ESD Systems - Questions And Answers

What is the general feeling towards paper as a contributor to static damage? Everyone I talk to seems to be split on this issue. Our company uses small (2"x4") paper tags indicating various stages of completion on loaded pc assemblies which are attached with a piece of wire through one of the mounting holes, and which lay in direct contact with the assembly when the boards are sitting in racks on our shelves. Is this practice detrimental to the assembly from a static perspective? - Anonymous, Parsippany, NJ

Paper is humidity dependent. Under normal conditions, let's say 40% RH, a paper tag may tribocharge up to 80 volts. The surface resistance will be rather high so the largest threat is to close proximity devices that could receive an induced charge from this paper tag. This will only be a concern if the ESD component classification of the device you are protecting is a HBM class 0 (sensitive to below 250 volts). Any other class devices (HBM class 1A - 3B) will not be harmed via ESD directly from these paper tags. There are exceptions, such as plastic coatings on the tag that may hold a significant charge. In general, paper and wood are not a large threat to more sensitive devices because they tend to not hold significant charges or tribocharge greatly. I've seen wood fixtures used in very sensitive environments as jigs for ESDS devices. This doesn't mean we endorse wood or paper as ESD safe, you should always test all materials and equipment for ESD control compliance to the most sensitive component classification of device(s) used.

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