The Response of Portable Electronics to Transient Conditions of Temperature and Humidity

The design of portable electronic systems for use in hot and humid conditions represents a significant design challenge for packaging engineers. Humidity drives a range of failure mechanisms: the alteration of material properties; hygro-mechanical stress phenomena; and the acceleration of corrosion and material migration. Moreover, portable electronic products such as mobile phones, CD players and digital cameras can experience rapidly varying conditions of temperature and humidity which, in certain conditions, can cause condensation to form on the internal and external surfaces of the product. Condensation — or even very high relative humidity — is a severe stimulus because it greatly accelerates corrosion and migration mechanisms. This paper considers the response of portable electronics to transient variations of temperature and humidity in order to assess the conditions under which condensation is likely to occur. A first-order coupled hygrothermal model is developed to represent the temperature and humidity response of a typical portable product using simple time constants. 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 precipitate condensation.   This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.