Interaction of Y and impurity P on the synergistic enhancement of elongation and electrical conductivity of single crystal copper rod

Abstract

Single-crystal copper rods with high conductivity and mechanical properties are the decisive material for the production of microwires for chip bonding. To further improve the product of strength and elongation as well as electrical conductivity, rare earth Y is added to a single-crystal copper rod to adjust the microstructure and impurity state. The results show that Cu-0.03Y copper rods have excellent comprehensive properties. The electrical conductivity improves to 103.72 % IACS, and the product of strength and elongation improves to 8.772 GPa%. The precipitates in the Cu-0.03Y single crystal copper rod are nano-sized spherical particles composed of YP (NaCl type) and Cu5Y (Cu5Ca type) phases. The enthalpy of formation of Y and P is calculated using Miedema thermodynamics as ΔH = −173.45 kJ·mol−1. The precipitates formed by the preferential reaction of Y and P reduce the solid dissolved atoms in the copper, and the electrical conductivity increases accordingly. The 〈001〉 texture of a single-crystal copper rod decreases with the addition of Y, while the 〈101〉 texture increases with good plasticity, leading to an improvement in elongation.

Keywords

• Heated-mold horizontal continuous casting
• Rare earth Y
• Electrical conductivity
• Product of strength and elongation
• Precipitation phase