Quantifying moisture diffusion into three-dimensional axisymmetric sealants

Moisture can be devastating for electronic components, causing corrosion and electrochemical metal migration, which leads to changes in resistance and short circuits. Although most products (the focus in this study is on solid state lighting products) have a sealed enclosure, the driver electronics are often not as well sealed against the environment. Moisture diffusion through surrounding sealants is a primary pathway of moisture ingress into the electronics enclosures. This study's focus is on quantifying the moisture diffusion rates for various sealant materials and on modeling the moisture ingress rates into sealed containers, using commercial FEA software. This paper also presents a simulation-assisted procedure to extract the moisture diffusion properties for the seal material because most seal structures (gaskets, O-rings, etc.) are not simple one-dimensional structures. The resulting geometric correction factor is obtained for toroidal O-rings of circular cross-section and also for elliptic cross-sections caused by compression forces.