Transient hygrothermal behaviour of portable electronics

The theme of this paper is the design of portable electronic systems for hot and humid conditions. In particular, portable products such as mobile phones. CD players and digital cameras can experience high relative humidity and condensation. It is important to understand the behaviour of portable products in different usage environments in order to develop more accurate specifications, simulation models and verification methods. In this paper, the response of portable electronics to time-varying conditions of temperature and humidity is considered in order to assess the conditions likely to precipitate condensation. A first-order coupled hygrothermal model is developed to represent the response of a typical portable product to variations in ambient temperature and humidity. Simple time constants are derived to describe transient hygrothermal response. Experimental characterisation of a sample product is performed to evaluate the parameters of the model, and it is demonstrated how movement from one environment to another can induce condensation to occur on the internal and external surfaces of a portable product.