Copper exchange plating on palladium and its relation to circuit repair

We describe a series of experiments using local heating to deposit copper from solution onto a palladium pattern. We show that palladium, the more noble metal, does not dissolve during thermally induced exchange plating when sacrificial copper is appropriately placed with respect to the palladium. Rather, the palladium becomes cathodic locally without dissolution, consistent with its position in the electronegativity series. However, without sacrificial copper, no deposition occurs. These results help to explain the mechanisms for a recently described electrochemical "open" microcircuit repair method.