The formation and growth of intermetallics at the interface during the thermosonic bonding of fine metal wires was studied. The nucleation of intermetallics relied upon deformation of the solid interdiffusion couple between the bonding elements. The interdiffusion of atoms played a critical role in the formation of intermetallics. The physical, thermal and atomic properties of the joined metals, especially the vacancy–solute binding energy and the atomic radii, significantly affected the interdiffusion of the atoms. The growth of intermetallics during thermal aging also depended upon the atomic properties of the bonding elements. Attention was also drawn to the importance of the vacancy-solute binding energy in the formation/growth of intermetallics.

Formation and Growth of Intermetallics in Thermosonic Wire Bonds - Significance of Vacancy–Solute Binding Energy. S.Murali: Journal of Alloys and Compounds, 2006, 426[1-2], 200-4