This paper investigates the microstructural evolution and reliability of two high-reliability solder alloys, SABN (Sn-Ag-Bi-Ni) and SACQ (Sn-Ag-Cu-Bi-Ni), in comparison with conventional SAC305. High-temperature storage, Charpy impact, drop, and thermal cycling tests were conducted to analyze the effects of alloy composition and interfacial intermetallic compounds (IMCs). In high-temperature storage, SAC305 exhibited the fastest growth and highest roughness of the Cu 6 Sn 5 layer, whereas the Ni-doped SABN and SACQ formed smoother, more stable (Cu,Ni) 6 Sn 5 layers. Charpy results showed that SAC305 possessed the highest absorbed impact energy, while SABN and SACQ absorbed less energy due to Bi-induced solid-solution strengthening and Ag 3 Sn precipitation. Reliability evaluations using CTBGA228 components identified the SAC-SABN joint (SAC305 ball/SABN paste) as the superior performer. In drop tests, SAC-SABN achieved the best reliability, attributed to the mechanical stability of the (Cu,Ni) 6 Sn 5 interface. In thermal cycling, SAC-SABN joints with a total Ag content between 3.0 wt.% and 4.0 wt.% exhibited superior fatigue life. This performance was driven by a microstructure featuring particle-like Ag 3 Sn and granular Cu 6 Sn 5 , which pinned grain boundaries and retarded crack propagation. Overall, SAC-SABN joints provided the optimal balance of drop and thermal reliability, making SABN paste with SAC305 balls a strong candidate for high-reliability electronic packages.
Lin et al. (Thu,) studied this question.