An SEM-based Finite Element Analysis of Cu-Ag Sintered Joints on Thermal Shock Reliability

Copper-silver (Cu-Ag) composite sintered joints are increasingly investigated in power module die-attach applications due to their cost-effectiveness and resistance to electromigration. However, the inherent porosity in such materials results in mechanical failures, such as cracking and delamination, especially during thermal shock (TS) tests. This research investigated the enhancement of thermal shock resistance in copper-silver sintered materials through the solvent modulation of epoxy resin to fill the sintering voids. Firstly, two types of copper-silver composite joints (with and without epoxy resin) were produced under identical conditions. Afterwards, scanning electron microscopy (SEM) cross-sectional analysis, electrical and thermal conductivity tests, as well as TS tests, were conducted. Then, a model based on finite element method (FEM) model was developed, using Python image processing code and the reconstructed SEM cross-section images. Such simulation, validated by experimental results, is capable of analyzing the influence of epoxy for such composite sintered joints. Though epoxy reduced the electrical and thermal conductivity, it improved the shear strength and thermal shock resistance with a more evenly distributed thermal stress within the sintered joint. This research demonstrated the importance of solvent modulation of Cu-Ag sintered joints for thermal shock reliability analysis.