A. Romana, B. Wua, B. Hana, G. M. Reinacherb, and S. G. Yousef, c
a Mechanical Engineering Department, University of Maryland, College Park, MD 20742, USA
b Robert Bosh GmbH, 72762 Reutlingen, Germany.
c Robert Bosch Kft., 1103 Budapest, Hungary.
In automotive electronics, humidity-sensitive electronics are encapsulated by protective housings that are attached to the car body. Typical housing materials are polymer composites, through which moisture transport occurs. The objective of this article is to provide a predictive capability for moisture transport through automotive housings enclosing a cavity with electronic modules. The temperature-dependent moisture properties, including moisture diffusivity, solubility, and saturated concentration of three material candidates, are characterized first. Then, the analogy between heat transfer and the mass transfer is implemented to model the moisture transport into the cavity enclosed by the materials. To cope with the transient boundary condition at the housing material and the cavity interface, the effective volume scheme is used, treating the cavity as an imaginary polymer with an extremely large diffusivity and "equivalent solubility" determined from the ideal gas law and Henry's law. The prediction is subsequently validated through an experimental setup designed to monitor the in situ humidity condition inside the cavity sealed by the materials. The prediction and experimental results agree well with each other, which corroborates the validity of the ?nite-element analysis (FEA) modeling and the measured moisture properties.