| 摘要 |
PURPOSE:To produce an extra soft copper material which permits easy ball bonding by refining a copper stock prepd. by incorporating slight amts. of Li, Na, K, Rb, and Cs into a high-purity copper by a zone melting method. CONSTITUTION:>=1 kinds of Li, Na, K, Rb, and Cs and further >=1 kinds of rare earth elements according to needs are incorporated as refining components at 0.1-100ppm into the high-purity copper which is a raw material. Such copper stock is subjected to a refining treatment by the zone melting method in a vacuum, etc. The unavoidable impurities such as S and Ag in the high-purity copper bind with the added refining components to form a compd. and since such compd. is removed in the refining treatment by the zone melting method, the copper stock is made soft. The extra soft copper material obtd. by the above-mentioned method has low hardness of about <=40Hv and is suitable for use as the bonding wire at the time of assembling semiconductor devices.
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