Electrolytic stainproofing of copper foils for printed circuit applications

Abstract

This paper describes electrolytic stainproofing of copper foils in chromic acid solution containing suitable additives to produce a very thin protective film. The quality of stainproofing was checked by a tarnish resistance test, a solderability test and an etchability test. The treatment also offers good protection to copper and its alloys for very many applications in day to day life. The optimum bath composition consists of chromic acid 10 g 1^-1 and acetic acid 5 g l^-1 and operates at a cathodic current density of 2.5 A dm^-2 for 30 s at 30 °C.