The electroless nickel plating process was used for protecting the copper pad of printed circuit boards from oxidation, which needs Pd catalytic treatment on the copper surface before Ni growth. The quantity of Pd deposition had a linear relationship with the activation time, while the Ni growth on the Pd-activated Cu films was accelerated with the deposition time by auto-catalytic reaction. It was confirmed that both Pd and Ni were grown coherently on the Cu (111) plane based on the high-resolution TEM measurement. The in-plane lattice misfits of Pd (111) and Ni (111) to Cu (111) are 7.6% (compressive) and 2.5% (tensile), respectively. The Pd grew in a dot-like rather than a two-dimensional form due to the large lattice mismatch. In addition, the lattice mismatch of Ni (111) to Pd (111) is 9.4% (tensile), and the larger lattice misfit seems to make it difficult for the Ni to nucleate on the Pd nuclei. It can be deduced that the Pd works simply as an electron supplier by oxidizing a reducing agent and the Ni reduction occurs preferably on the Cu surface by an electron from the Pd. (C) 2015 The Electrochemical Society.