In-Situ Wire Bond Lift-Off Detection in Three-Phase Inverters based on Magnetic Field Profiling

Abstract:
In this paper, a novel method of wire bond failure detection in a three-phase inverter during operation of an electric motor based on magnetic field measurements is applied and evaluated. For this purpose, a test bench simulating the behavior of an electrical inductive motor is constructed in the laboratory. While the test bench is operating, wire bonds are gradually cut to observe the effect it has on the measured magnetic field signals. Two data processing algorithms are used for wire bond cut-off detection: Using a healthy reference measurement, the normalized magnetic flux is calculated over all cuts. For the second method, a ratio between the sensor values and the corresponding phase current peak is calculated. The results show that both data processing techniques give clear information about location of wire bond lift-offs in the module. However, the current normalization technique is more stable for varying motor speeds.