JPH06333417A - Conductive paste - Google Patents

Abstract

PURPOSE:To provide conductive paste of high conductivity having low through hole resistance in a wiring board by composing the conductive paste for forming an electric circuit of a main component of almost spherical particles of plastic or the like and conductive metal powder. CONSTITUTION:Almost spherical particles of plastic or other inorganic material of a grain size of 30mum or less, and powder of conductive metal such as Au, Ag, Cu, Al, etc., of an aspect ratio of 3 or more and of a grain size of a longer diameter of 40mum or less are mixed at a ratio of 5:1 to 1:5. This mixture is mixed with solvent such as terpineol, micro-powder of graphite, corrosion restricting agent such as benzothiazole, etc., as necessary, as well as organic binding material such as liquid epoxy resin, where these are blended in such a way that total quantity of the particles and the conductive metal powder is 15 to 60wt.% to solid components of conductive paste. The conductive paste of low through hole resistance in a wiring board, can thus be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste for forming an electric circuit.

[0002]

2. Description of the Related Art Conventionally, as a method for forming a wiring conductor of a printed wiring board, an electronic component or the like, a method of applying or printing a paste containing silver powder having excellent conductivity is generally known. .

[0003]

Since a conductive paste using silver powder has good conductivity, it is used as a wiring conductor or an electrode for printed wiring boards, electronic parts, etc., but these are used under a high temperature and high humidity atmosphere. When an electric field is applied, there is a drawback that a wiring conductor or an electrode is electro-deposited with silver called migration and a short circuit occurs between electrodes or between wirings. Several measures have been taken to prevent this migration, and measures such as applying a moisture-proof coating to the surface of the conductor or adding a corrosion inhibitor such as a nitrogen compound to the conductive paste have been studied, but it is sufficient. It was not possible to obtain such an effect.

Further, in order to obtain a conductor having good conduction resistance, it is necessary to increase the amount of silver powder blended, and the silver paste is expensive, so that the conductive paste is also expensive.

The present invention provides a conductive paste that does not have such drawbacks.

[0006]

The present invention has a particle size of 30 μm.
The present invention relates to a conductive paste containing substantially spherical fine particles and highly conductive metal powder.

The substantially spherical fine particles in the present invention are made of plastic or an inorganic material, and the shape thereof is substantially spherical and at least the major axis thereof is 30 μm or less, and the conductivity is not limited. That is, it may be non-conductive fine particles or conductive fine particles, and does not require high conductivity such as silver and gold. It should be noted that the use of substantially spherical fine particles having a particle size of more than 30 μm causes defects such as clogging of the screen during printing, poor elongation of the paste and poor printability.

The material of the highly conductive metal powder is not particularly limited, but gold, silver, copper, aluminum or alloys of these metals, which have excellent conductivity, are used alone or in combination. Although the shape of the highly conductive metal powder is not particularly limited, it is preferably flaky, and the aspect ratio is preferably about 3 or more, more preferably 10 or more. In addition, the particle diameter is preferably 40 μm or less because the printability is not deteriorated.

The volume ratio of the substantially spherical fine particles to the highly conductive metal powder is 5: 1 to 1: 5 (substantially spherical fine particles: highly conductive metal powder) in terms of resistance of the conductor and prevention of migration. It is preferable.

In addition to the above materials, the conductive paste is an organic adhesive component such as liquid epoxy resin, phenol resin, unsaturated polyester resin and the like, if necessary, a solvent such as terpineol, ethyl carbitol, carbitol acetate, and fine graphite. It contains powders, corrosion inhibitors such as benzothiazole and benzimidazole. The content of the substantially spherical fine particles and the highly conductive metal powder is preferably 15 to 60% by weight, more preferably 30 to 60% by weight in terms of the resistance and economy of the conductor with respect to the solid content of the conductive paste. preferable.

[0011]

EXAMPLES Examples of the present invention will be described below. Example 1 60 parts by weight of bisphenol A type epoxy resin (Oilized shell epoxy, trade name Epicoat 834) and 40 parts by weight of bisphenol A type epoxy resin (Oilized shell epoxy, trade name Epicoat 828) were dissolved by heating in advance. ,
Then, after cooling to room temperature, 5 parts by weight of 2 ethyl 4-methyl imidazole (manufactured by Shikoku Kasei), 20 parts by weight of ethyl carbitol (manufactured by Wako Pure Chemicals, reagent) and 20 parts by weight of butyl cellosolve (manufactured by Wako Pure Chemicals, reagent) were added. The resin composition was prepared by uniformly mixing and 145 g of this resin composition had an average particle size of 20 μm.
40 g of polystyrene-made substantially spherical fine particles (made by Hitachi Chemical Co., Ltd.) with a maximum diameter of 28 μm, 110 g of flake-shaped silver powder (made by Tokuriki Kagaku Kenkyusho, product name TCG-1) and copper powder (made by Fukuda Metal Foil Powder) , Trade name SPC4-8) was added and uniformly dispersed with a stirrer and a three-roll mill to obtain a conductive paste.

