WO2021140926A1 - Electrically conductive adhesive, and joined structure and electronic component using same - Google Patents

Abstract

Provided are: an electrically conductive adhesive which exhibits excellent adhesive properties and storage stability and which is obtained using an ultraviolet radiation-curable resin; and a joined structure and electronic component obtained using the electrically conductive adhesive.　This electrically conductive adhesive contains a (meth)acrylate (A), a photopolymerization initiator (B), a phosphoric acid group-containing monomer (C), a polyester resin (D) that is soluble in an organic solvent, and electrically conductive particles (E). The phosphoric acid group-containing monomer (C) is preferably a phosphoric acid group-containing (meth)acrylate. The polyester resin (D) is preferably an amorphous polyester resin.

Description

Conductive adhesives, adhesive structures and electronic components using them

The present invention relates to an ultraviolet curable conductive adhesive, an adhesive structure using the same, and an electronic component.

As a method of bonding electronic components such as semiconductors and light emitting diodes to electrodes formed on a substrate such as film or paper using a conductive adhesive or an anisotropic conductive adhesive, the electronic components are thermocompression bonded by a face-down method. The method of making the material (thermocompression bonding method) is widely and generally used (for example, Patent Document 1). Specifically, an anisotropic conductive adhesive is applied onto the electrodes formed on the substrate, and a semiconductor having bumps called protruding electrodes is placed so that the bumps are located on the electrodes. The anisotropic conductive adhesive is cured by sandwiching the substrate on which the semiconductor is placed between the upper heat tool and the lower heat tool heated to 180 ° C., and the semiconductor is electrically connected to the electrodes and at the same time on the substrate. A semiconductor is mounted.

However, when a semiconductor is mounted on a substrate by the thermocompression bonding method, the substrate around the semiconductor is distorted due to the heat of the heat tool. As a measure to prevent such distortion, a method of lowering the temperature of the heat tool to reduce the distortion has been proposed, but it is not practical because the mounting time is extended. Further, although a low-temperature curing adhesive has been developed, it is still necessary to heat it to 130 ° C. or higher, so that it is not possible to completely prevent the distortion of the substrate.

As a method that does not require heating when mounting a semiconductor on a substrate, a method using an adhesive containing an ultraviolet curable resin is known (for example, Patent Document 2).

However, the adhesive containing the ultraviolet curable resin has a problem of low adhesion, and in order to improve this, a method of containing a phosphoric acid group-containing monomer has been proposed (for example, Patent Document 3 and non-patent). Document 1). However, a conductive adhesive using an ultraviolet curable resin containing such a phosphate group-containing monomer has a problem that storage stability (pot life) is shortened when it contains a metal, and has adhesion and storage stability. There is a demand for the development of a conductive adhesive using an ultraviolet curable resin, which is excellent in terms of quality.

Japanese Unexamined Patent Publication No. 2003-304003 Japanese Unexamined Patent Publication No. 2015-0533316 Japanese Unexamined Patent Publication No. 09-263744

Therefore, an object of the present invention is to provide a conductive adhesive using an ultraviolet curable resin, which has excellent adhesion and storage stability, and an adhesive structure and electronic components using the conductive adhesive. To provide.

As a result of diligent research in view of the above problems, the present inventors have made a conductive adhesive using an ultraviolet curable resin containing a phosphate group-containing monomer containing a polyester resin soluble in an organic solvent. The present invention has been completed by finding that it has excellent adhesion and storage stability.

That is, the first invention provided by the present invention includes (meth) acrylate (A), photopolymerization initiator (B), phosphate group-containing monomer (C), polyester resin (D) soluble in an organic solvent, and It is a conductive adhesive containing conductive particles (E).

Further, the second invention to be provided by the present invention is an adhesive structure in which members to be adhered to each other are adhered to each other via the conductive adhesive of the first invention.

According to the present invention, it is possible to provide a conductive adhesive using an ultraviolet curable resin, which has excellent adhesion and storage stability.

It is sectional drawing which shows the structure of the electronic component mounted on the substrate by the mounting method of the electronic component using the conductive adhesive of this invention. It is a schematic diagram which shows an example of the structure of the apparatus used in the mounting method of the electronic component using the conductive adhesive of this invention. It is a bottom view of the irradiation member of the apparatus used in the method of mounting an electronic component using the conductive adhesive of this invention. It is a top view which shows the structure of the electronic component mounted on the substrate by the method of mounting an electronic component using the conductive adhesive of this invention. It is sectional drawing for demonstrating the non-irradiation region which is not directly irradiated with ultraviolet-visible light when mounting an electronic component on a substrate by the method of mounting an electronic component using the conductive adhesive of this invention. It is sectional drawing for demonstrating the non-irradiation region which is not directly irradiated with ultraviolet-visible light when another electronic component is mounted on a substrate by the method of mounting an electronic component using the conductive adhesive of this invention.

Hereinafter, the present invention will be described based on preferred embodiments.
The conductive adhesive of the present invention includes a (meth) acrylate (A), a photopolymerization initiator (B), a phosphate group-containing monomer (C), and a polyester resin (D) soluble in an organic solvent (hereinafter, simply ". It may be referred to as "polyester resin (D)") and conductive particles (E). In other words, an ultraviolet curable resin composed of (meth) acrylate (A), a photopolymerization initiator (B) and a phosphate group-containing monomer (C) (hereinafter, may be simply referred to as "ultraviolet curable resin"). A conductive adhesive containing the polyester resin (D) and the conductive particles (E).

