Electrochemical investigations of copper etching by Cu(NH3)4Cl2 in ammoniacal solutions

Cyclic voltammetry has been employed to investigate the mechanism of copper etching in ammoniacal buffered solutions of cupric chloride. Experiments involving an increase in the solution copper content (up to 0.5 m) and in the thickness of the copper electrode have been used to obtain a better understanding of the copper oxidation. Whatever the Cu(ii) concentration, the reduction occurred in two one-electron stages leading successively to Cu(i) and Cu(0). The concentration of ammonia was an important parameter. Increasing the ratio of Cu : NH3 favoured the formation of transient solid compounds. The expected two-step oxidation of copper was observed only for thin layers of electroplated copper. The determination of the corrosion current in etching solutions suggests that copper oxidation involves the formation of solid cuprous compounds.