The Effect of Inclusions on the Ductility of Electroless Copper Deposits

Abstract

Electroless copper deposits grown epitaxially on large‐grained copper foils were investigated for ductility and inclusions, primarily hydrogen and carbon, before and after low temperature (≤150°C) annealing. Results show that the hydrogen exists in two different forms: diffusible, which escapes readily on annealing, and residual, which is not removable by annealing. Diffusible hydrogen impairs ductility. A separate study has shown that diffusible hydrogen consists essentially of molecular hydrogen existing in microvoids at a high pressure. It is shown here that both the pressure effect of molecular hydrogen and the structural effect of the voids influence the overall ductility. Ductility promoting additives inhibit both the inclusion of diffusible hydrogen and the formation of voids. Residual hydrogen together with additional elements constitutes other compounds, e.g., EDTA and , occluded from the plating solution. No general correlation was found between either residual hydrogen or carbon and ductility. However, when the incorporation of an additive causes an increase in residual hydrogen and carbon contents, the beneficial effect of the additive can be offset by its adverse influence on grain structure.