Modeling of humidity-related reliability in enclosures with electronics

Reliability of electronics that operate outdoor is strongly affected by environmental factors such as temperature and humidity. Fluctuations of these parameters can lead to water condensation inside enclosures. Therefore, modelling of humidity distribution in a container with air and freely exposed water is of importance for reliability engineering. Reliability assessment of large complex systems is often done by dividing the complex into decoupled subsystems. The reliability of such system is then obtained by combining the reliability of each subsystem. In this paper we set up a framework to predict humidity-related reliability of a printed circuit board (PCB) located in a cabinet by combining structural reliability methods and non-linear diffusion models. This framework can, thus, be used for reliability prediction from a climatic point-of-view. The proposed numerical approach is then tested to estimate the reliability of a case example with liquid water at the bottom of a cabinet and PCB positioned on one of the walls. The water vapor profile inside the enclosure is calculated using a diffusion equation whereas the release of vapor from the water surface is modeled using statistical rate theory. The novelty in this work lies within the reliability prediction based on physical modeling of the climate in the system of interest.