The Research On Thermal-conductivity And Degradation For IGBT Power Module

The development of insulated gate bipolar transistor(IGBT) characterized by high frequency, high-power and highly integrated, has made it possible to bear a higher operating temperature and a higher temperature shock. The thermophysical properties of heat conduction material inside the IGBT module degrade gradually due to reciprocating expansion and contraction. So it shows an increasing working temperature at a certain power and environment stress as well as a decreasing capacity in adapting the power stress,environment stress and system transient shock. The operational safety margin of modules will reduce at the same time. When the working temperature of module excesses its safety threshold, the module will suffer an irreversible failure. So the research of heat-transfer characteristics and degradation law of IGBT module is of great significance in improving the performance and reliability of IGBT module and power electronic equipment. This paper mainly research on heat-transfer characteristics and degradation trend of IGBT module through theory, experiment and simulation.Firstly, analyze the structure and working principle of IGBT module, and discuss the heating mechanism and degradation mechanisms of heat-transfer characteristics of IGBT modules under power stress. The physical quantities such as thermal electric parameters and temperature parameters, which can reflect the degradation of heat-transfer characteristics of IGBT module are studied, and then select the thermal resistance as the heat-transfer degradation characteristic parameter of IGBT modules, for it has nothing to do with power and environmental stress, but can reflect the structure and material properties.Determine the minimum value of thermal resistance according to the parameters offered by a factory, figure out the maximum value related to the maximum safety junction temperature and the reduction standard, and finally establish the fuzzy regression model H(R).Afterwards, design a single-phase IGBT module and temperature acquisition system with the feature of variable-frequency and controlled current, which can dynamically accommodate the collector current, collector-emitter voltage, frequency and duty ratio of IGBT module. Remote real-time monitor the case temperature based on the system constructed combined with the DS18B20 temperature sensor and wireless data acquisition,transition module. Monitor the module-junction temperature in real-time by means of fiber temperature sensor. The Teck high-speed memory oscillograph is adopted to record the collector-emitter voltage and collector current waveform in switching process. Design the orthogonal experiment which includes four current levels and four frequency levels, and analyze the thermal electric parameters as well as temperature data.In addition, three dimensional steady state and transient of IGBT modules are simulated by ANSYS with the measured average power loss as heat source and then the temperature field distribution, junction temperature and shell temperature curve of module can be obtained. The measured case temperature curves are compared with the simulation curve to verify the consistency of test results and the results of simulation.Finally, the network model and test method of thermal resistance are studied, and the thermal resistance parameters which based on the measured power loss, junction temperature and shell temperature are extracted. The fatigue state of IGBT model is quantitative evaluated, which is based on the fuzzy regression model H(R).