Enhancing mechanical response of hypoeutectic Sn–6.5Zn solder alloy using Ni and Sb additions

Abstract

In this paper, we report a convenient and informative procedure for improving the integrity and reliability of eutectic Sn–9Zn solder using minor alloying additions of Ni and Sb after reducing the amount of Zn phase. Results indicate that alloying of Ni or Sb into hypoeutectic Sn–6.5Zn resulted in slightly reduced the undercooling and pasty range with maintaining its melting temperature at the Sn–9Zn level. After 0.5% Sb addition, the enhanced solid solution effect and enlarged eutectic area with small needle-like α-Zn phase raised the creep resistance of hypoeutectic Sn–6.5Zn alloy, while the flower shaped (Ni,Zn)3Sn4 intermetallics (IMCs) and small spacing needle-like α-Zn phase produced by 0.5% Ni alloying results in small increase in its creep resistance. These results show that the creep strain rate of the entire alloys follows Garafalo hyperbolic sine equation, and the calculated creep stress exponent for three solders is reasonably close to other published data. Moreover, with the addition of Sb and Ni into Sn–6.5Zn solder, significant improvement in creep resistance of ∼270% and ∼182% is realized, respectively when compared with the hypoeutectic Sn–6.5Zn solder. This finding indicates the capability of newly developed ternary solder alloys to serve a much wider array of electronic applications.