JP7828541B2 - conductive paste - Google Patents

Description

This invention relates to a conductive paste.

Conventionally, thermosetting conductive paste containing silver particles has been used as an alternative connection method to solder for assembling electronic components and connecting them to circuit boards (Patent Document 1). Conductive paste is sometimes used in the manufacture of electronic devices such as camera modules and printed circuit boards to make electrical connections between multiple components, and for forming wiring and electrodes. For finer connections, wiring, and electrode formation, it is sometimes necessary to reduce the viscosity of the conductive paste. One known method for reducing the viscosity of conductive paste is to use a low-viscosity diluent. Furthermore, when used in electronic devices and printed circuit boards, impact resistance may be required for the cured product of the conductive paste. One known method for imparting impact resistance to the cured product is to use an epoxy resin with a flexible structure (flexible epoxy resin) (Patent Document 2).

Japanese Patent Publication No. 2015-42696 Patent No. 5786418

However, when using a flexible epoxy resin in a conductive paste, the viscosity of the conductive paste will also be high due to the high viscosity of the flexible epoxy resin. In this case, using a diluent to reduce viscosity is an option, but excessive use tends to decrease the physical properties of the cured product, such as mechanical strength. If the amount used is limited, the viscosity of the conductive paste may not be sufficiently reduced depending on the type of diluent. Furthermore, depending on the type of diluent, problems such as decreased conductivity (increased resistance) of the cured product may occur.

The object of this invention is to provide a low-viscosity resin composition that yields a cured product with high conductivity when used in combination with a flexible epoxy resin and a diluent.

The inventors of this invention have 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 while suppressing a decrease in the conductivity of the cured product, thus completing the present invention.

In other words, the present invention encompasses the following embodiments.
[1] (A) A flexible epoxy resin comprising linear hydrocarbon structural units having 4 to 20 carbon atoms and/or polyalkylene ether structural units 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) Epoxy resin hardener and
(D) Silver particles and
A resin composition containing [the specified ingredient].
[2] The resin composition according to [1], wherein the aliphatic hydrocarbon group (R) is a saturated aliphatic hydrocarbon group.
[3] The resin composition according to [1] or [2], 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], wherein the number of carbon atoms in the aliphatic hydrocarbon group (R) is 3 or more and 6 or less.
[5] The resin composition according to [4], 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 comprises bisphenol-type structural units.
[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 tertiary amino group-containing modified polyamines, urea bond-containing modified polyamines, and imidazole-containing modified polyamines.
[9] (E) The resin composition according to any one of [1] to [8], further comprising 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% by mass of the flexible epoxy resin (A) based on the total mass of the resin composition.
[11] The resin composition according to any one of [1] to [10], comprising 0.1 to 30% by mass of the reactive diluent (B) based on 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], comprising 30 to 95% by mass of the silver particles (D) based on the total mass of the resin composition.
[14] A cured product of any of the resin compositions described in [1] to [13] above.

This invention provides a low-viscosity resin composition that yields a highly conductive cured product by using a flexible epoxy resin and a diluent in combination.

Figure 1 shows a test sample for contact resistance measurement.

The present invention relates to a resin composition comprising: (A) a flexible epoxy resin containing linear hydrocarbon structural units having 4 to 20 carbon atoms and/or polyalkylene ether structural units 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 linear hydrocarbon structural units having 4 to 20 carbon atoms and/or polyalkylene ether structural units having 3 to 20 ether oxygen atoms.

The linear hydrocarbon structural unit contained in the flexible epoxy resin is represented as -( _CH2 ) _x- , where x is between 4 and 20. Preferably, x is between 4 and 10. The hydrogen atoms may be replaced by substituents such as hydroxyl groups, and furthermore, a form in which at least one of the hydrogen atoms is substituted with a hydrocarbon group, alkoxy group, aryl group, aryloxy group, etc., can also be used. The hydrocarbon and alkoxy groups used as substituents preferably have 4 or fewer carbon atoms, and the aryl group of the aryl group and 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 polyalkylene ether structural units contained in the flexible epoxy resin have 3 to 20 ether oxygen atoms, preferably 3 to 10. Specifically, examples include structural units derived from polymers of one or more alkylene oxides selected from ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, neopentylene oxide, tetramethylene oxide, etc. Furthermore, examples include those in which one or more hydrogen atoms of the alkylene oxide are substituted with, for example, a hydroxyl group, alkoxy group, aryl group, aryloxy group, or hydrocarbon group. The hydrocarbon or alkoxy group as the substituent preferably has 4 or fewer carbon atoms, and the aryl group of the aryl 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.

