Failure through expanding voids in bacterial streamers

We investigate the failure of thick bacterial floc-mediated streamers in a microfluidic device with micro-pillars. We found that streamers could fail due to the growth of voids in the biomass that originate near the pillar walls. The quantification of void growth was made possible by the use of 200 nm fluorescent polystyrene beads. The beads get trapped in the extra-cellular matrix of the streamer biomass and act as tracers. Void growth time-scales could be characterized into short-time scales and long time-scales and the crack/void propagation showed several instances of fracture-arrest ultimately leading to a catastrophic failure of the entire streamer structure. This mode of fracture stands in strong contrast to necking-type instability observed before in streamers.

Numerical Simulations of Electromigration and Stress Migration Driven Void Propagation in Pb Free Solder Interconnects

Increasing miniaturization has led a significant increase in the current densities seen in flip-chip solder joints. This has made the study of failure in solder joints by void propagation due to electromigration and stress migration more important. In this study, we develop a phase field model for the motion of voids through a flip chip solder interconnect. We derive equations of motion for the void accounting for energetic contributions from the active factors of surface energy, stress and electric potential, taking into account both surface diffusion and transfer of the material through the bulk of the material. We describe the implementation of this model using finite elements, coupled with a commercial finite element solver to solve for the fields driving the void motion.

Electromigration Simulation for Metal Lines

As the electronics industry continues to push for high performance and miniaturization, the demand for higher current densities, which may cause electromigration failures in an IC, interconnects. Electromigration is a phenomenon that metallic atoms constructing the line are transported by electron wind. The damage induced by electromigration appears as the formation of voids and hillocks. A numerical simulation method for electromigration void incubation, and afterwards, void propagation, based on commercial software ANSYS Multiphysics and FORTRAN code, is presented in this paper. The electronic migration formulation considering the effects of the electron wind force, stress gradients, temperature gradients, and the atomic concentration gradient has been developed for the electromigration failure mechanisms. Due to introducing the atomic concentration gradient driving force in atomic flux formulations, the conventional atomic flux divergence method is no longer valid in electromigration (EM) simulation. Therefore, the corresponding EM atomic concentration redistribution algorithm is proposed using FORTRAN code. Finally, the comparison of voids generation through the numerical example of a standard wafer electromigration accelerated test (SWEAT) structure with the measurement result is discussed.