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Morphological evolution of voids by surface drift diffusion driven by the capillary, electromigration, and thermal-stress gradient induced by the steady state heat flow in passivated metallic thin films and flip-chip solder joints. II. Applications

Ogurtani, Tarik Omer
Akyildiz, Oncu
The void growth and drift motion induced by the combined actions of the phase transformation (evaporation and condensation) and surface drift diffusion driven by the capillary and electromigration forces and thermal-stress gradients are investigated in passivated metallic thin films and flip-chip solder joints via computer simulation using the front-tracking method. As far as the device reliability is concerned, the most critical configuration for solder joint failure occurs even when thermal stresses are low if the void nucleation takes place close to the under bump metallurgy (UBM) where the heat and current flux crowding takes place due to the proximity effect associated with the confinement. The void growth induced by the condensation of excess (athermal) vacancies at the void-matrix dividing surface results in drastic spreading of pre-existing voids along transverse direction of solder joint due to the concurrently occurring heat and current crowding adjacent to the UBM. This accelerated transverse void spreading may eventually cause open-circuit interconnect failure as clearly demonstrated experimentally in literature. (C) 2008 American Institute of Physics.