboxyethyl acrylate, itaconic acid, crotonic acid, maleic acid, fumaric acid, maleic anhydride and other carboxyl-containing monomers; ( Monomers containing aliphatic ester groups other than alkyl groups, such as cyclohexyl methacrylate and isofluorenyl (meth) acrylate; aromatic esters containing phenyl (meth) acrylate, benzyl (meth) acrylate, etc. Monomers; 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, chloro-2-hydroxypropyl acrylate, diethylene glycol mono (meth) acrylate, allyl Hydroxyl-containing monomers such as alcohols; Amine-containing monomers such as aminomethyl (meth) acrylate and dimethylaminoethyl (meth) acrylate; acrylamide, hydroxymethyl (meth) acrylic acid Ammonium-containing monomers such as amines, methoxyethyl (meth) acrylamide; alkoxy-containing monomers, such as methacryloxypropylmethoxysilane; Acetamidine-containing monomers such as meth) acrylate; vinyl-based monomers other than styrene such as vinyl acetate and vinyl chloride; (meth) acrylonitrile and the like. These can be used alone or in combination of two or more.

The epoxy equivalent of acrylic resins particularly affects heat resistance. Therefore, it is preferably below 10,000 g / eq, more preferably below 9000 g / eq, and even more preferably below 8000 g / eq. In addition, it is preferably 1000 g / eq or more, more preferably 2000 g / eq or more, and more preferably 3000 g / eq or more. The epoxy equivalent can be measured in accordance with JIS K7236: 2001.

The Mw of the acrylic resin (A) of the present disclosure is 500,000 or more and 1 million or less. From the viewpoint of embedding, the Mw of the acrylic resin (A) is 500,000 or more, preferably 700,000 or more, and more preferably 750,000 or more. On the other hand, from the viewpoint of ensuring fluidity, Mw is 1 million or less, preferably 950,000 or less, and more preferably 900,000 or less. In addition, Mw can be a styrene conversion value measured by gel permeation chromatography (GPC).

From the viewpoint of embedding property, the glass transition temperature of the acrylic resin is preferably 0 ° C or higher, more preferably 5 ° C or higher, and even more preferably 10 ° C or higher. The temperature is preferably 50 ° C or lower, more preferably 30 ° C or lower, and even more preferably 20 ° C or lower. The glass transition temperature can be measured using a differential scanning calorimeter (DSC).

The polymerization method of the acrylic resin is not particularly limited, and a known polymerization method can be used. For example, if suspension polymerization is used, an acrylic resin having an epoxy group having an Mw of 500,000 or more and 1 million or less can be easily obtained.

Commercially available acrylic resins satisfying such characteristics include, for example, Teisanresin series (SG-70L, SG-708-6, SG-P3) manufactured by Nagase ChemteX Co. and the like.

Thermosetting resin (B) From the viewpoint of embedding, the glass transition temperature of the thermosetting resin of this embodiment is 5 ° C or higher, preferably 10 ° C or higher, and more preferably 30 ° C or higher. The temperature is 100 ° C or lower, preferably 90 ° C or lower, and more preferably 80 ° C or lower. The glass transition temperature can be measured using a differential scanning calorimeter (DSC).

From the viewpoint of embedding, the Mn of the thermosetting resin of this embodiment is preferably 10,000 or more. It should be less than 50,000, more preferably less than 30,000. In addition, Mn may be a styrene conversion value measured by gel permeation chromatography (GPC).

The thermosetting resin of this embodiment has a functional group which reacts with an epoxy group. The functional group that can react with the epoxy group is not particularly limited, and examples thereof include a hydroxyl group, a carboxyl group, an epoxy group, and an amine group. Among them, a hydroxyl group and a carboxyl group are suitable.

When the thermosetting resin has a carboxyl group, from the viewpoint of heat resistance, the acid value is preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, and more preferably 15 mgKOH / g or more. And it is preferably 50 mgKOH / g or less, more preferably 45 mgKOH / g or less, and even more preferably 40 mgKOH / g or less. The acid value can be measured in accordance with JIS K0070: 1992.

The thermosetting resin in this embodiment is not particularly limited, and is preferably a urethane-modified polyester resin. The urethane-modified polyester resin is a polyester resin containing a urethane resin as a copolymer component. The urethane-modified polyester resin can be prepared, for example, by condensation polymerization of an acid component such as a polycarboxylic acid or an anhydride thereof with a diol component, and then preparing a polyester resin by reacting a terminal hydroxyl group of the polyester resin with an isocyanate component. Got. In addition, an urethane-modified polyester resin can be produced by simultaneously reacting an acid component, a diol component, and an isocyanate component.

