JP2024141453A - Conductive Paste - Google Patents

Abstract

The present invention provides a low-viscosity resin composition that uses a flexible epoxy resin and a diluent in combination to produce a cured product with high electrical conductivity. The present invention uses a flexible epoxy resin in combination with a reactive diluent that has a structure (Gly-O-R-O-Gly) in which two glycidyl ether groups (-O-Gly) are bonded to a divalent aliphatic hydrocarbon group (R), and has a viscosity of 500 mPa·s or less at 25°C. [Selected Figure] None

Description

The present invention relates to a conductive paste.

It has been known that a thermosetting conductive paste containing silver particles is used as an alternative connection method to solder for assembling electronic components and connecting them to a substrate (Patent Document 1). Conductive pastes are sometimes used to make electrical connections between multiple components and to form wiring and electrodes in the manufacture of electronic devices such as camera modules and printed wiring boards. In order to make finer connections and form wiring and electrodes, it may be necessary to reduce the viscosity of the conductive paste. For example, a low-viscosity diluent is known as a means for reducing the viscosity of the conductive paste. In addition, when used in electronic devices, printed wiring boards, etc., the cured product of the conductive paste may be required to have impact resistance. For example, an epoxy resin with a flexible structure (flexible epoxy resin) is known as a means for imparting impact resistance to the cured product (Patent Document 2).

Patent Publication 2015-42696 Patent No. 5786418

However, when flexible epoxy resin is used in the conductive paste, the viscosity of the conductive paste also becomes high due to the high viscosity of the flexible epoxy resin. In this case, it is possible to use a diluent to lower the viscosity, but if a large amount is used, the physical properties of the cured product, such as the mechanical strength, tend to decrease, and if the amount used is limited, depending on the type of diluent, the viscosity of the conductive paste may not decrease sufficiently. In addition, depending on the type of diluent, problems such as a decrease in the conductivity of the cured product (higher resistance) may occur.

The objective of the present invention is to provide a low-viscosity resin composition that uses a flexible epoxy resin and a diluent in combination to produce a cured product with high electrical conductivity.

The inventors discovered that when a flexible epoxy resin is used in combination with a reactive diluent having a specific structure, it is possible to maintain an appropriate viscosity as a paste and also to suppress a decrease in the electrical conductivity of the cured product, and thus completed the present invention.

That is, the present invention includes the following aspects.
[1] (A) a flexible epoxy resin containing a linear hydrocarbon structural unit having 4 to 20 carbon atoms and/or a polyalkylene ether structural unit having 3 to 20 ether oxygen atoms;
(B) a reactive diluent having a structure (Gly-O-R-O-Gly) in which two glycidyl ether groups (-O-Gly) are bonded to a divalent aliphatic hydrocarbon group (R) and having a viscosity of 500 mPa s or less at 25°C;
(C) an epoxy resin curing agent; and
(D) silver particles;
A resin composition comprising:
[2] The resin composition according to [1] above, wherein the aliphatic hydrocarbon group (R) is a saturated aliphatic hydrocarbon group.
[3] The resin composition according to [1] or [2] above, wherein the aliphatic hydrocarbon group (R) is a non-alicyclic aliphatic hydrocarbon group.
[4] The resin composition according to any one of [1] to [3] above, wherein the aliphatic hydrocarbon group (R) has 3 or more and 6 or less carbon atoms.
[5] The resin composition according to [4] above, wherein the aliphatic hydrocarbon group (R) has 4 or 5 carbon atoms.
[6] The resin composition according to any one of [1] to [5], wherein the viscosity of the reactive diluent (B) at 25°C is 100 mPa·s or less.
[7] The resin composition according to any one of [1] to [6], wherein the flexible epoxy resin (A) further contains a bisphenol structural unit.
[8] The resin composition according to any one of [1] to [7], wherein the epoxy resin curing agent (C) is one or more selected from the group consisting of a tertiary amino group-containing modified polyamine, a urea bond-containing modified polyamine, and an imidazole-containing modified polyamine.
[9] The resin composition according to any one of [1] to [8], further comprising (E) an epoxy resin (excluding the flexible epoxy resin (A)).
[10] The resin composition according to any one of [1] to [9], comprising 0.1 to 40 mass% of the flexible epoxy resin (A) relative to the total mass of the resin composition.
[11] The resin composition according to any one of [1] to [10], comprising 0.1 to 30 mass% of the reactive diluent (B) relative to the total mass of the resin composition.
[12] The resin composition according to any one of [1] to [11], comprising 2 to 40 parts by weight of the epoxy resin curing agent (C) per 100 parts by weight of the epoxy resin contained in the resin composition.
[13] The resin composition according to any one of [1] to [12] above, comprising 30 to 95 mass% of the silver particles (D), based on the total mass of the resin composition.
[14] A cured product of the resin composition according to any one of [1] to [13] above.

