The Research On Test Method For Thermal Resistance And Degradation Estimation Of IGBT Module

IGBT,born in 1982,has gradually became one of the representative high-frequency and high-power semiconductor devices.With its unique and irreplaceable function,it has been quickly applied to the national economy in all walks of life,demonstrating strong vitality and development potential.When the module operating junction temperature exceeds the safety limit,irreversible failure may occur.Thermal resistance,as a physical reflection of the IGBT module's cooling capability,plays an important role in the research of module thermal failure.And with the continuous degradation of the module,thermal resistance will increase gradually.So study thermal resistance between junction to crust and its degradation estimation play important roles in improving performance and reliability of IGBT modules and power electronic equipment.In this thesis,the heat transfer mode and path of IGBT modules are studied in depth,and the temperature field distribution and heat transfer process are also analyzed through simulation.The defined theoretical calculation,computational test and R-C network method are used to extract thermal resistance of IGBT modules.While comparing advantages and disadvantages of these various methods,their limitations in obtaining the thermal resistance are found.According to the transient thermal impedance formula defined in JEDEC STANDARE 51-14,a fast and accurate method is proposed to calculate the thermal resistance of IGBT modules,a calculation model is designed to solve the resistance according to the separation point of the module temperature change curves under different heat dissipation coefficient,and specific steps are made.The simulation and experimental study of these proposed methods and computational model were carried out,and the feasibility has been verified under the laboratory conditions.The temperature cycling degradation test of the module is carried out by using aging equipment and measuring its thermal resistance every 1000 temperature cycles.Fitting analysis indicates that the module crusts resistance increased exponentially with the circulation times.In order to predict the module degradation degree,this thesis defines a characteristic quantity to describe the thermal resistance degradation,and establishes a model to realize the quantitative description of IGBT module degradation.And according to the range of characteristic quantity,the module degradation degree is divided into seven grades in this thesis,which makes the module degradation degree can be directly estimated by crust thermal resistance.