Thermo-Hygroscopic-Mechanical Coupling Simulation Method for Power Electronics Under Power Cycling Test

Recently, more attention has been paid to the humidity-related reliability of power electronics, such as lifetime, bond wire feet stress/strain, and thermal resistance under humidity environments. However, the humidity simulation, coupled with temperature and mechanics, for power electronics is still lacking, obstructing the understanding of the influence of humidity, especially under a large load current working profile. This article proposes a thermohygroscopic-mechanical multi-physics field coupling simulation method to explore the influence of humidity in the power cycling test (PCT). The simulation model is calibrated by transient thermal impedance
Z
_th
, moisture absorption weight
W
, and PCT settings. The simulation results find that when device under test is long time submerged in a humid environment, the strain at bond wire feet during PCT is more significant than that without moisture invasion, which shortens the lifetime of test devices. The moisture invasion is the root cause, and this finding ties well with the experimental results.