The present invention provides a low-viscosity resin composition that uses a flexible epoxy resin and a diluent in combination to produce a cured product with high electrical conductivity.

FIG. 1 shows a test sample for contact resistance measurement.

The present invention relates to a resin composition that contains (A) a flexible epoxy resin containing a linear hydrocarbon structural unit having 4 to 20 carbon atoms and/or a polyalkylene ether structural unit having 3 to 20 ether oxygen atoms, (B) a reactive diluent having a structure (Gly-O-R-O-Gly) in which two glycidyl ether groups (-O-Gly) are bonded to a divalent aliphatic hydrocarbon group (R) and having a viscosity of 500 mPa·s or less at 25°C, (C) an epoxy resin curing agent, and (D) silver particles.

(A) Flexible Epoxy Resin The flexible epoxy resin used in the present invention contains a linear hydrocarbon structural unit having from 4 to 20 carbon atoms and/or a polyalkylene ether structural unit having from 3 to 20 ether oxygen atoms.

The linear hydrocarbon structural unit contained in the flexible epoxy resin is represented by --(CH ₂ ) _x --, where x is 4 or more and 20 or less. x is preferably 4 or more and 10 or less. Instead of this hydrogen atom, a substituent such as a hydroxyl group may be included, and further, at least one of the hydrogen atoms may be substituted with a hydrocarbon group, an alkoxyl group, an aryl group, an aryloxy group, or the like. The hydrocarbon or alkoxyl group as the substituent preferably has 4 or less carbon atoms, and the aryl group of the aryl group or aryloxy group is preferably a phenyl group. These substituents can be included within a range that does not impair the flexibility of the structural unit.

The polyalkylene ether structural unit contained in the flexible epoxy resin has 3 to 20 ether oxygen atoms, preferably 3 to 10. Specific examples include structural units derived from a polymer of one or more alkylene oxides selected from ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, neopentylene oxide, tetramethylene oxide, etc. Also included are those in which one or more hydrogen atoms of this alkylene oxide are substituted with, for example, a hydroxyl group, an alkoxyl group, an aryl group, an aryloxy group, a hydrocarbon group, etc. The hydrocarbon or alkoxyl group as the substituent preferably has 4 or less carbon atoms, and the aryl group of the aryl group or aryloxy group is preferably a phenyl group. These substituents can be present within a range that does not impair the flexibility of the structural unit.

The linear hydrocarbon structural unit having 4 to 20 carbon atoms improves the heat resistance of the cured product, and the polyalkylene ether structural unit improves the adhesion and bonding properties to, for example, metal substrates. By appropriately selecting these structural units, it is possible to accommodate a variety of substrates, manufacturing processes, and required performance.

The flexible epoxy resin preferably contains a bisphenol-type structural unit in addition to the linear hydrocarbon structural unit and/or polyalkylene ether structural unit. Examples of the bisphenol-type structural unit include structural units derived from bisphenol A, bisphenol F, and bisphenol S. Specific examples include units obtained by removing the OH groups at the terminals of these units and units represented by the following general formula (1), and the rings may be hydrogenated. Furthermore, these rings may have a substituent such as a hydrocarbon group, an alkoxyl group, an aryl group, an aryloxy group, or a hydroxyl group.

When the flexible epoxy resin contains bisphenol structural units, the molar ratio of the linear hydrocarbon structural units and/or polyalkylene ether structural units to the bisphenol structural units is preferably 1:10 to 5:1, and more preferably 1:5 to 3:1. If the amount of bisphenol structural units is greater than this range, the cured product will not have sufficient flexibility. If the amount of bisphenol structural units is less than the above range, the Tg of the cured product will be lower, and heat resistance will be reduced.

Specifically, the flexible epoxy resin containing bisphenol-type structural units preferably has one or more of the structures shown in the following structural formulas (2-i) to (2-iv). In addition, multiple hydroxyl groups in the structural formulas shown below may undergo a crosslinking reaction, and the oxygen atoms of the hydroxyl groups may form nodes in an unspecified structure.

