JP6710120B2 - Conductive adhesive, electronic component, and method for manufacturing electronic component - Google Patents

Description

The present invention relates to a conductive adhesive, an electronic component and a method for manufacturing an electronic component.

As the density of printed wiring boards has increased due to the recent trend of lighter, thinner, shorter, and smaller electronic devices, as a technique used for electrical connection of electronic components, for example, electrical connection between wiring boards and electronic elements and electrical connection between wiring boards. The development and improvement of conductive adhesives are underway (for example, Patent Documents 1 and 2). The electrically conductive adhesive is applied between members to be electrically connected and thermocompression-bonded to enable electrical connection in a lightweight and space-saving manner.

Although the conductive adhesive itself is insulative, the conductive particles contained in the conductive adhesive are sandwiched between the electrodes and pressed against each other by thermocompression bonding to form a conductive path. Connection is possible. On the other hand, even after the thermocompression bonding, the conductive particles remain dispersed in the region where the electrodes are not sandwiched between the electrodes and the pressure is not applied, so that the insulating property is maintained. As a result, a so-called anisotropic conductive connection structure is obtained.

JP 2012-216770 A JP, 2013-045650, A

The anisotropic conductive connection structure formed using the conductive adhesive as described above, the insulating property is maintained in the region where no pressure is applied, but conductive particles are present in that region Therefore, it has been difficult to provide excellent withstand voltage.

Therefore, an object of the present invention is to provide a conductive adhesive capable of forming an anisotropic conductive connection structure having excellent withstand voltage while maintaining conductivity, and electrically using the conductive adhesive. An object of the present invention is to provide an electronic component including connected members and a method of manufacturing an electronic component using the conductive adhesive.

As a result of intensive studies in view of the above, the present inventors have found that the above problems can be solved by blending conductive particles made of a low melting point metal in a specific blending amount, and have completed the present invention.

That is, the conductive adhesive of the present invention is a conductive adhesive that anisotropically conductively bonds members by thermocompression bonding, and contains heat-meltable conductive particles, wherein the heat-meltable conductive particles are blended. The amount is 0.01 to 4.0% by volume in terms of solid content.

In the conductive adhesive of the present invention, the heat-meltable conductive particles are preferably low melting point solder particles.

The conductive adhesive of the present invention preferably further contains an organic component.

The conductive adhesive of the present invention preferably has an ethylenically unsaturated bond equivalent of 260 to 1,000 in the organic component (excluding the solvent when the solvent is included).

The electronic component of the present invention is characterized by including a member electrically connected using the conductive adhesive.

The method of manufacturing an electronic component of the present invention is characterized in that the conductive adhesive is applied and thermocompression-bonded to anisotropically bond the members to each other.

ADVANTAGE OF THE INVENTION According to this invention, while maintaining electroconductivity, the electroconductive adhesive which can form the anisotropic conductive connection structure excellent in withstand voltage, and electrical conductivity using this electroconductive adhesive. It is possible to provide an electronic component including a member connected to the electronic component and a method for manufacturing the electronic component using the conductive adhesive.

The conductive adhesive of the present invention is a conductive adhesive containing heat-meltable conductive particles (hereinafter, also simply referred to as “conductive particles”) for anisotropically conductively bonding members by thermocompression bonding, The blending amount of the heat-meltable conductive particles is 0.01 to 4.0% by volume in terms of solid content. When the conductive particles were blended in a small amount of 0.01 to 4.0% by volume, it was considered that sufficient conductivity could not be ensured due to a shortage of conductive particles, but in practice, a remarkable decrease in conductivity may occur. It was found that the withstand voltage was improved. Although the detailed mechanism is not clear, the conductive particles between the electrodes are reduced by reducing the blending amount of the conductive particles, but this increases the pressure applied to each conductive particle sandwiched between the electrodes during thermocompression bonding. As a result, the degree of collapse of the conductive particles (one-dimensional contraction in the pressing direction (Z-axis direction) and two-dimensional expansion in the XY direction) increases, and each conductive particle sandwiched between the electrodes contacts the electrode. It is considered that the conductivity was secured because the area to be covered increases. On the other hand, since the conductive particles are mixed in a small amount, the concentration of the conductive particles dispersed in the non-electrical connection portion is reduced, and the insulating property is further increased, and the electrodes between adjacent electrodes in the XY direction are increased. It is considered that the withstand voltage of is improved.
Here, the volume% is calculated by measuring the specific gravity of the composition (adhesive) other than the heat-meltable conductive particles using a 100-ml specific gravity cup in accordance with JIS K-5400 to determine the heat-meltability. It is calculated by the following formula using the true specific gravity of the conductive particles.
(formula)
Concentration of conductive particles (volume %)=100×(blending amount of heat-melting conductive particles/true specific gravity of heat-melting conductive particles)/((blending amount of heat-melting conductive particles/heat-melting conductivity) True specific gravity of particles) + (blending amount of composition other than heat-meltable conductive particles/specific gravity of composition other than heat-meltable conductive particles))

Hereinafter, the components contained in the conductive adhesive of the present invention will be described in detail.

