Pressure-Dependent Thermal Network for Press-Pack Power Module with Prognostics of Mechanical Status

Abstract

The press-pack power module with multi-chip layout has drawn increasing attention from industry and academia and its thermal analysis becomes an essential issue. However, the pressure-dependent thermal variables such as thermal contact resistance and thermal coupling resistance are often neglected. In this paper, a pressure-dependent thermal network model is developed to characterize the thermal performance and mechanical status of press-pack power modules. By including the thermal contact resistance and thermal coupling resistance as the function of pressure, the proposed model enables a more precise thermo-mechanical evaluation inside the press-pack power module. The influence of pressure on self-heating effects and thermal coupling effects of power modules is studied with the knowledge of elastic mechanics. A press-pack prototype with variable pressure loads is assembled. Then the thermal experiments under different pressure on chips are conducted and the pressure-variable temperature responses of thermal network are measured. Consequently, the feasibility of proposed thermal network model is validated. A cost-effective prognostic method on the mechanical status of press-pack power module is also achieved.