The effect of electrical current on tensile properties and vibration characteristics of Sn-9Zn-1Cu lead-free solder

The effect of electrical current on the microstructure, the tensile properties and vibration deformation mechanisms of the Sn-9Zn-1 Cu leadfree solder were examined in this study. Results showed that Zn-rich phase, Sn-Zn eutectic, Cu₅Zn₈ intermetallic compounds and proeutectic Sn-rich phase existed in the matrix of a Sn-9Zn-1Cu specimen. An electrical current flowing for a short duration was able to improve the tensile strength of the solder alloy. But prolonging the duration more than 7 hours led to a deterioration in the tensile mechanical properties and vibration resistance. Under both constant force and initial-deflection conditions, the electrical current caused the vibration life of the specimens to deteriorate. Lamellar-deformed structures (LDS) decreased and Cu₅Zn₈ fractured easily, which in turn decreased the crack propagation resistance.