Simulation-Assisted Competing Failure Mode Analysis of SMD MOSFETs under Bending Stress

SMD packaged MOSFETs are widely used in automotive applications relying on the reduced parasitism inductance and improved thermal behavior. Under thermal imbalance and mechanical strain from printed circuit boards (PCBs), MOSFETs are likely to suffering a flex strain, resulting in a high failure risk. Considering a SMD MOSFET on PCB, its failure mode is expressed as bending induced electrical parameter variations, interconnection cracks and device solder joint cracks, which occur competitively due to different stress levels and mount situations. This paper carries out a simulation-assisted analysis method to recognize the critical failure mode of SMD MOSFETs by establishing a mechanical simulation model with device package structure and PCB layout. The proposed analysis method is illustrated and verified by 3-point bending experiments under various conditions with different device vendors.