Investigation of Recrystallization and Grain Growth of Copper and Gold Bonding Wires

Copper bonding wires were characterized using electron backscatter diffraction (EBSD). During drawing, shear components are mainly located under the surface and ,111. and ,100. fiber texture components develop with similar volume fractions. Grain average misorientation (GAM) and scalar orientation spread (SOS) of the ,100. component are lower than those of the ,111. or other orientations. Also, ,100. components grow into other texture orientations during recrystallization. Copper wires experience three stages of microstructure change during annealing. The first stage is subgrain growth to keep elongated grain shapes overall and to be varied in aspect ratio. The grain sizes of the ,111. and ,100. components increase. The volume fraction of the ,100. component increases, whereas that of the ,111. decreases. The second stage is recrystallization, during which equiaxed grains appear and coexist with elongated ones. The third stage is grain growth, which eliminates the elongated grains. The ,111. and ,100. grains compete with each other, and the ,111. grains grow faster than the ,100. grains during the third stage. Comparison of recrystallization and grain growth processes in copper and gold wires reveals many common microstructural features.