Effect of rapid annealing on microstructure and properties of Cu–4 wt.% Ag alloy wire

Fine copper-silver (Cu–Ag) alloy wires are extensively used in microelectronic interconnects because of their exceptional combination of high electrical conductivity and mechanical strength. However, how rapid thermal processing controls recrystallization and texture evolution, and consequently governs the strength–conductivity trade-off, remains insufficiently understood. In this work, systematic annealing experiments were performed on Cu–4 wt.% Ag wires (0.09 mm in diameter) at temperatures ranging from 600 to 700 °C to elucidate the effects of rapid annealing on microstructural evolution and resulting properties. Annealing at 650 °C for 6 s produced a localized recrystallized microstructure, characterized by a reduced fraction of low-angle grain boundaries (LAGBs) and a dominant <111>//drawing direction (DD) texture. This microstructural state resulted in an optimal balance of mechanical–electrical performance, with a tensile strength of 433.5 ± 0.7 MPa, an electrical conductivity of 89.5 ± 0.2 % IACS, and an elongation of 20.3 ± 0.1 %. By contrast, annealing at 600 °C led primarily to recovery, yielding finer grains, a higher density of LAGBs, and a mixed <111>//DD and <100>//DD texture, which was accompanied by limited ductility. Annealing at 700 °C induced pronounced grain coarsening and a substantial texture transition toward <100>//DD, resulting in a marked degradation of both strength and electrical conductivity. These results reveal a strong correlation between annealing-induced recrystallization behavior, texture evolution, and functional performance, and provide practical processing guidelines for the optimization of high-performance Cu-based microconductors.