ULTRAHIGH-PURITY COPPER AND PROCESS FOR PRODUCING THE SAME, AND BONDING WIRE COMPRISING ULTRAHIGH-PURITY COPPER

摘要

This invention provides an ultrahigh-purity copper having a hardness of not more than 40 Hv and a purity of not less than 8 N (except for gas components such as O, C, N, H, S, and P). In the ultrahigh-pure copper, the content of each of O, S, and P elements as gas components is not more than 1 ppm by weight. There is also provided a process for producing an ultrahigh-purity copper. In the production of ultrahigh-purity copper by two-stage electrolysis using an electrolysis solution comprising copper nitrate solution, hydrochloric acid is added to the electrolysis solution formed of a copper nitrate solution, and the electrolysis solution is circulated, and, while temporarily bringing the circulating electrolysis solution to 10ºC or below and removing impurities by filtration, electrolysis is carried out by two stages. The above copper material is compatible with fine wire production (wire drawing). That is, the present invention can realize highly efficient production of an ultrahigh-purity copper having a purity of not less than 8 N (99.999999% by weight) usable particularly to provide a bonding wire for a semiconductor element, which can realize fine wire production.