Electrical Current Phase Transformation of Sn–9Zn–1Ag Alloy

Abstract

The current load not only easily induces the electromigration effect and thermal strain, but also destroys the effectiveness of solders. As of now, temperature and phase transformation problems caused by the high current load have still not been discussed. This study investigates the structural characteristics of the Sn–9Zn–1Ag alloy under an electrical current test and heat-treatment. The results indicate that the Ag existed mostly in Ag–Zn compounds, and the Zn concentration in the Ag–Zn compounds was higher than in the needle-like Zn-rich phase and Sn–Zn eutectic phase. The Sn–9Zn–1Ag alloy had no transformation during oil heat-treatment, while the structure underwent phase transformation under electrical current testing. After current testing, the needle-like Zn-rich phases had decomposed into finer particle-like features, the Ag–Zn compounds had grown and the Sn–Zn eutectic phases had increased, and the content of Sn-rich phase had decreased. Meanwhile, the current effect also caused the content of Sn to increase but Zn and O both decreased for the Zn-rich (SZO) phases in the relative composition.