Cyclic Electrolysis: Part II—The Influence of Periodic Reversal of Current Upon the Surface Roughness of Electrodeposited Copper

Abstract

An experimental study has been made of the effect of periodic reversal of current on the rate of roughening of copper deposited from cyanide, sulphate and phosphate baths under simplified plating conditions. In D.C. plating from cyanide solutions there is usually a period of induction, dependent upon the initial state of the surface, after which the rate of roughening accelerates rapidly. With P.R. however, under suitable conditions, the development of roughness can be restrained to a plateau value independent of plating thickness, and electrodes can be smoothed to the same value if they are initially rougher. In sulphate and phosphate solutions the rate of roughening is lower but approximately constant, and no such roughness plateau results under P.R. conditions, the roughness attained being proportional to the total effective plating time. The difference in behaviour is accounted for partly by the different manner of anodic smoothing in the various solutions and partly by the uniquely large cathode polarisation developed during deposition from cyanide solution.