摘要
The continuous downscaling of microbump dimensions to sub-10 mu m presents critical challenges to joint reliability in advanced electronic packaging. In such fine-pitch systems, applying low-temperature solders such as Sn-58Bi is considered to minimize thermal stress and ensure process compatibility. However, excessive growth of interfacial intermetallic compounds (IMCs), as well as the inherent brittleness and grain coarsening of Sn-58Bi solder, significantly degrade mechanical integrity. To address these limitations and improve mechanical properties, this study investigates the effect of Zn addition into Cu substrates on the microstructure and mechanical performance of Cu/Sn-58Bi/Cu microbumps. Doping Zn resulted in the formation of a Cu(Zn,Sn) layer, which served as a diffusion barrier to inhibit interfacial IMC growth. It also refined the eutectic microstructure through Zn diffusion into the solder. Shear tests revealed that Cu-36Zn/Sn-58Bi/Cu-36Zn samples exhibited improved mechanical performance compared to Cu/Sn-58Bi/Cu samples, with an increase of 20.5% in shear strength and 31.1% in energy absorption. Fracture analyses were also conducted to elucidate the mechanisms behind the strengthening effect of Zn.