Comparison of the Microstructural Characteristics and the Electrothermal Fracture Mechanism of Au-Pd-Coated Copper Wire and Cu-Ti Micro-alloyed Wire

This study compared the Au-Pd-coated copper (CPA) with the micro-alloyed copper wires (MAC) without a coating layer. Results have shown that heat treatment can improve the electrical properties of the wire, but excessive heating can lead to a deterioration in hardness and electrothermal fatigue. In addition, the surface temperature of the wire can be inferred from the Joule heating relationship. The formula derived from the study, T=IV2.7227×10^-3+25, can be utilized to assess the heating behavior during electrification at room temperature and standard pressure. To validate the accuracy of this formula, this research also compared the oxidation morphology of copper at high temperatures with other reports in the literature. It was found that the Au-Pd-coated copper (CPA) wire begins to dissolve at 0.38 A (370°C) and completely dissolves at 0.42 A (550°C). This phenomenon increases the wire resistance but decreases the fusing current. In comparison, Cu-Ti (CT) micro-alloyed wires showed no deterioration at 0.43 A. In addition, the electrothermal effect causes diffusion in the CPA wire’s coating layer and results in poor fatigue life. In conclusion, the CT wire has a longer electrothermal fatigue life and better stability, making it a promising candidate for future copper-based wires.