Abstract
The rate at which oxide films of copper can form, after copper has diffused through a gold overplate, is a topic of interest in many electronic components as gold overplates are increasingly thinned. This oxidation process was studied, independent of the defect path diffusion step, through the use of gold‐copper alloys with various copper concentrations between 2 and 30 weight percent. Results show that the oxidation of copper out of gold solution is analogous in all major respects to the oxidation of unalloyed copper. Film growth follows parabolic kinetics with the exact rate being a linear function of copper concentration. The activation energy for the process is between 1.54 and 1.7 eV. Low levels of atmospheric pollutants such as chlorine, which are present in a typical laboratory environment, have an accelerating influence on the rate of oxidation, all other conditions remaining equal. However, even in the presence of such pollutants in the air, the film formed continues to be an oxide of copper. The values of contact resistance (CR) recorded are consistent with parabolic growth kinetics and have been utilized to extrapolate to estimated lifetimes based on failure criteria of increases in CR to 10 mΩ and 100 mΩ levels.
Published Version
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