Effects of Additives on Polarization Curves in Electroless Copper Plating Bath Containing EDTA as Complexing Agent

As a comlexing agent for cuprous ion, 2, 9-dimethyl-1, 10-phenanthroline was added to the electroless copper plating bath containing EDTA as the complexing agent for cupric ion. The polarization characteristics of the copper electrode in the bath were examined by means of potential scanning method.The results obtained were as follows:1) The total polarization curve at 70°C in the bath containing no additives showed a peak on its cathode current curve in the same way as described in the previous paper (at 30°C).2) However, as would be expected, the peak completely disappeared at 70°C in the bath containing more than 30mg/l of 2, 9-dimethyl-1, 10 phenanthroline; then, it seemed that the mixed potential theory was held over the whole potential range.3) The copper, which had been deposited under the above conditions, was also improved in its ductility.4) It seemed that these effects are based on the prevention of copper electrode surface from its oxidation owing to the complexing of cuprous ion with 2, 9-dimethyl-1, 10-phenanthroline and keeping a constant copper surface over the whole potential range.