The conductive adhesive of the present invention is not particularly limited as long as it is a resin composition containing 0.01 to 4.0% by volume of the heat-meltable conductive particles in terms of solid content, and as other components, Well-known and commonly used components that can be used for the conductive adhesive may be used. Known and commonly used components include organic components and inorganic components, and organic components can be preferably used. The term "organic component" as used herein means all components other than the inorganic component, and specific examples thereof include a resin component, a peroxide, a wetting dispersant, and a defoaming agent which will be described later. As the resin component for the adhesive, at least one selected from known and commonly used thermosetting, heat-melting, ultraviolet-curing, and moisture-curing resins can be used. Among these resins, thermosetting and ultraviolet curable resins are preferable because they can be easily electrically connected by thermocompression. Examples of thermosetting resins include compounds having an ethylenically unsaturated bond such as acrylate resins, epoxy resins, and the like. Examples of the heat-melt type resin include thermoplastic polyester, polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyamide, polyacetal, polycarbonate, polyphenylene sulfide, and polyether ether ketone. Examples of the ultraviolet curable resin include urethane acrylate, acrylic resin acrylate (that is, acrylate of acrylic copolymer resin), and epoxy acrylate. Examples of moisture-curable resins include moisture-curable polyurethane resins, silicone resins, and cyanoacrylates.
Among them, thermosetting resins are more preferable, and compounds having an ethylenically unsaturated bond are particularly preferable. The thermosetting resin will be described below.

(Compound having an ethylenically unsaturated bond)
By blending a compound having an ethylenically unsaturated bond as a thermosetting resin, it is possible to easily obtain a conductive adhesive that can be thermocompression bonded even at a low temperature of 170° C. or lower and 2 MPa or lower at low pressure.

As the compound having an ethylenically unsaturated bond, a monofunctional or polyfunctional (meth)acryloyl group-containing compound can be preferably used. In the present specification, the (meth)acryloyl group is a general term for an acryloyl group and a methacryloyl group, and the same applies to other similar expressions.

Examples of such (meth)acryloyl group-containing compounds include substituted or unsubstituted aliphatic acrylates, alicyclic acrylates, aromatic acrylates, heterocycle-containing acrylates, and ethylene oxide-modified acrylates, epoxy acrylates, aromatics thereof. Group urethane acrylates, aliphatic urethane acrylates, polyester acrylates, polyether acrylates, polyol acrylates, alkyd acrylates, melamine acrylates, silicone acrylates, polybutadiene acrylates, and their corresponding methacrylates can be used.

More specifically, examples of the monofunctional (meth)acryloyl group-containing compound include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hydroxyethyl (meth)acrylate, and 4-hydroxybutyl (meth). ) Acrylate, hydroxypropyl (meth)acrylate, butoxymethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, isodecyl (meth)acrylate, glycerol mono (meth)acrylate and other aliphatic (meth)acrylates Alicyclic (meth)acrylates such as acrylate, cyclohexyl (meth)acrylate, 4-(meth)acryloxytricyclo[5.2.1.02,6]decane, isobornyl (meth)acrylate, phenoxyethyl (meth) Aromatic (meth)acrylates such as acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, modified (meth)acrylates such as aliphatic epoxy-modified (meth)acrylate, Tetrahydrofurfuryl (meth)acrylate, (meth)acryloyloxyethylphthalic acid, γ-(meth)acryloxyalkyltrialkoxysilane and the like can be used.

As the polyfunctional (meth)acryloyl group-containing compound, bisphenol-A-di(meth)acrylate, alkylene oxide-modified bisphenol-A-di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene Glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, bis[4-(meth)acryl Roxymethyl]tricyclo[5.2.1.02,6]decane, bis[4-(meth)acryloxy-2-hydroxypropyloxyphenyl]propane, isophorone diisocyanate-modified urethane (meth)acrylate, hexamethylene diisocyanate-modified urethane ( It is possible to use (meth)acrylate, oligosiloxanyl di(meth)acrylate, trimethylhexamethylene diisocyanate-modified urethane (meth)acrylate, triallyl isocyanurate, vinyl (meth)acrylate, allyl (meth)acrylate and the like.

In addition, the following compounds can also be used.
(1) Liquid polybutadiene urethane (meth)acrylate obtained by subjecting 2-hydroxyethyl (meth)acrylate to a urethane addition reaction with a hydroxyl group of liquid polybutadiene via 2,4-tolylene diisocyanate,
(2) Liquid polybutadiene acrylate obtained by esterifying 2-hydroxy acrylate with maleic polybutadiene to which maleic anhydride is added,
(3) Liquid polybutadiene (meth)acrylate obtained by an epoxy esterification reaction of a carboxyl group of polybutadiene and glycidyl (meth)acrylate,
(4) Liquid polybutadiene (meth)acrylate obtained by esterification reaction of epoxidized polybutadiene obtained by causing an epoxidizing agent to act on liquid polybutadiene, and (meth)acrylic acid,
(5) Liquid polybutadiene (meth)acrylate obtained by dechlorination reaction of liquid polybutadiene having a hydroxyl group and (meth)acrylic acid chloride, and
(6) Liquid hydrogenated 1,2 polybutadiene (meth)acrylate obtained by modifying urethane (meth)acrylate from liquid hydrogenated 1,2 polybutadiene glycol obtained by hydrogenating double bonds of liquid polybutadiene having hydroxyl groups at both ends of the molecule.

Examples of these commercially available products include NISSO PB TE-2000, NISSO PB TEA-1000, NISSO PB TE-3000, NISSO PB TEAI-1000 (all manufactured by Nippon Soda Co., Ltd.), MM-1000-80, MAC- 1000-80 (all manufactured by Nippon Petrochemical Co., Ltd.), Polybeck ACR-LC (manufactured by Nippon Hydrazine Industry Co., Ltd.), HYCAR VT VTR 2000×164 (manufactured by Ube Industries, Ltd.), Quinnbeam 101 (manufactured by Zeon Corporation), Chemlink 5000 (SARTOMER). BAC-15 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), BAC-45 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), UAT-2000 (manufactured by Kyoeisha Chemical Co., Ltd.), Epolide PB-3600 (manufactured by Daicel Chemical Co., Ltd.) EY RESIN, BR-45UAS (manufactured by Light Chemical Industry Co., Ltd.) and the like can be mentioned.

