Study of electrical and fatigue properties of copper micro-alloyed wires in IGBT subject to chloride corrosion

Abstract

In this study, the corrosion resistance and electrical and mechanical properties of 20 mil pure copper (Cu) and copper–phosphorus (CP) micro-alloyed wires were investigated. The experimental results show that both wires are equiaxed crystals containing twinning boundaries, and their similar grain sizes result in similar tensile properties and hardness values. In addition, both wires exhibit similar electrical performance characteristics; however, the CP wire has a more stable dynamic resistance and electrothermal impedance. The chloride corrosion tests showed that both wires experience pitting corrosion on the surface; chloride ions mainly corrode the twin boundaries and then the grain boundaries, which delays the corrosion process and prevents the significant degradation of the wire’s electrical properties after chlorination. Considering the application of wires in insulated gate bipolar transistors (IGBTs), the wire failure mechanism was evaluated through electrical and mechanical tests, including tests of the electrothermal fatigue mechanism to determine the electrical properties and bending fatigue tests to determine the mechanical properties. When subjected to chloride corrosion, the CP wire has fewer twin boundaries and a lower boundary corrosion resistance, resulting in a better basal effect that improves the corrosion resistance and promotes work hardening during bending. As a result, the CP wire has a longer current cycle life and better bending fatigue properties than the Cu wire. This confirms the excellent application reliability of CP wires subject to corrosion.