Next, the conductive paste obtained above has a thickness of 1.
The test pattern shown in FIG. 1 is printed on a paper phenol copper clad laminate (Hitachi Chemical Co., Ltd., trade name MCL-437F) in which a through hole having a diameter of 6 mm and a diameter of 0.8 mm (φ) is formed. The wiring board was obtained by heat-treating the material filled in the above in the atmosphere under the conditions of 60 ° C. for 30 minutes and 160 ° C. for 30 minutes. In FIG. 1, 2 is a paper phenol copper clad laminate. Next, the resistance of the obtained wiring board was measured. As a result, the resistance of the through hole 1 excluding the resistance of the silver foil was 22 mΩ / hole, and the insulation resistance between adjacent through holes was 10 ⁸ Ω or more. As a result of the thermal shock test of the wiring board, the resistance of the through hole 1 is 29 mΩ.
/ It was a hole. Moreover, as a result of performing a wet and medium load test on the wiring board, the insulation resistance between the through holes was 10 ⁸ Ω or more. The cold heat test conditions are 125 ° C. 30 minutes to −65 ° C. 3
100 cycles of 0 minutes, 90 ° C for humidity and medium load test
Apply a voltage of 50V between adjacent lines during% RH to set 1
Hold for 000 hours.

Example 2 To 145 g of the resin composition obtained in Example 1, 65 g of the substantially spherical fine particles used in Example 1, 200 g of silver powder and 6 of copper powder were used.
0 g was added and uniformly mixed and dispersed in the same manner as in Example 1 to obtain a conductive paste. A wiring board was manufactured through the same steps as in Example 1 and the characteristics thereof were evaluated. As a result, the resistance of the through holes was 21 mΩ / hole, and the insulation resistance between the through holes was 10 ⁸ Ω or more. As a result of the thermal shock test of the wiring board, the resistance of the through hole was 29.
It was mΩ / hole, and the insulation resistance between through holes was 10 ⁸ Ω or more as a result of the wet and medium load test.

Example 3 To 145 g of the resin composition obtained in Example 1, 30 g of the substantially spherical fine particles used in Example 1, 700 g of silver powder and 1 of copper powder were used.
00 g was added, and the mixture was uniformly mixed and dispersed in the same manner as in Example 1 to obtain a conductive paste. A wiring board was manufactured through the same steps as in Example 1 and the characteristics thereof were evaluated. As a result, the resistance of the through holes was 19 mΩ / hole, and the insulation resistance between the through holes was 10 ⁸ Ω or more. As a result of the thermal shock test of the wiring board, the resistance of the through hole was 2
It was 3 mΩ / hole, and the insulation resistance between through holes was 10 ⁸ Ω or more as a result of the wet and medium load test.

Comparative Example 1 To 145 g of the resin composition obtained in Example 1, 1000 g of the silver powder used in Example 1 was added and uniformly mixed and dispersed in the same manner as in Example 1 to obtain a conductive paste. A wiring board was manufactured through the same steps as in Example 1 and the characteristics thereof were evaluated. As a result, the resistance of the through holes was 18 mΩ / hole, and the insulation resistance between the through holes was 10 ⁸ Ω or more. As a result of the thermal shock test of the wiring board, the resistance of the through hole was 24 mΩ / hole, and in the result of the wet and medium load test, the insulation resistance between the through holes was 10 ⁷ Ω per 5 wiring boards. There was something that was falling on the table.

[0016]

The conductive paste according to the present invention is a highly conductive paste having a low resistance of through holes in a wiring board, has a small decrease in insulation resistance between through holes after a wet and medium load test, and has a grain size of Is an economically excellent conductive paste in which the amount of silver used can be reduced by using substantially spherical fine particles having a particle size of 30 μm or less and highly conductive metal powder, for example, by using silver powder and copper powder together.

[Brief description of drawings]

FIG. 1 is a plan view showing a state in which a conductive paste is printed on a paper phenol copper clad laminate and the through holes are filled.

[Explanation of symbols]

 1 Through hole 2 Paper phenol copper clad laminate

Claims (1)

[Claims] 1. A conductive paste containing substantially spherical fine particles having a particle diameter of 30 μm or less and highly conductive metal powder.