Among such (meth)acryloyl group-containing compounds, 2-hydroxy-3-phenoxypropyl acrylate, phenoxyethyl acrylate, 4-hydroxybutyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl, among others. Acrylate, 2-acryloyloxyethyl phthalic acid, and aliphatic urethane acrylate are preferable.

These compounds having an ethylenically unsaturated bond may be used either individually or in combination of two or more.

The compound having an ethylenically unsaturated bond as described above is preferably blended in the conductive adhesive so that the ethylenically unsaturated bond equivalent in the organic component excluding the solvent is 260 to 1000. It is more preferably 260 to 700, further preferably 350 to 700, particularly preferably 350 to 550, and most preferably 400 to 500. By setting the ethylenically unsaturated bond equivalent to 260 or more, curing shrinkage that occurs during curing can be suppressed, and sufficient adhesive strength can be obtained. Further, when the ethylenically unsaturated bond equivalent is 1000 or less, sufficient curability can be obtained. Here, the ethylenically unsaturated bond equivalent is a mass per number of ethylenically unsaturated bonds in gram equivalent. When the ethylenically unsaturated group is a (meth)acryloyl group, it is also generally called (meth)acrylic equivalent. For example, when the ethylenically unsaturated group is a (meth)acryloyl group, it is defined as the mass of the organic component (excluding the solvent when the solvent is contained) per one (meth)acryloyl group. That is, the ethylenically unsaturated bond equivalent can be obtained by dividing the total mass of the organic components (excluding the solvent when the solvent is included) by the number of ethylenically unsaturated bonds in the composition.

By using the below-mentioned peroxide as a polymerization initiator of the compound having such an ethylenically unsaturated bond, the reaction is started quickly, rapid curing becomes possible, and the adhesive strength becomes good.

The compounding amount of the compound having an ethylenically unsaturated bond is 10 to 90% by mass, preferably 30 to 60% by mass, and more preferably 40 to 55% by mass based on the total mass of the conductive adhesive. By setting the compounding amount of the compound having an ethylenically unsaturated bond to 10% by mass or more with respect to the total mass of the conductive adhesive, sufficient curability is obtained and the adhesive strength is also made good. Further, when the compounding amount of the compound having an ethylenically unsaturated bond is 90% by mass or less with respect to the total mass of the conductive adhesive, curing shrinkage is suppressed and adhesive strength becomes good.

When the conductive adhesive of the present invention contains the compound having an ethylenically unsaturated bond as a thermosetting resin, it is preferable that the conductive adhesive further contains an organic binder other than the compound. By adding the organic binder, the stress generated during thermosetting can be relaxed and the adhesive strength can be further improved.

The organic binder is an organic resin component, and a known and commonly used natural resin or synthetic resin can be used. Such organic binders include natural resins such as cellulose and rosin, polyethylene, polypropylene, polystyrene, polycarbonate, polyvinyl chloride, polyvinyl acetate, polyamide, acrylic resin, polyethylene terephthalate, fluororesin, silicone resin, polyester resin, Synthetic resins such as acetal resin and butyral resin can be used. Among them, acrylic resin, butyral resin, and saturated polyester resin are preferably used, and saturated polyester resin is more preferable.

Specific examples of the acrylic resin include Clarity LA2330 of Clarity series (manufactured by Kuraray Co., Ltd.) and the like.

Specific examples of the butyral resin include S-REC BL-1, BL-1H, BL-2, BL-2H, BL-5, BL-10, BL-10 of Sekisui Chemical S-REC series (manufactured by Sekisui Chemical Co., Ltd.). BL-S, BL-L, etc. are mentioned.

Specific examples of the saturated polyester resin include Byron 200, 220, 240, 245, 270, 280, 290, 296, 300, 337, 500, 530, 550, 560, 600 of Toyobo Byron series (manufactured by Toyobo Co., Ltd.). 630, 650, BX1001, GK110, 130, 140, 150, 180, 190, 250, 330, 590, 640, 680, 780, 810, 880, 890 and the like.

The organic binder is preferably solid at room temperature (25° C.) and atmospheric pressure. By using a solid organic binder, it becomes easier to maintain the strength of the conductive adhesive after curing. The Tg (glass transition temperature) of the organic binder is preferably -20 to 150°C, preferably 0 to 120°C, more preferably 10 to 70°C.

The molecular weight of the organic binder is preferably 1,000 to 100,000, preferably 3,000 to 80,000, and more preferably 5,000 to 60,000. If the molecular weight is 1,000 or more, the stress can be relaxed without bleeding out during curing, and if it is 100,000 or less, it is easily compatible with a compound having an ethylenically unsaturated bond to obtain sufficient fluidity. be able to.

The compounding amount of the organic binder is 1 to 90% by mass, preferably 3 to 60% by mass, more preferably 5 to 60% by mass, further preferably 5 to 45% by mass, and further, the total mass of the conductive adhesive. It is preferably 10 to 45% by mass, particularly preferably 20 to 40% by mass.

