JPS5920371A - Conductive adhesive - Google Patents

Abstract

PURPOSE:To provide a conductive adhesive excellent in adhesion and conductivity, well suited for bonding of a variety of electronic parts, by incorporating an epoxy compd., a particular hardener, a conducting material, and lactones. CONSTITUTION:An imidazole compd. (e.g., 2-ethyl-4-methyl-cyanoethylimidazole) is reacted with phosphoric acid or an org. carboxylic acid (e.g., formic acid) in an amt. not exceeding equivalent to yield a hardener comprising a salt of the imidazole compd. with phosphoric acid or org. carboxylic acid. Then, 1- 30pts.wt. imidazole compd. or said hardener, 1-35pts.wt. lactones (e.g., beta-propiolactone), and 50-95wt% conducting material (e.g., silver powder) are incorporated with 100pts.wt. epoxy compd. (e.g., bisphenol A type epoxy resin).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive adhesive used for bonding various electronic components, such as bonding an IC chip to a substrate.

Conventionally, IC chips have been bonded to substrates using gold-silicon eutectic or solder materials, but in recent years there has been a rapid shift to conductive adhesives in view of cost and workability. As conductive adhesives, those having a composition containing an epoxy resin, a curing agent, and a conductive material are known, and imidazole-based compounds are known as curing agents for epoxy resins. The present inventors tested the performance of a conductive adhesive using various imidazole compounds as curing agents, and found that this composition did not have sufficient conductivity and adhesive properties, and was not suitable for practical use. It turned out that it could not be used. Therefore, as a result of further investigation, it was discovered that the conductive adhesive described above containing lactones has extremely excellent conductivity, and the present invention was achieved. That is, the present invention provides a conductive adhesive containing an epoxy compound, a curing agent, and a conductive material, in which an imidazole compound or its organic carboxylate or phosphate is used as a curing agent, and lactones are used as a curing agent. Epoxy compound 100
! The above conductive adhesive is characterized in that the conductive adhesive contains 1 to 35 parts by weight based on the amount of the conductive adhesive.

The imidazole compounds used in the present invention include imizole, an alkyl group having 1 to 18 carbon atoms such as a methyl group, an ethyl group, a hebutadecyl group, an undecyl group, a cyclohexyl group, etc. Substituted imidazoles substituted with cycloalkyl groups, phenyl groups, aryl groups such as tolyl groups, and hydrogen atoms bonded to the nitrogen of imidazole or the above-mentioned substituted imidazoles are substituted with alkyl groups, cyanoethyl groups, benzyl groups, 2-guanidylethyl groups, etc. N-substituted products are included.

In addition to the imidazole compounds mentioned above, the curing agents used in the present invention include organic carboxylates or phosphates thereof.

Examples of organic carboxylic acid salts include formic acid, acetic acid, acetic anhydride, propionic acid, propionic anhydride, butyric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, noclumitic acid, stearic acid, Acrylic acid, oleic acid, lactic acid, co-phosphoric acid, co-phosphoric anhydride,
Oxalic acid, malonic acid, adipic acid, monomethyl succinate, monoethyl succinate, motuptil succinate, monopropyl succinate, maleic acid, maleic anhydride, monomethyl maleate, monoethyl maleate, motuptil maleate, monoglobil maleate, etc. There are aromatic carboxylic acids such as aliphatic carboxylic acids, benzoic acid, phthalic acid, naphthoic acid, trimellitic acid, hemimellitic acid, trimesic acid, diphenic acid, and salicylic acid.

Phosphoric acids include metaphosphoric acid, birophosphoric acid, orthophosphoric acid, triphosphoric acid, tetraphosphoric acid, and the like.

The above-mentioned organic carboxylate or phosphate of the imidazole compound is obtained by heating the imidazole compound and the organic carboxylic acid or phosphoric acid at 50 to 100°C. In practice, it is used as a mixture obtained by reacting an imidazole compound with an equivalent or less amount of organic carboxylic acid or phosphoric acid.

The amount of the curing agent used is 1 to 30 parts by weight per 100 parts by weight of the epoxy compound described below.

The epoxy compounds used in the present invention include bisphenol A type epoxy resin, bisphenol F type epoxy resin,
Resin type epoxy compounds such as novolac type epoxy resins and optionally alkylphenol glycidyl ether, phenyl glycidyl ether, butyl glycidyl ether, N, N~diglycidyl-〇-toluidine, p-tert-butylbenzoic acid glycidyl ester,
1,6-hexanesiol diglycidyl ether Δ and a lower molecular weight epoxy compound can be used together.

The lactones used in the present invention do not by themselves contain any
Or is it due to the fact that it hardly has the curing effect of an epoxy compound, but is blended with it? It has remarkable conductive properties. Such lactones include β-propiolactone, dimethylpropiolactone, r-butyrolactone, γ-valerolactone, γ-caprolactone, γ-caprylolactone,
γ-laurolactone, γ-palmitolactone, γ-stearolactone, crotolactone, α-angelicalactone, β-angelicalactone, δ-valerolactone, δ
These include hecaprolactone and macrocyclic lactones.

The amount of the lactones used is preferably 1 to 35 parts by weight per 160 parts by weight of the epoxy compound; if the amount is less than 1 part by weight, sufficient conductivity cannot be obtained, and if the amount is more than 35 parts by weight. Although the conductivity is sufficient, the adhesive strength does not reach a practical level.

The conductive materials used in the present invention include gold powder, silver powder, copper powder, aluminum powder, nickel powder, carbon powder, graphite, carbon fiber, silver plating fine powder (glass beads carrier), etc. is preferred. The shape of the silver powder can be spherical, flaky, or dendritic, and the average particle size is preferably 0.5 to 5.0 μm.

