Hygroscopic fine mode particle deposition on electronic circuits and resulting degradation of circuit performance: an...

A portion of electronic equipment failures is a consequence of particle deposition on electronic circuits in normal indoor environments. Deposited hygroscopic particles reduce the electrical isolation (EI) between conductors. In laboratory experiments, we investigated the mechanisms, locations, and effects of particle deposition on electronic circuits with surface mounted chips (SMCs) and also on small television sets. One set of electronics was exposed for 281 h to an unusually high concentration of artificially-generated ammonium sulfate particles while a second set (experimental controls) was exposed to normal indoor particles. The particle mass concentration in the high-exposure chamber was 500 times higher than normal. Television reliability was observed and the changes in EI between adjacent legs of SMCs were measured. The experiments demonstrate the strong influence of electrostatic forces on the locations and rates of particle deposition. Although televisions did not fail after exposure to concentrated aerosols, the EI between adjacent legs of the SMCs was, in many cases, greatly diminished. Relative humidity had a very strong influence on the magnitude of EI. A qualitative explanation of the mechanisms of particle deposition and circuit degradation is proposed, including the role of fibers. Finally, a potential method to reduce particle deposition on electronic components is discussed.