Research On Transient Thermal Characteristics And Control Methods Of Chips In High Voltage And High Power SiC Modules

As new broadband semiconductor power devices,the transient thermal characteristics within silicon carbide(SiC)MOSFET modules have not yet been fully investigated.Compared to silicon-based devices,SiC MOSFETs have a smaller chip area and higher current density,and as their power level,power density and switching frequency continue to increase,SiC MOSFETs need to withstand higher operating temperatures.Under cyclic temperature shocks,the transient maximum junction temperature at each layer of the module is often higher than the steady-state junction temperature,and long-time temperature fluctuations have a significant impact on the reliability of the module.Therefore,it is important to study the transient thermal characteristics of SiC MOSFET modules for the transient thermal regulation of the chip in the module and to improve the reliability of the power module.Firstly,based on the heat transfer principle,this paper optimizes the traditional Cauer thermal network model considering multi-chip thermal coupling,derives the calculation equations of thermal resistance thermal capacity and mutual thermal resistance mutual thermal capacity in the transient thermal network model,and later combines the calculation methods of different thermal diffusion angles to establish a transient Cauer thermal network model considering multi-chip thermal coupling.Secondly,a three-dimensional finite element model of the SiC MOSFET is established,and the heat flow path of the SiC MOSFET module is analysed.The simulation results of the finite element simulation and the transient Cauer thermal network model are compared and analysed to verify the validity of the transient Cauer thermal network model of the SiC MOSFET.Finally,the transient thermal characteristics of the chip inside the SiC MOSFET module are investigated under SPWM modulation conditions,and the effects of different chip layouts and different DBC ceramic layer materials and thicknesses on the transient thermal characteristics of the module are obtained using simulation software.The results are summarized as a reference for the internal layout of power modules.