| Abstract Scope |
Low-temperature eutectic Sn-Bi solder, owing to its relatively low melting point, has attracted attention for its ability to mitigate heat accumulation during the assembly process. Nevertheless, the Bi phase exhibits high hardness, high electrical resistivity, and low thermal conductivity, which pose significant challenges to mechanical performance, electrical behavior, and heat dissipation. To overcome these limitations, hybrid solder joints composed of SAC and Sn-Bi have emerged as promising candidates to mitigate the reliability concerns associated with eutectic Sn-Bi solder. By controlling the amount of solder paste, the overall Bi concentration in the solder can be adjusted, enabling low-temperature bonding that alleviates thermal warpage and improves the board-level reliability.
In this study, the SAC305/Sn58Bi hybrid solder bumps were fabricated. twining structure and random-oriented grain structure were observed in SAC305 and Sn58Bi region, respectively, through EBSD analysis. After aging process, the de-twin phenomena and recrystallization occur because Bi diffuse toward the SAC305 region. the thermal stability of twin structure and Bi diffusion-induced de-twining phenomena were discussed in this study. |