Reflow discoloration formation on pure tin (Sn) surface finish

Pure tin finish is popularly used as the end finish for semiconductor leadframes and electrical connectors. However, the problem of reflow discoloration formation on pure tin surface finish degrades the packaging reliability of the integrated circuits (ICs), which greatly limits the application of pure tin plating. This paper reported on the aspect of the reflow discoloration formation on pure tin finish, and the effects of impurities of the substrate and the electroplating conditions on the tin finish discoloration after reflow were discussed. A significant improvement in the tin finish reflow discoloration is obtained by taking suitable electroplating process.