The acid component is not particularly limited, and for example, terephthalic acid, isophthalic acid, phthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-diphenyldiamine can be used. Formic acid, 2,2'-diphenyldicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, adipic acid, azelaic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, 1, 3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dimer acid, trimellitic anhydride, 1, 2, 4 , 5-benzenetetracarboxylic anhydride, 5- (2,5-dioxotetrahydro-3-furanyl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, and the like.

The diol component is not particularly limited, and for example, ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, and 1,3-butanediol can be used. , 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol , 2,2,4-trimethyl-1,5-pentanediol, cyclohexanedimethanol, neopentylhydroxytrimethylacetate, ethylene oxide adducts of bisphenol A and epoxy Propane adduct, ethylene oxide adduct and propylene oxide adduct of hydrogenated bisphenol A, 1,9-nonanediol, 2-methyloctanediol, 1,10-decanediol, 2 -Butyl-2-ethyl-1,3-propanediol, tricyclodecanedimethanol, polyethylene glycol, polypropylene glycol, polybutylene glycol and other glycols; or trimethylolpropane, Polyols of trivalent or higher such as trimethylolethane and neopentyl alcohol.

The isocyanate component is not particularly limited, and for example, 2,4-methylphenylene diisocyanate, 2,6-methylphenylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate can be used , Hexamethylene diisocyanate, tetramethylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,6-naphthalene Diisocyanate, 3,3'-dimethyl-4,4'-diisocyanate, 4,4'-diisocyanate diphenyl ether, 1,5-diisocyanate, 1,3 diisocyanate methyl ring Hexane, 1,4-diisocyanate methylcyclohexane, isophorone diisocyanate and the like.

The thermosetting resin is not limited to a urethane-modified polyester resin, and an acid-modified polyester resin, an epoxy resin, or the like may be used.

In the conductive adhesive of this embodiment, the ratio (A / (A + B)) of the mass of the acrylic resin (A) to the total mass of the acrylic resin (A) and the thermosetting resin (B) can be set as : 15 mass% or more, preferably 20 mass% or more, more preferably 30 mass% or more, and 95 mass% or less, preferably 90 mass% or less, and more preferably 80 mass% or less. By setting the acrylic resin (A) and the thermosetting resin (B) at such a ratio, it is possible to achieve both the embedding property and the adhesion to the insulating film and the gold plating layer.

Conductive filler (C) In the conductive adhesive of this embodiment, the conductive filler 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 can be produced by an electrolytic method, an atomization method, a reduction method, or the like. Among them, any one of silver powder, silver-coated copper powder and copper powder is suitable.

The conductive filler is not particularly limited, and from the viewpoint of contact between the fillers, the average particle diameter is preferably 1 μm or more, more preferably 3 μm or more, and preferably 50 μm or less, and more preferably 40 μm or less. The shape of the conductive filler is not particularly limited, and may be spherical, sheet-like, dendritic, or fibrous, and is preferably dendritic from the viewpoint of obtaining a good connection resistance value.

In the conductive adhesive of this embodiment, the content of the conductive filler may be appropriately selected according to the application, but it is preferably 5 mass% or more, more preferably 10 mass% or more, and 95 mass% or less in the total solid content. It is more preferably 90% by mass or less. From the viewpoint of embedding, it is preferably 70% by mass or less, and more preferably 60% by mass or less. When anisotropy is to be achieved, it is preferably 40% by mass or less, and more preferably 35% by mass or less.

(Other curable resin components) In the conductive adhesive of this embodiment, a curable resin other than the above-mentioned acrylic resin having an epoxy group and a thermosetting resin having a functional group that can react with an epoxy group may be added. ingredient. As such a curable resin component, an epoxy resin which is solid at normal temperature or an epoxy resin which is liquid at normal temperature can be used. The term “solid at normal temperature” means that the epoxy resin has no fluidity at 25 ° C. without a solvent, and “liquid at normal temperature” means a fluidity under the same conditions.

Epoxy resins that are solid or liquid at room temperature can be exemplified by bisphenol epoxy resins such as bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin; Epoxy resin, naphthalene-type epoxy resin, biphenyl-type epoxy resin, terpene-type epoxy resin, ginseng (glycidoxyphenyl) methane, epoxy (glycidoxyphenyl) ethane, etc. Propyl ether epoxy resin; epoxypropylamine epoxy resin such as tetraglycidylaminodiphenylmethane, tetrabromobisphenol A epoxy resin, cresol novolac epoxy resin, phenol novolac Type epoxy resin, α-naphthol novolac epoxy resin, brominated phenol novolac epoxy resin and other phenolic epoxy resins; rubber modified epoxy resins. These may be used individually by 1 type, and may use 2 or more types together. When adding another curable resin component to the conductive adhesive of this embodiment, it is preferable to add 100 parts by mass to the total of 100 parts by mass of the acrylic resin having an epoxy group and the thermosetting resin having a functional group capable of reacting with the epoxy group. Total 1.0 ~ 10.0 parts by mass.

