Comprehensive Moisture Diffusion Characteristics of Epoxy Molding Compounds Over Solder Reflow Process Temperature

We address moisture diffusion in epoxy molding compounds (EMCs) at temperatures higher than 100^°C. The objectives of this paper are thus: 1) to obtain diffusion properties of EMCs in both absorption and desorption modes at a wide range of temperatures; 2) to establish a non-Fickian correlation for diffusivity; and 3) to assess moisture diffusion behaviors during a solder reflow process, described by two different Fickian diffusivities of absorption and desorption and the non-Fickian diffusivity. An experimental procedure is established to measure the diffusivity and solubility of selected EMC materials. The results are utilized in a numerical simulation to analyze the effect of the non-Fickian diffusion characteristics on the moisture distribution during the reflow process.