The present report summarizes microstructure variation of solder alloys including SnPb, SnCu, SnAg, and SnZn systems, under electrical current stressing. Electrical current stressing may induce electromigration and thermomigration to the solder joint. The electromigration force causes disruption of the crystal lattice structure as indicated by XRD peak shift and intensity diminishing under in situ investigations. The disrupted lattice structure may restore when the current stops. The second phase of solder alloy may dissolve upon current stressing at above critical current density, which results in supersaturation of the second phase elements in the matrix. The dissolution of the precipitates occurs anisotropically as directed by the electrical current. Both the matrix and the second phase of the solder alloy experience recrystallization after current stops. The recrystallization of the second phase, such as Zn in Sn9Zn and Sn in Pb5Sn, gives rise to nano fibrous structure within the matrix as revealed by TEM and in situ SEM investigations. The nanorefining of the second phase is resulted from the Gibbs-Thomson effect. The combination of electromigration and thermomigration effect may result in redistribution and segregation of the recrystallized intermetallic compounds.

Biography:
Professor Lin received his PhD in Metallurgy from the Department of Materials Science and Engineering, Pennsylvania State University. He joined MSE-NCKU as faculty in 1985. His major interest of research includes surface modification, interfacial interaction, solders and soldering technology, electromigration, and reliability of electronic packaging. Part of his recent research are focusing on the electromigration behavior of solder joints. Prof. Lin has published more than 190 refereed journal papers, 16 patents, and delivered more than 90 international conference presentations. He has been the editor-in-chief of Materials Chemistry and Physics (Elsevier publisher) since 2003, guest editor of the Journal of Electronic Materials. Prof. Lin is IEEE Fellow and MRS-T(Taiwan) Fellow.