Accurate Assessment of Young's Modulus of Sintered Ag Joints by Nanoindentation

In recent years, wide band gap (WBG) semiconductors, represented by SiC and GaN, have been utilized in power devices due to their superior properties. High operating temperatures of WBG devices present a challenge to conventional die-attach materials. Ag sintering technology provides a decent solution for realizing the die attachment of WBG power devices because of the numerous advantages of sintered Ag joints. The low Young's modulus of sintered Ag layer can effectively alleviate the thermal stress Generally, Young's modulus of sintered Ag layer has a close relationship with its microstructure, which is significantly influenced by the sintering process. In order to accurately assess Young's modulus of sintered Ag joints, we designed different methods by modulating the solvent evaporation mode and interfacial contact mode to find a more accurate and convenient way to measure Young's modulus of sintered Ag by nanoindentation. By placing a surface-modified Polytetrafluoroethylene (PTFE) sheet on the sintered Ag layer (the PTFE sheet can be removed after sintering), Young's modulus of the sintered Ag joint can be more accurately and conveniently tested. When comparing sintered Ag joints of different print thicknesses, Young's modulus obtained using this method is close to that of a real sintered Ag joint, with a difference of less than 10%, due to the fact that the microstructure of the samples obtained by this method is close to that of a real joint. In addition, we construct the relationship between print thickness and Young's modulus and find that the print thickness of the sintered Ag joints does not significantly affect Young's modulus due to the similar microstructure of the samples at different thicknesses, which have very similar porosity. We think that this research provides a new perspective on the study of Young's modulus of sintered Ag and can better promote the development of sintering Ag technology.