[(Meta) Acrylate (A)]
The (meth) acrylate (A) according to the conductive adhesive of the present invention is cured by irradiation with ultraviolet-visible light and becomes the main agent of the ultraviolet curable resin, and has at least a (meth) acryloyl group. It is a compound having one. The (meth) acrylate (A) may be a monomer or an oligomer, but is preferably a monomer.
In the present invention, "(meth) acrylate" is a concept including acrylate and methacrylate, that is, acrylic acid ester and methacrylic acid ester.

As the (meth) acrylate monomer, a compound having one (meth) acryloyl group (hereinafter, may be referred to as “monofunctional (meth) acrylic monomer”), and a compound having two or more (meth) acryloyl groups. (Hereinafter, it may be referred to as "polyfunctional (meth) acrylic monomer"). In the present invention, known (meth) acrylates can be used without particular limitation.

Examples of the monofunctional (meth) acrylic monomer include a ring structure such as an alkyl (meth) acrylate, an alkoxyalkyl (meth) acrylate, a (meth) acrylate having an amino group, an aliphatic ring, an aromatic ring, and a heterocyclic ring. Examples thereof include (meth) acrylate having (meth) acrylate and (meth) acrylate having a hydroxyl group.

Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, amyl (meth) acrylate, and isobutyl (meth) acrylate. Acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl ( Meta) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, cetyl (meth) Examples thereof include acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, and isomyristyl (meth) acrylate.

Examples of the alkoxyalkyl (meth) acrylate include methoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, 2-ethylhexyl carbitol (meth) acrylate, and ethoxyethoxyethyl (meth) acrylate. ) Acrylate, butoxyethyl (meth) acrylate, methoxyethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, ethoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxy Polypropylene glycol (meth) acrylate and the like can be mentioned.

Examples of the (meth) acrylate having an amino group include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 7-amino-3,7-dimethyloctyl (meth) acrylate, dimethylacrylamide, diethylacrylamide, and hydroxy. Examples thereof include ethyl acrylamide, acryloyl morpholine, isopropyl acrylamide, dimethylaminoprolyl acrylamide and the like.

Examples of the (meth) acrylate having a ring structure such as an aliphatic ring, an aromatic ring and a heterocyclic ring include tricyclodecane (meth) acrylate, dicyclopentenyl (meth) acrylate, isobolonyl (meth) acrylate, and adamantyl (meth). ) Acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, morpholine acrylate, phenylglycidyl (meth) acrylate, acryloyloxyethyl hexahydrophthalimide, (2-methyl-2-ethyl-) 1,3-Dioxolan-4-yl) methyl acrylate, tetrahydrofurfuryl acrylate and the like can be mentioned.
In addition, alkylene oxide-modified products of these (meth) acrylates can also be used.

Examples of the (meth) acrylate having a hydroxyl group include (meth) acrylate in which a hydroxyl group is bonded to an aliphatic group having 2 to 9 carbon atoms. Substituents such as phenoxy groups may be attached to the (meth) acrylate. Examples of the (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxy-3-phenoxypropyl (meth) acrylate. Can be mentioned.

The polyfunctional (meth) acrylic monomer includes a bifunctional (meth) acrylic monomer and a trifunctional or higher functional (meth) acrylic monomer. Examples of the bifunctional (meth) acrylic monomer include (meth) acrylate compounds of aliphatic diols having 4 to 9 carbon atoms, alkylene oxide type (meth) acrylate compounds, and (meth) acrylate compounds having a ring structure. Can be mentioned.

Examples of the acrylate compound of the aliphatic diol having 4 to 9 carbon atoms include neopentyl glycol di (meth) acrylate and 1,6-hexanediol di (meth) acrylate. The (meth) acrylate of these aliphatic diols may be modified with an aliphatic ester or an alkylene oxide. Examples of the aliphatic ester-modified (meth) acrylate compound include neopentyl glycol hydroxypivalate di (meth) acrylate and caprolactone-modified neopentyl glycol hydroxypivalate di (meth) acrylate. Examples of the alkylene oxide-modified (meth) acrylate compound include diethylene oxide-modified neopentyl glycol di (meth) acrylate, dipropylene oxide-modified neopentyl glycol di (meth) acrylate, and diethylene oxide-modified 1,6-hexanediol di (meth). ) Acrylate and dipropylene oxide-modified 1,6-hexanediol di (meth) acrylate and the like can be mentioned.

Examples of the alkylene oxide type (meth) acrylate compound include neopentyl glycol-modified trimethylolpropane di (meth) acrylate, polyethylene glycol di (meth) acrylate, and polypropylene glycol di (meth) acrylate.

Examples of the (meth) acrylate compound having a ring structure include trimethylolpropane di (meth) acrylate and dicyclopentanyldi (meth) acrylate.

Examples of the trifunctional or higher functional (meth) acrylic monomer include trimethylpropantri (meth) acrylate, pentaerythritol tri (meth) acrylate, and aliphatic modified dipentaerythritol penta (meth) acrylate having 2 to 5 carbon atoms. Aliper-modified dipentaerythritol tetra (meth) acrylate having 2 to 5 carbon atoms, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, pentaerythritol tetra (Meta) Acrylate, Tris [(Meta) Acryloxyethyl] Isocyanurate, Caprolactone Modified Tris [(Meta) Acryloxyethyl] Isocyanurate and Ditrimethylol Propantetra (Meta) Acrylate, Trimethylol Prohantriacrylate, Trimethylol Examples thereof include propanepropylene oxide-modified triacrylate, ethoxylated glycerin triacrylate, and isocyanurate ethylene oxide-modified di and triacrylate.