Linear hydrocarbon structural units with 4 to 20 carbon atoms improve the heat resistance of cured products, while polyalkylene ether structural units improve adhesion and bonding to materials such as metal substrates. By appropriately selecting these structural units, it is possible to accommodate various substrates, manufacturing processes, and required performance.

The flexible epoxy resin preferably contains bisphenol-type structural units in addition to the linear hydrocarbon structural units and/or polyalkylene ether structural units described above. Examples of bisphenol-type structural units include those derived from bisphenol A, bisphenol F, and bisphenol S. Specifically, these include units with the terminal OH groups removed and units represented by the following general formula (1), and the rings may be hydrogenated. Furthermore, these rings may have substituents such as hydrocarbon groups, alkoxy groups, aryl groups, aryloxy groups, and hydroxyl groups.

When a flexible epoxy resin contains bisphenol-type structural units, the molar ratio of linear hydrocarbon structural units and/or polyalkylene ether structural units to bisphenol-type structural units is preferably 1:10 to 5:1, and more preferably 1:5 to 3:1. If the amount of bisphenol-type structural units exceeds this range, the cured product will not have sufficient flexibility. Conversely, if the amount of bisphenol-type structural units is too low, the Tg of the cured product will be low, resulting in reduced heat resistance.

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). Furthermore, multiple hydroxyl groups in the following structural formulas may undergo crosslinking reactions, and the oxygen atoms of the hydroxyl groups may form unspecified structures.

In structural formulas (2-i) to (2-iv), ^Ar1 and ^Ar2 may be the same or different, may be hydrogenated, and may have substituents; X is a linear hydrocarbon group having 4 to 20 carbon atoms and/or a polyalkylene ether structure having 1 to 18 ether oxygen atoms. When X is a linear hydrocarbon group having 4 to 20 carbon atoms, X is a linear hydrocarbon structural unit; when X is a polyalkylene ether structure having 1 to 18 ether oxygen atoms, -O-X-O- is a polyalkylene ether structural unit. Also, n is the average value of the repeating units, ranging from 1 to 30.

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

The content of the flexible epoxy resin is preferably 0.1 to 40% by mass of the total mass of the resin composition, more preferably 0.2 to 35% by mass, and even more preferably 0.5 to 30% by mass. For example, it may be 0.8 to 20% by mass, 1 to 10% by mass, or 1.5 to 6% by mass. If the amount of 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 of 500 mPa·s or less at 25°C.

The aliphatic hydrocarbon group (R) may be unsaturated or saturated, and may be alicyclic or acyclic. From the viewpoint of obtaining a cured product with good impact resistance and conductivity while keeping the viscosity of the resin composition low, the aliphatic hydrocarbon group (R) is preferably saturated and preferably acyclic. The number of carbon atoms in the aliphatic hydrocarbon group (R) is preferably 6 or less, more preferably 5 or less, and 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 greater than 500 mPa·s at 25°C (for example, a viscosity greater than 100 Pa·s at 25°C), a diluent having a viscosity of 500 mPa·s or less can lower the viscosity of the resin composition containing the 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 low viscosities 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 the viscosity can be measured using a 1.34° × R24 rotor at 25°C, 5 rpm, and 2 minutes, following the procedure compliant with JIS-K7117-2. For viscosities exceeding 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 the viscosity can be measured using a 3° × R9.7 rotor at 25°C, 20 rpm, and 2 minutes, following the 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 Gosei Co., Ltd.), and "ZX-1658GS" (manufactured by Nippon Steel Chemical Corporation).

