Simulation On Thermal Performance And Thermal Stress Based On Finite Element Method

With current density increasing, power rising and volume shrinking of IGBT modules, there comes a new serious problem which is the internal heat of IGBT modules multiplied. Thermal and mechanical loads are even more serious because of temperature increment. The accumulation of internal heat is hard to distribute, so it will cause temperature and thermal stress of IGBT modules increasing. And it will lead to material fatigue, reliability reduced, and even affect the service life if IGBT modules long run in this condition. Therefore, IGBT module thermal problem has become a major issue. Issues related to thermal reliability of IGBT module packages for further exploration, revealed the main factors affecting reliability. It has important guiding significance and practical value on optimizing the structure design, improving thermal performance and reliability for IGBT modules. In this paper, for the purpose of improving IGBT module thermal performance, composites thermal conductivity, thermal performance and thermal stress of IGBT modules were studied respectively based on ANSYS. Besides, some advices were given on thermal design and structure optimization of IGBT modules in this paper.Firstly, the finite element model of composites were established to calculate the thermal conductivity of composite material. And the results closely matched the theoretical and experimental value, indicating the feasibility of the finite element method. On this basis, factors that affected composites thermal performance were analyzed: the thermal conductivity, volume fraction, distribution, shape, orientation, elliptical particle aspect ratio of fillers material and thermal conductivity of matrix material. Then some suggestions on the method of improving the thermal conductivity of the composite material were put forward.Secondly, the thermal performance of IGBT modules was studied. Three dimensional Finite Element Models were established to simulate temperature field. Then the factors affecting IGBT modules thermal dissipation were analyzed: substrate, solder layer, sub-frame and their thickness. In order to improve thermal performance of IGBT models, the thermal design of IGBT module was studied to give some reference on structural optimization.Finally, some thermal-structure coupled analysis were conducted using indirect analysis to obtain the maximum thermal stress of IGBT modules. We did the research on factors including substrate, solder layer, sub-frame material and their thickness affecting the maximum thermal stress of IGBT modules, and put forward optimization structure measures of IGBT modules.