Moisture-induced package failures such as interfacial delamination and pop-corn cracking are common failure phenomena that occur during the solder reflow process in the semiconductor industry. Therefore, the hygroscopic properties of the package materials are crucial factors in the reliability of electronic packaging products. In this work, molecular dynamics (MD) simulation was performed to study the hygroscopic properties, including diffusivity and swelling strain, of epoxy materials with respect to temperature and moisture concentration. Hygroscopic material properties predicted by MD are discussed and compared with the experimental data. (C) 2011 Elsevier Ltd. All rights reserved.