Abstract
Sn-Zn-Bi alloys are promising Pb-free solders. Interfacial reactions between the Sn-8wt.%Zn-3wt.%Bi (Sn-13.80at.%Zn-1.62at.%Bi) alloy and the Cu, Ag, and Ni substrates are examined. Two different kinds of substrates, the bulk plate and the electroplating layer, are used, and the reactions are carried out at 250°C and 220°C. Although the Zn content is only 13.8 at.%, two Zn-Cu compounds, γ-Cu 5 Zn 8 and ε-CuZn 5 phases, are formed in the Sn-13.80at.%Zn-1.62at.%Bi/Cu couples. The ε-CuZn 5 phase is scallop shaped, and the γ-Cu 5 Zn 8 phase is planar. In the Sn-13.80at.%Zn-1.62at.%Bi/Ag couples, three Zn-Ag compounds are observed, and they are ε-AgZn 3 , γ-Ag 5 Zn 8 , and ζ-AgZn phases. In the Sn-13.80at.%Zn-1.62at.%Bi/Ni couples, a Zn-Ni compound, γ-Ni 5 Zn 21 phase, is formed. Similar results are found in the couples prepared with an electroplating layer: the reaction phases are the same, but the growth rates are different. © 2007 TMS.