JPH08283624A - Electroconductive paste - Google Patents

Abstract

PURPOSE: To obtain an electroconductive paste by using cheap powdery copper, having a good electroconductivity and little change in the electroconductivity under a high moisture condition by dispersing powdery copper coated with a mixture of specific two compounds in an organic solvent containing a thermosetting resin. CONSTITUTION: In this electroconductive paste, the surface of powdery copper or silver plated powdery copper having <=30μm average particle size is coated with a mixture of an imidazole compound of formula I (R1 and R2 are each an alkyl, etc.) (e.g.; 2-ethyl-4-methylimidazole) with a glycidoxyalkoxysilane compound of formula II (R3 to R5 are each H, an alkoxy, etc.; (n) is 1-5) (e.g.; 3-glycidoxypropyltrimethoxysilane) in an amount of 0.0001-5wt.% based on the powdery metal and the coated powdery metal is dispersed in an organic solvent (preferably butyl cellosolve, etc.) containing a thermosetting resin (preferably a phenolic resin and/or an epoxy resin). The powdery metal is preferably flaky or arborescent for improving the electroconductivity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a conductive paste for electronic materials.

[0002]

2. Description of the Related Art Conventionally, metal powder such as silver, copper or nickel has been used as a conductive component of a conductive paste.

However, the conductive paste using silver has the drawbacks that the conductive component, silver, is expensive, and that electroplating of silver, which is called migration, tends to occur, resulting in poor insulation. Therefore, various conductive pastes have been proposed in which copper, which is cheaper than silver, is used as a main conductive component and the surface oxidation of copper is suppressed. As a copper antioxidant, Japanese Patent Publication No. 61-1417
5, fatty acid amides described in JP-B No. 61-36796, anthracene or a derivative thereof described in JP-B No. 61-36796, JP-A-57-5597.
Derivatives of hydroquinone described in JP-A-4, JP-A-58-2
Phenylenediamine derivatives described in JP-A No. 25168, higher fatty acid amines described in JP-A No. 61-200179,
Although there are unsaturated fatty acids and the like described in JP-A No. 61-211378, there is a drawback that the change in conductivity under high humidity is large.

[0004]

Claim 1 of the present invention
The described invention provides an electrically conductive paste that uses inexpensive metal powder, has good electrical conductivity, and has little electrical conductivity change under high humidity. In addition to the effect of the invention described in claim 1, the invention described in claim 2 provides a conductive paste in which contact between metal powders is good and conductivity is improved. In addition to the effect of the invention of claim 1 or 2, the invention of claim 3 provides a conductive paste having excellent adhesiveness.

[0005]

The present invention has an average particle size of 3
An imidazole compound represented by Chemical Formula 3 [general formula (1)] and a glycidoxyalkoxysilane compound represented by Chemical formula 4 [general formula (2)] on the surface of a metal powder containing copper powder of 0 μm or less or silver-plated copper powder; 0.0001 to the metal powder.
The present invention relates to a conductive paste in which an applied amount of ˜5% by weight is dispersed in an organic solvent containing a thermosetting resin.

[0006]

Embedded image (In the formula, R ₁ and R ₂ are each a hydrogen atom, an alkyl group,
Indicates a phenyl group or a cyano group).

[0007]

[Chemical 4] (In the formula, R ₃ , R ₄ and R ₅ each represent a hydrogen atom, an alkyl group or an alkoxy group, and n represents an integer of 1 to 5).

The present invention also relates to the above conductive paste, wherein the metal powder is flaky or dendritic. Furthermore, the present invention relates to the above conductive paste, in which the thermosetting resin is a phenol resin and / or an epoxy resin.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as the conductive component, use is made of copper powder having an average particle size of 30 μm or less, or metal powder containing silver-plated copper powder (hereinafter referred to as silver-plated copper powder). Is required. The average particle size of the metal powder is 30μ
If it exceeds m, the screen may become clogged during printing,
The elongation of the paste is poor and the printability is poor. Flake-shaped or dendritic metal powders are preferable because the contact between the metal powders is improved and the conductivity is improved. Further, metal powder having another shape may be processed into a flake by stamping or the like. The silver plating in the silver-plated copper powder may be plated by any of an electrolytic plating method, an electroless plating method, a displacement plating method, etc. and is not particularly limited.

The imidazole compound is mixed with the glycidoxyalkoxysilane compound and applied to the surface of the metal powder to form a chelate compound on the surface of the metal to prevent contact between copper and oxygen and prevent copper oxidation. To work. Examples of the imidazole compound used in the present invention include imidazole, 2-methylimidazole, 4-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenyl. -4-Methylimidazole and the like can be mentioned. Examples of the glycidoxyalkoxysilane compound include 3-glycidoxypropyltrimethoxysilane, dimethylethoxy-3-glycidoxypropylsilane, diethoxy-3-glycidoxypropylmethylsilane and the like.

