ELECTROLYTIC REGENERATION OF COPPER(II) CHLORIDE ETCHANT FOR COPPER

Electrolytic regeneration of an aged etchant for copper containing copper(II) chloride (1.9M, 120g/l) and hydrochlorlc acid (4.7M) was examined. The best condition was as follows. The etchant was continuously added to an electrolytic cell containing copper(II) chloride In lower concentration (20g/l) and at the same rate the electrolyte was drawn out. Commercially available filter cloth of polyacrylronytryl-vinyl chloride 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 copper(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 high porosity and high durability for chlorine gas.