Online Condition Monitoring of Bonding Wires Lift-Off in Power Modules Based on Magnetic Field Measurement

Wire-bonding type power modules are among the most widely used power semiconductor module packages in recent years, with bonding wires being one of the weakest links in these modules. Under the long-term effects of power cycling and temperature fluctuations, stress and strain make bonding wires prone to cracking, eventually leading to breakage or detachment, which affects the reliability of power modules. Therefore, monitoring the health condition of power modules is crucial. This article proposes a method for real-time monitoring of bonding wire lift-off using a single-axis magnetic field sensor. The article first analyzes the magnetic field near the bonding wires of the power module, indicating that the magnetic field changes when bonding wires lift off. Second, finite-element method is used to simulate the magnetic field and identify the region with the highest rate of magnetic field change due to bonding wires lift off, where the magnetic field sensor is placed to achieve the highest monitoring sensitivity. Additionally, by using a temperature compensation method, the change in magnetic field sensor sensitivity due to temperature variations was reduced. This method decreased the sensitivity deviation caused by temperature changes from approximately 30% to less than 1%. In the experiment, the bonding wires of two types of power semiconductor modules were monitored. Using a magnetic field to current ratio deviation of ±5% as the standard, the occurrence of bonding wire lift-off could be accurately detected.