The content of the reactive diluent is preferably 0.1 to 30% by mass of the total mass of the resin composition, more preferably 0.2 to 25% by mass, and even more preferably 0.5 to 20% by mass. For example, it may be 1 to 15% by mass, 1.5 to 12.5% by mass, or 2 to 10% by mass. If the amount of reactive diluent is within the above range, a cured product with good conductivity can be obtained while keeping the viscosity of the resin composition low.

(C) Epoxy resin curing agent In the present invention, known epoxy resin curing agents can be used without particular limitation.

From the viewpoint of handling the resin composition, it is preferable that the epoxy resin curing agent be a latent curing agent. In this specification, a latent curing agent is a compound blended into a resin composition for the purpose of curing the epoxy resin. While such a resin composition does not react with functional groups such as epoxy groups under normal storage conditions (room temperature, under visible light, etc.), it exhibits reactive activity towards functional groups upon exposure to heat or light, thereby curing the resin composition. These may be used individually or in combination of two or more.

From the viewpoint of viscosity of the resin composition and conductivity and adhesion of the cured product, the epoxy resin curing agent is preferably 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. From the viewpoint of adhesion, it is even more preferable to use a combination of urea-bond-containing modified polyamines and imidazole-containing modified polyamines.

In this specification, a tertiary amino group-containing modified polyamine is a compound having a polymer structure containing an aliphatic tertiary amine other than imidazole, where the active amine forms a stabilized structure with epoxy resin and/or 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 with a polymer structure containing imidazole, where the active amine is stabilized by epoxy resin and/or phenolic resin, making them usable as latent curing agents. Examples of imidazole-containing modified polyamines include PN-23, PN-H, and PN-40 from Ajinomoto Fine Techno Co., Ltd., EH4346S from ADEKA Corporation, FXR-1121 from T&K TOKA Corporation, and Sanmide LH210 from Air Products Japan Co., Ltd.

Urea-bonded modified polyamines are compounds in which an active amine is stabilized by a urea bond formed by an isocyanate resin, making them usable as latent curing agents. Examples of urea-bonded modified polyamines include FXR-1020 and FXR-1081, manufactured by T&K TOKA Corporation.

The epoxy resin curing agent is preferably added in an amount of 1 to 50 parts by weight per 100 parts by weight of epoxy resin contained in the resin composition. Considering the curing speed of the epoxy resin, sufficient crosslinking formation, viscosity of the resin composition, and applicability, the amount of curing agent is more preferably 2 to 40 parts by weight, even more preferably 5 to 35 parts by weight, for example, 10 to 30 parts by weight, 15 to 28 parts by weight, or 20 to 27 parts by weight per 100 parts by weight of epoxy resin contained in the resin composition.

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

The average particle size of the silver particles used in this invention is preferably 1 to 15 μm. Considering the handling properties of the resin composition (appropriate viscosity) and the occurrence of nozzle clogging during dispensing 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 analyzer as the particle size (median diameter) 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 graphed with respect to total particle amount and particle size).

When using flake-shaped silver particles, the specific surface area is preferably 0.1 to 1.5 ^m² /g. From the viewpoint of the conductivity of the cured product or the dispensability of the resin composition (in this specification, dispensability refers to the ease of application when filling a syringe with the resin composition and applying it with a dispenser, etc.), 0.15 to 1.0 ^m² /g is more preferable, and 0.2 to 0.9 ^m² /g is even more preferable. The specific surface area is measured using a specific surface area measuring device with the BET (Brunauer, Emmett and Teller's extended multi-layer adsorption model for measuring specific surface area, abbreviated as BET from the first letters of their names) single-point method.

