A New Approach for Detection of Aging of Power Modules by Evaluation of the Magnetic Field

In this paper, a new approach for the on-line detection of chip-solder and bond-wire degradation inside of a power module is presented. The approach focuses on changes of the magnetic field pattern around the power semiconductor module caused by a presumed change of the current density distribution within the module due to aging and fatigue of bond wire joints and solder connections. The approach is based on the assumption, that changes in bond wire connection or relevant chip or CDB solder degradation will cause a significant change within the spatial magnetic field, which can be detected by means of magnetic field sensors. As a baseline the magnetic flux density distribution above an IGBT module was investigated and a comparison between simulation and measurements was conducted in order to get reliable “starting” values. The investigation was extended on power semiconductor samples with partially interrupted solder connection to find whether there is a significant change in the magnetic field pattern.