(Sclerosing Compound) In the conductive adhesive of the present embodiment, in order to promote an acrylic resin having an epoxy group, a thermosetting resin having a functional group capable of reacting with an epoxy group, and other curing resins as required The reaction of the components may be blended with a hardening compound. As such a hardening compound, an imidazole-based hardener, a phenol-based hardener, and a cationic hardener can be used. These may be used individually by 1 type, and may use 2 or more types together.

Examples of the imidazole-based hardener include an alkyl group, an ethyl cyano group, a hydroxyl group, and an acryl group added to the imidazole ring. And other compounds, such as 2-phenyl-4,5-dihydroxymethylimidazole, 2-heptadecylimidazole, 2,4-diamino-6- (2'-undecylimidazolyl) ethyl Radical-S-triazine , 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole, 5-cyano-2-phenylimidazole, 2,4-diamino-6- [2'methylimidazolyl- (1 ′)]-Ethyl-S-triazine Isotricyanic acid adduct, 2-phenylimidazole isotricyanic acid adduct, 2-methylimidazole isotricyanic acid adduct, 1-cyanoethyl-2-phenyl-4, 5-bis (2-cyanoethoxy) methylimidazole and the like.

Examples of the phenol-based hardener include phenol novolac, naphthol-based compounds, and the like.

Examples of the cationic hardener include amine salts of boron trifluoride, antimony pentachloride-acetamidine chloride complexes, and sulfonium salts having phenethyl or allyl groups.

(Optional component) To the conductive adhesive of this embodiment, an antifoaming agent, an antioxidant, a viscosity adjusting agent, a diluent, an anti-settling agent, a leveling agent, a coupling agent, a coloring agent, a flame retardant, and the like can be added. Among these, a flame retardant is preferably added in order to impart flame retardancy to the conductive adhesive.

Examples of such flame retardants include: nitrogen-based flame retardants such as melamine cyanurate or melamine polyphosphate; metal hydrates such as magnesium hydroxide and aluminum hydroxide; and phosphates, red phosphorus, and phosphate compounds. Phosphorous flame retardants, etc. Among these, phosphate compounds are preferred.

When a flame retardant is added to the conductive adhesive of this embodiment, the thermosetting resin (and other hardening resins according to demand) are different from the acrylic resin having an epoxy group and the functional group that can react with the epoxy group. Ingredients) total 100 parts by mass, preferably 10 to 60 parts by mass.

(Usage method) As an example of a method of using the conductive adhesive of this embodiment, a method of mounting a metal reinforcing plate on a flexible printed wiring board will be described below. First, as shown in FIG. 1, a flexible printed wiring board 110 and a metal reinforcing plate 135 are prepared, and the metal reinforcing plate 135 is provided on one side with a conductive adhesive layer 130 composed of the conductive adhesive of the present embodiment.

A method of providing a conductive adhesive layer 130 on the surface of the metal reinforcing plate 135. For example, as shown in FIG. 2, first, a conductive adhesive is applied on a release substrate (separation film) 142 to form a conductive adhesive layer. The conductive film of 130 is 141. Then, the conductive adhesive film 141 and the metal reinforcing plate 135 are pressed to make them adhere to each other, and the metal reinforcing plate 135 having the conductive adhesive layer 130 can be formed. The peeling base material 142 may be peeled before use.

The release substrate 142 can be used on a base film such as polyethylene terephthalate, polyethylene naphthalate, and the like, and the surface of the side where the conductive adhesive layer 130 is to be formed can be coated with silicon or non-silicon. Release agent thing. In addition, the thickness of the release base material 142 is not particularly limited, and can be determined in consideration of ease of use as appropriate.

The thickness of the conductive adhesive layer 130 is preferably 15 μm to 100 μm. By setting it to 15 μm or more, sufficient embedding can be achieved, and sufficient connection with a ground circuit can be achieved. In addition, if the thickness is set to 100 μm or less, it can respond to the requirements of thin film, and it is also advantageous in terms of cost.

The flexible printed wiring board 110 includes, for example, a base member 112 and an insulating film 111. The insulating film 111 passes through the adhesive layer 113 and is adhered to the base member 112. An opening 160 is provided in the insulating film 111 to expose the ground circuit 115. A surface layer 116 that is a gold plating layer is provided on the exposed portion of the ground circuit 115. Alternatively, the flexible printed wiring board 110 may be changed to a rigid substrate.