In the present invention, it is preferable to use a monofunctional (meth) acrylic monomer and a polyfunctional (meth) acrylic monomer in combination from the viewpoint of hardness, heat resistance and shrinkage of the cured product. In this case, the blending ratio of the polyfunctional (meth) acrylic monomer is preferably 5 to 80 parts by mass with respect to 100 parts by mass of the monofunctional (meth) acrylic monomer, and the flexibility is preferably 10 to 60 parts by mass. It is more preferable from the viewpoint of the balance between shrinkage and shrinkage.

In the present invention, the (meth) acrylate monomer and the (meth) acrylate oligomer can be used in combination as the (meth) acrylate (A) in order to improve the adhesion to the substrate.

The (meth) acrylate oligomer used in the present invention is preferably one that dissolves in the above (meth) acrylate monomer, and examples of such oligomers include epoxy (meth) acrylate, polyester (meth) acrylate, and urethane (meth) acrylate. And so on. In the present invention, the oligomer means an oligomer having a molecular weight of 500 or more.

Epoxy (meth) acrylate is obtained by the reaction of epoxy resin and (meth) acrylic acid. Examples of the epoxy resin include bisphenol type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, and novolak type epoxy resins.

Polyester (meth) acrylate is obtained by reacting polyester polyol with (meth) acrylic acid. The polyester polyol is obtained by reacting a polyhydric alcohol with a polybasic acid. Examples of the polyhydric alcohol include neopentyl glycol, ethylene glycol, propylene glycol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, tricyclodecanedimethylol and bis (hydroxymethyl) cyclohexane. Examples of the polybasic acid include succinic acid, phthalic acid, hexahydrophthalic anhydride, terephthalic acid, adipic acid, azelaic acid, tetrahydrophthalic anhydride and the like.

Urethane (meth) acrylate is produced by a three-component reaction of a polyol, an organic polyisocyanate, and a hydroxy (meth) acrylate compound, or a two-component reaction of an organic polyisocyanate and a hydroxy (meth) acrylate compound without using a polyol. It is what you get. Examples of the polyol include polyether polyols such as polypropylene glycol and polytetramethylene glycol, polyester polyols obtained by reacting the polyhydric alcohol with the polybasic acid, and the polyhydric alcohol, the polybasic acid, and ε-caprolactone. Examples thereof include a caprolactone polyol obtained by the reaction and a polycarbonate polyol (for example, a polycarbonate polyol obtained by the reaction of 1,6-hexanediol and diphenyl carbonate). Examples of the organic polyisocyanate include isophorone diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, xylene diisocyanate, diphenylmethane-4,4'-diisocyanate and dicyclopentanyl diisocyanate.

As these (meth) acrylate monomers and (meth) acrylate oligomers, only one kind may be used, or two or more kinds may be mixed and used at an arbitrary ratio.

Further, in the present invention, these (meth) acrylate monomers and (meth) acrylate oligomers, (meth) acrylate having an amino group, N-acryloyloxyethyl hexahydrophthalimide, isocyanurate ethylene oxide-modified di and triacrylate, It is preferable to use a (meth) acrylic monomer containing a nitrogen atom such as urethane (meth) acrylate and / or a (meth) acrylate oligomer in combination from the viewpoint of further improving adhesion, heat resistance and hardness. When a (meth) acrylic monomer containing a nitrogen atom and / or a (meth) acrylate oligomer is used in combination, the blending ratio of the (meth) acrylic monomer containing a nitrogen atom is 15% by mass in the (meth) acrylate (A). It is preferably about 95% by mass, and preferably 20 to 80% by mass from the viewpoint of further improving the adhesion.

The blending amount of the (meth) acrylate (A) in the conductive adhesive is preferably 15 to 95% by mass, more preferably 30 to 90% by mass from the viewpoint of curability and adhesion.

[Photopolymerization Initiator (B)]
The photopolymerization initiator (B) according to the conductive adhesive of the present invention is a component that efficiently photocures the ultraviolet curable resin. The photopolymerization initiator (B) that can be used in the present invention is not particularly limited, and is, for example, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -1-butanone, 2- (dimethylamino). -2-[(4-Methylphenyl) methyl]-[4- (4-morpholinyl) phenyl] -1-butanone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1- On, benzophenone, methylbenzophenone, o-benzoylbenzoic acid, benzoylethyl ether, 2,2-diethoxyacetophenone, 2,4-diethylthioxanthone, diphenyl- (2,4,6-trimethylbenzoyl) phosphine oxide, ethyl- ( 2,4,6-trimethylbenzoyl) phenylphosphinate, 4,4'-bis (diethylamino) benzophenone, 1-hydroxycyclohexyl-phenylketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1, -[4- (2-Hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one, 2,2-dimethoxy-2-phenylacetophenol and 1- [4- (2-) Hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one and other alkylphenone-based photopolymerization initiators, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide and diphenyl (2,4,6-trimethylbenzoyl) Acylphosphine oxide-based photopolymerization initiators such as 2,4,6-trimethylbenzoyl) phosphine oxide, 1,2-octanedione, 1- [4- (phenylthio) -2- (O-benzoyloxime)], etc. Examples thereof include an oxime ester-based photopolymerization initiator and a sulfonium salt-based photopolymerization initiator. Only one of these photopolymerization initiators may be used, or two or more of these photopolymerization initiators may be mixed and used at an arbitrary ratio.

In the present invention, it is preferable to use an alkylphenone-based photopolymerization initiator as the photopolymerization initiator (B) from the viewpoint of curability, and it is particularly preferable to use 1-hydroxycyclohexyl-phenylketone.

The amount of the photopolymerization initiator (B) used is preferably 0.5 to 15 parts by mass with respect to 100 parts by mass of the (meth) acrylate (A), and it is preferably 1 to 12 parts by mass from the viewpoint of curability. Therefore, it is more preferable.

