TEM observation of general growth behavior for silver electroplating on copper rod

The electroplating process is essential to process Cu-Ag complex wires. Therefore, general growth behavior of silver film plated on copper substrate has an instructive effect on the subsequent processes of pinching-out and annealing. In this paper, the substrate, the interface and the coated silver film are mainly characterized in terms of transmission electron microscope (TEM), especially the techniques of selected area electron diffraction (SAED) and displaced-aperture dark field (DADF). The silver grains are random distributed in the intermediate layer between the copper substrate and the coated silver film. Columnar grains with the orientation of {110}//axis direction, are observed prolongating along the normal direction of copper rod in the outer coated film. Two kinds of competing mechanism for grain growth are put forward to reason for the different growth behaviors during electroplating process, on the basis of the results deduced by TEM. Specifically, the formation of the intermediate layer is governed by the chemical reactions, while the electrochemical reactions are responsible for the generation of silver film.