《Rapid directional solid in Sn_Cu lead_free》.pdf

Journal of University of Science and Technology Beijing Materials Volume 13, Number 4, August 2006, Page 333 Rapid directional solidification in Sn-Cu lead-free solder 1) 2) 2) Jun Shen , Yongchang Liu , and Houxiu Gao 1) College of Mechanical Engineering, Chongqing University, Chongqing 400044, China 2) College of Materials Science Engineering, Tianjin University, Tianjin 300072, China (Received 2006-01-16) Abstract: An experimental study on the microstructures of a rapid directionally solidified metallo-eutectic Sn-Cu alloy was carried out. This material is an important alloy that is used as a lead-free solder. The results showed that the kinetic undercooling due to the rapid solidification process led to the formation of a pseudoeutectic zone, whereas the hypereutectic reaction produced the regular lamellar structure in the hypereutectic Sn-1.0Cu alloy. The corresponding arm spacing in the obtained lamellar phases decreased gradually with the increase of the applied cooling rate, which corresponded well with the prediction of a rapid directional solidification model. Key words: lead-free solder; rapid directional solidification; intermetallic compounds (IMCs); pseudoeutectic [This work was financially supported by the National Natural Science Foundation of China (No., Fok Ying Tong Education Foundation (No. 104015), and the Natural Science Foundation of Tianjin City (No. 033608811).] 1. Introduction experienced complex solidification conditions and thus had complex microstructures. Rapid directional solidi- In recent years, increasing environmental and health fication studies can provide an insight into the origin of concerns over the toxi