[Phosphate group-containing monomer (C)]
The phosphoric acid group-containing monomer (C) according to the conductive adhesive of the present invention is a component that contributes to improving the adhesion of the ultraviolet curable resin. The phosphoric acid group-containing monomer (C) that can be used in the present invention is not particularly limited, and may be any monomer that is polymerizable and has a phosphoric acid group.

Examples of the phosphoric acid group-containing monomer (C) include 2-methacryloyloxyethyl acid phosphate, di-2-methacryloyloxyethyl acid phosphate, 3-methacryloyloxypropyl acid phosphate, and di-3-methacryloyloxypropyl. Examples thereof include acid phosphate, ethylene oxide-modified dimethacrylate phosphate, phosphate (meth) acrylates such as phosphoric acid-containing epoxy methacrylate, and vinyl phosphate compounds such as vinylphosphonic acid.

As the phosphoric acid group-containing monomer (C), a phosphoric acid (meth) acrylate represented by the following general formula (1) or (2) is preferable.

(In the formula, R ¹ represents a hydrogen atom or a methyl group. A represents a linear or branched alkylene group having 1 to 4 carbon atoms. M represents an integer of 1 to 4, preferably 1 to 2. .)

As these phosphoric acid group-containing monomers, only one kind may be used, or two or more kinds may be mixed and used at an arbitrary ratio.

The blending amount of the phosphoric acid group-containing monomer (C) is preferably 0.5 to 50 parts by mass with respect to 100 parts by mass of the (meth) acrylate (A), and 3 to 30 parts by mass improves the adhesion. It is more preferable from the viewpoint of making it.

[Polyester resin (D)]
The polyester resin (D) according to the conductive adhesive of the present invention is a component that imparts storage stability to the conductive adhesive containing the ultraviolet curable resin and conductive particles. The present inventors have excellent solubility and compatibility of the polyester resin (D) soluble in an organic solvent with respect to the main component (meth) acrylate (A), and further have conductivity with the above-mentioned ultraviolet curable resin. It has been found that an excellent storage stability can be imparted to a conductive adhesive containing particles.
The polyester resin that can be used in the present invention may be any one that is soluble in an organic solvent, and can be obtained, for example, by polymerizing a polyvalent carboxylic acid component and a glycol component.

The polyvalent carboxylic acid component consists of a group consisting of a divalent or higher polyvalent carboxylic acid and an ester-forming derivative in which the carboxyl group in the polyvalent carboxylic acid is replaced with an ester-forming inducer derived from the carboxyl group. One or more selected.

Examples of the polyvalent carboxylic acid component include aromatic dicarboxylic acids and aliphatic dicarboxylic acids. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, diphenylic acid, naphthalic acid, 1,2-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2, Examples of the aliphatic dicarboxylic acid include 6-naphthalenedicarboxylic acid and the like, and examples of the aliphatic dicarboxylic acid include linear, branched or alicyclic oxalic acid, malonic acid, succinic acid, maleic acid, itaconic acid, glutaric acid and adipic acid. , Pimeric acid, 2,2-dimethylglutaric acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, diglycolic acid, thiodipropion Examples include acids.

Examples of the polyvalent carboxylic acid component include dicarboxylic acids having a metal sulfonate group, tribasic acid anhydrides, tetravalent or higher polyvalent carboxylic acids such as tetrabasic acid anhydrides, and ester-forming derivatives thereof. Be done. Examples of the dicarboxylic acid having a metal sulfonate group and its ester-forming derivative (hereinafter, collectively referred to as a dicarboxylic acid having a metal sulfonate group) include 5-sulfoisophthalic acid, 2-sulfoisophthalic acid, and 4-sulfo. Examples thereof include alkali metal salts such as isophthalic acid, sulfoterephthalic acid and 4-sulfonaphthalene-2,6-dicarboxylic acid and ester-forming derivatives thereof. Examples of trivalent or higher valent carboxylic acids and ester-forming derivatives thereof include hemmellitic acid, trimellitic acid, trimedic acid, melophonic acid, pyromellitic acid, benzenepentacarboxylic acid, merit acid, and cyclopropane-. Examples thereof include 1,2,3-tricarboxylic acid, cyclopentane-1,2,3,4-tetracarboxylic acid, ethanetetracarboxylic acid and ester-forming derivatives thereof. The polyvalent carboxylic acid component can be used alone or in combination of two or more.

Examples of the glycol component include polyethylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, heptaethylene glycol and octaethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol. , Polypropylene glycol such as tetrapropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl- 1,3-Propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 2,2,4-trimethyl-1,6-hexane Diol, 1,2-Cyclohexanedimethanol, 1,3-Cyclohexanedimethanol, 1,4-Cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4'-dihydroxy Biphenol, 4,4'-methylenediphenol, 4,4'-isopropyridenediphenol, 1,5-dihydroxynaphthalin, 2,5-dihydroxynaphthalin, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) ), Bisphenol S and the like. The glycol component can be used alone or in combination of two or more.

In the present invention, "soluble in an organic solvent" means that it dissolves in 5 parts by mass or more with respect to 100 parts by mass of an organic solvent at room temperature (25 ° C.).
Examples of the organic solvent include alcohol solvents such as methanol, ethanol and isopropyl alcohol, ester solvents such as ethyl acetate, butyl acetate, isobutyl acetate and γ-butyrolactone, and ketone solvents such as acetone, cyclohexanone, methyl ethyl ketone and methyl isobutyl ketone. Solvents, cellosolve solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, glycol ester solvents such as ethylene glycol monoethyl ether acetate and propylene glycol monomethyl ether acetate, hexane, heptane, cyclohexane, toluene, Hydrocarbon solvents such as xylene, halogen solvents such as dichloromethane, chloroform, orthodichlorobenzene, tetrahydrofuran, acetonitrile, dimethylsulfoxide, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, etc. Can be mentioned.

