Atomistic simulation of mechanical behavior of Cu/Cu3Sn solder interface with Kirkendall void under shear and tensile deformation

The effects of a Kirkendall void at the nanoscale on the mechanical behavior of a Cu/Cu3Sn solder interface under shear and tensile tests, respectively, are studied using molecular dynamics simulations. The simulation results show that for a solder interface without a Kirkendall void under tension, fracture is induced by a collapse of the interface, and that for a solder interface without a Kirkendall void under shearing, plastic deformation is dominated by shear bands. A shear band propagates through a small void (radius <= 3 nm) but is stopped by a large void (radius = 4 nm) or neighboring dislocations. For a solder interface with a Kirkendall void under tension, a collapse of the solder interface occurs faster with increasing void radius. When the void is far away from the solder interface, fracture is dominated by a competition between a collapse of the solder interface and void deformation and growth. A solder interface has the maximum shear and tensile strength when a pre-existing void (radius = 1 nm) locates at the interface. For a solder interface with a Kirkendall void, the ultimate shear stress, tensile stress, and tensile strain decrease with increasing initial void radius.