MENDA - Questions And Answers

1) How do the particles get charged in a corona discharge? 2) Do we add any electronegative impurities along with the charge and if so can you give some examples of those impurities? - Anonymous, Arkansas

The typical mechanism for ionization for ESD Control is corona discharge. The emitter tips are very sharp and when a 6 - 8 kV potential is applied to the pin, there is an electrical breakdown [ionization] of the air (or corona discharge) in the air surrounding the tip. Depending on the polarity of the electric field at the tip, the emitter will either strip electrons from nearby air molecules or add electrons to them. Once the air molecule’s polarity changes to the same as the tip, the molecule is accelerated away from the tip and becomes one of the multitude of air ions for ESD neutralization. Air ions are molecular clusters consisting of about 10 molecules (often water) around a singly charged oxygen or nitrogen molecule. The corona type ionizers may generate a very small amount of ozone, usually well below OSHA’s limits. Whatever air impurities that are currently airborne may become ionized and added to the other air ions for control purposes. If impurities must be controlled, then a clean room environment is recommended. Air filters placed at the intake of air carrier ionizers help to filter some of the bigger airborne impurities, such as hair and dust.

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