In the present invention, from the viewpoint of adhesion and storage stability, the polyester resin (D) is UV-cured composed of (meth) acrylate (A), photopolymerization initiator (B) and phosphate group-containing monomer (C). It is preferably soluble in the mold resin.

In the present invention, the polyester resin (D) is preferably an amorphous polyester resin from the viewpoint of excellent solubility in (meth) acrylate (A) and excellent transparency. Here, the amorphous polyester resin is a polyester resin that does not have a clear melting point found in crystalline resins because it has almost no regular arrangement of molecular chains and has a low crystallinity.
As the amorphous polyester resin, one having a number average molecular weight (Mw) of 1,000 to 40,000, preferably 1,500 to 30,000 is obtained with solubility in (meth) acrylate (A). It is preferable from the viewpoint of adhesion of the conductive adhesive.
The glass transition temperature (Tg) of the amorphous polyester is preferably −20 ° C. to 50 ° C., and more preferably −10 ° C. to 20 ° C. from the viewpoint of adhesion. If the glass transition temperature is excessively low, the adhesiveness may become strong, and if the glass transition temperature is excessively high, the adhesiveness may decrease.

As the polyester resin (D), a known one can be used, or a commercially available product may be used. Examples of commercially available products include Toyobo's Byron 550, 670, GK680, GK780, GK810, GK890, BX1001, Unitika's Elitel UE-3220, UE-3300, UE-3500, UE-3210, UE-3320 and the like. Be done.
The blending amount of the polyester resin (D) is preferably 10 to 2000 parts by mass, and 50 to 400 parts by mass with respect to 100 parts by mass of the phosphoric acid group-containing monomer (C) from the viewpoint of storage stability and adhesion. Therefore, it is more preferable.

[Conductive particles (E)]
The conductive particles (E) according to the conductive adhesive of the present invention are components that impart conductivity. In the present invention, as the conductive particles (E), known particles used in a conductive adhesive, an anisotropic conductive film, and an anisotropic conductive adhesive can be used. Examples of the conductive particles (E) include metal particles such as gold, silver, copper, nickel, palladium, and solder, those having conductivity by themselves such as carbon particles, and conductive metals on the surface of the core material particles. Examples thereof include conductive particles coated with.

The size of the conductive particles may be appropriately selected according to the specific use of the conductive adhesive of the present invention, but when used as a conductive material for connecting an electronic circuit, the particle size is too small. Conduction between the counter electrodes becomes impossible, while if it is too large, a short circuit occurs between the adjacent electrodes. Therefore, the average particle size of the conductive particles is preferably 0.1 to 1000 μm, particularly preferably 0.5 to 100 μm, as a value measured by the electric resistance method.

The shape of the conductive particles is not particularly limited, but is generally powdery and granular, and may have other shapes such as fibrous, hollow, plate-like, and needle-like, and has a large number of protrusions on the particle surface. It may be a thing or an irregular shape. From the viewpoint of dispersibility, the shape of the conductive particles is preferably spherical.

When the conductive adhesive of the present invention is used as an anisotropic conductive adhesive, the conductive particles (E) are preferably metal-coated particles in which the surface of the core material particles is coated with a conductive metal.

The core material particles can be used without particular limitation regardless of whether they are inorganic or organic. Examples of the inorganic core material particles include metal particles such as gold, silver, copper, nickel, palladium, and solder, alloys, glass, ceramics, silica, metal or non-metal oxides (including hydrous substances), and aluminosilicates. Examples thereof include metal silicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal acid salts, metal halides and carbons. Examples of the organic core particles include thermoplastic resins such as natural fibers, natural resins, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic acid ester, polyacrylic nitrile, polyacetal, ionomer, and polyester. Examples thereof include alkyd resin, phenol resin, urea resin, benzoguanamine resin, melamine resin, xylene resin, silicone resin, epoxy resin and diallyl phthalate resin. It is preferable to use a resin as the core material particles because the specific gravity of the metal-coated particles becomes lighter, so that they do not easily settle, the dispersion stability becomes good, and the electrical connection can be maintained by the elasticity of the resin.

The shape of the core material particles is not particularly limited, but is generally powdery and granular, and may have other shapes such as fibrous, hollow, plate-like, and needle-like, and has a large number of protrusions on the particle surface. It may be a thing or an irregular shape. From the viewpoint of dispersibility, the shape of the conductive particles is preferably spherical.

The size of the core material particles is preferably 0.1 to 1000 μm, particularly preferably 0.5 to 100 μm, as a value measured by the electric resistance method. If the particle size is too small, conduction between the counter electrodes will not be possible, while if it is too large, a short circuit will occur between the adjacent electrodes.

As a method of coating the surface of the core material particles with a conductive metal, a dry method such as a vapor deposition method, a sputtering method, a mechanochemical method, a hybridization treatment, an electrolytic plating method, a wet method such as an electrolytic plating method, etc. , Or a method combining these can be used.

The metal-coated particles are preferably coated with one or more conductive metals selected from gold, silver, copper, nickel, palladium, solder and the like, and in particular, the surface of the core material particles is electroless. Metal-plated particles having a metal film formed by plating are preferable in that the surface of the particles can be uniformly and densely coated, and those in which the metal film is gold or palladium are particularly preferable in that the conductivity can be increased. The metal film may be an alloy (for example, a nickel-phosphorus alloy or a nickel-boron alloy).

