Failure of Flip-Chip Circuit Interconnects under High Current Density
Both Al interconnects and flip-chip solder bumps were sensitive to high current. The failure mechanism of circuits interconnects would be more complicated if the current density in circuits was exceed the critical magnitudes of electromigration in both Al interconnects and solder bumps. The failure of circuit interconnects under different magnitudes of current density was studied and the interaction of electromigration in solder bumps and Al interconnects was discussed. The circuit interconnects of flip chip show three failure phenomena under high current density: voids in Al final metal, inter-diffusion of Al and SnPb, and melting of solder bumps. The voids in Al metal show the directional diffusion of Al atoms was mainly controlled by the electron wind fore. However the inter-diffusion of Al and SnPb demonstrated the electron wind force to Sn and Pb atoms would be ignored in contrast with chemical potential gradient or intrinsic stress. The flow of Sn and Pb atoms under high current density was in opposite direction with electron wind force and uniform with chemical potential gradient.
L.Y. Xie, M.N. James, Y.X. Zhao and W.X. Qian
Y. D. Lu et al., "Failure of Flip-Chip Circuit Interconnects under High Current Density", Advanced Materials Research, Vols. 118-120, pp. 449-453, 2010