One of the design objectives of military electronic equipments is to withstand the degradation of humid tropical exposures. Many study programs and tropical field experiences have shown that jungle and marine localities possess environments which produce corrosive failure mechanisms which contribute to electronic part and/or assembly failures. For many years, laboratory tests, such as the Moisture Resistance Test, Method 106 of MIL-STD-202, have been used to determine the resistance of applied protective designs, coatings and finishes to tropical atmospheres. The moisture resistance test, however, was developed for use over twenty years ago and at that time it appeared suitable for designs and materials in usage. Since then, tropical field experience in Southeast Asia and improvement of parts, materials and processes made possible the achievement of extended field service lives, maintenance cycles and reliability performance which needed to be reflected in more effective and correlated laboratory test cycles. Many predicted service lives of parts or assemblies must be based upon known acceleration factors of laboratory testing. Recently, a fungus test per Method 508 and a salt-fog test per Method 509 of MIL-STD-810 were added to equipment specifications to assure increased fungus and corrosion resistance of parts, materials and processes. The continued use of such tests, however, must be based upon; their ability to eliminate designs and qualities which fail in the tropics, and their ability to predict field service life in short term accelerated laboratory exposure tests.