As a method of applying a mixture of an imidazole compound and a glycidoxyalkoxysilane compound to the surface of the metal powder, a method of adding the imidazole compound and the glycidoxyalkoxysilane compound when the metal powder is processed into flakes. , A method of immersing a metal powder in an organic solvent solution of an imidazole compound and a glycidoxyalkoxysilane compound and vaporizing and removing the organic solvent, an organic solvent solution of the imidazole compound and a glycidoxyalkoxysilane compound in which the metal powder is immersed Method of separating metal powder by filtration,
There is a method of separating an organic solvent solution of an imidazole compound and a glycidoxyalkoxysilane compound, in which metal powder is immersed, by decantation.

The coating amount of the mixture of the imidazole compound and the glycidoxyalkoxysilane compound on the surface of the metal powder is
Although it varies depending on the types of the imidazole compound and the glycidoxyalkoxysilane compound, the average particle size of the metal powder, the shape of the metal powder, etc., it is in the range of 0.0001 to 5% by weight based on the metal powder. The coating amount of the mixture of the imidazole compound and the glycidoxyalkoxysilane compound was 0.0001.
If it is less than 5% by weight, the exposed surface of copper cannot be sufficiently protected, so that the rate of change in resistance becomes large, and if it exceeds 5% by weight, the pot life and conductivity of the paste are deteriorated. The mixing ratio of the imidazole compound and the glycidoxyalkoxysilane compound is preferably 1: 4 to 4: 1, and more preferably 2: 3 to 3: 2 by weight of the imidazole compound: glycidoxyalkoxysilane compound. It is more preferably 1: 1 and if it deviates from the range of 1: 4 to 4: 1, the pot life of the paste tends to decrease.

The thermosetting resin functions as an adhesive and is not particularly limited, but a phenol resin and / or an epoxy resin is preferable. As a phenolic resin,
Resol-type phenol resin and novolac-type phenol resin are mentioned. If necessary, these phenol resins may be modified and used. When a novolac type phenol resin is used, a curing agent such as hexamethylenetetramine is used. These resins may be used alone or in combination of two or more kinds.

As the epoxy resin, bisphenol type epoxy resin, phenol novolac type epoxy resin,
Examples thereof include cresol novolac type epoxy resin, epoxidized polybutadiene, alicyclic epoxy resin, flexible epoxy resin and polyfunctional epoxy resin. These resins may be used alone or in combination of two or more.
Further, in order to accelerate the curing of the epoxy resin, tertiary amines such as triethanolamine, triethylamine, piperidine, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, etc. Imidazoles, tertiary phosphines such as triphenylphosphine, tetrabutylphosphonium bromide, quaternary phosphonium salts such as tetraphenylphosphonium bromide, and curing accelerators such as quaternary ammonium salts such as tetramethylammonium bromide Good.

The organic solvent is not particularly limited, but butyl cellosolve, ethyl carbitol, butyl ethyl carbitol, ethyl cellosolve, ethyl cellosolve acetate, butyl cellosolve acetate, ethyl carbitol acetate, butyl carbitol acetate and the like are preferable. The conductive paste of the present invention, for example, a mixture of an imidazole compound and a glycidoxyalkoxysilane compound is applied to the surface of the metal powder by adding the metal powder to a solvent solution of an imidazole compound and a glycidoxyalkoxysilane compound, After vaporizing and removing the organic solvent, put it in a crushing machine, kneader, etc. together with the thermosetting resin and the organic solvent and mix them, and then apply the applied metal powder to the organic solvent containing the thermosetting resin and mix it uniformly. It is obtained by dispersing in. The content of the thermosetting resin and the organic solvent is preferably in the range of 3 to 30% by weight of the thermosetting resin and 5 to 40% by weight of the solvent with respect to the conductive paste.

[0016]

EXAMPLES Examples will be described below, but the present invention is not limited thereto. Example 1 2-Ethyl-4-methylimidazole (Shikoku Chemicals
0.16 parts by weight of trade name, 2E4MZ manufactured by Co., Ltd. and 3-glycidoxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd.)
Co., Ltd., trade name LS-2940) (however, 2E4MZ: L
The molar ratio of S-2940 is 1: 1 and the weight ratio is about 1: 2).
To a solution prepared by dissolving 0.34 parts by weight in 20 parts by weight of acetone (manufactured by Wako Pure Chemical Industries, Ltd., reagent), 100 parts by weight of flaky copper powder (homemade) having an average particle size of 7 μm was added and stirred. On the other hand, acetone was vaporized and removed to obtain a copper powder coated with a mixture of an imidazole compound and a glycidoxyalkoxysilane compound. Copper powder coated with a mixture of this imidazole compound and a glycidoxyalkoxysilane compound is a resole-type phenol resin (Hitachi Chemical Co., Ltd.,
Product name VP-13N concentrate, solid content 95% by weight) 15
Part by weight and 20 parts by weight of butyl cellosolve (manufactured by Wako Pure Chemical Industries, Ltd., reagent) were put into a crusher, mixed and uniformly dispersed to obtain a conductive paste.

