The properties of solder determine product applications. Aerospace, automotive and consumer electronics need different type of solder. Melting point is one of the important criterions. The aim of this study is to develop lead-free solder for consumer electronics. Low-temperature lead-free solder is indispensable to consumer electronics. The advantages of lowering process temperature include easing device damage and carbon emission. We regard Bi and In as low-temperature solder candidates. Microstructural observations between low-temperature solder and Cu during reflow and aging reactions were investigated in this study. The experimental results are as follows: (1) Reflow temperature and Bi diffusion are responsible for Bi segregation at the interface; (2) A mixed layer of Cu-In compounds formed at low temperature; (3) The storage time of In-based solder could not be ignored.
