Microstructure, interfacial IMC and mechanical properties of Sn–0.7Cu–xAl (x=0–0.075) lead-free solder alloy

Abstract

• Microstructure and wettability of Sn–Cu–Al solder alloy are improved by adding Al. • IMC Cu 6 Sn 5 varies to Al 2 Cu with increasing Al concentration in the Sn–Cu–Al. • Scalloped interfacial IMC thickness is decreased with increasing Al concentration. • UTS and creep resistance of Sn–0.7Cu–(0.05–0.075)Al are guaranteed by disperse Al 2 Cu inhibiting the dislocation movement. • Sn–0.7Cu–(0.05–0.075)Al is considered as an applicable lead-free solder alloy. The effect of aluminum concentration on the microstructure, wettability, interfacial IMC and mechanical properties of Sn–0.7Cu lead-free solder alloy is investigated. The results show that the microstructure of Sn–Cu–Al solder alloy consists of β-Sn, eutectic and IMC, and the microstructure of Sn–0.7Cu alloy is refined by adding aluminum. The interfacial IMC at the boundary of β-Sn in the Sn–0.7Cu–(0.01–0.025)Al is Cu 6 Sn 5 , and it is varied to Al 2 Cu in the Sn–0.7Cu–(0.05–0.075)Al. The wettability of Sn–Cu–Al solder alloy is improved by aluminum, the spreading coefficient of Sn–0.7Cu–0.075Al reaches about 70%. The thickness of the scalloped interfacial IMC is dominated by the IMC variation, and the chemical reaction between Cu and segregated Al. The mechanical properties of Sn–Cu–Al solder alloy are decreased slightly by adding aluminum. The tensile strength and the creep resistance of Sn–0.7Cu–(0.05–0.075)Al are superior to Sn–0.7Cu–(0.01–0.025)Al due to the hindering dislocation slipping by the disperse Al 2 Cu. Sn–0.7Cu–(0.05–0.075)Al is an applicable lead-free solder alloy for the Cu substrate.