When the conductive adhesive of the present invention contains a compound having an ethylenically unsaturated bond as a thermosetting resin, it preferably contains peroxide as a polymerization initiator. The peroxide initiates a radical reaction of the compound having an ethylenically unsaturated bond. As a result, the compound having an ethylenically unsaturated bond is cured at a low temperature in a short time, and the adhesive force between the members in the electronic component can be improved.

The peroxide includes liquid and powdered peroxides, and specific examples thereof include the following materials.

Ketone peroxides such as methyl ethyl ketone peroxide, cyclohexanone peroxide, and acetylacetone peroxide, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-hexylperoxide) Peroxyketals such as (oxy)cyclohexane, 1,1-di(t-butylperoxy)-2-methylcyclohexane, and 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t- Butylperoxy)butane, n-butyl 4,4-di-(t-butylperoxy)valerate, and 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane Hydroperoxides such as oxyketal, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutylhydroperoxide, cumene hydroperoxide, and t-butylhydroperoxide; (2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-hexylper Dialkyl peroxides such as oxide, di-t-butylperoxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, diisobutylperoxide, di(3,5,5- Trimethylhexanoyl) peroxide, dilauroyl peroxide, disuccinic acid peroxide, di-(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide, dibenzoyl peroxide, and di-(4-methyl Benzoyl)peroxide, etc., diacyl peroxide, di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate , Peroxydicarbonate such as di-sec-butylperoxydicarbonate, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, t-hexylperoxyneodeca Noate, t-butylperoxyneodecanoate, t-butylperoxyneopeptanoate, t-hexylperoxypyvale , T-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy) ) Hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylper Oxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexylmonocarbonate, t-hexylperoxybenzoate, 2 ,5-Dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, t-butylperoxy-3-methylbenzoate, t-butylperoxybenzoate, and t-butylperoxyallylmono Peroxyesters such as carbonate, and 3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone.

Of these peroxides, liquid ones are preferably used. By using liquid peroxide, a conductive adhesive having excellent storage stability can be obtained. Here, the liquid peroxide means liquid peroxide at room temperature (25° C.) and atmospheric pressure.

Usually, in a thermosetting resin composition, a powder curing agent is blended to impart a function as a latent curing agent, but when it contains a compound having the ethylenically unsaturated bond, Unexpectedly, the use of liquid peroxide improves the storage stability of the conductive adhesive. As a result, the liquid peroxide disperses satisfactorily in the conductive adhesive, acts well on the compound having an ethylenically unsaturated bond, and accelerates curing.

Examples of liquid peroxides include ketone peroxides such as methyl ethyl ketone peroxide, cyclohexanone peroxide, and acetylacetone peroxide, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1 Peroxyketals such as 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)-2-methylcyclohexane, and 1,1-di(t-butylperoxy)cyclohexane 2,2-di(t-butylperoxy)butane, n-butyl 4,4-di-(t-butylperoxy)valerate, and 2,2-di(4,4-di-(t-butyl) Peroxyketals such as peroxy)cyclohexyl)propane, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutylhydroperoxide, cumene hydroperoxide, and t-butylhydro. Hydroperoxides such as peroxides, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-hexyl peroxide, di-t-butylperoxide , And dialkyl peroxides such as 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, diisobutyl peroxide, di(3,5,5-trimethylhexanoyl) peroxide, di- (3-Methylbenzoyl)peroxide, diacyl peroxide such as benzoyl(3-methylbenzoyl)peroxide and dibenzoylperoxide, di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, di(2- Ethylhexyl) peroxydicarbonate, peroxydicarbonate such as di-sec-butylperoxydicarbonate, cumyl peroxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, t -Hexyl peroxy neodecanoate, t-butyl peroxyne neodecanoate, t-butyl peroxy neo heptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, 1,1,3 ,3-Tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, t-hexylpa -Oxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t- Butyl peroxy laurate, t-butyl peroxy isopropyl monocarbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, t-butyl peroxy acetate, t-butyl peroxy-3-methyl Mention may be made of peroxyesters such as benzoate, t-butylperoxybenzoate and t-butylperoxyallyl monocarbonate, and 3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone. .

（式中、ＲおよびＲ´はそれぞれ独立にアルキル基を表す。） Among them, preferred peroxides in the present invention are 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, n- Peroxyketals such as butyl-4,4-di-(t-butylperoxy)valerate, hydroperoxides such as 1,1,3,3-tetramethylbutylhydroperoxide, 2,5-dimethyl-2, 5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-hexyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butyl) Peroxy)3-hexyne and other dialkyl peroxides, diacyl peroxides, peroxycarbonates, and 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-hexylperoxy-2- Ethyl hexanoate, t-butyl peroxy-2-ethyl hexanoate, t-hexyl peroxy isopropyl monocarbonate, t-butyl peroxy-3,3,5-trimethyl hexanoate, t-butyl peroxy laurate And peroxyesters such as t-butylperoxy-2-ethylhexylmonocarbonate, t-hexylperoxybenzoate, t-butylperoxy-3-methylbenzoate, and t-butylperoxybenzoate. Further, among the above particularly preferable peroxides, excellent adhesion can be obtained by using peroxyester. Above all, by using an alkyl peroxy ester having the following structure, extremely excellent adhesive strength can be obtained.

(In the formula, R and R′ each independently represent an alkyl group.)

As the peroxide as described above, one having a one-minute half-life temperature of 80 to 160° C., preferably 85 to 145° C., more preferably 90 to 135° C. is preferably used. By setting the one-minute half-life temperature to 80° C. or higher, it is possible to secure a sufficient pot life in use at room temperature. Further, by setting the one-minute half-life temperature to 160° C. or lower, sufficient curability can be secured.

