Press-pack insulated-gate bipolar transistor (PP-IGBT) device is used in high-power modular multilevel converter high-voltage direct current (MMC-HVDC) system due to the advantages of high reliability and short-circuit failure. Considering safeties and stable operations, it is necessary to model and analyze the fatigue failure evolution of PP-IGBT device that improves the reliability of MMC-HVDC system. This paper proposes a method to analyze from fretting wear failure to short-circuit failure in PP-IGBT device. First, a multiphysics coupling model of a single-chip 3.3-kV/50-A PP-IGBT device is presented to analyze the fretting wear failure, and the weak layer and the fatigue effect are obtained by power cycling simulation. Second, considering the Al-Si diffusion reaction mechanism on the interface of IGBT chip, the short-circuit failure is investigated by the finite-element method model of PP-IGBT device with Al-Si osmotic hole, and the changing trend of characteristic parameters is estimated during short-circuit failure process. Finally, the steady state, power cycling, and short-circuit tests are used to verify the multiphysics coupling model, fretting wear failure, and short-circuit failure. The experiment indicates that the fatigue failure evolution of PP-IGBT device occurs from fretting wear failure to short-circuit failure, and it suggests that the proposed method can be applied to optimize design and condition monitoring of PP-IGBT device.

Press pack packaging technology has been widely used in insulated gate bipolar transistors for highvoltage and high-power density applications. The effects of unbalanced internal pressure, which occurs frequently within large-scale press-pack modules, remain unclear, and thermal parameters within modules cannot be directly measured due to the pressure-type package structure. Current and temperature distribution within 3300 V/1500 A modules are investigated to determine module reliability characteristics and derive future lifetime models using multi-physics models. Unbalanced clamping force causes extremely uneven temperature stress and electrical stress in spatial distribution. It indicates that partial chips must withstand high stresses that cause the initial fatigue of largescale press-pack modules. Junction temperature difference reaches up to 53.6 °C among chips at chip surface roughness of 1.27 μm. This condition shows that aging of modules will accelerate at the onset of partial chips degradation. Finite element modeling and equivalent test are utilized to verify the multi-physics model by using single-chip devices in parallel.

Thermal contact resistances usually account for more than 50% of the total thermal resistance in a press-pack insulated-gate bipolar transistor (PP-IGBT) device, which affect the heat dissipation of the PP-IGBT device and lead to a high junction temperature. In this article, a method for optimizing the thermal contact resistances of the PP-IGBT device is proposed by filling the liquid metal thermal interface materials in the contact surface. Bismuth-based liquid metal with high thermal conductivity and electrical conductivity is chosen, and the material is used for filling between the insulated-gate bipolar transistor chip and the molybdenum layers. The thermal characteristics are compared with the traditional commercial PP-IGBT device using finite-element simulation and experimental methods. The high-voltage insulation reliability of the proposed optimized method is verified by blocking voltage test, and the long-term reliability of the device is verified by a power cycling test. The results show that the junction-to-case thermal resistance of the optimized PP-IGBT device can be reduced by more than 30%, which is helpful for improving the thermal reliability of large-capacity PP-IGBT devices.

This study presents a study on non‐linear accumulative modelling for power module lifetime estimation in non‐accelerated operation. The model focuses on solder fatigue based on monitoring the internal thermal resistance of the module. Initially, the relatively small junction temperature variation (Δ T _j ) cycles contribute little to the lifetime consumption, but with an initial damage the effect becomes noticeable. The original Coffin–Manson accumulation approach is extended for complex mission profiles. The proposed non‐linear accumulation model has three aspects: a Coffin–Manson relationship is first established; the thermal resistance degradation is then used to quantify damage accumulation; the effects of the average junction temperature ( T _jmean ) and Δ T _j on the rate of degradation are finally included through the parameters of the non‐linear accumulation model which also depends on the effect of the present condition of the module. Experiments demonstrate the phenomena and verify the proposed model.

Junction temperature is the most important factor to induce the insulated gate bipolar transistor module failure and conduct operational management. In-situ calibrated method and junction temperature calculation model are proposed to timely indicate the junction temperature for the electric vehicle drive system. It aims to solve that the conventional calibration methods need to be calibrated in the temperature chamber and the model cannot meet variable current conditions, which ignores the effects of the stray parameters of electrode connection on the on-state voltage. A mathematical junction temperature estimation model based on the relationship between saturation voltage drop and different currents is established, whose accuracy depends on the prior narrow range junction temperature calibration. A control strategy for the in-situ calibration is proposed to generate an instantaneous large current by creating a zero-torque condition and using integrated negative temperature coefficient thermistors, current sensor, and on-state voltage measured circuit when the new-energy vehicle is in an idle state. Experimental results prove that the proposed in-situ calibration method can be realized totally inside the electric vehicle, which can serve the full-service lifetime of the electric vehicle with high precision.