Simulation-Based Analysis of Thermo-Mechanical Constraints in Packages for Diamond Power Devices

Diamond is one of the best wide band-gap semiconductor materials available for high power devices development in terms of high current capability, high temperature operability, breakdown voltage and switching speed. Unfortunately, fabrication technology for diamond devices is still experimental and immature. Furthermore, one of the most critical fields to be addressed for practical diamond devices implementation concerns the development of power packaging solutions, given that limitations in the device packaging would hinder the performance of the device and act as the limiting factor for a technology that is still in a development state. Of special interest are the induced stresses and deformations caused by the thermo-mechanical mismatch between materials. These stresses and strains will be considerably different than the ones obtained with silicon or SiC dies, and it will be especially noticeable in high temperature applications due to the higher temperature swings and the reliability constraints that arise from the coefficient of thermal expansion mismatch and stiffness difference. In this paper, a Finite Element Method for thermo-mechanical simulation of a high-temperature thermal cycle for a full-stacked diamond die SOT-227 power module is introduced and compared to silicon- and SiC-die modules. Special interest is addressed to the analysis of stress and deformations generated in the die and die-attach solder layer.