Thermal fatigue analysis of power modules

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Thermal fatigue analysis of power modules [Copy link]

With the development of science and technology, the power module is required to be smaller and smaller in size and higher in power in applications. The heating and heat dissipation of the module has become one of the key factors affecting the performance and life of components. Generally, the module has a multi-material layered structure. Different material layers have different thermal expansion coefficients. When the temperature changes, thermal stress will be generated on different material layers. It is usually said that the module will generate thermal stress cycles when it is turned on and off. As the number of operations increases, when a component reaches the fatigue limit, the entire power module will fail. Small-volume, high-power-density products are the future choice of the power module market, and high reliability is a major issue that all engineers need to solve. They need to ensure that the product operates normally for many years with little failure. The thermal fatigue phenomenon and auxiliary circuit failure caused by the high power density of the large number of components and packages inside the module affect the reliability of the module and have become an important issue that technicians must solve. The thermal fatigue of the power module is mainly caused by power conversion, low efficiency, and limited heat dissipation space, which leads to temperature rise and shortens the service life of the product. In order to reduce the impact of temperature on the mean time between failures (MTBF), engineers need to consider heat dissipation, airflow, and power loss of the module. When comparing derating curves, we should not only care about the electrical performance at room temperature of 25°C, but also consider the system ambient temperature, airflow, and heat dissipation method of the module. At present, in many applications, power modules need to work in harsh environments, and these issues should be considered more. High temperature has a great impact on high-power-density power modules, which will lead to reduced life of electrolytic capacitors, damage to transistors, reduced insulation characteristics of transformers, aging of component materials, and falling off of solder joints. Therefore, reducing losses and improving heat dissipation conditions are fundamental.