Effect of temperature gradient on moisture diffusion in high power devices and the applications in LED packages

High power electronic devices create hot spots, which give rise to the junction temperature significantly higher than the ambient temperature. This induces a situation that the moisture diffusion from environment to device is in the direction against temperature gradient direction. In addition, far field relative humidity is different from the environment surrounding the packaged devices. In this paper, two mechanisms of moisture transport are studied. First, the localized relative humidity related to the far field ambient environment is investigated. Second, moisture diffusion in the presence of temperature gradient inside package is studied. Several scenarios are investigated with the use of an LED package as example.