Advanced Thermal-Moisture Analogy Scheme for Anisothermal Moisture Diffusion Problem

We propose an advanced thermal-moisture analogy scheme to cope with the inherent limitations of the existing schemes. The new scheme is based on the experimentally-observed unique hygroscopic behavior of polymeric materials used in microelectronics; i.e., the saturated concentration is only a function of relative humidity regardless of temperature. A new analogy formulation based on the modified solubility is presented and the scheme is implemented to investigate its accuracy and applicability. The results from a simple case study corroborate that the advanced scheme can be used effectively for package assemblies subjected to general anisothermal loading conditions.