In structural formulae (2-i) to (2-iv), Ar ¹ and Ar ² may be the same or different and are bisphenol-type structural units which may be hydrogenated or which may have a substituent, and X is a linear hydrocarbon group having from 4 to 20 carbon atoms and/or a polyalkylene ether structure having from 1 to 18 ether oxygen atoms. When X is a linear hydrocarbon group having from 4 to 20 carbon atoms, X is a linear hydrocarbon structural unit, and when X is a polyalkylene ether structure having from 1 to 18 ether oxygen atoms, -O-X-O- is a polyalkylene ether structural unit. In addition, n is the average value of the repeating units and is 1 to 30.

Examples of flexible epoxy resins containing bisphenol-type structural units include "EPICLON EXA4816" and "EPICLON EXA4822" (both manufactured by DIC Corporation), "YL7175-500" and "YL7175-1000" (both manufactured by Mitsubishi Chemical Corporation).

The content of the flexible epoxy resin is preferably 0.1 to 40 mass% of the total mass of the resin composition, more preferably 0.2 to 35 mass%, even more preferably 0.5 to 30 mass%, and may be, for example, 0.8 to 20 mass%, 1 to 10 mass%, or 1.5 to 6 mass%. If the amount of the flexible epoxy resin is within the above range, it is possible to improve the impact resistance and adhesion of the cured product while suppressing an increase in the viscosity of the resin composition.

(B) Reactive Diluent The reactive diluent used in the present invention has a structure (Gly-O-R-O-Gly) in which two glycidyl ether groups (-O-Gly) are bonded to a divalent aliphatic hydrocarbon group (R), and has a viscosity at 25°C of 500 mPa s or less.

The aliphatic hydrocarbon group (R) may be unsaturated or saturated, and may be alicyclic or acyclic. From the viewpoint of obtaining a cured product having good impact resistance and electrical conductivity while reducing the viscosity of the resin composition, the aliphatic hydrocarbon group (R) is preferably saturated and is preferably acyclic. The number of carbon atoms in the aliphatic hydrocarbon group (R) is preferably 6 or less, more preferably 5 or less, and is preferably 3 or more, more preferably 4 or more.

The reactive diluent has a viscosity of 500 mPa·s or less at 25°C. Since the flexible epoxy resin (A) is usually highly viscous and has a viscosity of more than 500 mPa·s at 25°C (for example, a viscosity of more than 100 Pa·s at 25°C), a diluent having a viscosity of 500 mPa·s or less can reduce the viscosity of a resin composition containing a flexible epoxy resin. The reactive diluent preferably has a viscosity of 100 mPa·s or less at 25°C, more preferably 75 mPa·s or less, even more preferably 50 mPa·s or less, preferably 1 mPa·s or more, more preferably 3 mPa·s or more, and even more preferably 5 mPa·s or more. For a low viscosity of 500 mPa·s or less, for example, 1.2 ml of sample can be placed in an E-type viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) and measured at 25°C, 5 rpm, and 2 minutes using a rotor of 1.34°×R24 according to a procedure compliant with JIS-K7117-2. For a viscosity of more than 1 Pa·s, for example, 0.22 ml of sample can be placed in an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.) and measured at 25°C, 20 rpm, and 2 minutes using a rotor of 3°×R9.7 according to a procedure compliant with JIS-K7117-2.

Examples of reactive diluents include "ED-523L" and "ED-503G" (both manufactured by ADEKA Corporation), "BD(D)" (manufactured by Yokkaichi Chemical Co., Ltd.), and "ZX-1658GS" (manufactured by Nippon Steel Chemical Co., Ltd.).

The content of the reactive diluent is preferably 0.1 to 30 mass% of the total mass of the resin composition, more preferably 0.2 to 25 mass%, even more preferably 0.5 to 20 mass%, and may be, for example, 1 to 15 mass%, 1.5 to 12.5 mass%, or 2 to 10 mass%. If the amount of the reactive diluent is within the above range, it is possible to obtain a cured product having good electrical conductivity while reducing the viscosity of the resin composition.

(C) Epoxy Resin Curing Agent As the epoxy resin curing agent in the present invention, any known epoxy resin curing agent can be used without particular limitation.

From the viewpoint of handling the resin composition, it is preferable that the epoxy resin curing agent is a latent curing agent. In this specification, a latent curing agent is a compound that is blended into a resin composition for the purpose of curing the epoxy resin, and does not react with functional groups such as epoxy groups under normal storage conditions of the resin composition (room temperature, visible light, etc.), but exhibits reactive activity toward functional groups by heat or light, and can cure the resin composition. These may be used alone or in combination of two or more types.

