Finite Element Analysis and Reliability Evaluation of Thermal Shock Behavior in Ag Sintered Joints with Varying Bond-Line Thicknesses

Ag sintering has emerged as a reliable high-temperature die-attach material owing to its high thermal conductivity and mechanical stability. This study investigated the effect of bond-line thickness (BLT) on the thermal shock reliability of Ag-sintered joints through experiments and finite element analysis (FEA). Ag-sintered layers with BLTs of 50, 100, and 200 ㎛ were fabricated, and their microstructural evolution and shear strength were evaluated after thermal shock cycling between -45 ℃ and 150 ℃. Thermomechanical stress and strain distributions at 150 ℃ were analyzed using FEA. Cross-sectional SEM observations showed that cracks and delamination occurred near the Ni/Ag and Ag/AlN interface edges in the 50 ㎛ sample after thermal shock, whereas no significant interfacial damage was observed in thicker joints. The shear strength decreased with the number of cycles, dropping to about 3 MPa for the 50 ㎛ sample after 1000 cycles, while the 200 ㎛ joint maintained approximately 24 MPa. FEA showed that increasing BLT reduced interfacial stress concentration. The maximum equivalent stress decreased from 251 MPa to 141 MPa (?44%) as the BLT increased from 50 to 200 ㎛, and the equivalent strain also decreased. The experimentally observed crack locations corresponded to the high-stress regions predicted by FEA, showing consistent trends between experiment and simulation. Overall, increasing the BLT alleviated interfacial stress concentration and improved thermal shock reliability. These results provide insight into optimizing BLT for reliable high-temperature applications.