The silver particle content is preferably 30 to 95% by mass of the total mass of the resin composition, more preferably 40 to 80% by mass from the viewpoint of the conductivity of the cured product and the viscosity of the resin composition, and may also 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) to impart high adhesion. The epoxy resin (E) may be solid or liquid at 25°C, and in the case of a liquid, it is preferable that its viscosity at 25°C is greater than 500 mPa·s. Preferably, the viscosity at 25°C is 750 mPa·s or more, more preferably 1000 mPa·s or more, preferably 20000 mPa·s or less, and more preferably 10000 mPa·s or less, for example, 5000 mPa·s or less, or 4000 mPa·s or less. The viscosity of the epoxy resin (E) at 25°C can be measured, for example, by placing a 0.22 ml 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, using a rotor of 3° × R9.7 in accordance with the procedure in accordance with JIS-K7117-2.

The epoxy resin (E) is not particularly limited, but it is preferable that it has an average of two or more epoxy groups per molecule. Examples 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, diglycidyltoluidine, diglycidylaniline, 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 naphthalenediols, 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 a bisphenol-type epoxy resin with low viscosity and good stability, more preferably a bisphenol A-type epoxy resin or a bisphenol F-type resin, and more preferably a mixture of bisphenol A-type epoxy resin and bisphenol F-type resin.

Examples of readily available bisphenol-type epoxy resins include RE-310S, RE-304S, RE-404S from 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 from 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- 927H, ZX-1059, YDF-8170, YDF-170, YDF-175S, YDF-2001, YDF-2004, and the Epiclon series manufactured by Dainippon Ink and Chemicals, Inc.: 840, 840S, 850, 850S, 850CRP, 855, 857, D-515, 860, 900-IM, 1050, 1055, 2055, 3050, 40 Examples include 50, 4055, 7050, 9055, 830, 830S, 830LVP, 835, 835LV, EXA-1514, EXA-4004, Mitsubishi Chemical Corporation's 828, 828EL, 827, 806, 807, YL980, YL983, and ADEKA Corporation's ADEKA Resin series EP-4100, EP-4500, and EP-4901.

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

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

The particle size of the metal powder (F) is preferably 1 to 15 μm, and more preferably 1 to 10 μm, considering factors such as the handling of the resin composition and the occurrence of nozzle clogging during application with a dispenser.

The specific surface area of the metal powder (F) is preferably 0.1 to 1.5 ^m² /g, and more preferably 0.1 to 1.0 ^m² /g, from the viewpoint of the conductivity of the cured product and the dispensability of the resin composition.

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

(G) Core-shell polymer The resin composition of the present invention may be blended with a core-shell polymer to improve adhesion and provide stress relaxation properties. A core-shell polymer is a polymer having a core and a shell, and is obtained by polymerizing a relatively hard shell layer, prepared from (meth)acrylic acid ester, aromatic vinyl, vinyl cyanide, epoxyalkyl vinyl ether, unsaturated acid derivative, (meth)acrylamide derivative and/or maleimide derivative, etc., onto a relatively soft core portion prepared from a diene monomer, (meth)acrylic acid ester monomer and/or vinyl monomer, etc., a rubber elastic body, a polysiloxane rubber elastic body, or a mixture thereof. Available core-shell polymers include MX-120, MX-125, MX-130, MX-135, MX-960, MX-965 from Kaneka Corporation, RKB-3040, RKB-1133 from Reginas Chemicals Co., Ltd., JF-001, JF-003 from Mitsubishi Rayon Co., Ltd., and F351G from Gantz Chemicals Co., Ltd. Known core-shell polymers can be used in powder form or dispersed in epoxy resin. These may be used alone or in combination of powder and epoxy resin dispersion. The core-shell polymer content is preferably 0.1 to 20% by mass of the total mass of the resin composition, more preferably 0.5 to 10% by mass, 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 that is fluid at 25°C. Considering its application in adhering to gaps in a substrate, its 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 placing a 0.22 ml 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, using a rotor with a radius of 3° × R9.7, in accordance with the procedure compliant with JIS-K7117-2.

The resin composition of the present invention may also contain other additives, such as 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 thixotropic agents such as boric acid esters and aerosil as appropriate.

