Considerations for Aluminum Wire Bonds in Next-Generation Power Electronic Systems

While there is continued discussion about the eventual elimination of wire bonded interconnects from power electronics architectures, their ease of integration, relative low cost, and versatility have outweighed their drawbacks. So, in expectation of their continued use in next-generation systems, it will be critical to ensure that these interconnect structures are capable of sustaining performance under the increasingly harsh operating environments and demanding power levels that are being achieved. This work will compile information from multiple recent studies to present a focused examination on the performance of aluminum wire bonds under these exceedingly stressful conditions. Specifically, the effects of thermal expansion related mechanical stressing in combination with high temperatures and current densities within wire bonds will be discussed, emphasizing the need for designing next-generation systems for reliability under the influence of multiple simultaneous stressors. Beyond the lifetime performance of bonds under high-stress conditions, a closer examination of wire bond degradation under the influence of high ambient temperature and current density pairs will also be discussed, illustrating the progressive nature of failure modes under these conditions. These studies on wire bonds under this swath of conditions will show how individual failure modes contribute to eventual wire failure. In addition to describing the behavior of these bonds under stress, it will also be shown that additional fabrication steps can be executed in an effort to combat wire bond degradation under high temperatures and current densities. This compilation of results from recent studies will communicate that the increasing power densities in power electronic systems make wire bonds far more susceptible to failure than they have been in the past.