Next, as shown in FIG. 3, the metal reinforcing plate 135 is arranged on the flexible printed wiring board 110 such that the conductive adhesive layer 130 is positioned above the opening 160. Then, the metal reinforcing plate 135 and the flexible printed wiring board 110 are sandwiched from above and below by two heating plates (not shown) heated to a predetermined temperature (for example, 120 ° C.), and pressed with a predetermined pressure (for example, 0.5 MPa). A short time (such as 5 seconds). Thereby, the metal reinforcing plate 135 can be temporarily fixed to the flexible printed wiring board 110.

Next, the temperature of the two heating plates is set to a predetermined temperature (for example, 170 ° C.) which is higher than the above-mentioned temporary fixation, and the pressure is applied for a predetermined time (for example, 30 minutes) at a predetermined pressure (for example, 3 MPa). Thereby, the conductive adhesive layer 130 can be filled in the opening 160 and the metal reinforcing plate 135 can be fixed to the flexible printed wiring board 110 in this state.

Then, a solder reflow step is performed to mount the parts. In the reflow step, the flexible printed wiring board 110 is exposed to a high temperature of about 260 ° C. There are no particular restrictions on the parts to be mounted, such as connectors or integrated circuits, and also chip parts such as resistors and capacitors.

Since the embedding property of the conductive adhesive in this embodiment is high, even when the diameter of the opening 160 is as small as 1 mm or less, the opening 160 can be fully embedded, and the metal reinforcing plate 135 and the ground circuit 115 can be ensured. Good connection. If the embedding property is insufficient, fine bubbles may enter between the surface layer 116 and the insulating film 111 and the conductive adhesive layer 130. Therefore, when exposed to a high temperature in the reflow step, the bubbles become large, and the conductive adhesive layer 130 may be peeled off. However, the adhesion of the conductive adhesive layer 130, the surface layer 116, and the insulating film 111 of this embodiment is good, and good adhesion can be maintained after the reflow step.

From the viewpoint of firmly bonding the metal reinforcing plate 135, the peel strength of the conductive adhesive layer 130 and the metal reinforcing plate 135 should be high, specifically 4N / 10mm or more, and more preferably 5N / 10mm or more. The peel strength of the conductive adhesive layer 130 and the surface layer 116 should be high, and specifically, it should be 2N / 10mm or more, and more preferably 3N / 10mm or more. The peel strength of the conductive adhesive layer 130 and the metal reinforcing plate 135 or the surface layer 116 can be measured by the method shown in the examples.

The metal reinforcing plate 135 may be formed of a conductive material having a moderate strength. For example, a conductive material containing nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc can be used. Among them, stainless steel is preferred from the viewpoint of corrosion resistance and strength.

The thickness of the metal reinforcing plate 135 is not particularly limited, but from the viewpoint of reinforcement, it is preferably 0.05 mm or more and more preferably 0.1 mm or more, and preferably 1.0 mm or less and more preferably 0.3 mm or less.

In addition, a nickel layer is preferably formed on the surface of the metal reinforcing plate 135. The method for forming the nickel layer is not particularly limited, and it can be formed by electroless plating, electroplating, or the like. If a nickel layer is formed, the adhesion between the metal reinforcing plate and the conductive adhesive can be improved.

The base member 112 may be, for example, a resin film. Specifically, the base member 112 may be made of polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide, imide, or polyetherimide. Or polystyrene sulfide.

The insulating film 111 is not particularly limited, and examples thereof include polyethylene terephthalate, polypropylene, crosslinked polyethylene, polyester, polybenzimidazole, polyimide, polyimide, and polyether. Resin and other resins such as polyimide. The thickness of the insulating film is not particularly limited, and may be about 10 μm to 30 μm.

The surface layer 116 is not limited to a gold plating layer, and may be a layer composed of copper, nickel, silver, tin, or the like. In addition, the surface layer 116 may be provided as required, and a structure without the surface layer 116 may be used.

The conductive adhesive of this embodiment has excellent embedding property and adhesion with a surface layer and an insulating film composed of a gold plating layer, etc., and it is particularly preferable to display a metal reinforcing plate on a flexible printed wiring board. Effect. However, it is also quite useful in other applications where a conductive adhesive can be used. For example, it can be used as an adhesive layer of an electromagnetic wave shielding film. Examples

Hereinafter, the conductive adhesive of the present disclosure will be described in more detail using examples. The following examples are examples, which are not intended to limit the present invention.

<Production of conductive adhesive film> The conductive adhesive films of Examples 1 to 13 and Comparative Examples 1 to 7 having the compositions shown in Tables 1 to 5 were produced by the following production methods.

