The authors have modeled the copper ion concentration and internal electric field profiles in a SiO2 dielectric by solving the transient nonlinear continuity/Poisson equations. The predicted time-to-failure of the dielectric correlates well with the theory that failure occurs once copper ions accumulate to the point where the induced electric field at the cathode exceeds a critical value. However, the copper ion concentration at the cathode required for failure was much higher than the reported ion solubility, raising doubts about the validity of the model. More realistic values for the required copper ion concentration were obtained by incorporating an "elastic" diffusion term in the continuity equation. Adding this new term and increasing solubility, C-e, to the maximum value reported in the literature reduces the concentration at the cathode to a logically consistent value but does not significantly alter the predicted time-to-failure. The new formulation predicts a higher minimum applied electric field required to induce breakdown. This minimum field is larger than current devices see during operation.