Impacts of the Pressure Distribution on Dynamic Avalanche in Single Press-Pack IGBT Chip

Within a press-pack insulated gate bipolar transistor (PP IGBT) submodule, the components are packaged by external clamping force. This external clamping force significantly affects the chip's dynamic avalanche and further degrades its turn-off capability, which needs to be focused. In this paper, it is found for the first time that the pressure distribution is the key factor for the IGBT chip's dynamic avalanche during a single turn-off period. Simulation results indicate that the maximum pressure difference on the chip surface rises by 1.5 times when the clamping force increases from 1 kN to 2.5 kN. During turn-off, that pressure distribution leads to a 21.21% increase in the maximum current density inside the single chip, which strengthens the dynamic avalanche. To verify this mechanism, the turn-off waveforms of a single chip under different forces are then measured and compared in detail. Meanwhile, these conclusions regarding the pressure distribution effect are applicable to the single chip inside the multi-chip device in practical applications. Moreover, suggestions for the packaging design and practical operation are put forward to improve the PP IGBT device's turn-off capability effectively.