With the densification and increased power and operating temperatures of power electronics, solder joint reliability is increasingly important to study at high temperature, current, and mechanical stresses. This paper demonstrates the application of an accelerated stress test using a novel combined loading apparatus where a constant shear stress is applied to a test sample in an oven, with an applied constant current. Average shear stress is varied for three conditions, and it is demonstrated that increasing shear stress reduces lifetime of the solder joints. Cross-sectioned solder joints show corroboration between resistance measurement and joint failure. Further studies will develop a combined stress reliability model, and will include varying temperatures and constant current, as well as the individual measurement of the solder spheres in the circuit. High temperature solder alloys such as gold tin (AuSn) will also be considered.

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