A Preliminary EBSD Study of Microstructures and Microtextures Evolution during Au Stud and Flip-chip Thermosonic Bonding

Microstructures and microtextures of the Au bumps after ball bonding and flip-chip bonding were analyzed using electron backscatter diffraction (EBSD) technique. For comparison, the microstructure and texture of gold wire and gold free air ball (FAB) were also examined. It is demonstrated that process parameters, such as bonding power, bonding force and temperature have significant influences on the microstructure and microtextures of the gold bumps. The deformation of the bumps is generally non-uniform. The <111> and <100> structures in gold bumps are the inheritance of the original columnar structure in FAB. In the subsequent flip chip bonding, severed deformation occurs with a typical compression texture of <110>, but not a strong preferred orientation as under the pure compressive loading. The non-uniform deformation behavior, the associated microstructure defects, the texture and their changes of the Au bumps under the vertical force and the horizontal ultrasonic wave applied are, for the first time, presented and discussed