Finite element modeling of anomalous moisture diffusion with dual stage model

In this paper, finite element modeling of anomalous moisture diffusion using commercial finite element code is developed. The modeling method and numerical implementation is based on a dual stage model with both stages described by Fickian terms mathematically. The method is also extended to desorption process at reflow, in which the permanently trapped moisture content is a function of temperature. This paper details the finite element modeling implementation steps for both moisture absorption and desorption. The results are compared to the analytical solutions, and are also compared to the experimental data. A single script using ANSYS APDL is developed for the whole process including absorption and desorption phases.