Copper-Platinum Deposition by Pulse Plating

Abstract

In order to improve the mechanical properties of copper, pulse plating techniques were investigated for deposition of Cu-Pt alloys employing a pyrophosphate bath containing chloroplatinic acid as a source of platinum. Cyclic voltammetry experiments showed that the copper reduction is a two-step process and that platinum reduction occurs at potentials close to that observed for copper deposition. Forward peak current densities ranging from 2.5 to 7.5 A dm-2 were employed for the bulk electrodeposition experiments. Bright, shiny, and crack-free deposits were obtained at low current densities. The amount of platinum observed in the deposits was found to increase with the current impressed for both forward pulse and pulse reverse techniques. The Knoop hardness was found to increase with the platinum content of the deposits. The corrosion rate of the deposits measured in a solution of NaCl was found to decrease with platinum content. The data show that deposits containing up to 5.6 and 6.5 wt % of platinum can be obtained by forward pulse (only) and pulse reverse plating, respectively. As compared to a copper sample, the Cu-Pt deposits obtained by forward pulse and reverse pulse techniques exhibited a 31 and 55.4% increase in Knoop hardness, respectively. As compared to copper, up to a 45.4% increase in corrosion resistance was observed for deposits produced by the application of a forward pulse. The deposits obtained by pulse reverse exhibited a 35.6% improvement in corrosion resistance over those obtained by the forward pulse technique under identical forward peak current density. © 2006 The Electrochemical Society.