In situ vibration measurements on power modules under operating conditions

The subject of this investigation was determination of thermo-mechanically induced displacement of the components inside a power module under operation conditions. It is well known that lifetime of insulated gate bipolar transistor (IGBT) modules is limited by thermo-mechanical fatigue. Wire bonded interconnects inside the IGBTs count as critical sites where crack initiation and failure is observed. In this study the temperature dependent periodic deformation of wire-bonds under operating conditions was determined by using a laser Doppler vibrometer (LDV) and thermal imaging camera. Furthermore finite element analyses (FEA) were conducted to obtain the strain values needed for lifetime assessments.