A comprehensive study on variations of discrete IGBT characteristics due to package degradation triggered by thermal stress

Identification of power device failure precursors is essential for condition monitoring, fault severity assessment and lifetime estimation. These tools constitute the fundamental elements to achieve highly reliable power converters with self-diagnosis capability, which can report incipient faults at very early stage. In this paper, several discrete IGBTs are thermally aged on a custom-built modular test-bed. I-V characteristics are monitored periodically using an automated curve tracer throughout the aging, and the fault/aging related patterns are comprehensively analyzed. The variations in saturation voltage, gate threshold voltage, transfer capacitances, and gate charge, which are the potential candidates for aging precursors, are analyzed in detail. The experimental and failure analysis results suggest that on-state voltage drop and gate threshold voltage are the two essential aging precursors for monitoring die-attach solder and gate oxide degradations.