Enhancement of turn-off gate voltage waveform change by digital gate control for bond wire lift-off detection in IGBT module

The bond wire lift-off is the one of main failures for insulated gate bipolar transistors (IGBT) power modules. The wire lift-off increases parasitic inductance L_eE in the module and the gate voltage V_ge waveform is modulated by L_eE·dI_e/dt. Therefore, the V_ge waveform has the potential for an indicator of condition monitoring. The Digital gate control (DGC) can control switching behavior precisely for low-loss and low-noise switching. It is also effective for sensitivity enhancement of V_ge waveform changed by the wire lift-off. This paper reports how the DGC 2-step vector control (2-sVC) can improve the wire lift-off failure detection sensitivity by V_ge waveform. The experiment results showed that the V_ge spike was generated by L_eE·dI_e/dt at the turn-off switching and the spike generation timing depended on the wire number. The DGC obtained the larger timing-shift Δt_wire and the amplitude ΔV_ge-surge than those at the conventional gate control. In addition, the best vector condition improved the trade-off between turn-off loss and collector voltage overshoot compared with the conventional gate control. From these results, the DGC is effective to enhance the sensitivity of bond wire lift-off detection by V_ge waveform maintaining the best switching performance.