Superplasticity Deformation of Sn-Bi-Based Solder Alloys

Low-temperature solderLow-temperature solder alloys have drawn a large amount of attention. Because using low-temperature soldering also reduces the energy cost of fabrication processesProcess. It allows the fabrication of inexpensive assembly materialsMaterials, such as printed circuit boards, without high-assembly temperatureTemperature resistance and temperatureTemperature-sensitive components, such as LEDs, by avoiding thermal damage. The superplasticitySuperplasticity mechanism of Sn-based alloys has not yet been clearly established. Therefore, this study investigated the effects of third-element addition on the microstructureMicrostructure and superplastic behavior of Sn-Bi-based alloys. Low-melting-point Pb-free Sn-Bi-Sb and Sn-Bi-Zn solder alloys were used in this study. Tensile tests were carried out on the alloys under various cooling ratesCooling rate, temperaturesTemperature (25, 40, 60, and 80 °C), and strain rates (10–3–10–1/s). The Sb- and Zn-added Sn-Bi-based alloys demonstrated superplastic deformation at 80 °C. The strain-rate sensitivity index of the Sn-Bi-based alloys at 80 °C exceeded 3, which is the threshold considered for superplastic deformation behavior. These results suggest that the superplastic deformation of Sn-Bi-based alloys is independent of the grain size of the primary Sn phase.