Online Deformation Characterization for Electrothermal-Mechanical Effect of Power Module via Confocal Methodology

Motivated by the dramatic increase of renewable energy and electric vehicle, a variety of customized power modules are rapidly designed and developed. However, it is necessary to expend a long time to examine the new power modules to ensure the reliability concerns via massive experiments, such as power cycling. The deformation characterization of the bare die has a grave impact on the failure of the power module. Therefore, to observe the weak point and presume the cycling lifetime of the power module package, the online characterization of deformation under the field application is significant. Besides, the outcomes can provide confident evidence for the finite element simulation model to conduct research on electrothermal-mechanical stress. In this letter, the mathematical model is created to understand the mechanical deformation induced by electrothermal coupling. To characterize the deformation of the power module in real-time for field application, a noninvasive confocal methodology is proposed. In addition, to confirm the feasibility of the proposed routine, an experimental setup is set up by using the front-to-front converter. The experiment results show that the maximal overall deformation occurs on the middle surface of the die while the edge of the bare die suffers minimal deformation, which corresponds to the simulation results. Besides, the overall and partial deformation errors between experimental and simulation results are within 5% and 7%, respectively.