Influence of Geometry Effects on Thermo-Mechanical Reliability of Aluminum Bond Wires in Discrete SiC MOSFETs

Bond wire reliability remains as one of the major challenges in power electronics as device miniaturization progresses and demands on performance increase. Physics-of-failure models are commonly formulated to determine the lifetime of wire bonding interconnects. Such approach relies on damage metrics derived from finite element models, often based on simplified geometries and modeling assumptions.This paper addresses the influence of various bond wire geometry features on the thermo-mechanical reliability of PCB-mounted discrete SiC power devices. For this purpose, the bond wire geometry is characterized and the component is subjected to active power cycling until failure occurs due to bond wire lift-off. Finite element models are solved using a two-stage simulation approach: First, an upstream wire bonding simulation is performed to obtain a realistic bond foot geometry, and then the active power cycling tests are simulated. A physics-of-failure lifetime model is calibrated using damage quantities derived from the simulation results. Finally, geometry variations of the bond foot and different bond wire positions and rotations are evaluated to determine their significance for the thermo-mechanical reliability of thick Al bond wires.