From the viewpoint of the viscosity of the resin composition and the electrical conductivity and adhesiveness of the cured product, it is preferable that the epoxy resin curing agent is one or more selected from the group consisting of tertiary amino group-containing modified polyamines, urea bond-containing modified polyamines, and imidazole-containing modified polyamines, and from the viewpoint of adhesiveness, it is even more preferable to use a urea bond-containing modified polyamine and an imidazole-containing modified polyamine in combination.

In this specification, a tertiary amino group-containing modified polyamine is a compound that has a polymer structure containing an aliphatic tertiary amine other than imidazole, in which the active amine forms a stabilized structure with an epoxy resin and/or a phenolic resin and can be used as a latent curing agent. Examples of tertiary amino group-containing modified polyamines include EH4380S, EH3616S, EH5001P, and EH4357S manufactured by ADEKA Corporation.

Imidazole-containing modified polyamines are compounds that have a polymer structure containing imidazole, in which active amines form a stabilized structure with epoxy resins and/or phenolic resins and can be used as latent curing agents. Examples of imidazole-containing modified polyamines include PN-23, PN-H, and PN-40 manufactured by Ajinomoto Fine-Techno Co., Ltd., EH4346S manufactured by ADEKA Corporation, FXR-1121 manufactured by T&K Toka Corporation, and Sunmide LH210 manufactured by Air Products Japan Co., Ltd.

A urea bond-containing modified polyamine is a compound in which an active amine forms a stabilized structure through the urea bond formed by an isocyanate resin, and can be used as a latent curing agent. Examples of urea bond-containing modified polyamines include FXR-1020 and FXR-1081 manufactured by T&K Toka Corporation.

The epoxy resin hardener is preferably used in an amount of 1 to 50 parts by weight per 100 parts by weight of the epoxy resin contained in the resin composition. Taking into consideration the curing speed of the epoxy resin, sufficient crosslinking formation, viscosity of the resin composition, and coatability, the amount is more preferably 2 to 40 parts by weight per 100 parts by weight of the epoxy resin contained in the resin composition, and even more preferably 5 to 35 parts by weight, and may be, for example, 10 to 30 parts by weight, 15 to 28 parts by weight, or 20 to 27 parts by weight.

(D) Silver particles The resin composition of the present invention contains silver particles to impart electrical conductivity. The shape of the silver particles used in the present invention is not particularly limited, and known ones such as spherical, flake, and needle-shaped ones can be used, but flake-shaped ones are preferred from the viewpoint of obtaining good electrical conductivity in the cured product. The flake-shaped ones are plate-like in shape (see JIS Z2500:2000), and are also called scale-shaped ones because they are thin and plate-like like scales.

The average particle size of the silver particles used in the present invention is preferably 1 to 15 μm. Considering the ease of handling of the resin composition (adequate viscosity) and the occurrence of nozzle clogging when applying with a dispenser, 1.5 to 12.5 μm is more preferable, and 2 to 10 μm is even more preferable. In this specification, the average particle size is measured using a laser diffraction particle size distribution analyzer as the particle size (median size) at which the relative particle amount is 50% (50% of the total particle amount, the particle size at the midpoint of the particle amount when the total particle amount and particle size are graphed).

When flake-shaped silver particles are used, the specific surface area is preferably 0.1 to 1.5 m ² /g. From the viewpoint of the electrical conductivity of the cured product or the dispensability of the resin composition (herein, dispensability means application performance such as ease of application when filling a syringe with a resin composition and applying it with a dispenser), 0.15 to 1.0 m ² /g is more preferable, and 0.2 to 0.9 m ² /g is even more preferable. The specific surface area is measured by the BET (a method for measuring specific surface area based on a multilayer adsorption model expanded by Brunauer, Emmett and Teller, and is named after the initials of the three authors) single-point method using a specific surface area measuring device.

The content of silver particles is preferably 30 to 95% by mass of the total mass of the resin composition, and from the viewpoint of the electrical conductivity of the cured product and the viscosity of the resin composition, is more preferably 40 to 80% by mass, and may be, for example, 50 to 80% by mass or 60 to 75% by mass.

