PRODUCTION OF HIGH-PURITY COPPER

摘要

PURPOSE:To produce the title high-purity copper capable of being used for bonding wire by specifying the relation between the current densities of the main and auxiliary electrolytic baths constituting an electrolytic cell, and carrying out electrolytic refining while circulating an electrolyte from the main electrolytic bath to the auxiliary electrolytic bath. CONSTITUTION:A connecting pipe 4 provided with a pump 3 is furnished at the bottom of the electrolytic cell A wherein the main electrolytic bath 1 and the auxiliary electrolytic bath 2 are formed adjacent to each other, and an inflow hole 5 is bored through the upper part of a partition wall separating the baths 1 and 2. The anode Cu plates (n) and (n') of the baths 1 and 2 are made of electrolytically refined copper, and the cathodes (s) and (s') are made of stainless steel sheet insoluble in the electrolyte. The current density of the auxiliary electrolytic bath 2 is made 1-5 times higher than that of the main electrolytic bath 1, and electrolytic refining is carried out while circulating the electrolytes (m) and (m') from the bath 1 to the bath 2 through the pump 3 and the hole 5. Accordingly, since a trace amt. of impurities eluted from the anode (n) in the bath 1 into the electrolyte (m) is deposited on the cathode (s'), the pure electrolyte (m') is returned to the bath 1. As a result, the copper eluted from the anode (n) practically contains no impurities and is deposited on the cathode (s), and high-purity copper is obtained.