A planetary stirring and defoaming device is used to mix and stir predetermined materials to prepare a paste-like conductive adhesive composition. Next, using a plate-shaped spatula (blade), the prepared conductive adhesive composition was manually applied to a release-treated polyethylene terephthalate film (separation film), and then subjected to 100 Drying at 3 ° C for 3 minutes to produce a conductive adhesive film. In addition, the squeegee blade is appropriately selected from 1 mil to 5 mil (1 mil = 1/1000 inch = 25.4 μm) according to the thickness of the conductive adhesive film to be produced. In each of the Examples and Comparative Examples, each of the conductive adhesive films was prepared to a predetermined thickness shown in Table 1. The thickness of the conductive adhesive film was measured with a micrometer.

<Adhesion with Gold Plating Layer and Polyimide> The adhesion between the gold plating layer or polyimide and the conductive adhesive was measured by a 90 ° peel test. Specifically, first, a pressure bonding machine was used to temporarily attach a conductive adhesive film and a 200 μm-thick SUS plate metal reinforcing plate under the conditions of temperature: 120 ° C., time: 5 seconds, and pressure: 0.5 MPa using a press machine, and produced A conductive adhesive film 201 of a metal reinforcing plate with a conductive adhesive layer 212 is provided on the surface of the metal reinforcing plate 211. Next, a gold plating layer 224 is formed on the surface of the copper foil 222 of the copper foil laminated film 203 in which the copper foil 222 is formed on the surface of the polyimide film 221. Next, using a press, the gold plating layer 224 of the copper foil laminated film 203 and the conductive adhesive film 201 of a metal-reinforced plate were bonded under the conditions of temperature: 120 ° C., time: 5 seconds, and pressure: 0.5 MPa. Then, using a press, the temperature was 170 ° C., the time was 3 minutes, and the pressure was 2 to 3 MPa. Then, a copper foil laminated film with a metal reinforcing plate was produced, and the temperature was 150 ° C. for 1 hour. After curing. Next, as shown in FIG. 4, the copper foil laminate film 203 was peeled at a normal temperature using a tensile tester (manufactured by Shimadzu Corporation, trade name AGS-X50S) at a tensile speed of 50 mm / min and a peeling angle of 90 °. And the maximum value at the time of breaking is taken as the peeling strength to the gold plating layer.

The polyimide film 221 surface of the copper foil laminated film 203 and the conductive adhesive film 201 were bonded under the same conditions as the gold plating layer 224 to form a sample, and a 90 ° peel test was performed on the sample under the same conditions to obtain Peel strength to polyimide.

<Production of a circuit board with a metal reinforcing plate> Next, the conductive adhesive films prepared in the examples and comparative examples were subjected to a temperature: 120 ° C, time: 5 seconds, and pressure: 0.5MPa using a press. (With a separation film) and a metal reinforcing plate (the surface of the SUS plate is Ni-plated, thickness: 200 μm) is heated and pressed to produce a conductive adhesive film with a metal reinforcing plate. Next, the separation film on the conductive adhesive film was peeled off, and the conductive adhesive film with a metal reinforcing plate was adhered to the flexible substrate under the same conditions as the above-mentioned thermocompression bonding. Then, the temperature was 170 with a press. ℃, time: 3 minutes, pressure: 2 ~ 3MPa, and then a circuit board with a metal reinforcing plate was produced.

As the flexible substrate, as shown in FIG. 1, a copper foil pattern 115 of a virtual ground circuit is formed on a base member 112 composed of a polyimide film, and an insulating adhesive layer is formed thereon. 113 and a covering layer (insulating film) 111 made of a polyimide film. A gold plating layer is provided on the surface of the copper foil pattern 115 as the surface layer 116. In addition, an opening portion 160 of a pseudo ground connection portion having a diameter of 0.8 mm is formed in the cover layer 111.

<Measurement of connection resistance value> As shown in FIG. 5, using a circuit board with a metal reinforcing plate prepared in Examples and Comparative Examples, two copper foil patterns with a surface layer 116 having a gold plating layer on the surface were measured with a resistance meter 205. The resistance value between 115 is used to evaluate the connection between the copper foil pattern 115 and the metal reinforcing plate 135 and used as the initial connection resistance value (connection resistance value before re-soldering).

Next, the circuit boards of the metal-reinforced boards having the prepared examples and comparative examples were subjected to hot air reflow 5 times, and the connection resistance value after reflow was measured by the above method. The reflow conditions are assumed to be lead-free solder, and the temperature profile of the polyimide film in the circuit board with the metal reinforcing plate is exposed to 265 ° C for 5 seconds.

In addition, the case where the connection resistance value after reflow is 0.1 Ω / 1 hole or less is evaluated as the one having excellent conductivity after reflow.

