Sn-40Bi-xZn Low Temperature Solder for Cu-Al Dissimilar Welding
The article investigates the influence of zinc(Zn)content on the melting process,solder wettability and spreading,microstructure,and mechanical properties of Sn-40Bi-x Zn solder alloys by changing the Zn content in the Sn-40Bi-x Zn alloy and comparing it with Sn-58Bi eutectic solder alloy.The results indicate that with an increase in the Zn content,the melting point(T)of the Sn-40Bi-x Zn solder alloy remains rela-tively unchanged,but the melting range(ΔT)gradually decreases until it stabilizes.When the mass fraction of Zn is 2.0％,the spreading rate of the Sn-40Bi-x Zn solder alloy is maximized,and the wetting effect on an Al plate is optimal.At Zn mass fractions of 1.0％and above,the interface layer in Sn-40Bi-x Zn/Cu is primarily composed of Cu6 Sn5 and Cu5 Zn8 intermetallic compounds,with a decreasing trend in Cu6 Sn5 content as Zn increa-ses.No intermetallic compound layer forms at the Sn-40Bi-x Zn/Al interface;instead,an increasing Zn ele-ment results in an enrichment of Zn phase,forming a coexistence of rich Bi phase,Sn-Zn-Bi phase,and Al-Zn-Sn solid solution at the welding interface.Simultaneously,an increase in Zn content leads to an upward trend in strain rate and shear strength of the copper-aluminum solder joints.
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