A Theoretical Model for Gas Separation in a Glow Discharge: Cataphoresis

A theoretical model for transient and steady-state cataphoresis is developed starting with the macroscopic equations of continuity. After a brief breakdown period, the impurity ions are assumed to be closely coupled with their neutral counterparts. The basic assumptions in the model are that after breakdown, the level of ionization of the impurity, and the axial electric field remain constant; it is demonstrated that under these conditions a system involving rapid ionization-recombination reactions is equivalent to a system in which no reaction occurs, but in which the effective\u27\u27 ion mobility is a product of the true ion mobility and the fraction of impurity ionization. The influence of endbulbs commonly employed in experiments is analyzed and found to influence greatly the characteristic time required to reach steady state. Agreement is found between the model and available experimental data. Particular emphasis is placed upon mass spectrometer data reported by Matveeva, and by Beckey, Groth, and Welge; these data are for mixtures of rare gases and for mixtures of hydrogen and deuterium, and involve endbulbs. The ordinary diffusion case, associated with the collapse of the steady-state cataphoretic profile, is also analyzed for a system containing endbulbs

Thermomigration induced degradation in solder alloys

Miniaturization of electronics to the nanoscale brings new challenges. Because of their small size and immense information and power processing capacity, large temperature gradients exist across nanoelectronics and power electronics solder joints. In this paper, a fully coupled thermomechanical-diffusion model is introduced to study the thermomigration induced strength degradation. A nonlinear viscoplastic material model with kinematic and isotropic hardening features is utilized. The model takes into account microstructural evolution of the material. A grain coarsening capability is built into the model to study its influence on thermomigration in solder alloys. The model is validated by comparing the simulation results with experimental data

Simulating damage mechanics of electromigration and thermomigration

Electromigration (EM) and thermomigration (TM) are processes of mass transport which are critical reliability issues for next generation nanoelectronics and power electronics. The purpose of this project is to develop a computational tool for simulating damage mechanics of EM and TM and their interaction. In this paper, a model for EM and TM processes is proposed and has been implemented in a general purpose finite-element code. The governing equations utilized for the model include mass conservation, force equilibrium, heat transfer and electricity conduction. A damage evolution model based on thermodynamics is introduced to evaluate the degradation in solder joints subjected to high current densities and high temperature gradients. The simulation results are compared with experimental data to validate the model