(Example 1) As the acrylic resin (A), a resin (SG-P3, manufactured by Nagase ChemteX Co.) having a Mw of 850,000, an epoxy equivalent of 4,700 g / eq, and a glass transition temperature of 12 ° C was used. As the thermosetting resin (B), a polyurethane-modified polyester resin (UR3600, manufactured by Toyobo Co., Ltd.) having a Mn of 18,000, an acid value of 20 mgKOH / g, and a glass transition temperature of 40 ° C was used. The blending amount is 30 parts by mass of the acrylic resin (A) and 70 parts by mass of the thermosetting resin (B) (A / (A + B) = 30% by mass). As the conductive filler, a dendritic silver-clad copper powder (D-1) having an average particle diameter of 6 μm and a silver coverage of 9% by mass was used. The conductive filler is set to 150 parts by mass based on 100 parts by mass of the resin component.

The peeling strength of the obtained conductive adhesive to polyimide was 8 N / 10 mm, and the peeling strength to the gold plating layer was 3 N / 10 mm. In addition, the initial connection resistance at a hole diameter of 0.8 mmφ is 40 mΩ / 1 hole, and the connection resistance after reflow is 28 mΩ / 1 hole.

(Example 2) Except that 50 parts by mass of the acrylic resin and 50 parts by mass of the thermosetting resin (A / (A + B) = 50% by mass) were used, the rest were the same as in Example 1.

The peeling strength of the obtained conductive adhesive to polyimide was 9N / 10mm, and the peeling strength to the gold plating layer was 4N / 10mm. The initial connection resistance is 39mΩ / 1 hole, and the connection resistance after reflow is 30mΩ / 1 hole.

(Example 3) Except that the acrylic resin was 70 parts by mass and the thermosetting resin was 30 parts by mass (A / (A + B) = 70% by mass), the rest were the same as those in Example 1.

The peel strength of the obtained conductive adhesive to polyimide was 19 N / 10 mm, and the peel strength to the gold plating layer was 5 N / 10 mm. The initial connection resistance is 32mΩ / 1 hole, and the connection resistance after reflow is 26mΩ / 1 hole.

(Example 4) A polyurethane-modified polyester resin (BX-39SS, manufactured by Toyobo Co., Ltd.) was used except that the thermosetting resin was set to Mn of 16000, acid value of 17 mgKOH / g, and glass transition temperature of 15 ° C. Other than that, the rest is the same as in Example 1.

The peeling strength of the obtained conductive adhesive to polyimide was 5N / 10mm, and the peeling strength to the gold plating layer was 7N / 10mm. In addition, the initial connection resistance is 133mΩ / 1 hole, and the connection resistance after reflow is 100mΩ / 1 hole.

(Example 5) Except that the acrylic resin was 50 parts by mass and the thermosetting resin was 50 parts by mass (A / (A + B) = 50% by mass), the rest were the same as in Example 4.

The peeling strength of the obtained conductive adhesive to polyimide was 10 N / 10 mm, and the peeling strength to the gold plating layer was 7 N / 10 mm. In addition, the initial connection resistance was 91mΩ / 1 hole, and the connection resistance after reflow was 58mΩ / 1 hole.

(Example 6) Except that the acrylic resin was 60 parts by mass and the thermosetting resin was 40 parts by mass (A / (A + B) = 60% by mass), the rest were the same as those in Example 4.

The peeling strength of the obtained conductive adhesive to polyimide was 12 N / 10 mm, and the peeling strength to the gold plating layer was 6 N / 10 mm. In addition, the initial connection resistance was 83mΩ / 1 hole, and the connection resistance after reflow was 62mΩ / 1 hole.

(Example 7) Except that the acrylic resin was 70 parts by mass and the thermosetting resin was 30 parts by mass (A / (A + B) = 70% by mass), the rest were the same as those in Example 4.

The peeling strength of the obtained conductive adhesive to polyimide was 10 N / 10 mm, and the peeling strength to the gold plating layer was 6 N / 10 mm. The initial connection resistance was 71mΩ / 1 hole, and the connection resistance after reflow was 67mΩ / 1 hole.

(Example 8) Except that the acrylic resin was 80 parts by mass and the thermosetting resin was 20 parts by mass (A / (A + B) = 80% by mass), the rest were the same as those in Example 4.

The peeling strength of the obtained conductive adhesive to polyimide was 7 N / 10 mm, and the peeling strength to the gold plating layer was 6/10 mm. The initial connection resistance is 72mΩ / 1 hole, and the connection resistance after reflow is 54mΩ / 1 hole.