The blending amount of the conductive particles (E) is preferably 2 to 40 parts by mass, more preferably 3 to 25 parts by mass, still more preferably 5 to 20 parts by mass with respect to 100 parts by mass of the (meth) acrylate (A). When the amount of the conductive particles (E) used is within the above range, the connection resistance is suppressed from being increased and the connection reliability is improved.

In addition to the conductive adhesive according to the present invention, an additive known in the art can be used, and the amount of the additive can be contained in an amount within a range in which ultraviolet visible light can reach the inside. Examples of other additives include a photosensitizer, a defoaming agent, a thixotropic agent, a viscosity modifier, a leveling powder, a silane coupling agent, a stabilizer, an ion exchanger and the like. In addition, a solvent can be contained if necessary.

The conductive adhesive of the present invention can be cured by irradiating with ultraviolet-visible light. The wavelength range of ultraviolet-visible light is preferably 100 to 700 nm, more preferably 150 to 500 nm, and even more preferably 180 to 400 nm.

As a method for adhering electronic components using the conductive adhesive of the present invention, a known method can be used. For example, the conductive adhesive of the present invention is applied to the surface of a transparent substrate on which an electrode is formed. , Slit coater, roll coater, spin coater, screen printing method, metal mask printing method, dispenser, jet dispenser, etc. The electronic component can be adhered by placing the electronic component on the substrate so that a part of the electronic component is located above the electrode and irradiating the transparent substrate side with ultraviolet visible light.

Dose of ultraviolet-visible light is preferably 50 ~ 20,000mJ / cm ^2, particularly preferably 300 ~ 10,000mJ / cm ^2. In the curing by irradiation with ultraviolet visible light, the light source does not matter as long as the lamp irradiates ultraviolet to near-ultraviolet rays. Examples of the light source include low-voltage, high-pressure or ultra-high-voltage mercury lamps, metal halide lamps, (pulse) xenon lamps, electrodeless lamps, LEDs, and the like.

The conductive adhesive according to the present invention can be used as an anisotropic conductive adhesive, and can be connected with high reliability to the electrode connection of electronic parts such as IC chips and light emitting diodes to be miniaturized and circuit boards. ..

Examples of the adhesive structure in which the members to be adhered are bonded to each other via the conductive adhesive of the present invention include RFID-related products such as IC cards and IC tags in which an IC chip is bonded to a substrate having an electrode. Examples thereof include light emitting electronic components in which a light emitting diode is adhered to a substrate having an electrode.

As the adhesive structure according to the present invention, for example, the electronic component mounted on the substrate shown in FIG. 1 can be exemplified.
An aluminum antenna 2 as an electrode is formed on a surface 1a which is one surface of a substrate 1 such as a film or paper. The conductive adhesive 3 of the present invention is applied to the surface 1a in a range including at least the entire aluminum antenna 2, and is cured by ultraviolet-visible light. On the substrate 1, an electronic component having a metal electrode 5, that is, an IC chip 4, which is a semiconductor, is placed on the surface 1a so that the metal electrode 5 is located above the aluminum antenna 2. The IC chip 4 is adhered to the surface 1a side of the substrate 1 by the conductive adhesive 3 (including the conductive particles 6) of the present invention. The aluminum antenna 2 and the metal electrode 5, that is, the IC chip 4 are configured to be energized via the conductive particles 6.

Among the methods for mounting electronic components using the conductive adhesive of the present invention, as a particularly preferable method, adhesion containing a resin that is cured by irradiating the surface of a substrate on which an electrode is formed with ultraviolet visible light. A step of applying the agent, a step of placing the electronic component on the substrate so that a part of the electronic component is located above the electrode, and a step of irradiating the substrate with ultraviolet visible light perpendicularly. In the method for mounting an electronic component including, a non-transmissive portion that does not transmit ultraviolet visible light exists on the surface side of the substrate, and the length of the short side of the circumscribing rectangle of the non-transmissive portion is set to 2 mm or less. , Before the step of irradiating the ultraviolet visible light, or at the same time as the step, a method of pressurizing the substrate with a transparent or translucent flat plate member capable of transmitting the ultraviolet visible light can be mentioned (Japanese Patent Laid-Open No. 2015-). 53316 (see).

FIG. 2 shows an example of an apparatus for mounting an electronic component using the conductive adhesive of the present invention.
The device 30 for mounting the electronic component of FIG. 2 has a heat table 31 which is a heating member for mounting the substrate 1 and heating the substrate 1, an irradiation member 32 for irradiating ultraviolet visible light, and a heat table for the irradiation member 32. It includes a drive device 33 that moves toward or away from the heat table 31, and a control unit 34. The control unit 34 is electrically connected to the heat table 31, the irradiation member 32, and the drive device 33, respectively.

FIG. 3 shows the configuration of the contact surface 35 in which the irradiation member 32 contacts the substrate 1 (see FIG. 2). The contact surface 35 is composed of a transparent or translucent flat plate member 36 capable of transmitting ultraviolet visible light, and the light source 37 of ultraviolet visible light provided inside the irradiation member 32 can be seen through the plate member 36. It has become like. The light source 37 is adapted to irradiate ultraviolet-visible light by supplying power from the control unit 34 (see FIG. 2). As the light source 37, an LED, a metal halide lamp, a xenon lamp, a pressurized mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a carbon arc lamp, or any other light source that emits light having a light emission distribution at a wavelength of 100 to 700 nm is used. Can be done.

