Effect of Zinc Element on Mechanical and Welding Properties of Cu–1.8Ni–0.45Si Alloy

Abstract

Cu–Ni–Si alloy is widely used as the main material of lead frame. The process of alloying is an important method to improve the comprehensive performance of the alloy. Herein, Cu–1.8Ni–0.45Si (−0.5Zn) alloys are prepared. The variation trend and mechanism of Zn on the mechanical properties and welding properties are analyzed with scanning electron microscopy and electron backscattering diffraction. The results show that the addition of 0.5 wt% Zn can improve the brazing properties of the alloy while ensuring the tensile strength and conductivity of the material. Further quantitative analysis reveals that Zn addition enhances the contribution of precipitation strengthening to the alloy's mechanical properties, which is due to the reduction of the size of the particles of the precipitated phase by the addition of Zn. In addition, the addition of Zn can form a Zn-enriched layer at the welding interface of the alloy, which has an obstructive effect on the diffusion and growth of the intermetallic compound (IMC) layer, effectively reducing the thickness of the IMC layer, inhibiting the formation of the Cu₃Sn phase, and improving the mechanical properties of the alloy brazed joints.