Charge transfer to MEMS pressure sensors by glow discharge plasmas

Electrical charging resulting in temporary performance degradation of automotive MEMS pressure sensors has been observed. A method of charge transfer from the outside of a statically charged hose, along the inside the hose, through the module port, to a sensor inside the module is proposed. Specifically, the existence of a glow discharge plasma through the hose, is analyzed with respect to temporary performance degradation. The Paschen equation is used to theoretically predict the breakdown voltage in terms of pressure and distance in the rarified, charged environment to which the ports of the pressure sensors are exposed. Experimental results show no glow or performance degradation in the dark discharge regime, over repeated trials. In the glow discharge regime, visible purple glow with accompanying degradation is observed. At the transition point between the dark and glow regimes, at 20 torr and 5000 V for a discharge distance of 3.5 cm in this experiment, repeated trials resulted in a mixture of glow/degradation and nonglow/unaffected cases. Other proposed modes of charge transfer are qualitatively ruled out, while a quantitative correlation between glow and performance degradation is observed. Therefore, the glow discharge plasma is indicated as the most likely charge transfer mechanism.