Geometry-driven physics-of-failure lifetime analysis of aluminum bonding wires in discrete SiC power electronics

Bonding wire reliability remains 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 bond interconnects, relying on damage metrics derived from finite element models often based on modeling assumptions, especially when dealing with molded packages. These conventional approaches neglect the effect of the actual geometries of the bond foot and encapsulation cavity.

In this work, the reliability of encapsulated Al bonding wires in SiC power devices is investigated using active power cycling tests. The bonding wire material is characterized across various strain rates and temperatures, while its geometry is measured using high-resolution white light interferometry. Finite element models are solved using a two-stage simulation approach: First, an upstream wire bonding simulation is performed to obtain realistic bond foot and mold cavity geometries, and then the active power cycling tests are simulated. A Coffin–Manson lifetime model is calibrated using damage quantities derived from the simulation results, and the effect of various bond foot geometries on lifetime is analyzed. The results demonstrate that the modeled bond foot geometry can significantly influence lifetime predictions. By addressing the limitations of conventional simplified models, the presented approach offers a more accurate prediction.

The aim of the presented methodology is to accelerate the design of ECUs for automotive applications with the help of robust simulation models, reducing the experimental effort and ultimately the time to market.