Abstract
The effect of aluminum on the microstructure and mechanical properties of Sn–0.7Cu–xAl (x=0–0.075) solder alloy is investigated. The results show that the microstructure of Sn–Cu solder alloy is refined by Al. The intermetallic compounds (IMC) in the Sn–Cu–Al solder alloy is varied from Cu6Sn5 in the Sn–Cu–(0.01–0.025)Al to Al2Cu in the Sn–0.7Cu–(0.05–0.075)Al. The volume fraction of the IMC and eutectic is raised with increasing aluminum concentration. The wettability of Sn–Cu–Al solder alloy is improved by aluminum. The spreading coefficient of Sn–0.7Cu–0.075Al is reached 70%. The tensile strength of Sn–Cu–Al alloy is decreased after aluminum adding to 0.025wt.% and then is increased after aluminum adding to 0.075wt.% due to the IMC variation and the volume fraction increasement of Al2Cu/Sn eutectic with high microhardness. The superior mechanical properties of Sn–0.7Cu–0.075Al are guaranteed by the refined microstructure, the dispersed IMC and the uniform stress distribution. The Sn–0.7Cu–0.075Al is an optimized lead-free solder alloy for the copper substrate.
Published Version
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