Au-induced improvements in the grain stability and mechanical properties of Ag-based alloy wires under electrical current stressing

摘要

The evolutions of the surface morphologies, cross-sectional microstructures, and mechanical properties of two types of Ag-based alloy wires with different Au contents under a 10(5) A/cm(2) electrical current density across various times were compared in this study. Ag-based alloy wires that contain 8 wt% Au and 15 wt% Au with 3 wt% Pd were produced via rapid drawing and multiple annealing processes to replace commercial Au-bonded wires in the electronic packaging industry. The surface morphologies of these wires were revealed by scanning electron microscopy (SEM), and cross-sectional microstructures were analyzed by electron back scattering diffraction (EBSD). The SEM observations showed grain- and step-like structures in the Ag-8Au-3Pd and Ag-15Au-3Pd wires after a 5-h treatment, respectively. EBSD results revealed a change in the main preferred orientation from slender grains to equiaxed grains because the high-angle grain boundaries (HAGB) were reduced, and the twin boundaries (TB) were multiplied along the drawing direction. In terms of mechanical properties, Ag-15Au-3Pd wire showed better breaking loads and elongations than Ag-8Au-3Pd wire. The Au effect in Ag-based alloy wires reduced the atomic diffusion to stabilize grain structures and induce a dislocation accumulation, which subsequently improved the mechanical properties by retaining and forming HAGBs, LAGBs, and TBs under high current stressing.