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

The present invention further relates to a cured product of a resin composition. By using a resin composition of the present invention, which combines a flexible epoxy resin with a reactive diluent having a specific structure, a cured product with excellent impact resistance and conductivity can be obtained. The cured product of the present invention also exhibits good conductivity (contact resistance) and adhesive strength even under high temperature and high humidity conditions. Heating is preferred as the curing method, and the heating conditions can be adjusted as appropriate. For example, the resin composition may be cured by holding it at a temperature of 60 to 100°C, preferably 70 to 90°C, for, 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 a substrate, and mounting chip components onto a substrate.

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 with the composition shown in Table 1 was prepared. Components other than (E) and (F) were mixed for 30 minutes in a planetary mixer (Dalton Co., Ltd. 5DMV-01-r). Then, components (E) and (F) were added and mixed for 20 minutes, followed by degassing and mixing in the planetary mixer for 30 minutes. The materials used are as follows:

EXA-4816: Manufactured by DIC Corporation, modified epoxy resin (flexible and tough), viscosity 100 Pa·s or higher. ZX-1059: Manufactured by Nippon Steel Chemical Co., Ltd., 1:1 mixture of bisphenol A type resin and bisphenol F type resin, viscosity 2500 mPa·s.
YDF-8170: Manufactured by Nippon Steel Chemical Co., Ltd., bisphenol F type resin, viscosity 1300 mPa·s
RKB-3040: Manufactured by Reginas Chemicals Co., Ltd., product name: Reginas Bond, core-shell polymer-containing epoxy resin. Core-shell polymer 30% by weight, bisphenol A type resin and bisphenol F type resin 70% by weight (viscosity of epoxy resin component cannot be measured due to mixture).
ED-523L: Manufactured by ADEKA Corporation, neopentyl glycol diglycidyl ether, viscosity 8 mPa·s
BD(D): Manufactured by Yokkaichi Synthetic Co., Ltd., trade name "Epogosei", 1,4-butanediol diglycidyl ether, 8 mPa·s
ED-503G: Manufactured by ADEKA Corporation, 1,6-hexanediol diglycidyl ether, viscosity 24 mPa·s
ZX-1658GS: Manufactured by Nippon Steel Chemical Co., Ltd., 1,4-cyclohexanedimethanol diglycidyl ether, viscosity 32 mPa·s
EX-201: Manufactured by 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: Manufactured by Nagase ChemteX Corporation, polyethylene glycol diglycidyl ether, viscosity 70 mPa·s
EX-841: Manufactured by Nagase ChemteX Corporation, polyethylene glycol diglycidyl ether, viscosity 110 mPa·s
ZX-1542: Manufactured by Nippon Steel Chemical Co., Ltd., trimethylolpropane triglycidyl ether, viscosity 61 mPa·s
PN-H: Manufactured by Ajinomoto Fine Techno Co., Ltd., product name "Amicure", imidazole group-containing modified polyamine FXR-1081: Manufactured by T&K Toka, product name "Fujicure", urea-bonded modified polyamine silver particles: Manufactured by Metalo, product name EA-0101, average particle size 6.8 μm, specific surface area 0.28 ^m² /g, flake-shaped zinc particles: Manufactured by Hakusui Tech Co., Ltd., product name Zinc Powder R Powder, average particle size 5.2 μm, specific surface area 0.25 ^m² /g, spherical JF-003: Manufactured by Mitsubishi Rayon Co., Ltd., product name Pregelling Agent, Core Shell Polymer

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

(1) Measurement of viscosity (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.) in accordance with the procedure of JIS-K7117-2, using a 3° × R9.7 rotor, at 20 rpm, and the value after 2 minutes was taken as the measured value.

(2) Measurement of conductivity (resistivity) A line approximately 2 mm wide and 80 μm thick, 120 mm long was bar-coated onto the FR-4 substrate with the resin compositions of the examples and comparative examples. The samples were cured in a thermal circulation oven (DF-610, manufactured by Yamato Scientific Co., Ltd.) at 80°C for 60 minutes to prepare test samples for resistivity measurement. The resistance of the cured material was measured in 4-terminal mode at a distance of 100 mm using a digital multimeter (R6552, manufactured by Advantest Corporation), and the resistivity was calculated.

