Surface Topographical Characterization of Gold Aluminide Compound for Thermosonic Ball Bonding

Relatively little information is available on the growth patterns of gold aluminide compound in accurate 3D measurement as compared with 2D images of the projected surface. A 3D surface imaging technique by using infinite focus microscope (IFM) was proposed in this study to observe and explain the effects of bonding parameters on growth pattern of gold aluminide compound formed between a $25.48μm$ 4N gold wire and an aluminum pad metallization. Two bonding factors, which were varied, were ball bonding force and ultrasonic current while bonding time and temperature were kept constant. The 3D surface measurement provides topographical and color information of the bonded region, which indicates that optimum bonding condition has a significant effect on uniform growth and wide coverage area of gold aluminide compound. Results illustrated by this technique were used as additional information to the results produce by the conventional methods such as cross section optical image and scanning electron microscope (SEM) micrographs, to gain a better understanding on the physical behavior of gold aluminide compound.