Thermal Effect on Sinusoidal Vibration Fatigue of Bond Wire in IGBT Gate Loop

Understanding the thermal effect on the vibration fatigue of bond wires within insulated-gate bipolar transistor (IGBT) modules is of utmost importance. This article addresses this concern by developing a vibration-temperature test bench specifically designed for IGBT modules. Through a preliminary test, it was discovered that the bond wires in gate loops are particularly sensitive components in the used IGBT modules. As a result, a high-frequency impedance measurement between the gate- and Kelvin-emitter terminals is proposed as an in situ counting indicator during vibration tests. The impedance, reflected by the peak voltage of a sampling resistor, exhibits noticeable variation before the complete disconnection of the bond wire. Subsequently, the study investigates the number of cycles to failure (NCF) at various temperatures, revealing a decreasing trend with rising temperatures. In addition, a mechanical stress and strain simulation model is developed, accounting for the viscoelastic effect of silicone gel. The damping effect of silicone gel is found to be dominant in the vibration process and this effect is temperature dependent. Based on measurement results of the storage and loss modulus, the increment in von Mises stress and strain on the root of the bond wire over temperature is derived, which theoretically explains the decreasing trend in NCF.