The Effect of Low-Temperature Solute Elements on Nonequilibrium Eutectic Solidification of Sn-Ag Eutectic Solders

• Published in: Journal of electronic materials 2007-12, Vol.36 (12), p.1608-1614
• Main Authors: SONG, Jenn-Ming, WU, Zong-Mou, HUANG, De-An, CHUANG, Hsin-Yi
• Format: Article
• Language: English
• Subjects: Applied sciences; Brazing. Soldering; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electronics; Eutectics; Exact sciences and technology; Joining, thermal cutting: metallurgical aspects; Materials science; Metals. Metallurgy; Microelectronic fabrication (materials and surfaces technology); Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silver; Soldering; Solidification; Temperature; Thermal expansion; thermomechanical effects and density; Thermal properties of condensed matter; Thermal properties of crystalline solids; Tin
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-007-0238-x

The microstructure and thermal behavior of the Sn-Ag-Ga alloy, as well as those of the Sn-Ag and Sn-Ag-Bi alloys, were examined in this study. Results show that, similarly to Bi, Ga can decrease the melting point and extend the solidus/liquidus range. Both these low-temperature elements distributed nonuniformly and resulted in a mixed normal-coarse structure. However, unlike Bi, which was only detected in the Sn matrix, Ga dissolved in Ag^sub 3^Sn and even transformed Ag^sub 3^Sn into a new intermetallic phase, Ag^sub 72^Ga^sub 28^, within the coarse eutectic cells. It is believed that this could give rise to a specific two-stage nonequilibrium eutectic solidification feature. [PUBLICATION ABSTRACT]