(E) Epoxy resin (excluding flexible epoxy resin (A))
The resin composition of the present invention may optionally contain an epoxy resin different from the flexible epoxy resin (A) in order to impart high adhesion. The epoxy resin (E) may be solid or liquid at 25 ° C., and in the case of a liquid, the viscosity at 25 ° C. is preferably greater than 500 mPa · s. The viscosity at 25 ° C. is preferably 750 mPa · s or more, more preferably 1000 mPa · s or more, preferably 20000 mPa · s or less, more preferably 10000 mPa · s or less, for example, 5000 mPa · s or less, or 4000 mPa · s or less. The viscosity at 25 ° C. of the epoxy resin (E) can be measured, for example, by putting 0.22 ml of a sample into an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.) and measuring the value after 2 minutes at 25 ° C., 20 rpm, in accordance with a procedure based on JIS-K7117-2 using a rotor of 3 ° × R9.7.

The epoxy resin (E) is not particularly limited, but it is preferable that the epoxy resin has an average of two or more epoxy groups per molecule. Examples of the epoxy resin include bisphenol A type epoxy resins, biphenyl type epoxy resins, biphenyl aralkyl type epoxy resins, phenol aralkyl type epoxy resins, naphthol type epoxy resins, naphthalene type epoxy resins, bisphenol F type epoxy resins, phosphorus-containing epoxy resins, bisphenol S type epoxy resins, aromatic glycidylamine type epoxy resins (e.g., tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, diglycidyl toluidine, diglycidyl aniline, etc.), alicyclic epoxy resins, aliphatic chain epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, epoxy resins having a butadiene structure, epoxy resins having a dicyclopentadiene structure, diglycidyl ethers of bisphenols, diglycidyl ethers of naphthalene diols, glycidyl ethers of phenols, and diglycidyl ethers of alcohols, as well as alkyl-substituted, halogenated and hydrogenated versions of these epoxy resins. One or more of these may be used. Of these, it is preferable to use bisphenol type epoxy resins, which have low viscosity and good stability, and it is more preferable to use bisphenol A type epoxy resins or bisphenol F type resins, and it is preferable to use a mixture of bisphenol A type epoxy resins and bisphenol F type resins.

Available bisphenol-type epoxy resins include, for example, RE-310S, RE-304S, and RE-404S manufactured by Nippon Kayaku Co., Ltd., and YD-115, YD-115G, YD-115CA, YD-118P, YD-127, YD-128, YD-128G, YD-128S, YD-128CA, YD-134, and YD-134 manufactured by Nippon Steel Chemical Co., Ltd. N, YD-011, YD-012, YD-013, YD-014, YD-017, YD-019, YD-020, YD-8125, YD-7011R, YD-7014R, YD-7017, YD-7019, YD-7020, YD-900, YD-901, YD-902 , YD-903, YD-904, YD-907, YD-909, YD-9 27H, ZX-1059, YDF-8170, YDF-170, YDF-175S, YDF-2001, YDF-2004, Epicron series 840, 840S, 850, 850S, 850CRP, 855, 857, D-515, 860, 900-IM, 1050, 1055, 2055, 3050, 405 manufactured by Dainippon Ink and Chemicals, Inc. Examples include 0, 4055, 7050, 9055, 830, 830S, 830LVP, 835, 835LV, EXA-1514, EXA-4004, 828, 828EL, 827, 806, 807, YL980, YL983 manufactured by Mitsubishi Chemical Corporation, and EP-4100, EP-4500, and EP-4901 from the Adeka Resin series manufactured by ADEKA Corporation.

The epoxy resin (E) can be blended in the resin composition of the present invention in an amount of preferably 0.5% by mass to 50% by mass, more preferably 1% by mass to 40% by mass, for example, 5% by mass to 30% by mass, or 10% by mass to 20% by mass.

<(F) Metal powder other than silver particles (D)>
The resin composition of the present invention may contain a metal powder other than silver particles (D) in order to suppress the increase in contact resistance value of the cured product under high temperature and high humidity. As the metal powder other than silver particles (D), preferably, tin powder, zinc powder, and aluminum powder are mentioned. The shape of the metal powder (F) is not particularly limited, and known ones such as spherical, flake, and needle-shaped can be used, but spherical is preferable from the viewpoint of the viscosity of the resin composition.

The particle size of the metal powder (F) is preferably 1 to 15 μm, more preferably 1 to 10 μm, taking into consideration the ease of handling of the resin composition and the occurrence of nozzle clogging when applying with a dispenser.

The specific surface area of the metal powder (F) is preferably 0.1 to 1.5 m ² /g, more preferably 0.1 to 1.0 m ² /g, from the viewpoints of the electrical conductivity of the cured product, the dispensability of the resin composition, etc.

