Formation and growth of intermetallics in thermosonic wire bonds: Significance of vacancy–solute binding energy

This paper reviews the formation and growth of intermetallics at the interface during thermosonic bonding of fine metal wires in microelectronics packaging. The nucleation of intermetallics relies on deformation of solid, inter diffusion couple of the bonding elements and energies supplied. Inter diffusion of atoms play crucial role on the formation of intermetallics. The physical, thermal and atomic properties of the joining metals, especially the vacancy–solute binding energy and the atomic radii significantly influences the inter diffusion of atoms. Growth of intermetallics on thermal aging also depends on the atomic properties of the bonding elements. The paper also introduces the importance of vacancy solute binding energy on the formation/growth of intermetallics.