Mitsubishi Denki Kabushiki Kaisha

Mitsubishi Kinzoku Kabushiki Kaisha

Ryusuke Kawanaka

Naoyuki Hosoda

Naoki Uchiyama

Toshiaki Ono

An inexpensive, very fine wire of high-purity copper is disclosed as an alternative to the fine gold wire which is currently used in the bonding of semiconductor devices. The very fine wire of high-purity copper is prepared from a copper ingot that contains 0-2 ppm of S, 0-2 ppm of Ag, 0-1 ppm of Se and 0-1 ppm of Te as incidental impurities with the total content of these and any other incidental impurities present being held at a level not exceeding 10 ppm. By subjecting it to an appropriate heat treatment, the wire acquires an elongation of 5-22%, a breaking strength of 14-33 kg/mm.sup.2, and a Vickers hardness of 38-50, the latter value being measured with respect to said high-purity copper in an ingot form. By reducing the amounts of these impurities to even lower levels, very fine wires are obtained that can be used in the bonding of a semiconductor device without abnormally shaped loops being formed or wire breakage being experienced and the characteristics of the wires can be adapted to specific conditions of use by performing an appropriate heat treatment.

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Toyonaka, Japan

Ryusuke Kawanaka