The conductive material is blended in an amount of 50 to 95% by weight based on the total weight.

The conductive adhesive of the present invention is used as a two-component type consisting of a main agent containing an epoxy compound and a curing agent, but the conductive material and lactones are blended in either the main agent, the curing agent, or both. do.

Hereinafter, the present invention will be specifically explained with reference to Examples. In the examples, parts indicate parts by weight.

Example 1 The main component and curing agent component shown in the following formulation were kneaded using three rolls, and then mixed to obtain a two-component conductive adhesive. Sample pieces were prepared using this conductive adhesive, and the volume resistivity and tensile shear adhesive strength were measured. The results are shown in Table 1.

Main ingredient: Bisphenol F type epoxy resin 40
Flake-like silver powder (average particle size 3.0μ)
60 parts hardening agent 2-'L-4-Meth-'A'1-I9"
zo part γ-butyrolactone 10 parts flaky silver powder (average particle size i, 5μ) 70
Section Example 2 Example 1 except that the curing agent component was changed to the formulation shown below.
A conductive adhesive was obtained in the same manner, and the same test as in Example 1 was conducted. However, 2-ethyl-4-methyl-cyanoethylimidazole containing formate is prepared by adding 4 parts of formic acid to 100 parts of 2-ethyl-4-methyl-cyanoethylimidazole and making 75%
The mixture was reacted at ℃ for 1 hour and then used.

Hardening agent component - Butyrolactone 4 parts Flake silver powder (average particle size 1.5μ) 90 parts Comparative example 1 Example 1 except that the hardening agent component was changed to the formulation shown below.
A conductive adhesive was obtained in the same manner as in Example 1, and the same test as in Example 1 was conducted.

Hardening agent component flaky silver powder (average particle size 1.5μ) 9
0 parts Comparative Example 2 Example 1 except that the curing agent component was changed to the formulation shown below.
A conductive adhesive was obtained by the same operation as in Example 1, and the same test as in Example 1 was conducted. However, 2-ethyl-4-methyl-cyanoethylimidazole containing formate was obtained in the same manner as in Example 2.

Hardening agent component flaky silver powder (average particle size 1.5μ) 9
0 parts Example 3 A conductive adhesive was obtained in the same manner as in Example 1 using the main component and curing agent component shown in the following formulation, and the same test as in Example 1 was conducted. However, 2-ethyl-4-methyl-cyanoethylimidazole containing lactate is 2-ethyl-4-methyl-
Add 4 parts of lactic acid to 100 parts of cyanoethyl imidazole,
The reactant was reacted at 75°C for 1 hour and used.

Main component Phenylgrindyl ether 5 parts Flake-like silver powder (3.0μ) 60 parts Curing inhibitor molecule - butyrolactone 2 parts Flake-like silver powder (average number diameter 1.5μ) 90 parts Example 4' □ As shown in the following treatment 2-Ethyl-4-methyl-cyanoethylimidazole, which uses the main component and curing agent component, is obtained by adding 2 parts of orthophosphoric acid to 100 parts of 2-ethyl-4-methyl-cyanoethylimidazole and reacting at 75°C for 1 hour. It was used.

Main ingredient 1.6-hexanethiol diglycidether 5
Part dendritic silver powder (average particle size 3.0μ) 60 parts Curing agent γ-caprolactone 4 parts Flaky silver powder (average particle size 1.5μ) 80 parts Example 5 The hardening component was changed to the formulation shown below. In other respects, a conductive adhesive was obtained in the same manner as in Example 1, and the same tests and tests as in Example 91JI were carried out.

Curing agent component 1-benzyl-2-methylimidazole
8 parts r-butyrolactone
2 parts flaky silver powder (average particle size 1.5 μl
90 parts Comparative Example 3 Example 1 except that the curing agent component was changed to the formulation shown below.
A conductive adhesive was obtained in the same manner as in Example 1, and the same test as in Example 1 was conducted.

Curing agent component 2-ethyl-4-methylone anoethyl imidazole
10 parts r Butyrolactone XX&'*
JUe' 20 parts Flake silver powder (average particle size 1.5μ) 70 parts Table 1 Table 1 shows the conductive adhesives obtained in each example and comparative example.
The volume resistance and tensile shear adhesive strength after curing at 0° C. for 15 minutes are shown.

Volume resistivity was measured using a striped sample. 1. Glue two copper plates as leads on a glass plate with a distance of 2.0 cm. Then, a groove with a width of 3 mm was made between the copper plates using two pieces of pressure-sensitive tape with a thickness of 180μ, and after applying the mixture of the above-mentioned main agent and curing agent into the groove, the tape was peeled off.
Stripes with a cross-sectional area of 5.4XlO''crI and a length of 2 m were made.

Then, it was cured at 120° C. for 15 minutes, the resistance between the copper leads was measured, and the volume resistance was calculated.

Tensile shear adhesive strength is 1.6 mm thick and 10 mm long.
After polishing and degreasing two copper plates with a width of 25 mm and a width of 0 mr+1, a 12 m
The adhesive strength was measured after bonding with a width of rn and curing at 120° C. for 15 minutes.

patent applicant Toyo Ink Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. In a conductive adhesive containing an epoxy compound, a curing agent, and a conductive material, an imidazole compound or an organic carboxylate or phosphate thereof is used as a curing agent,
The conductive adhesive described above contains lactones in an amount of 1 to 35 parts by weight based on 100 parts by weight of the epoxy compound.