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

The amount of such a peroxide is in the range of 0.1 to 20 parts by mass, preferably 3 to 15 parts by mass, and more preferably 5 to 10 parts by mass with respect to 100 parts by mass of the compound having an ethylenically unsaturated bond. Is selected appropriately. Sufficient curability can be ensured by adjusting the amount of the peroxide to be 0.1 part by mass or more based on 100 parts by mass of the compound having an ethylenically unsaturated bond. Sufficient adhesion can be ensured by adjusting the amount of the peroxide to be 20 parts by mass or less with respect to 100 parts by mass of the compound having an ethylenically unsaturated bond.

[Heat-melting conductive particles]
The conductive adhesive of the present invention contains heat-meltable conductive particles. Here, the conductive particles mean particles of a substance having a volume resistivity of 1×10 ⁶ Ω·cm or less.

By sandwiching the conductive particles between the electrodes, the members are electrically connected to each other.

The conductive particles are not particularly limited as long as they can be melted by heat. In particular, it is preferable to use conductive particles that melt by thermocompression bonding at 170° C. or lower and 2 MPa or lower, and among them, low melting point solder particles are more preferable.

Here, the low melting point solder particles mean solder particles having a melting point of 200° C. or lower, preferably 170° C. or lower, and more preferably 150° C. or lower.

The low melting point solder particles are preferably lead-free solder particles, and the lead-free solder particles are defined by JIS Z 3282 (solder-chemical composition and shape) and have a lead content of 0.10. It means solder particles of not more than mass %.

As the lead-free solder particles, a low melting point solder composed of one or more kinds of metals selected from tin, bismuth, indium, copper, silver and antimony is preferably used. In particular, an alloy of tin (Sn) and bismuth (Bi) is preferably used from the viewpoint of the balance of cost, handleability, and bonding strength.

The content of Bi in such solder particles is appropriately selected within a range of 15 to 65% by mass, preferably 35 to 65% by mass, and more preferably 55 to 60% by mass.

When the Bi content is 15% by mass or more, the alloy starts melting at about 160°C. When the content of Bi is further increased, the melting start temperature is lowered, and the melting start temperature becomes 139° C. at 20 mass% or more and the eutectic composition becomes at 58 mass %. By setting the Bi content in the range of 15 to 65 mass %, the effect of lowering the melting point can be sufficiently obtained, and as a result, sufficient conductive connection can be obtained even at a low temperature.

Such conductive particles are preferably spherical and have an average particle diameter D50 measured by a laser diffraction type particle size distribution of 0.1 to 20 μm, preferably 3 to 17 μm, and more preferably 7 to 15 μm. By setting the average particle diameter D50 of the conductive particles to 20 μm or less, sufficient conductive connection can be achieved even at a fine portion. Further, by setting the average particle diameter D50 of the conductive particles to 0.1 μm or more, the aggregation of the conductive particles in the conductive adhesive can be suppressed. In the present invention, the spherical conductive particles mean particles containing 90% or more of spherical powders having a ratio of major axis to minor axis of 1 to 1.5 at a magnification at which the shape of the conductive particles can be confirmed.

The content of the conductive particles is 0.01 to 4.0% by volume in terms of solid content in the conductive adhesive. As described above, it is possible to achieve both conductivity and electric resistance. It is preferably 0.01 to 3.5% by volume, more preferably 0.1 to 3.0% by volume, still more preferably 0.1 to 2.5% by volume, and particularly preferably 0.1 to 3.5% by volume. It is 2.0% by volume.

The conductive adhesive of the present invention preferably contains a thixotropic agent. By incorporating the thixotropy imparting agent, it is possible to prevent the conductive particles having a high specific gravity from settling.

As the thixotropy-imparting agent, a conventionally known one can be used, and for example, bentonite, wax, stearic acid metal salt, modified urea, silica and the like can be used. Of these, silica is preferable. The silica is preferably amorphous silica, more preferably amorphous silica having an average primary particle diameter of 50 nm or less, and particularly preferably hydrophobic amorphous silica having a surface subjected to a hydrophobic treatment.

The content of such a thixotropy-imparting agent is 0.01 to 20% by mass, preferably 0.1 to 10% by mass, more preferably 100% by mass based on the total mass of the resin composition containing a resin component for an adhesive. It is appropriately selected within the range of 1 to 5% by mass. The content of 0.01% by mass or more can prevent the conductive particles having a high specific gravity from settling, and the content of 20% by mass or less can ensure sufficient adhesion.

The conductive adhesive of the present invention preferably contains a wetting and dispersing agent. By blending the wetting and dispersing agent, the conductive powder is well dispersed and the generation of coarse particles due to aggregation can be prevented.

As the wetting and dispersing agent, known and commonly used ones can be used, for example, aliphatic carboxylic acid, aliphatic carboxylic acid salt, higher alcohol sulfuric acid ester, alkyl sulfonic acid, phosphoric acid ester, polyether, polyester carboxylic acid and salts thereof. Can be used. Among these, phosphoric acid ester is preferable.

The blending amount of such a wetting and dispersing agent is 0.01 to 10% by mass, preferably 0.05 to 5% by mass, more preferably 0, with respect to the total mass of the resin composition containing the resin component for an adhesive. It is appropriately selected within a range of 0.1 to 3% by mass. The content of 0.01% by mass or more can prevent the generation of coarse particles, and the content of 10% by mass or less can ensure sufficient insulation.

The electrically conductive adhesive of the present invention preferably contains an antifoaming agent. By adding an antifoaming agent, it is possible to suppress the generation of bubbles and prevent the generation of voids.