From the viewpoint of suppressing the contact resistance of the cured product under high temperature and high humidity conditions, the content of the metal powder (F) is preferably 3 mass% or more, more preferably 5 mass% or more, and preferably 20 mass% or less, and more preferably 15 mass% or less, based on 100 mass% of the non-volatile components in the resin composition. In one embodiment of the present invention, the content of the metal powder (F) is preferably 3 mass% or more and 20 mass% or less, and more preferably 5 mass% or more and 15 mass% or less, based on 100 mass% of the non-volatile components in the resin composition.

(G) Core-shell polymer The resin composition of the present invention can be blended with a core-shell polymer to improve adhesion and impart stress relaxation. The core-shell polymer is a polymer having a core and a shell, and is obtained by polymerizing a relatively soft core portion prepared from a rubber elastomer, a polysiloxane rubber elastomer, or a mixture thereof, which is prepared from a diene monomer, a (meth)acrylic acid ester monomer, and/or a vinyl monomer, with a relatively hard shell layer prepared from a (meth)acrylic acid ester, an aromatic vinyl, a vinyl cyanide, an epoxy alkyl vinyl ether, an unsaturated acid derivative, a (meth)acrylamide derivative, and/or a maleimide derivative. Available core-shell polymers include MX-120, MX-125, MX-130, MX-135, MX-960, and MX-965 from Kaneka Corporation, RKB-3040 and RKB-1133 from Resinous Chemicals, JF-001 and JF-003 from Mitsubishi Rayon Co., Ltd., and F351G from Ganz Chemicals. The core-shell polymer may be a known one in the form of a single powder or dispersed in an epoxy resin. These may be used alone or in combination of a powder and one dispersed in an epoxy resin. The content of the core-shell polymer is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, of the total mass of the resin composition, and may be, for example, 0.5 to 5% by mass, or 1 to 3% by mass.

The resin composition of the present invention is a liquid resin composition having fluidity at 25°C. In consideration of the use of the resin composition in which the resin composition is allowed to soak into the gaps of the adherend for adhesion, the viscosity at 25°C is preferably less than 20 Pa·s, more preferably 10 Pa·s or less, preferably 1 Pa·s or more, and more preferably 5 Pa·s or more. In one embodiment of the present invention, the viscosity of the resin composition at 25°C is preferably 1 Pa·s or more and less than 20 Pa·s, more preferably 5 Pa·s or more and less than 15 Pa·s, and even more preferably 5 Pa·s or more and 10 Pa·s or less. In the present invention, the viscosity of the resin composition at 25°C can be measured, for example, by putting 0.22 ml of a sample into an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.) and measuring the viscosity at 25°C, 20 rpm, and 2 minutes after the procedure conforming to JIS-K7117-2 using a rotor of 3° x R9.7.

Other additives that may be added to the resin composition of the present invention include a silane coupling agent to improve the adhesion of the resin composition to the substrate, a corrosion inhibitor such as benzimidazole to protect the connection terminals, and a thixotropic agent such as boric acid ester or aerosil.

The resin composition of the present invention is produced by mixing the above-mentioned components according to a conventional method and dispersing them uniformly using a planetary mixer, roll mill, or the like to form a paste.

The present invention further relates to a cured product of the resin composition. The resin composition of the present invention, which uses a flexible epoxy resin in combination with a reactive diluent having a specific structure, can provide a cured product with excellent impact resistance and electrical conductivity. The cured product of the present invention also exhibits good electrical conductivity (contact resistance value) and adhesive strength even under high temperature and high humidity conditions. Heating is preferred as a curing method, and the heating conditions can be appropriately adjusted. For example, the resin composition may be cured by maintaining the temperature at 60 to 100°C, preferably 70°C to 90°C, for example, for 20 minutes to 3 hours, preferably 40 minutes to 2 hours.

The resin composition of the present invention can be used as a conductive adhesive for assembling electronic components, connecting them to substrates, and mounting chip components on substrates.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

A resin composition was prepared with the composition shown in Table 1. All components except for components (E) and (F) were mixed for 30 minutes in a planetary mixer (5DMV-01-r, Dalton Co., Ltd.). Then, components (E) and (F) were added and mixed for 20 minutes, and then degassed and mixed for 30 minutes in the planetary mixer to prepare the resin composition. The materials used are as follows:

