Effects of Temperature on the Comproportionation of Metallic Copper and Cupric Ions to Cuprous Ions

Abstract The temperature dependence of the comproportionation reaction of metallic copper and cupric ions to cuprous ions was studied by means of conventional polarization experiments. The bulk concentration of cuprous ions was determined by means of Levich plots based on mass‐transport limitations at very small cathodic overpotentials. The corresponding temperature dependence revealed increasing concentration with increasing temperature. This effect could be ascribed to enthalpy and entropy contributions to the Gibbs free energy of the equilibrium between the copper ion species, which were obtained by Van't Hoff analysis of the equilibrium constant. Formation of cuprous ions from metallic copper and cupric ions was found to be endothermic, but slightly favored by entropy. The results provide insights into the temperature dependence of industrial plating electrolytes, which is of increasing importance for upcoming advanced packaging applications like tall copper pillars. This approach should be especially suitable to determine the effects of industrially relevant additives in complicated, multi‐component electrolytes in the future.