In-situ Monitoring Solder Layer Degradation in Multichip IGBT Power Modules Using Auxiliary Emitter Voltage

Asymmetric chip placement and initial die-attach defects within a multichip IGBT power module (MIPM) can cause uneven junction temperature distribution and further accelerate the solder layer degradation. This is one of the main factors which affect the performance and reliability. This study uses the auxiliary emitter voltage veE to indirectly measure the turn-on delay time and the maximum rate of change of the collector current. The physical significance of the virtual junction temperature extracted from the two measurands is clarified. The correspondence between the veE and the degradation level of the solder layer is established using the difference between the two estimated temperatures. A novel condition monitoring method is then proposed in this paper to identify the degradation level of individual solder layers using veE, which separate the effects of solder layer fatigue and bonding wires lift-off. The current dependence of the proposed method is negligible. Simulation and experimental results indicate that the proposed method can sensitively detect the highest degradation level of the chip in a MIPM in real-time.