Detection of aging of power electronic modules through the evaluation of the magnetic field pattern

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Aging of power semiconductor modules is one of the key factor for expected lifetime and reliability of power electronics systems such as wind power converter, electrified vehicles, rolling stock and industrial drives. Especially for safety relevant and mobile application it is highly recommended to detect the state of health (SOH) and to schedule maintenance according to the SOH in order to avoid unexpected failures and system shut down.According to the state of the art the detection of fatigue of power electronic and more in particular its packaging and joining elements uses an estimate of the junction temperature based upon temperatures sensitive parameters and the total power losses and the thermal impedance. If there is a mismatch between both estimated values this is assumed to be a result of an increased thermal impedance due to cracks within the chip solder or delamination. The new method is based on the assumption that with propagating cracks in the chip solder or disconnected bond wires the current distribution within the chip and the DCB will change and therefore the spatial distribution of the magnetic field will change as well. Therefore, magnetic field sensors have to be installed as close as possible to the chips. With this method, the fatigue of the joints could be detected more directly in situ during operation and it does not require to intervene the power module. Within the project, the correlation between fatigue and the change of the magnetic field pattern has to be investigated. Furthermore, placement of magnetic field sensor, real time data processing and compensation of unwanted effects such as external magnetic fields are major challenges in order to receive reliable results even under challenging EMI conditions during operation.