Characterization of Space Charge Transport in Power Module Packaging Systems Under Different Operating Conditions

The electrode-substrate-packaging material triple region in power modules is a critical insulation weak point that has attracted significant attention. However, most existing studies on electric field characteristics within power modules ignore space charges or oversimplify the insulation structure, thereby lacking a thorough understanding of the charge distribution inside the packaging system. In this study, a surface potential decay test was employed to determine the charge transport characteristics of the packaging material. Subsequently, A physical model was developed to reproduce the actual structure of the power module, and a bipolar charge transport mathematical model was developed to study the charge and electric field distribution within the encapsulated system under off and on conditions. The findings reveal that charge injection leads to decreased electric fields in the triple region while increasing electric fields at the interface between packaging material and ceramic substrate regions. The AlN substrate packaging system exhibits higher charge density due to its high shallow trap density which facilitates the charge transport process. This study reveals the charging behavior in the power module under different working conditions and provides data support for optimizing the electric field design.