Influence of the Initial Microstructure of Snbi Solder on the Microstructure of the Melting Region Under the Action of a Self-Propagating High-Speed Heat Source

Due to the rapid cooling rate (230 mm/s) and large temperature gradient (107°C/m) produced by the self-propagating high-speed heat source, the liquid solder solidification procedure is extremely non-equilibrium, implying that the solder's original microstructure will invariably have a significant effect on the microstructure after melting and solidification. In this paper, a 300μm thick low-temperature eutectic solder Sn42Bi58 was heated by a 40μm AlNi self-propagating thin foil to investigate the impact of the solder's initial microstructure uniformity on the post-soldering microstructure. The results indicated that the melting time of SnBi solder was short due to the action of a self-propagating high-speed heat source, which resulted in the incomplete melting of heterogeneous phases and the non-uniform distribution of elements during the solder melting process, which had a significant effect on the morphology and composition distribution of the solidified microstructure. The preceding conclusions have the potential to improve the interconnection process based on the self-propagation reaction of AlNi thin foil, which is critical for both theoretical guidance and engineering application