The Effect of Some Addition Agents on the Kinetics of Copper Electrodeposition from a Sulfate Solution

Abstract

The manner in which certain organic addition agents affect the crystal growth of copper electrodeposits was investigated with the aid of the rotating disk electrode technique. The results indicate that thiourea and 1 (−) cystine are cathodically reduced during copper plating. It is proposed that thiourea and 1 (−) cystine, or their reduction products, decompose to form sulfide ions which combine with cupric ions and precipitate as on the cathode. Gelatin inhibits pyramidal crystal growth at low current densities by adsorbing on the apex of the pyramids. Above a transition current density, cubic layer crystal growth predominates, and much larger quantities of gelatin are required to inhibit crystal growth. Glycine and dextrin have little or no effect on the polarization curve for copper plating. Therefore, the rotating disk electrode technique was not useful in studying the mechanism whereby they act as addition agents.