MOSFET Short Circuit Failure — Root Cause & 8D Corre...
Diagnose MOSFET short circuit failures: overvoltage, ESD, thermal runaway. 5-Why analysis and fishbone diagram.
What Is a MOSFET Short-Circuit Failure? A short-circuit failure is the most common destructive failure mode of power MOSFETs. The drain-source channel becomes a near-zero resistance path, the gate oxide usually ruptures as well, and the device is destroyed — often explosively. In motor drives, DC-DC converters and inverters the root cause is frequently not the MOSFET itself but the circuit around it: parasitic inductance, gate drive design, or a design review that did not include a power-electronics specialist. This makes it a textbook D4 investigation where the evidence lives in the switching waveform. Symptoms Drain-source resistance near zero (a dead short) Gate-source also short (usually below 100 Ω) from gate oxide rupture Crater or burn mark on the package; localised PCB discolouration Fuse blown or over-current protection tripped Failure immediately at power-up, or after a period of running under load Avalanche or thermal-runaway signature in the failure analysis Affected Components Power MOSFETs (Si, SiC, GaN) in motor drives, DC-DC converters and inverters Gate driver ICs and gate resistors PCB switching loops (the high dV/dt and dI/dt commutation path) Snubber circuits, TVS diodes and gate-source zener clamps Detection Methods Curve tracer / semiconductor analyser: measure Vgs(th), Rds(on) and BVdss against...
