Copper powder

a technology of copper powder and weatherability, which is applied in the direction of manufacturing tools, solventing apparatus, transportation and packaging, etc., can solve the problems of inadequate response to the need for improving the weatherability of copper powder for use in conductive paste, and achieve excellent weatherability, stable operation of electronic equipment, and stable surface condition. , the effect of reducing the risk of aging

Inactive Publication Date: 2006-08-24
DOWA ELECTRONICS MATERIALS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006] The prior art processes enable production of a fine copper powder having relatively uniform particle size. However, the use of electronic equipment utilizing conductive paste in an increasingly broad range of applications in recent years has led to a need for conductive pastes with aging deterioration resistance property capable of ensuring long-term, stable operation of electronic equipment in various environments. A need has also arisen for the copper powder used as a conductive filler to exhibit stability of surface condition and resistance against aging deterioration during the storage period between production and use in a paste. Basic properties strongly desired of a copper powder for use in conductive paste have therefore come to include resistance to oxidation during storage at room temperature, i.e., excellent weatherability.
[0009] This invention enables improvement of the weatherability of a copper powder by means of incorporating Sn therein. The copper powder can be efficiently produced by a method capable of utilizing electrolytic cuprous oxide as the Cu sarting material developed by the inventors, using Sn contained in the electrolytic cuprous oxide as impurity, without need for any special process for weatherability improvement. By optimizing the Sn content, a copper powder having the properties fundamentally required by a copper powder for conductive paste can be obtained. The present invention therefore contributes to improvement of electronic equipment reliability by providing a copper powder for conductive paste imparted with weatherability and high in cost performance.

Problems solved by technology

Nevertheless, the response to the need for improvement of the weatherability of copper powder for use in conductive paste has so far been inadequate.

Method used

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Examples

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example 1

[0027] Electrolytic cuprous oxide of an average particle diameter of 3 μm was prepared. The prepared electrolytic cuprous oxide had a broad particle size distribution, i.e., 50% or more of all particles fell outside the range of 3 μm±1 μm. The Sn content of the electrolytic cuprous oxide was 0.01 mass %. This electrolytic cuprous oxide, 135 g, was dispersed in 3,750 g of pure water. The dispersion was added with 7.5 g of cuprous chloride as water-soluble copper salt and 15 g of polyvinyl alcohol as protective colloid and then heated to 40° C. under stirring. To the heated mixture were added 100 g of 80% hydrazine hydrate as reducing agent and 22.5 g of acetic acid as complexing agent. The resulting liquor was heated to 60° C. over one hour and then held at 60° C. for another hour to allow the reduction reaction to proceed. The liquor after reaction was subjected to solid-liquid separation and the recovered solids were washed with water and dried to obtain a copper powder. The copper...

example 2

[0029] To 3,750 g of pure water were added 7.5 g of cuprous chloride as water-soluble copper salt and 15 g of polyvinyl alcohol as protective colloid. The result was heated to 40° C. under stirring, whereafter 100 g of hydrazine hydrate was added as reducing agent. To the resulting reaction liquor was added 135 g of the same electrolytic cuprous oxide as used in Example 1, 0.43 g of stannic chloride as stannic salt and 22.5 g of acetic acid as complexing agent. The resulting liquor was heated to 60° C. over one hour and then held at 60° C. for another hour to allow the reduction reaction to proceed. The liquor after reaction was subjected to solid-liquid separation and the recovered solids were washed with water and dried to obtain a copper powder. The copper powder was observed under a scanning electron microscope (SEM) and the diameters of the particles within the field of vision were measured. It was found that the average particle diameter DM was 0.3 μm and that the particle dia...

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Abstract

A copper powder that is excellent in weatherability and adapted for use in conductive paste is provided that contains 10-20,000 ppm, preferably 100-2,000 ppm, of Sn. The copper powder is particularly preferably one having an average particle diameter DM of 0.1-2 μm and, further, one wherein the particle diameter of at least 80% of all particles is in the range of 0.5 DM-1.5 DM. This copper powder can be produced, for example, by precipitating Cu metal by reduction of Cu ions in the presence of Sn ions.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to a fine copper powder suitable for use as filler in a conductive paste or the like, particularly to such a copper powder having improved weatherability. [0003] 2. Background Art [0004] Conductive pastes are widely used for forming electronic circuits and the external electrodes of ceramic capacitors. Typical conductive fillers used in conductive pastes include copper, nickel, silver and the like. Among these, copper is used extensively nowadays because it is inexpensive, low in resistance and excellent in anti-migration property. A conductive filler comprising a mixture of copper powders of various particle diameters is usually used in a conductive paste for the external electrodes of a ceramic capacitor. However, in order to form a dense film for improving electrode reliability, the copper powder prior to mixing needs to be one of high fineness, e.g., of a particle diameter of not greater t...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22C9/00B22F1/00B22F1/05
CPCB22F1/0011B22F2998/00B23K35/302C22B15/0091C22C9/02H05K1/092B22F9/24Y02P10/20B22F1/05B22F1/00B22F9/20
Inventor YAMADA, TOMOYAHIRATA, KOJI
Owner DOWA ELECTRONICS MATERIALS CO LTD
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