(3) Measurement of tensile shear bond strength Bond test specimens were prepared from nickel-plated 100 mm x 25 mm x 1.5 mm stainless steel according to the procedure in accordance with JIS-K6850 and cured at 80°C for 60 minutes. The tensile shear bond strength was measured using a universal tensile testing machine (AC-50kN, manufactured by TSE Corporation) according to the procedure in accordance with JIS-K6850.

(4) Increase in contact resistance under high temperature and high humidity conditions As shown in Figure 1, a wire 2 was placed and fixed on a 100 mm x 25 mm x 1.5 mm stainless steel 4 that was nickel-plated. A resin composition 3 was applied to the wire 2 in a diameter of 1 mm so as to be in contact with the nickel surface, and cured in a heat-circulating oven at 80°C for 60 minutes to prepare a test sample for contact resistance measurement. The resistance value between the wire 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. Subsequently, the time until the contact resistance after exposure to conditions of 85°C and 85% humidity exceeded 10 times the initial value was defined 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 high humidity conditions according to the following criteria.

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

(2) Resistivity ◎: Less than 4.0 × ^10⁻³ Ω·cm
○: 4.0 × ^10⁻³ Ω·cm or greater, 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 ○: Tensile shear adhesive strength (N/ ^mm² ) is 8 or higher.
△: Tensile shear bond strength (N/ ^mm² ) is 6 or greater and less than 8 ×: Tensile shear bond strength (N/ ^mm² ) is less than 6

(4) Reliability under high temperature and high humidity conditions ◎: Retention time of 300 hours or more ○: Retention time of 200 hours or more but less than 300 hours ×: Retention time of less than 200 hours

When using diluents containing aromatic rings (Comparative Example 2) or diluents having three glycidyl ether groups (Comparative Example 6), the viscosity of the resin composition did not decrease sufficiently compared to when no diluent was used (Comparative Example 1). Furthermore, even with low-viscosity diluents containing two glycidyl ether groups, using diluents with aromatic rings (Comparative Example 2) or polyether structures (Comparative Examples 3-5) resulted in a significant increase in resistivity compared to when no diluent was used (Comparative Example 1).

On the other hand, in Examples 1 to 4 using the reactive diluent of the present invention, both low viscosity of the resin composition and high conductivity of the cured product were achieved, and adhesion and reliability under high temperature and high humidity conditions were also good. Furthermore, in Examples 1 to 3, where the diluent had a non-alicyclic aliphatic hydrocarbon group (R), the conductivity was even higher. Moreover, in Examples 1 and 2, where the diluent had a four- or five-carbon aliphatic hydrocarbon group (R), high reliability under high temperature and high humidity conditions was demonstrated.

Claims (12)

(A) A flexible epoxy resin comprising linear hydrocarbon structural units having 4 to 20 carbon atoms and/or polyalkylene ether structural units having 3 to 20 ether oxygen atoms, and having a viscosity greater than 500 mPa·s at 25°C,
(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) Epoxy resin hardener and
(D) Silver particles and
A resin composition containing,
The aliphatic hydrocarbon group (R) is a non-alicyclic aliphatic hydrocarbon group and/or the number of carbon atoms of the aliphatic hydrocarbon group (R) is 3 or more and 6 or less.
The epoxy resin curing agent (C) 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.
The resin composition contains 30 to 80% by mass of the silver particles (D) based on the total mass of the resin composition.
A resin composition having a viscosity of less than 10 Pa·s at 25°C. 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) 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 comprises bisphenol-type structural units. (E) The resin composition according to claim 1, further comprising an epoxy resin (excluding the flexible epoxy resin (A)). The resin composition according to claim 1, comprising 0.1 to 40% by mass of the flexible epoxy resin (A) based on the total mass of the resin composition. The resin composition according to claim 1, comprising 0.1 to 30% by mass of the reactive diluent (B) based on the total mass of the resin composition. The resin composition according to claim 1, 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. The resin composition according to claim 1, comprising 40 to 80% by mass of the silver particles (D) based on the total mass of the resin composition. The resin composition according to claim 1, which does not contain a solvent. A cured product of the resin composition according to any one of claims 1 to 11 .