(Example 9) In addition to acrylic resin (SG-P3, manufactured by Nagase ChemteX Co.) and thermosetting resin (Vylon BX-39SS, manufactured by Toyobo Co., Ltd.), a bisphenol A-type solid epoxy resin was added. (JER1003, manufactured by Mitsubishi Chemical Corporation). The blending amount is 60 parts by mass of an acrylic resin, 30 parts by mass of a thermosetting resin, and 10 parts by mass of a solid epoxy resin (A / (A + B) = 66.6% by mass). The conductive filler was set as a dendritic silver-clad copper powder (D-2) having an average particle diameter of 12 μm and a silver coverage of 8% by mass.

The peeling strength of the obtained conductive adhesive to polyimide was 10 N / 10 mm, and the peeling strength to the gold plating layer was 7 N / 10 mm. In addition, the initial connection resistance is 99mΩ / 1 hole, and the connection resistance after reflow is 42mΩ / 1 hole.

(Example 10) Except that the conductive filler was a dendritic silver-clad copper powder (D-3) having an average particle diameter of 12 μm and a silver coverage of 9% by mass, the rest were the same as in Example 9 (A / (A + B) = 66.6 mass%).

The peeling strength of the obtained conductive adhesive to polyimide was 9N / 10mm, and the peeling strength to the gold plating layer was 7N / 10mm. In addition, the initial connection resistance was 179mΩ / 1 hole, and the connection resistance after reflow was 93mΩ / 1 hole.

(Example 11) In addition to an acrylic resin (SG-P3, manufactured by Nagase ChemteX Co.) and a thermosetting resin (UR3600, manufactured by Toyobo Co., Ltd.), a bisphenol A-type solid epoxy resin (JER1003, Manufactured by Mitsubishi Chemical Corporation). The blending amount is 85 parts by mass of an acrylic resin, 10 parts by mass of a thermosetting resin, and 5 parts by mass of a solid epoxy resin (A / (A + B) = 89.5% by mass). Furthermore, 2-phenyl-1H-imidazole-4,5-dimethanol (2PHZPW, manufactured by Shikoku Chemical Industry Co., Ltd.) was added as a hardener in an amount of 3 parts by mass based on 100 parts by mass of the resin component and the resin component As a flame retardant, 100 parts by mass and 35 parts by mass of aluminum diphenylphosphonate (OP935, manufactured by Clariant Japan KK) were used. The conductive filler is a dendritic silver-clad copper powder (D-1) having an average particle diameter of 6 μm and a silver coverage of 9% by mass, and the blending amount is set to 150 parts by mass relative to 100 parts by mass of the resin component .

The peeling strength of the obtained conductive adhesive to polyimide was 14 N / 10 mm, and the peeling strength to the gold plating layer was 7 N / 10 mm. In addition, the initial connection resistance is 20mΩ / 1 hole, and the connection resistance after reflow is 12mΩ / 1 hole.

(Example 12) Except that 35 parts by mass of aluminum stilbene diethylphosphonate (OP935, manufactured by Clariant Japan KK) was added as a flame retardant with respect to 100 parts by mass of the resin component, the rest were the same as in Example 8 (A / (A + B) = 80% by mass).

The peeling strength of the obtained conductive adhesive to polyimide was 14 N / 10 mm, and the peeling strength to the gold plating layer was 8 N / 10 mm. The initial connection resistance is 32mΩ / 1 hole, and the connection resistance after reflow is 23mΩ / 1 hole.

(Example 13) Except that the thermosetting resin is a polyurethane-modified polyester resin (UR3500, Toyobo Except for the company), the rest are the same as in Example 8 (A / (A + B) = 80% by mass).

The peeling strength of the obtained conductive adhesive to polyimide was 8 N / 10 mm, and the peeling strength to the gold plating layer was 6 N / 10 mm. The initial connection resistance is 38mΩ / 1 hole, and the connection resistance after reflow is 38mΩ / 1 hole.

(Comparative Example 1) Except that only an acrylic resin was used and no thermosetting resin was added (A / (A + B) = 100% by mass), the rest were the same as in Example 1.

The obtained conductive adhesive was not adhered to any of polyimide and gold plating. The initial connection resistance is 27mΩ / 1 hole, and the connection resistance after reflow is 64mΩ / 1 hole.

(Comparative Example 2) Except that the acrylic resin was 10 parts by mass and the thermosetting resin was 90 parts by mass (A / (A + B) = 10% by mass), the rest were the same as those of Example 1.

The peeling strength of the obtained conductive adhesive to polyimide was 3N / 10mm, and the peeling strength to the gold plating layer was 3N / 10mm. The initial connection resistance is 34mΩ / 1 hole, and the connection resistance after reflow is above the measurement limit (OL).

(Comparative Example 3) Except that only a thermosetting resin was used and no acrylic resin was added (A / (A + B) = 0% by mass), the same procedure as in Example 1 was performed.

