Effects of reliability testing methods on microstructure and strength at the Cu wire-Al pad interface

As the adoption of Cu bond wires continues, increasing quantity of component families are being qualified by component suppliers using standard acceleration test methods and durations. While these tests provide a benchmark comparison with conventional technologies such as Au wire bonding, for users of these components for high-reliability applications, a frequent discussion on reliability assessment is which particular test would be the most practical or effective in detecting material and process issues. In this work, we evaluate the effects of bond wire material and process variations using three acceleration tests including autoclave, unbiased HAST, and biased-HAST. Both bare Cu and Pd-coated Cu wires are included and process variations are also introduced. The results from the acceleration tests and microstructure analysis of the failed components will offer insight into the effectiveness of these acceleration tests and responses of the various bond wire materials and bond processes.