Development of Anode Slime Free-System for Copper Plating Using Acid Copper Sulfate Bath

The behavior of Cu+ ions produced in the course of copper anode dissolution in an acid copper sulfate solution was investigated electrochemically using a rotating Pt disc electrode system. The Cu+ ion concentration of the solution was proven to be related to the natural potentials, Er, of the Pt electrode. The amount of Cu+ ions produced by a phosphorous deoxidized copper anode was found to be much smaller than that from an electrolytic copper anode as noted by monitoring the Er of Pt electrode dipped in the solution. In addition, Cu+ ions accumulating in the solution were easily oxidized by air bubbling, resulting in suppression of copper slime generation. Therefore, an anode slime free-copper plating system was proposed. The system was equipped with double anodes, a copper anode and a dimensionally stable anode, in an anode compartment cell separated from the plating solution by a cation exchange membrane. No copper slime was observed in the anode compartment and the bath composition remained practically constant during a long period of plating operations.