Accelerated flowers of sulfur test method for power semiconductor modules

Abstract

In humid sulfur-bearing gas application environments, power semiconductor modules can be susceptible to a corrosion failure mechanism consisting of electrically conductive copper sulfide dendrite filaments formed within insulation trenches leading to electrical shorting. A simple, safe, and low-cost corrosion test method is presented here for reliability testing for this type of failure mechanism. The test method is based on a modified version of ASTM B809–95 that was first reported for use on sulfur resistant thick film chip resistors. Here, the test was further modified to include DC voltage for accelerated reliability testing of commercially available power semiconductor modules. It is shown that the field corrosion failure mechanism can be replicated by this accelerated test within as little as 120 h in fully populated commercial modules and can discern comparative susceptibility of packaging between manufacturers. This test method adds to the collection of accelerated corrosion tests previously reported for investigation of the dendritic filament corrosion failure mechanism and stands as an option that is less complex and less toxic. A three-stage hypothesis for the corrosion dendritic failure mechanism is also presented.