JPH0714428A - Conductive paste - Google Patents

Abstract

PURPOSE:To reduce the resistance of through holes in a wiring board by including a high conductive metal powder and a specific grain size of solder grains. CONSTITUTION:A bis-phenol A type epoxy resin is heated and dissolved beforehand, and after cooling to the room temperature, 2-ethyl 4-methyl imidazole, ethylcarbitol, and butylcerosolve are mixed evenly so as to form a resin composite. A flake form silver powder, and solder grains with the mean grain size 10mum and the maximum diameter 20mum are added to the above composite, and dispersed evenly so as to obtain this conductive paste. While a test pattern is printed on a paper phenol copper-plated layered plate 2 on which through holes are formed, by using this conductive paste, a heat treatment is applied to the conductive paste filled in the through holes so as to obtain a wiring board.

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, etc., 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 electroplating of silver called migration occurs on wiring conductors and electrodes and the distance between electrodes or between wirings is shortened. 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 relates to a conductive paste containing highly conductive metal powder and solder particles having a particle size of 20 μm or less.

As the highly conductive metal powder in the present invention, one or a mixture of silver powder, copper powder, gold powder, palladium powder and aluminum powder, which are excellent in conductivity, is used, and the shape thereof is not limited, but is flaky. Is preferred,
The aspect ratio is preferably about 3 or more, and 10
The above is more preferable. In addition, the particle diameter is preferably 40 μm or less because the printability is not deteriorated. The solder particles are made of an alloy of Pb and Sn, have a substantially spherical shape, and have a particle size of 20 μm or less.
When it exceeds 20 μm, the printability is poor and the conductivity is reduced.
The melting point of the solder changes depending on the ratio of Pb and Sn, but the ratio is not limited.

The volume ratio of the solder particles to the highly conductive metal powder is preferably 2: 1 to 1: 5 (solder particles: highly conductive metal powder), and the content of the highly conductive metal powder is less than this range. And the resistance of the conductor becomes high, and the thermal shock test etc.
When the solder is melted when heated to near 0 ° C. or 250 ° C., the connection state of the conductive particles may change and the conduction resistance may decrease. If the amount of high-conductivity metal powder is more than this range, the amount of expensive metal such as silver used increases, so that the conductor paste becomes expensive, and when silver is used alone, silver migration easily occurs.

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

[0010]

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 the resin composition with 145 g of flake silver powder (trade name TCG-1 manufactured by Tokuriki Kagaku Kenkyusho) and solder particles (Pb having an average particle size of 10 μm and a maximum diameter of 20 μm). 40 g of (/ Sn = 40/60 (weight ratio)) was added and uniformly dispersed by a stirrer and a three-roll mill to obtain a conductive paste.

Next, using the conductive paste obtained above, a paper phenol copper clad laminate having a thickness of 1.6 mm and a through hole having a diameter of 0.8 mm (φ) (manufactured by Hitachi Chemical Co., Ltd., trade name MCL-). 437F) was printed with the test pattern shown in FIG. 1 and the through hole 1 was filled with the test pattern and heated in the atmosphere at 60 ° C. for 30 minutes and at 160 ° C. for 30 minutes to obtain a wiring board. 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 copper foil was 19 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 was 2
It was 4 mΩ / 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 −6.
100 cycles of 30 minutes at 5 ℃, 40 in the humidity load test
At 90 ° C. and 90% RH, a voltage of 50 V was applied between adjacent lines and held for 1000 hours.

Example 2 To 145 g of the resin composition obtained in Example 1, 200 g of the flake silver powder used in Example 1 and 65 g of solder particles were added, and the mixture was uniformly mixed and dispersed in the same manner as in Example 1 to conduct electricity. I got a 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 a thermal shock test of the wiring board, the resistance of the through holes was 27 mΩ / hole, and the result of the wet and medium load test showed that the insulation resistance between the through holes was 10 ⁸ Ω or more.

Example 3 To 145 g of the resin composition obtained in Example 1, 500 g of the flake silver powder used in Example 1 and 230 g of solder particles were added, and the mixture was uniformly mixed and dispersed in the same manner as in Example 1 to conduct electricity. I got a 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 14 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 20 mΩ /
As a result of the humidity and medium load test, the insulation resistance between through holes was 10 ⁸ Ω or more.

