Effects of Ga–Ag, Ga–Al and Al–Ag additions on the wetting characteristics of Sn–9Zn–X–Y lead-free solders.

The effects of Ga–Al, Ga–Ag and Al–Ag binary additions on the wetting characteristics of Sn–9Zn–X–Y lead-free solders are studied by the wetting balance method. Experimental results show that Sn–9Zn–1.0Ga–0.3Ag, Sn–9Zn–0.005Al–0.3Ag, and Sn–9Zn–0.3Ga–0.002Al possess better wettability than the other alloys tested. The mechanism by which Ga, Al, and Ag additions improve the wettability is also proposed. It appears that dense aluminum oxide film formation and the enrichment of Ga on the surface may protect the bulk liquid solder from further oxidation. Moreover, results also indicate that, AgZn₃ IMCs layer formed at the interface, which may release reaction energy during the wetting, results in improving the wettability of the solder. [ABSTRACT FROM AUTHOR]