Cyclic temperature and humidity profile for mixed flowing gas tests of power semiconductor modules

Reliability testing of power electronics in corrosive environments is relevant and topical as the devices are used in increasingly harsh environments that impose a risk of corrosion phenomena taking place. On components protected with silicone gel, resin, or other potting and encapsulation polymers the corrosive gases and humidity need to permeate through the protective layers before dendrite growth is initiated on the component surface. Testing packaged power semiconductor modules in a static temperature and humidity environment does not reflect fluctuating field conditions and may lead to erroneous conclusions e.g. when evaluating different potting materials. In this study, gas transfer through the silicone gel potting used in power semiconductor modules is expedited. Based on the properties of the gel, a cycling scheme for temperature and humidity is introduced to increase the gas permeation rate and so the dendrite growth rate.