Example 4 To 145 g of the resin composition obtained in Example 1, 110 g of the flake silver powder used in Example 1, 40 g of solder particles and copper powder (Fukuda Metal Foil Powder, trade name SPC4-8) were added. 50 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 20 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 27 mΩ /
As a result of the humidity and medium load test, the insulation resistance between through holes was 10 ⁸ Ω or more.

Example 5 To 145 g of the resin composition obtained in Example 1, 200 g of the flake silver powder used in Example 1, 65 g of solder particles and 60 g of the copper powder used in Example 4 were added. A conductive paste was obtained by uniformly mixing and dispersing by the same method. 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 holes was 25 mΩ / hole, and the result of the wet and medium load test showed that the insulation resistance between the through holes was 10 ⁸ Ω or more.

Example 6 To 145 g of the resin composition obtained in Example 1, 400 g of the flake silver powder used in Example 1, 200 g of solder particles and 100 g of the copper powder used in Example 4 were added. A conductive paste was obtained by uniformly mixing and dispersing by the same method. 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 hole is 15 mΩ.
/ Hole, and the insulation resistance between 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 20 mΩ / hole, and the result of the wet and medium load test showed that the insulation resistance between the through holes was 10 ^8.
It was more than Ω.

Comparative Example 1 1000 g of the flake silver powder used in Example 1 was added to 145 g of the resin composition obtained in the same manner as in Example 1, and the mixture was uniformly mixed and dispersed in the same manner as in Example 1 to obtain a conductive paste. Got 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 is 18 mΩ / hole, and the insulation resistance between the through holes is 10
It was more than ⁸ Ω. As a result of the thermal shock test of the wiring board, the resistance of the through hole was 24 mΩ / hole,
According to the results of the wet and medium load test, the insulation resistance between the through holes was lowered to the order of 10 ⁷ Ω per 5 wiring boards.

[0018]

EFFECT OF THE INVENTION The conductive paste according to the present invention is a highly conductive paste having a low through-hole resistance in a wiring board even if the content of silver is low, and the insulation resistance between the through-holes after a wet and medium load test. Is small, and by using a highly conductive metal powder, for example, copper powder and solder particles together, the amount of silver used can be reduced, and the conductive paste is economically and excellent in characteristics.

[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

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[Procedure amendment]

[Submission date] January 24, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

The present invention relates to a conductive paste containing highly conductive metal powder and solder particles having a particle size of 20 μm or less.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

As the highly conductive metal powder in the present invention, one or a mixture of silver powder, copper powder, gold powder, palladium powder and aluminum powder, which are excellent in conductivity, is used, and the shape thereof is not limited, but is flaky. Is preferred,
The aspect ratio is preferably about 3 or more, and 10
The above is more preferable. In addition, the particle diameter is preferably 40 μm or less because the printability is not deteriorated. The solder particles are made of an alloy of Pb and Sn, have a substantially spherical shape, and have a particle size of 20 μm or less.
When it exceeds 20 μm, the printability is poor and the conductivity is reduced.
The melting point of the solder changes depending on the ratio of Pb and Sn, but the ratio is not limited.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008] The ratio of the solder particles and highly conductive metal powder in a volume ratio of 2: 1 to 1: 5: preferably a (solder particles highly conductive metal powder), are less highly conductive metal powder than this range And the resistance of the conductor becomes high, and the thermal shock test etc.
When the solder is melted when heated to near 0 ° C. or 250 ° C., the connection state of the conductive particles may change and the conduction resistance may decrease. If the amount of the highly conductive metal powder is more than this range, the amount of expensive metal such as silver used increases, so that the conductor paste becomes expensive, and when silver is used alone, silver migration easily occurs.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

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

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

[0018]

EFFECT OF THE INVENTION The conductive paste according to the present invention is a highly conductive paste having a low through-hole resistance in a wiring board even if the content of silver is low, and the insulation resistance between the through-holes after a wet and medium load test. Is small, and by using a highly conductive metal powder , for example, copper powder and solder particles together, the amount of silver used can be reduced, and the conductive paste is economical and excellent in characteristics.

Claims (2)

[Claims] 1. A conductive paste containing highly conductive metal powder and solder particles having a particle size of 20 μm or less. 2. The conductive paste according to claim 1, wherein the highly conductive metal powder is one of silver powder, copper powder, gold powder, palladium powder and aluminum powder or a mixture thereof.