EXA-4816: Modified epoxy resin (flexible and tough), manufactured by DIC Corporation, viscosity 100 Pa·s or more ZX-1059: Manufactured by Nippon Steel Chemical Co., Ltd., 1:1 mixture of bisphenol A resin and bisphenol F resin, viscosity 2500 mPa·s
YDF-8170: manufactured by Nippon Steel Chemical Co., Ltd., bisphenol F type resin, viscosity 1300 mPa·s
RKB-3040: Resinous Bond, product name, manufactured by Resinous Chemical Co., Ltd., core-shell polymer-containing epoxy resin, 30% by weight of core-shell polymer, 70% by weight of bisphenol A resin and bisphenol F resin (viscosity measurement of epoxy resin component is not possible because it is a mixture)
ED-523L: Neopentyl glycol diglycidyl ether, manufactured by ADEKA Corporation, viscosity 8 mPa·s
BD(D): Yokkaichi Chemical Co., Ltd., trade name "Epogosey", 1,4-butanediol diglycidyl ether, 8 mPa·s
ED-503G: ADEKA Corporation, 1,6-hexanediol diglycidyl ether, viscosity 24 mPa·s
ZX-1658GS: 1,4-cyclohexanedimethanol diglycidyl ether, manufactured by Nippon Steel Chemical Co., Ltd., viscosity 32 mPa·s
EX-201: Nagase ChemteX Corporation, resorcinol diglycidyl ether, viscosity 350 mPa·s
Epolite 200P (N): manufactured by Kyoeisha Chemical Co., Ltd., tripropylene glycol diglycidyl ether, viscosity 30 mPa·s
EX-830: Nagase ChemteX Corporation, polyethylene glycol diglycidyl ether, viscosity 70 mPa·s
EX-841: Nagase ChemteX Corporation, polyethylene glycol diglycidyl ether, viscosity 110 mPa·s
ZX-1542: Trimethylolpropane triglycidyl ether, manufactured by Nippon Steel Chemical Co., Ltd., viscosity 61 mPa·s
PN-H: Ajinomoto Fine-Techno Co., Ltd., trade name "Amicure", imidazole group-containing modified polyamine FXR-1081: T&K Toka, trade name "Fujicure", urea bond-containing modified polyamine Silver particles: Metalo, trade name EA-0101, average particle size 6.8 μm, specific surface area 0.28 m ² /g, flake-shaped zinc particles: Hakusui Tech Co., Ltd., trade name Zinc Powder R Powder, average particle size 5.2 μm, specific surface area 0.25 m ² /g, spherical JF-003: Mitsubishi Rayon Co., Ltd., trade name pregelling agent, core-shell polymer

The viscosity of the resin compositions of the examples and comparative examples, and the resistivity, tensile shear adhesive strength, and increase in contact resistance under high temperature and high humidity of the cured products were measured using the following methods. The results are shown in Table 1.

(1) Viscosity measurement (25°C)
0.22 ml of the resin composition was added, and the viscosity was measured using an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.) according to a procedure in accordance with JIS-K7117-2, using a 3°×R9.7 rotor at 20 rpm for 2 minutes.

(2) Measurement of Electrical Conductivity (Specific Resistivity) A 120 mm line with a width of 2 mm and a thickness of about 80 μm was bar-coated on an FR-4 substrate with the resin compositions of the Examples and Comparative Examples, and cured at 80° C. for 60 minutes in a heat circulation oven (DF-610, manufactured by Yamato Scientific Co., Ltd.) to prepare a test sample for measuring specific resistance. The resistance of the cured product was measured in four-terminal mode at a distance of 100 mm using a digital multimeter (R6552, manufactured by Advantest Corporation), and the specific resistance was calculated.

(3) Measurement of Tensile Shear Adhesive Strength Adhesive test pieces were prepared from nickel-plated stainless steel measuring 100 mm x 25 mm x 1.5 mm according to the procedure of JIS-K6850 and cured at 80°C for 60 minutes. The tensile shear adhesive strength was measured according to the procedure of JIS-K6850 using a universal tensile tester (AC-50kN, manufactured by TSE Co., Ltd.).

(4) Increase in contact resistance value under high temperature and high humidity As shown in FIG. 1, a conductor 2 was fixed on a nickel-plated stainless steel 4 measuring 100 mm x 25 mm x 1.5 mm. A resin composition 3 was applied to the conductor 2 so that the resin composition 3 was in contact with the nickel surface at a diameter of 1 mm, and cured in a heat circulation oven at 80°C for 60 minutes to prepare a test sample for measuring contact resistance. The resistance value between the conductor 2 and the nickel-plated surface was measured using a digital multimeter 1 (R6552 manufactured by Advantest Corporation), and this was taken as the contact resistance value between the resin composition 3 and nickel. The time until the contact resistance after exposure to a temperature of 85°C and a humidity of 85% exceeded 10 times the initial value was taken as the reliability retention time.

