Compositions – Electrically conductive or emissive compositions – Free metal containing
Patent
1991-11-05
1993-03-30
Lieberman, Paul
Compositions
Electrically conductive or emissive compositions
Free metal containing
252512, 252518, 420483, 420502, 428547, 428610, H01B 106
Patent
active
051981548
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to less expensive electroconductive compositions having excellent electroconductivity, oxidation resistance, electromigration resistance, and stability. These compositions can be applied to an electromagnetic wave shield, electrodes for a ceramic capacitor, micro capacitor, piezo-electric element, variable resistor, thermistor or solar cell, electroconductive pastes for a chip resistor, resistance network or variable resistor, and pastes for an electroconductive circuit, and the like.
BACKGROUND ART
As electrically conductive thick film pastes, metal powder and glass frit dispersed to an organic binder and solvent, as necessary, are well known. The metal powder and glass frit are printed on a substrate such as a ceramic substrate or the like, having an excellent heat resistance baked at about 600.degree. to 900.degree. C. to form a thick film electric conductor. Suitable metal powder for such use includes gold powder, silver powder, platinum powder, silver-palladium powder, copper powder, and the like.
The metal powders previously used in thick film pastes, e.g., gold powder, platinum powder, silver powder, silver-palladium powder, silver-plated composite powder have the following defects. The noble metals, such as gold, platinum, silver, silver-palladium and the like, are very expensive; silver tends to cause electromigration; and silver-palladium has inferior electroconductivity. Electroconductive pastes using copper powder encounter other problems; that the electroconductivity thereof is lowered due to oxidation caused while they are preserved; the pastes tend to oxidize when baked; the atmosphere in which the pastes are baked is difficult to control and thus the yield of the pastes is bad. Further, electroconductive thick film pastes using silver-copper alloy powder composed mainly of silver and dispersed in an organic vehicle together with glass frit are disclosed [Japanese Patent Kokai (Laid-Open) SHO 62 (1987)- 140304]. The disclosure describes that silver-copper alloy powder containing 72 wt % of silver can be baked at 600.degree. C., but this alloy is expensive because it contains a large amount of silver, and there is a tendency toward electromigration of silver.
Silver-plated copper powder is disclosed to reduce the amount of precious metal required [for example, Japanese Patent Kokai SHO 52 (1977)-71531], but this power involves problems that when the copper powder is made into paste, silver is exfoliated, electromigration occurs and electroconductivity reproduction is difficult.
DISCLOSURE OF THE INVENTION
The present invention relates to high temperature baking copper alloy compositions which have excellent electroconductivity, oxidation resistance, electromigration resistance and soldering ability and have less solder leachability.
BEST MODE FOR CONDUCTING THE INVENTION
Copper alloy powder used in the present invention is produced by atomization, including water atomization and gas atomization. In particular, copper alloy powder made by gas atomization is preferable. For example, the gas atomization is preferably that disclosed in U.S. patent application Ser. No. 07/395,531. More specifically, this process is such that a mixture of metals, such as silver and copper, and Pb if desired and the like, having a specific composition is melted by high-frequency induction heating, resistance heating, an external burner or the like in an inert gas atmosphere or in vacuo. In this case, a crucible used for this purpose is preferably made of a material which does not react with the melt at all or reacts therewith very slowly. The material is mainly composed of, for example, graphite, boron nitride, silicon carbide, quartz, magnesia, silicon nitride, and silicon carbide. Then, the melt is jetted from an end of the crucible into an inert gas atmosphere. Simultaneously with the jetting, a high speed gas stream of an inert gas is jetted against the melt, so that the melt is atomized and made into fine particles. The inert gas is a gas which does not re
REFERENCES:
patent: 4485153 (1984-11-01), Janikowski
patent: 4728580 (1988-03-01), Grasselli et al.
patent: 5091114 (1992-02-01), Nakajima et al.
Katsumata Tsutomu
Nakajima Hitoshi
Yokoyama Akinori
Asahi Kasei Kogyo Kabushiki Kaisha
Kopec M.
Lieberman Paul
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