As the defoaming agent, known and conventional ones can be used, and for example, a silicone resin, a modified silicone resin, an organic polymer, an organic oligomer or the like can be used. Among these, organic high molecular polymers and organic oligomers are preferable, and vinyl ether polymers are more preferable.

The content of such an antifoaming agent is 0.01 to 10% by mass, preferably 0.1 to 5% by mass, more preferably 0, with respect to the total mass of the resin composition containing the resin component for an adhesive. It is appropriately selected within the range of 0.5 to 3 mass %. Void generation can be prevented by setting the blending amount to 0.01% by mass or more, and sufficient adhesion can be secured by setting the blending amount to 10% by mass or less.

The resin composition containing the resin component for the adhesive may be mixed with known and commonly used additives such as a leveling agent, if necessary.

The conductive adhesive of the present invention preferably contains no solvent. Here, “without using a solvent” means that a resin composition containing a resin component for an adhesive does not substantially contain a solvent, and a resin composition containing a resin component for an adhesive has a temperature of 150° C. for 30 minutes. It means that the decrease in mass due to heating is 3% by mass or less as compared with the mass before heating.

The conductive adhesive of the present invention can be used for electrically connecting members in an electronic component. For example, it can be used for electrical connection between a printed wiring board and an electronic element or electrical connection between printed wiring boards, and above all, it is preferably used for electrical connection between a rigid printed wiring board and a flexible printed wiring board. Further, it can be suitably used for electrical connection in smartphones, tablet terminals, and wearable terminals. Further, since the high frequency characteristic is good, it can be suitably used for electrical connection in an electronic device that requires high frequency characteristics.

The method of applying the conductive adhesive according to the present invention is not particularly limited, and for example, the conductive adhesive of the present invention is applied to the electrically connecting portion of the connecting member in the printed wiring board or the like with a screen mesh or a metal mask, Alternatively, it can be applied by an application device such as a dispenser.

After confirming that the conductive adhesive has been sufficiently supplied to the connection point, place the member to be connected (component) on the connection point of the connection member (board) and perform thermocompression bonding at a predetermined temperature and pressure. Harden. As a result, the connecting member (substrate) and the connected member (component) can be electrically connected.

The thermocompression bonding temperature is 100 to 240° C., preferably 120 to 200° C., more preferably 140 to 160° C., and the thermocompression bonding pressure is 0.05 to 2.0 MPa, preferably 0.1 to 1.5 MPa. More preferably 0.5 to 1.0 MPa, and thermocompression bonding time is 1 to 60 seconds, preferably 1 to 20 seconds, more preferably 1 to 9 seconds. When the treatment is performed at a temperature of 100° C. or higher, the thermal reaction proceeds well, and by performing the treatment at a temperature of 240° C. or lower, the electronic components to be bonded are not damaged by heating and the original performance is maintained. Hold. Further, by setting the pressure to 0.05 MPa or more, sufficient bonding is formed between the electronic components and the conductivity is also sufficient. Further, by reducing the thermocompression bonding pressure, damage due to application of an excessive load to the electronic component can be avoided. Further, by making the thermocompression bonding time short, damage to electronic components due to heat can be avoided. The thickness of the electrically connected portion after thermocompression bonding is not particularly limited, but the thickness is 10 μm or less, preferably 0.01 to 5 μm, more preferably 0.01 to 3 μm, and particularly preferably 0.01 to 1 μm. Just crimp.

According to the conductive adhesive of the present invention, by setting the conductive particles to 0.01 to 4.0% by volume, the number of conductive particles sandwiched between the electrodes is reduced, and the pressure applied to the conductive particles is increased. The members can also be anisotropically conductively bonded to each other by thermocompression bonding at a low temperature and a low pressure, specifically 170° C. or lower, further 150° C. or lower and 2.0 MPa or lower, 1.5 MPa or lower, further 1.0 MPa or lower. As a result, anisotropic conductive adhesion can be easily performed even at a considerably low temperature of 150° C. and 0.8 MPa and a low pressure.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Further, in the following, "part" and "%" are based on mass unless otherwise specified.

(Examples 1 to 4 and Comparative Examples 1 and 2)
(Preparation of conductive adhesive)
Each component was mixed and stirred at the mixing ratio (parts by mass) shown in Table 1 to prepare the conductive adhesives of Examples 1 to 4 and Comparative Examples 1 and 2.

(Evaluation of conduction resistance)
Preparation of Test Pieces The conductive adhesives of Examples 1 to 4 and Comparative Examples 1 and 2 prepared above were prepared using a rigid substrate (base material: FR-4, electrode width: 100 μm, electrode length: 6 mm, pitch width). : 0.2 mm, U-shaped electrode number 70, linear electrode 1, flash Au treatment), and applied with a scraper through a metal mask (mask thickness: 80 μm, opening: 15 mm×1 mm). Next, a flexible substrate (width: 16 mm, base material: polyimide, electrode width: 100 μm, electrode length: 6 mm, pitch width: 0.2 mm, U-shaped) was applied to the rigid substrate coated with the curable composition. 70 mold electrodes, 1 linear electrode, and flash Au treatment) were mounted. During this placement, the positions of the electrodes on the rigid substrate and the electrodes on the flexible substrate were aligned so that a daisy chain was formed, and the overlapping length of both electrodes was 3.5 mm. With respect to the joint surface between the substrates thus mounted, thermocompression bonding was performed at 0.79 MPa (tool: width 3 mm, length 18 mm, load: 42.7 N) at 150° C. for 6 seconds, and 70 electrical pieces were electrically connected. A daisy chain circuit test piece having connection points was produced.

