|About this Abstract
||2022 TMS Annual Meeting & Exhibition
||Electronic Packaging and Interconnections
||Surface Precipitation and growth of Bismuth particles in Sn-Ag-Cu-Bi solder joints
||John Wu, Amey Luktuke, Nikhilesh Chawla
|On-Site Speaker (Planned)
Since the widespread of Pb-free solders, many different types of elements have been added into solders to form alloys with improved mechanical behavior. It has been previously reported that a low percentage Bi composition in SAC305 solders would result in Bi precipitation on the polished exposure surface. However, the mechanisms of the Bi precipitates at the early stages of surface exposure have not been carefully observed. The cause of surface Bi precipitation has also not been carefully explained. In order to study the growth mechanisms of Bi precipitates in SAC305 solders, samples were prepared and polished and re-exposed multiple times to reset the precipitation cycle. Once the samples surfaces were exposed, Bi precipitation coarsening was observed via scanning electron microscopy (SEM). Our results indicate that precipitation in this system is driven by surface diffusion effects. A parametric correlation between growth rate and growth mechanism is presented for this unique phenomenon.