The peeling strength of the obtained conductive adhesive to polyimide was 2N / 10mm, and the peeling strength to the gold plating layer was 3N / 10mm. In addition, the initial connection resistance is 30mΩ / 1 hole, and the connection resistance after reflow is above the measurement limit.

(Comparative Example 4) Except that the acrylic resin was a resin (SG-P3-MW1, manufactured by Nagase ChemteX Co.) having a Mw of 300,000, an epoxy equivalent of 1,680 g / eq, and a glass transition temperature of 11 ° C. Comparative Example 1 (A / (A + B) = 100% by mass).

The obtained conductive adhesive was not adhered to any of polyimide and gold plating. In addition, the initial connection resistance is 50mΩ / 1 hole, and the connection resistance after reflow is above the measurement limit.

(Comparative Example 5) Except that the acrylic resin was a resin (SG-P3-MW8, manufactured by Nagase ChemteX Co.) having an Mw of 600,000 and an epoxy equivalent of 3300 g / eq, the rest were the same as in Comparative Example 1 (A / ( A + B) = 100% by mass).

The obtained conductive adhesive was not adhered to any of polyimide and gold plating. In addition, the initial connection resistance was 43mΩ / 1 hole, and the connection resistance after reflow was 88mΩ / 1 hole.

(Comparative Example 6) Except that the conductive filler was set to a sheet-like silver-clad copper powder (D-4) having an average particle diameter of 5 μm and a silver coverage of 10% by mass, the rest were the same as in Example 7 (A / (A + B) = 70% by mass).

The peeling strength of the obtained conductive adhesive to polyimide was 12 N / 10 mm, and the peeling strength to the gold plating layer was 8 N / 10 mm. In addition, the initial connection resistance and the connection resistance after reflow are both above the measurement limit.

(Comparative Example 7) Except that the conductive filler was an atomized silver-clad copper powder (D-5) having an average particle diameter of 5 μm and a silver coverage of 10% by mass, the rest were the same as in Example 7 (A / (A + B) = 70% by mass).

The peeling strength of the obtained conductive adhesive to the metal reinforcing plate was 10 N / 10 mm, and the peeling strength to the gold plating layer was 8 N / 10 mm. In addition, the initial connection resistance and the connection resistance after reflow are both above the measurement limit.

The composition and measurement results of each Example and Comparative Example are listed in Tables 1 to 5.

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

Industrial Applicability The conductive adhesive of the present disclosure can have both embedding and adhesion properties, and can be used as a conductive adhesive for flexible printed wiring boards and the like.

110‧‧‧flexible printed wiring board

111‧‧‧Insulation film (covering layer)

112‧‧‧ base member

113‧‧‧ Adhesive layer

115‧‧‧ ground circuit (copper foil pattern)

116‧‧‧ surface layer

130‧‧‧ conductive adhesive layer

135‧‧‧Metal reinforcement board

141‧‧‧ conductive adhesive film

142‧‧‧ peeling substrate (separation film)

160‧‧‧ opening

201‧‧‧ conductive adhesive film

203‧‧‧Cu foil laminated film

205‧‧‧ resistance meter

211‧‧‧ metal reinforcement board

212‧‧‧ conductive adhesive layer

221‧‧‧Polyimide film

222‧‧‧copper foil

224‧‧‧Gold plating

FIG. 1 is a cross-sectional view showing a step of bonding a metal plate. FIG. 2 is a cross-sectional view showing a step of bonding a metal plate. FIG. 3 is a cross-sectional view showing one step of the bonding and reinforcing metal plate. Fig. 4 is a diagram showing a method for measuring peel strength. Fig. 5 is a diagram showing a method for measuring the connection resistance.

Claims (5)

A conductive adhesive containing: an acrylic resin having a weight average molecular weight of 500,000 to 1 million and having an epoxy group; a thermosetting resin having a glass transition temperature of 5 ° C to 100 ° C and a number average A molecular weight of 10,000 or more and 50,000 or less and having a functional group capable of reacting with an epoxy group; and a conductive filler; and a ratio of the acrylic resin to the total amount of the acrylic resin and the thermosetting resin is 15 Above mass% and below 95 mass%. The conductive adhesive according to claim 1, wherein the glass transition temperature of the acrylic resin is 0 ° C or higher and 50 ° C or lower. The conductive adhesive according to claim 1 or 2, wherein the thermosetting resin is a urethane-modified polyester resin. The conductive adhesive according to any one of claims 1 to 3, wherein the epoxy equivalent of the acrylic resin is 1,000 g / eq or more and 10,000 g / eq or less. The conductive adhesive according to any one of claims 1 to 4, wherein the acid value of the thermosetting resin is 5 mgKOH / g or more and 50 mgKOH / g or less.