Example 2 Instead of the flake-shaped copper powder used in Example 1, flake-shaped silver-plated copper powder (homemade) was used, and the resol-type phenol resin used in Example 1 was adjusted to 10 parts by weight, and bisphenol was further added. A type epoxy resin (Mitsui Petrochemical Industry Co., Ltd.
A conductive paste was obtained through the same steps as in Example 1 except that 5 parts by weight of the product name R367) was added. Examples 3, 4, 5, 6 and 7 The flake silver-plated copper powder used in Example 2 was used in place of the flake copper powder used in Example 1, and 2-ethyl-4 was used.
-Methylimidazole and 3-glycidoxypropyltrimethoxysilane, 0.003 parts by weight and 0.
007 parts by weight (Example 3), 0.03 parts by weight and 0.0
7 parts by weight (Example 4), 0.16 parts by weight and 0.34 parts by weight (Example 5), 0.3 parts by weight and 0.7 parts by weight (Example 6) and 1.0 parts by weight and 2 A conductive paste was obtained through the same steps as in Example 1 except that the amount was 0.0 parts by weight (Example 7).

Comparative Example 1 A conductive paste was prepared in the same manner as in Example 1 except that the mixture of 2-ethyl-4-methylimidazole and 3-glycidoxypropyltrimethoxysilane in Example 1 was not used. Obtained. Comparative Example 2 A conductive paste was prepared through the same steps as in Comparative Example 1 except that the flaky silver-plated copper powder (homemade) used in Example 2 was used instead of the flaky copper powder used in Comparative Example 1. Obtained.

Comparative Example 3 Instead of the mixture of 2-ethyl-4-methylimidazole and 3-glycidoxypropyltrimethoxysilane used in Examples 3 to 7, it is generally known as an antioxidant for copper. A conductive paste was obtained through the same steps as in Examples 3 to 7 except that 0.5 part by weight of triethanolamine (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) was used. Comparative Examples 4, 5 and 6 The 2-ethyl-4-methylimidazole and 3-glycidoxypropyltrimethoxysilane used in Examples 3 to 7 were 0.000016 parts by weight and 0.00003, respectively.
Example 3 except 4 parts by weight (comparative example 4), 2.23 parts by weight and 4.77 parts by weight (comparative example 5), 3.2 parts by weight and 6.8 parts by weight (comparative example 6). Conductive pastes were obtained through the same steps as in Steps 7 to 7.

Next, regarding the conductive pastes obtained in the respective examples and comparative examples, the initial specific resistance (μΩ-cm) and temperature 6
The resistance change rate and the storage stability of the paste were measured and evaluated when left for 1000 hours in a thermo-hygrostat at 0 ° C. and a humidity of 95%. The storage stability was the number of days until the viscosity of the paste (measured with a B-type rotational viscometer) increased by 10% at room temperature of 25 ° C. The results are shown in Tables 1 and 2.

[0021]

[Table 1]

[0022]

[Table 2]

As is clear from Tables 1 and 2, the conductive pastes of the examples are compared with the conductive pastes of the comparative examples.
It can be seen that the initial specific resistance is low, the rate of resistance change is small, and the storage stability is excellent.

[0024]

The conductive paste according to the first aspect of the invention has good conductivity and little change in conductivity under high humidity. Moreover, since copper powder is used, it is inexpensive. Claim 2
The conductive paste in (1) has the effect of the conductive paste in (1), the contact between the metal powders is improved, and the conductivity is improved. The conductive paste according to claim 3 has the effect of the conductive paste according to claim 1 or 2, and is further excellent in adhesiveness.

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Claims (3)

[Claims] 1. An imidazole compound represented by the chemical formula 1 [general formula (1)] and a chemical formula 2 [general formula (2)] on the surface of a metal powder containing copper powder having an average particle diameter of 30 μm or less or silver-plated copper powder. A conductive paste in which a mixture of the glycidoxyalkoxysilane compound shown in (1) and 0.0001 to 5% by weight of the metal powder is applied and dispersed in an organic solvent containing a thermosetting resin. Embedded image (In the formula, R ₁ and R ₂ are each a hydrogen atom, an alkyl group,
Indicates a phenyl group or a cyano group). Embedded image (In the formula, R ₃ , R ₄ and R ₅ each represent a hydrogen atom, an alkyl group or an alkoxy group, and n represents an integer of 1 to 5). 2. The conductive paste according to claim 1, wherein the metal powder is flaky or dendritic. 3. The conductive paste according to claim 1, wherein the thermosetting resin is a phenol resin and / or an epoxy resin.