Multimodal Characterization of Sn‐Bi Solder Alloy Solidification Using Synchrotron X‐Ray Microtomography and Energy Dispersive Diffraction

Sn‐Bi solder alloys have generated significant interest in recent times due to their potential use in electronic packaging. The microstructural evolution during solidification of these alloys plays a crucial role in determining the mechanical and reliability properties of a solder joint. In order to understand the intricate interplay between the evolution of microstructure and composition during solidification, an in situ, multi‐modal characterization approach is necessary. In this study, for the first time, simultaneous 4D X‐ray microtomography (XRM) and energy‐dispersive diffraction (EDD) are employed to understand Sn‐Bi alloy solidification. The XRM analysis yields unique insights into microstructural evolution while the EDD data offer complementary information about phase formation and lattice strains. The growth mechanisms controlling the formation of primary Bi in the liquid melt are studied using tomography data. Diffraction peak broadening analysis reveals a remarkable correlation with the growth of Bi phase. The quantitative correlation between microstructure and diffraction enables phase identification and fraction analysis during the dynamic solidification process.