Measurement of Conduction Resistance The resistance value of the test piece obtained by the above method was measured using a tester (Milliohm HiTester 3540 manufactured by Hioki Electric Co., Ltd.).

(Evaluation of withstand voltage)
Preparation of Test Pieces The conductive adhesives of Examples 1 to 4 and Comparative Examples 1 and 2 prepared above were prepared using a rigid substrate (base material: FR-4, electrode width: 100 μm, electrode length: 6 mm, pitch width). : 0.2 mm, number of comb-shaped electrodes 71, flash Au treatment), was applied by a scraper through a metal mask (mask thickness: 80 μm, opening: 15 mm×1 mm). Next, a flexible substrate (width: 16 mm, base material: polyimide, electrode width: 100 μm, electrode length: 6 mm, pitch width: 0.2 mm, comb-shaped electrode) was applied to the rigid substrate with the conductive adhesive applied. (Number 71, flash Au treatment) was placed. In this placement, the positions of the electrodes on the rigid substrate and the electrodes on the flexible substrate were aligned so that the withstand voltage could be measured, and the overlapping length of both electrodes was 3.5 mm. The bonded surfaces of the substrates thus mounted were thermocompression bonded at 0.79 MPa (tool: width 3 mm, length 18 mm, load: 42.7 N) at 150° C. for 6 seconds to prepare a test piece. ..

Measurement of withstand voltage The withstand voltage of the test piece obtained by the above method was measured using a tester (TR8601 HIGH MEGOHM METER manufactured by Advantest Corporation).

(Evaluation of adhesion strength)
Preparation of Test Pieces The conductive adhesives of Examples 1 to 4 and Comparative Examples 1 and 2 prepared above were prepared using a rigid substrate (base material: FR-4, electrode width: 100 μm, electrode length: 6 mm, pitch width). : 0.2 mm, U-shaped electrode number 70, linear electrode 1, flash Au treatment), and applied with a scraper through a metal mask (mask thickness: 80 μm, opening: 15 mm×1 mm). Next, a flexible substrate (width: 16 mm, base material: polyimide, electrode width: 100 μm, electrode length: 6 mm, pitch width: 0.2 mm, U-shaped) was applied to the rigid substrate with the conductive adhesive applied. 70 mold electrodes, 1 linear electrode, and flash Au treatment) were mounted. During this placement, the positions of the electrodes on the rigid substrate and the electrodes on the flexible substrate were aligned so that a daisy chain was formed, and the overlapping length of both electrodes was 3.5 mm. With respect to the joint surface between the substrates thus mounted, thermocompression bonding was performed at 0.79 MPa (tool: width 3 mm, length 18 mm, load: 42.7 N) at 150° C. for 6 seconds, and 70 electrical pieces were electrically connected. A daisy chain circuit test piece having connection points was produced.

Measurement of Adhesion Strength The adhesion strength of the test piece obtained by the above method was measured by using a bond tester (4000Plus manufactured by Nordson Advanced Technology Co., Ltd.) and peeling the flexible substrate in the vertical direction according to JIS K 6854-1. Was measured.

(Evaluation of the degree of collapse of conductive particles viewed from the Z-axis direction)
The rigid substrate peeled off by the measurement of the adhesive strength is observed with an electron microscope (JSM-5610LV manufactured by JEOL Ltd.), and on the electrode located in the center of the substrate (one, overlapping length 3.5 mm). (Part) was measured in the longitudinal direction of the conductive particles as viewed in the Z-axis direction (major axis in the case of an elliptical shape, diameter in the case of a circular shape), and the average value was defined as A. Next, the diameter of the conductive particles in the longitudinal direction as seen from the Z-axis direction between the electrodes located in the central portion of the substrate (one overlapped portion having a length of 3.5 mm) (long diameter in the case of an ellipse, long diameter in the case of a circle) (Diameter) were all measured, and the average value was defined as a.
The obtained value of A was divided by the value of a to obtain the degree of collapse (times) of the conductive particles.

(Temperature cycle test)
A test piece was prepared by the same method as the above-mentioned conduction resistance. The test piece was measured using Kusunoki Kasei's WINTECH NT1531W at -40° C. for 1 minute and 125° C. for 1 minute to measure the conduction resistance of the test piece after 1000 cycles, and the rate of change (%) from the initial value When the change rate was 0 to 2%, it was evaluated as ○, 2% to 10% was evaluated as Δ, and 10% or more was evaluated as ×.

