Experimental and Numerical Characterization of Non-Fickian Moisture Diffusion in Electronic Packages

This study investigates moisture diffusion characteristics of electronic packaging materials exhibiting Fickian and non-Fickian behaviors. The experimental investigation involves moisture absorption and desorption tests of homogenous underfill materials and inhomogeneous organic substrates representing Fickian and non-Fickian solids, respectively. In absorption tests, samples are dried out in an oven prior to testing in a humid environmental chamber. In desorption tests, samples are saturated in an environmental chamber under a specified temperature and relative humidity prior to the moisture desorption inside an oven. Samples in both tests are removed from the test environments and weighed frequently to obtain moisture weight change data. Using the test measurements of several different Fickian and non-Fickian materials, diffusivity/moisture concentration relationships are constructed. These relationships are implemented into a customized finite element simulation tool under the ANSYS platform. This tool is validated by using the experimental measurements on multimaterial samples prepared from underfill and substrates.