The Thermal Design For Intelligent Power Module Package

Due of Intelligent Power Module(shortened from IPM) with the characteristics of high integration, high current density, high withstand voltage and high switching frequency, it has gradually been used in the new energy transportation, industrial control and smart home appliances and other fields. However, compared with the conventional power modules, IPM has a smaller size, compact structure and contains multiple power devices, its power density is greater and local heat is more serious. Failure caused by overheating has become one of the bottlenecks in the development of IPMs. It's an urgent need to make deep study of the thermal design for the package, which is important to improve the thermal reliability of IPM.Based on Fairchild's Intelligent Power Module (FSB50550A), the thermal resistance's testing methods of the module were studied in the thesis, and the accurate resistance testing was realized. Subsequently, through the ANSYS thermal simulation platform, starting from the structure and materials, the heat radiation and thermal stress simulation were completed from four aspects which are substrate, lead frame, solder layer and plastic shell. Studies have shown that the use of a certain size ceramic substrate can reduce the thermal resistance by more than 80%,and the solder layer and the chip's stress is obviously reduced; by changing the portion of the lead frame longitudinal dimension can effectively reduce the thermal resistance and reduce local overheating problem; with the increase of the thickness of solder layer, the power chip's junction temperature will rise, and the stress of the solder layer appears the overall upward trend; the size of the plastic shell has little effect to heat radiation and thermal stress.Through the study of heat radiation and thermal stress, the thermal design optimization program was further proposed in the thesis. Verification results show that compared with the original IPM, the thermal resistance reduces by 80.1%, the normal working junction temperature reduces by 19.5%,and the solder layer and the chip's equivalent stress are 1.48×108 Pa and 1.93 ×108 Pa,each decreases 69.5% and 80.6%. In this thesis, the thermal resistance test and simulation study provide guiding significance for the thermal design of IPM package.