Next, a mounting method using the device 30 for mounting the above-mentioned electronic components will be described.
The planar shape of the IC chip 4 may be any shape, but here, it will be described as having an elliptical shape as shown in FIG. The IC chip 4 mounted on the substrate 1 is used for RFID-related products such as IC cards and IC tags. Further, the light emitting diode 14 mounted on the substrate 1 is used for a light emitting electronic component.

Assume an circumscribed rectangle 20 to which the IC chip 4 circumscribes when the IC chip 4 is viewed from a direction perpendicular to the substrate 1. The circumscribing rectangle 20 has two long sides 21 parallel to each other and two short sides 22 parallel to each other, and the length of the short sides 22 is 2 mm or less, preferably 1.5 mm or less. .. When the circumscribed rectangle is a square, the lengths of the long side and the short side are the same, so that the length of one side may be 2 mm or less, preferably 1.5 mm or less. Since the IC chip 4 does not transmit ultraviolet visible light, as shown in FIG. 5, the region where the IC chip 4 is projected in the direction perpendicular to the substrate 1 (the shaded area) is the region where the ultraviolet visible light is transmitted to the substrate 1. When irradiated perpendicularly to the conductive adhesive 3, the ultraviolet-visible light is not directly irradiated to the conductive adhesive 3 (not shown in FIG. 5), that is, the non-irradiated region 23. Since the short side 22 (see FIG. 4) of the circumscribing rectangle 20 of the IC chip 4 is 2 mm or less, preferably 1.5 mm or less, the width W of the non-transparent portion in the direction parallel to the short side 22 is the entire IC chip 4. It is 2 mm or less, preferably 1.5 mm or less.

On the other hand, as shown in FIG. 6, when the light emitting diode 14 made of a transparent material is mounted on the substrate 1 as an electronic component, the ultraviolet visible light emitted perpendicularly to the substrate 1 is transmitted through the light emitting diode 14. Then, the conductive adhesive 3 (not shown in FIG. 6) is irradiated with the conductive adhesive 3. However, even if the light emitting diode 14 is transparent, the metal electrode 5 is not transparent, and ultraviolet visible light does not pass through the metal electrode 5, so that the metal electrode 5 becomes a non-transmissive portion and the metal is formed in a direction perpendicular to the substrate 1. The region where the electrode 5 is projected (the shaded area) is the non-irradiated region 23. In this case, if the length of the short side of the circumscribing rectangle of the metal electrode 5 is 2 mm or less, preferably 1.5 mm or less, the width W'of the non-transmissive portion in the direction parallel to the short side of the circumscribing rectangle of the metal electrode 5. Is 2 mm or less, preferably 1.5 mm or less over the entire metal electrode 5. That is, as shown in FIG. 5, when an electronic component such as the IC chip 4 that does not transmit ultraviolet visible light is mounted on the substrate 1, the IC chip 4 becomes a non-transmissive portion that does not transmit ultraviolet visible light. As shown in FIG. 6, when an electronic component that transmits ultraviolet visible light such as a light emitting diode 14 is mounted on the substrate 1, the metal electrode 5 of the light emitting diode 14 is a non-transmissive portion that does not transmit ultraviolet visible light. It becomes.

As shown in FIG. 2, the substrate 1 is placed on the heat table 31. An aluminum antenna 2 is already formed on the surface 1a of the substrate 1, a conductive adhesive 3 is applied to a range including at least the entire aluminum antenna 2, and an IC is provided so that the metal electrode 5 is located above the aluminum antenna 2. The chip 4 is placed. Before placing the substrate 1 on the heat table 31, the control unit 34 may preheat the heat table 31 to an appropriate temperature in the range of 15 to 100 ° C. After placing the substrate 1 on the heat table 31, the control unit 34 activates the drive device 33 to move the irradiation member 32 toward the heat table 31, and moves the substrate 1 to the heat table 31 and the irradiation member 32. Sandwiched by. Further, the control unit 34 irradiates the irradiation member 32 with ultraviolet visible light, and pressurizes the substrate 1 by the heat table 31 and the irradiation member 32. The pressure applied at this time is appropriately set in the range of ^{0.01 to 500 N / mm 2} , more preferably in the range of 0.03 to 300 N / mm ^2. During this pressurization, the conductive adhesive 3 is cured by irradiating the conductive adhesive 3 with ultraviolet visible light. After pressurizing and heating the conductive adhesive 3 for a time sufficient to completely cure, the control unit 34 moves the irradiation member 32 away from the heat table 31 by the driving device 33, and uses the heat table 31. By completing the heating and irradiation of ultraviolet visible light from the irradiation member 32, the mounting of the IC chip 4 on the substrate 1 is completed.

In this embodiment, the IC chip 4 and the light emitting diode 14 have been described as examples of electronic components, but the present invention is not limited to these. Any electronic component that is adhered by an adhesive that cures when irradiated with ultraviolet-visible light may be used.

In this embodiment, the control unit 34 moves the irradiation member 32 toward the heat table 31, but the present invention is not limited to this embodiment. The irradiation member 32 may be fixed and the heat table 31 may be moved toward the irradiation member 32, or both may be moved toward each other at the same time or alternately.

In this embodiment, when the conductive adhesive 3 is irradiated with ultraviolet-visible light, it is also heated by the heat table 31, but the present invention is not limited to this embodiment. Since this heating is performed to accelerate the curing reaction of the conductive adhesive 3, instead of the heat table 31, a simple fixing table that does not heat is used to irradiate only ultraviolet visible light. May be good.

