Revisiting mechanisms to inhibit Ag3Sn plates in Sn-Ag-Cu solders with 1Â wt.% Zn addition

Two mechanisms to inhibit Ag3Sn plates were discovered in Sn-1.0Ag-0.5Cu and Sn-3.0Ag-0.5Cu with 1 wt.% Zn addition. It was revealed that 1 wt.% Zn not only reduced the supercooling of β-Sn, but also promoted the formation of γ-(Cu,Ag)5Zn8 compounds. The amount of γ-(Cu,Ag)5Zn8 was larger in Sn-3.0Ag-0.5Cu than that in Sn-1.0Ag-0.5Cu. Meanwhile, the Ag content in γ-(Cu,Ag)5Zn8 was higher in the high-Ag solder. Although more γ particles formed under slow cooling rate, the Ag content varied a little with cooling rate.