Humidity Robustness of IGBT Guard Ring Termination

Abstract:
IGBT power semiconductor modules are used in various high power applications including traction, industrial drives, grid systems and renewables such as in wind-power generation, conversion and automotive. Many of these applications are subject to harsh environmental conditions and in particular, when the inverter cabinets do not shield the power electronics, including the IGBT modules, from such conditions. Therefore, IGBT modules can be exposed to severe humidity levels. In this paper, we investigate the influence of the combination of humidity and high voltage on the blocking reliability of IGBT devices with guard-ring terminations. An improved testing approach HV-H³TRB (High Temperature, High Humidity & High Voltage), when compared to classical THB (High Temperature, High Humidity & Biased) is applied to assess the robustness of different termination designs and passivation stacks. Full description of the failure mode and of its correlation to the humidity induced electrical field modifications is also provided. This analysis offers an insight on the design and testing aspects, which are of key importance to the development of environmentally robust high power IGBTs.