Effect of low Bi content on mechanical properties of Sn-Bi-Zn-In alloy and its joint with Cu

Low-temperature-processable interconnect materials are recently desirable for electronics. In recent years, wearable electronics have been the trend in electronic industries. Wearable devices are integrated on soft and flexible objects made with organic substances. Accordingly, the electronic assembly industry needs low-temperature bonding processes, and the demand for low-temperature lead-free solder alloys has increased significantly in the electronics industry. In this study, Sn-Bi-Zn-In alloy with low Bi content was examined by tensile tests before and after aging. Then, the applicability of Cu/Cu joints formed using Sn-Bi-Zn-In alloy was investigated. As a result, as mechanical properties of the Sn-Bi-Zn-In alloy, higher ultimate tensile strength and better elongation than the eutectic Sn-58Bi alloy were obtained. Then, the shear strengths of the Sn-Bi-Zn-In alloy joints remained unchanged after aging for 1008 h, suggesting that the alloy joint demonstrated the better long-term reliability.