＊１：エチレン性不飽和結合を有する化合物（Ａ−１）：２−ヒドロキシ−３−フェノキシプロピルアクリレート（東亞合成社製アロニックス Ｍ−５７００、分子量：２２２、Ｔｇ：１７℃、粘度：１．６５ｄＰａ・ｓ／２５℃）
＊２：エチレン性不飽和結合を有する化合物（Ａ−２）：フェノキシエチルアクリレート（共栄社化学社製ライトアクリレートＰＯ−Ａ、分子量:１９２ 、Ｔｇ：−２２℃、粘度：０．１２５ｄＰａ・ｓ／２５℃）
＊３：エチレン性不飽和結合を有する化合物（Ａ−３）：脂肪族ウレタンアクリレート（ダイセル・オルネクス株式会社製ＥＢＥＣＲＹＬ２７０、分子量：１５００、Ｔｇ：−２７℃、粘度：３０ｄＰａ・ｓ／６０℃）
＊４：飽和ポリエステル樹脂（東洋紡績社製バイロン３３７、分子量：１００００、Ｔｇ：１４℃）
＊５：１，１，３，３−テトラメチルブチルパーオキシ−２−エチルヘキサノエート（日油社製パーオクタＯ、性状：液体、１分間半減期温度：１２４．３℃、１０時間半減期温度：６５．３℃）
＊６：低融点はんだ粒子（４２Ｓｎ−５８Ｂｉ［４２Ｓｎ−５８Ｂｉ組成の球状粒子：平均粒径（レーザー回折式粒度分計測定による平均粒子径Ｄ５０）、１３．１２μｍ）］）＊７：シリカ微粒子[比表面積１７０ｍ^２／ｇ](日本アエロジル社製アエロジルＲ９７４)＊８：リン酸エステル（共栄社化学社製ライトエステルＰ−２Ｍ）
＊９：ビニルエーテルポリマー（共栄社化学社製フローレンＡＣ−３２６Ｆ）
＊ 各実施例、比較例の樹脂組成物（導電性接着剤）に含まれる、有機成分中のエチレン性不飽和結合当量は、実施例１〜４、比較例１〜２いずれも、４５７であった（実施例、比較例はいずれも無溶剤）。
（有機成分中のエチレン性不飽和結合当量の算出方法）
（有機成分の質量合計）／（組成物中のエチレン性不飽和結合の数）
＝６７．０／０．１４６６＝４５７

*1: Compound (A-1) having an ethylenically unsaturated bond: 2-hydroxy-3-phenoxypropyl acrylate (Aronix M-5700 manufactured by Toagosei Co., Ltd., molecular weight: 222, Tg: 17° C., viscosity: 1.65 dPa・S/25℃)
*2: Compound (A-2) having an ethylenically unsaturated bond: phenoxyethyl acrylate (light acrylate PO-A manufactured by Kyoeisha Chemical Co., Ltd., molecular weight: 192, Tg: -22°C, viscosity: 0.125 dPa·s/25. ℃)
*3: Compound having an ethylenically unsaturated bond (A-3): Aliphatic urethane acrylate (EBECRYL270 manufactured by Daicel Ornex Co., molecular weight: 1500, Tg: -27°C, viscosity: 30 dPa·s/60°C)
*4: Saturated polyester resin (Byron 337 manufactured by Toyobo Co., molecular weight: 10,000, Tg: 14°C)
*5: 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (Perocta O manufactured by NOF CORPORATION, Property: liquid, 1 minute half-life temperature: 124.3°C, 10 hour half-life (Temperature: 65.3°C)
*6: Low melting point solder particles (42Sn-58Bi [spherical particles having a composition of 42Sn-58Bi: average particle size (average particle size D50 measured by a laser diffraction particle size analyzer), 13.12 μm)]) *7: silica fine particles [ Specific surface area 170 m ² /g] (Aerosil R974 manufactured by Nippon Aerosil Co., Ltd.)*8: Phosphate ester (light ester P-2M manufactured by Kyoeisha Chemical Co., Ltd.)
*9: Vinyl ether polymer (Floren AC-326F manufactured by Kyoeisha Chemical Co., Ltd.)
* The ethylenically unsaturated bond equivalent in the organic component contained in the resin composition (conductive adhesive) of each Example and Comparative Example is 457 in each of Examples 1 to 4 and Comparative Examples 1 and 2. (No solvent was used in the examples and comparative examples).
(Calculation method of ethylenically unsaturated bond equivalent in organic component)
(Total mass of organic components)/(Number of ethylenically unsaturated bonds in the composition)
=67.0/0.1466=457

(Method of calculating content of heat-meltable conductive particles (concentration of conductive particles) (volume %))
According to JIS K-5400, the specific gravity of the composition (adhesive) other than the solder powder (low melting point solder particles) was measured using a 100 ml specific gravity cup (Yoshimitsu Seiki Co., Ltd.), and the solder powder (low melting point solder particles) was measured. ) Was used to calculate the volume% by the following formula.
The true specific gravity of 42Sn-58Bi was 8.7, and the specific gravity of the composition (adhesive) other than the solder powder was 1.13.
(formula)
Concentration of conductive particles (volume %)=100×(blending amount of solder powder/true specific gravity of solder powder)/((blending amount of solder powder/true specific gravity of solder powder)+(blending amount of composition other than solder powder /Specific gravity of the composition other than solder powder))

As shown in the above table, the conductive adhesive having a blending amount of the heat-meltable conductive particles of 0.01 to 4.0% by volume in terms of solid content has a high withstand voltage while maintaining conductivity. It can be seen that a connection structure having excellent anisotropic conductivity is formed.

Claims (5)

Bonding the anisotropic conductive member to each other by thermocompression bonding, a conductive adhesive containing conductive particles,
The conductive particles consist only of low melting point solder particles that are heat-meltable conductive particles,
A conductive adhesive characterized in that the compounding amount of the low melting point solder particles is 0.01 to 3.5 % by volume in terms of solid content. The conductive adhesive according to claim 1, further comprising an organic component. The conductive adhesive according to claim 2 , wherein the organic component (excluding the solvent when the solvent is included) has an ethylenically unsaturated bond equivalent of 260 to 1,000. Electronic component, characterized in that it comprises a member which is electrically connected using a conductive adhesive according to any one of claims 1-3. The method of manufacturing an electronic component, characterized in that according to claim 1 applying a conductive adhesive according to any one of 3 to conductive bonding the members to each other by thermocompression bonding.