In this embodiment, the substrate 1 is placed on the heat table 31, but the present invention is not limited to this embodiment. The irradiation member 32 may be arranged so that the contact surface 35 faces upward, and the substrate 1 may be placed on the contact surface 35. In this case, the heat table 31 may be arranged above the irradiation member 32, and the heat table 31 may be moved toward the irradiation member 32, or the irradiation member 32 may be moved toward the heat table 31. Both may be moved toward each other at the same time or alternately.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.

[(Meta) Acrylate (A)]
As the (meth) acrylate (A), the following commercially available one was used.

[Photopolymerization Initiator (B)]
The following commercially available photopolymerization initiator (B) was used.

[Phosphate group-containing monomer (C)]
As the phosphoric acid group-containing monomer (C), the following commercially available one was used.

[Polyester resin (D)]
As the polyester resin (D), the following commercially available one was used. All of these were dissolved in an amount of 5 parts by mass or more at 25 ° C. with respect to 100 parts by mass of methyl ethyl ketone.

[Conductive particles (E)]
As the conductive particles, gold-plated particles (manufactured by Nippon Kagaku Kogyo Co., Ltd.) having a gold-nickel conductive layer on the surface of the spherical resin particles and having an average particle diameter of 3.0 μm were used.

{Examples 1 to 8 and Comparative Examples 1 to 2}
With the composition shown in Table 5, (meth) acrylate (A), photopolymerization initiator (B), phosphate group-containing monomer (C), polyester resin (D) and Aerosil RX200 as an additive (thixotropic agent: Japan) (Aerosil) was mixed at 25 ° C. for 1 hour using a rotating / revolving vacuum mixer to prepare conductive adhesives of Examples 1 to 8 and Comparative Examples 1 and 2.

<Evaluation of storage stability (pot life)>
5 g of the conductive adhesive was placed in a container, the container was kept at 30 ° C., and the state after 1 day and 3 days was visually observed and the state was evaluated. The results are also shown in Table 5.
The evaluation results of storage stability in the table are as follows.
X: Hardened after 1 day.
〇: No change in condition after 1 day, gel is observed after 3 days.
⊚: No change in condition after 1 day and 3 days.

<Evaluation of adhesion>
After curing, the conductive adhesives prepared in Examples and Comparative Examples were applied to a range including the entire aluminum wiring on a substrate (size: length 2.5 cm, width 8 cm) in which aluminum wiring was formed on a PET film. It was applied by the dispense method so as to have a thickness of 50 μm, and an IC having a gold pump was placed. An adhesive structure for evaluation by irradiating ultraviolet visible light (wavelength 365 nm, illuminance 5,000 mW / cm ² ) for 2 seconds under a pressure of 25 ° C. and 1 N / mm ^{2 to cure the conductive adhesive.} Was produced. The conductive adhesive used was prepared and used within 2 hours.
The die shear strength of the conductive adhesive was measured for the produced adhesive structure. The die shear strength was measured by using a digital force gauge to measure ^{the strength (N / mm 2} ) when the IC chip was peeled off from the substrate. The results are also shown in Table 5. The die-share strength results in the table show the following.
◯: 20 N / mm ² or more ×: 20 N / mm less than ²

The conductive adhesives of Examples 1 to 8 using the phosphoric acid group-containing monomer (C) and the polyester resin (D) were excellent in the adhesiveness of the adhesive structure and had a good pot life. The conductive adhesive of Comparative Example 1 in which the phosphoric acid group-containing monomer (C) was used and the polyester resin (D) was not used had excellent adhesion of the adhesive structure, but had a problem in pot life. The conductive adhesive of Comparative Example 2 in which the phosphoric acid group-containing monomer (C) was not used had generally good pot life, but was inferior in adhesion of the adhesive structure.

1 Substrate 1a (of the substrate) Surface 1b (of the substrate) Bottom surface 2 Aluminum antenna (electrode)
3 Conductive adhesive 4 IC chip (semiconductor, electronic component)
5 Metal electrode 6 Conductive particles 14 Light emitting diode (electronic component)
20 Circumscribed rectangle 21 Long side (of circumscribed rectangle) 22 Short side of (circumscribed rectangle) 23 Non-irradiated area 30 Device 31 Heat table (heating member)
32 Irradiation member 33 Drive device 34 Control unit 35 Contact surface 36 Plate member 37 Light source

Claims (10)

1. (Meta) A conductive adhesive containing an acrylate (A), a photopolymerization initiator (B), a phosphate group-containing monomer (C), a polyester resin (D) soluble in an organic solvent, and conductive particles (E). ..
2. The conductive adhesive according to claim 1, wherein the phosphoric acid group-containing monomer (C) is a phosphoric acid group-containing (meth) acrylate.
3. The conductive adhesive according to claim 1, wherein the content of the phosphoric acid group-containing monomer (C) is 1 to 50 parts by mass with respect to 100 parts by weight of the (meth) acrylate (A).
4. The conductive adhesive according to claim 1, wherein the polyester resin (D) is an amorphous polyester resin.
5. The conductive adhesive according to claim 1, wherein the blending amount of the polyester resin (D) is 10 to 2000 parts by mass with respect to 100 parts by mass of the phosphoric acid group-containing monomer (C).
6. The conductive adhesive according to claim 1, wherein the conductive particles (E) are conductive particles in which the surface of the core material particles is coated with a conductive metal.
7. The conductive adhesive according to any one of claims 1 to 6, which is an anisotropic conductive adhesive.
8. An adhesive structure in which members to be adhered are bonded to each other via the conductive adhesive according to any one of claims 1 to 7.
9. An electronic component using the conductive adhesive according to any one of claims 1 to 7.
10. The electronic component according to claim 9, wherein the electronic component is selected from an IC card, an IC tag, and a light emitting electronic component.

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