A new type short circuit failures of high power IGBT's
The Next Linear Collider accelerator proposal at SLAC requires a high efficiency, highly reliable, and low cost pulsed-power modulator to drive the 500 KV, X band klystrons. A Solid State Induction Modulator to power the klystrons is under development uses high voltage 3.3 kV high current (3 KA pulses for 3 /spl mu/S) IGBT modules develop for traction and electric train application. Testing of these IGBTs under pulsed conditions have been very successful, however the IGBTs failed under short circuit testing. Unpredicted current and gate waveforms and eventual IGBT failures occur when short circuit tests were performed into extremely low short circuit inductances (< 50 nH). The failures appeared to be gate related and not the anticipated collector to emitter overvoltage. The internal connection structure of the IGBT package was analyzed and its performance simulated, which resulted in an understanding of the strange current response under short circuit and the resulting failures. Test results will be presented, IGBT package layout, circuit simulation and recommendation for modification to the standard IGBT layout to improve performance of IGBT's under extremely low inductance short circuits.