ESD Systems - Questions And Answers

Describe how and electronic field (i.e. computor screen or separating mylar tape) damage ESD sensitive components? Is ESD damage dependent on the voltage generated or distance. Will unrolling TFE tubing 2 meters away damage MOSFETs on a PCB laying on a conductive tray? - Anonymous, Liberty, SC

When using charge generators in an ESD protected area, the electric fields they generate can induce charges on nearby conductors and if they are electrically isolated, will become charged through charge induction. The level of induced charge will depend on the magnitude of the generated electric field, the proximity and the repeated exposure (an isolated conductor can build up a charge over continual exposure). Process essential insulators should be controlled via either topical antistat treatments or ionizers. The ESD Association has recently done a study on electric fields and safe distances as stated in ANSI/ESD S20.20: All process essential insulators that have electrostatic fields that exceed 2,000 volts should be kept at a minimum distance of 12 inches from ESDS items. 2,000 volts is a measure of the electrostatic field at the point of measurement and is not necessarily directly related to the electrical potential of the item. The accurate measurement of electrostatic fields requires that the person making the measurement is familiar with the operation of the measuring equipment. Most hand held meters require that the reading be taken at a fixed distance from the object. Equipment manufacturers typically specify that the object being measured needs to have certain minimum dimensions. Objects smaller than the minimum dimensions may not provide an accurate reading. Additional guidance related to Protected Areas may be obtained in ESD ADV 2.0. shed particles that may cause production-related problems. It is important that the Organization evaluate ESDS protective packaging materials for process, storage and environmental compatibility.

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