Experimental study of water absorption of electronic components and internal local temperature and humidity into electronic enclosure

Corrosion reliability of electronic products is a key factor for electronics industry, and today there is a large demand for performance reliability in large spans of temperature and humidity during day and night shifts. Corrosion failures are still seen due to the effects of temperature, humidity and corrosion accelerating species in the atmosphere, and moreover the surface region of printed circuit board assemblies is often contaminated by various contaminating species. In order to evaluate the level of humidity at which failures such as electrochemical migration start to appear on printed circuit board assemblies, a study of combined electric field, hygroscopic contamination and humidity on inter-digitated test comb patterns contaminated with sodium chloride and further exposed to increasing humidity has been performed. Results showed a significant increase in leakage current when only 70-75 % RH was reached, corresponding to the deliquescence relative humidity level of NaCl. The overall effect of climate (humidity and temperature) has been studied on the internal climate of typical electronic enclosures. The varied parameters included material used for casing, s ize of opening, differential humidity, and temperature effects simulating day/night, and the use of desiccants.