The resin compositions or cured products of the examples and comparative examples were evaluated for viscosity, resistivity, adhesion, and reliability under high temperature and humidity conditions according to the following criteria.

(1) Viscosity: ○: Viscosity (Pa·s) is less than 10
×: Viscosity (Pa·s) is 10 or more

(2) Specific resistance: less than 4.0 x ^10-3 Ω·cm
○: 4.0×10 ⁻³ Ω·cm or more and less than 5.0×10 ⁻³ Ω·cm
△: 5.0×10 ^-3 Ω・cm or more, less than 7.0×10 ⁻³ Ω・cm ×: 7.0×10 ⁻³ Ω・cm or more

(3) Adhesion: Good: Tensile shear adhesive strength (N/mm ² ) of 8 or more
△: Tensile shear adhesive strength (N/mm ² ) is 6 or more and less than 8. ×: Tensile shear adhesive strength (N/mm ² ) is less than 6.

(4) Reliability retention time under high temperature and high humidity conditions: ⊚: retention time is 300 hours or more; ◯: retention time is 200 hours or more but less than 300 hours; ×: retention time is less than 200 hours

When a diluent containing an aromatic ring (Comparative Example 2) or a diluent having three glycidyl ether groups (Comparative Example 6) was used, the viscosity of the resin composition did not decrease sufficiently compared to when no diluent was used (Comparative Example 1). In addition, even when a low-viscosity diluent having two glycidyl ether groups was used, when a diluent having an aromatic ring (Comparative Example 2) or a polyether structure (Comparative Examples 3 to 5) was used, the resistivity increased significantly compared to when no diluent was used (Comparative Example 1).

On the other hand, in Examples 1 to 4, which used the reactive diluent of the present invention, both low viscosity of the resin composition and high electrical conductivity of the cured product were achieved, and the adhesiveness and reliability under high temperature and high humidity were also good. Among them, Examples 1 to 3, which used a diluent having a non-alicyclic aliphatic hydrocarbon group as the aliphatic hydrocarbon group (R), had higher electrical conductivity, and Examples 1 and 2, which used a diluent with an aliphatic hydrocarbon group (R) having 4 or 5 carbon atoms, demonstrated high reliability under high temperature and high humidity.

Claims (14)

(A) a flexible epoxy resin containing a linear hydrocarbon structural unit having from 4 to 20 carbon atoms and/or a polyalkylene ether structural unit having from 3 to 20 ether oxygen atoms;
(B) a reactive diluent having a structure (Gly-O-R-O-Gly) in which two glycidyl ether groups (-O-Gly) are bonded to a divalent aliphatic hydrocarbon group (R) and having a viscosity of 500 mPa s or less at 25°C;
(C) an epoxy resin curing agent; and
(D) silver particles;
A resin composition comprising: The resin composition according to claim 1, wherein the aliphatic hydrocarbon group (R) is a saturated aliphatic hydrocarbon group. The resin composition according to claim 1, wherein the aliphatic hydrocarbon group (R) is a non-alicyclic aliphatic hydrocarbon group. The resin composition according to claim 1, wherein the aliphatic hydrocarbon group (R) has 3 or more and 6 or less carbon atoms. The resin composition according to claim 4, wherein the aliphatic hydrocarbon group (R) has 4 or 5 carbon atoms. The resin composition according to claim 1, wherein the viscosity of the reactive diluent (B) at 25°C is 100 mPa·s or less. The resin composition according to claim 1, wherein the flexible epoxy resin (A) further contains a bisphenol-type structural unit. The resin composition according to claim 1, wherein the epoxy resin curing agent (C) is at least one selected from the group consisting of a tertiary amino group-containing modified polyamine, a urea bond-containing modified polyamine, and an imidazole-containing modified polyamine. The resin composition according to claim 1, further comprising (E) an epoxy resin (excluding the flexible epoxy resin (A)). The resin composition according to claim 1, comprising 0.1 to 40 mass% of the flexible epoxy resin (A) relative to the total mass of the resin composition. The resin composition according to claim 1, comprising 0.1 to 30 mass% of the reactive diluent (B) relative to the total mass of the resin composition. The resin composition according to claim 1, which contains 2 to 40 parts by weight of the epoxy resin curing agent (C) per 100 parts by weight of the epoxy resin contained in the resin composition. The resin composition according to claim 1, comprising 30 to 95% by mass of the silver particles (D) relative to the total mass of the resin composition. A cured product of the resin composition according to any one of claims 1 to 13.