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

电力半导体组件的老化是影响风电变流器、电动汽车、机车车辆和工业传动等电力电子系统预期寿命和可靠性的关键因素之一。特别是对于安全相关和移动应用，强烈建议检测健康状态(SOH)并根据SOH安排维护计划，以避免意外故障和系统关闭。根据最新技术，电力电子，特别是其封装和连接元件的疲劳检测使用基于温度敏感参数和总功率损耗和热阻抗的结温估计。如果两个估计值之间存在不匹配，则认为这是由于芯片焊料中的裂纹或分层导致热阻抗增加的结果。这种新方法是基于这样的假设：随着芯片焊料或断开的焊线中裂纹的扩展，芯片和DCB内部的电流分布将发生变化，从而磁场的空间分布也将发生变化。因此，磁场传感器必须安装在尽可能靠近芯片的位置。该方法可以在运行过程中更直接地现场检测接头的疲劳情况，而不需要干预电源模块。在该项目中，必须研究疲劳与磁场模式变化之间的相关性。此外，磁场传感器的放置、实时数据处理和外部磁场等有害影响的补偿是主要挑战，以便即使在操作期间具有挑战性的EMI条件下也能获得可靠的结果。

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.