ELECTROLYTIC REGENERATION OF COPPER(II) C HLORIDE ETCHANT FOR COPPER

Electrolytic regeneration of an aged etchant for copper containing cop per(II) chloride (1.9M, 120g/l) and hydrochlorlc acid (4.7M) was exami ned. The best condition was as follows. The etchant was continuously a dded to an electrolytic cell containing copper(II) chloride In lower c oncentration (20g/l) and at the same rate the electrolyte was drawn ou t. Commercially available filter cloth of polyacrylronytryl-vinyl chlo ride copolymer was used as a diaphragm. Through consecutive reduction, Cu(II) --> Cu(I) --> Cu, nonadherent powdery copper was deposited on the cathode, which was easily removed from the surface by scratching. Chlorine gas generated from the anode was utilized for oxidation of co pper(I) chloride present in an aged etchant. The filter cloth adopted in place of an ion exchange membrane showed an excellent performance, i.e., low voltage (2.0V), high current efficiency (80%) in spite of hi gh porosity and high durability for chlorine gas.