In S20.20, the resistance of the personnel wrist band system is required to be less than 3.5×10E7Ω, and it is stated that this can control the electrostatic voltage of personnel within 100V. I would like to know what experimental data are used to prove this conclusion? Or what is the principle?
Thank you very much!
Hello and welcome to the forum.
The experiment was to use non-ESD control flooring and footwear, connect the person through various resistors and then maximize the voltage the person could generate. The result can be found in the ESD Technology Roadmap (https://www.esda.org/assets/Documents/72fb930055/EOS-ESD-Association-Inc-v2.-Technology-Roadmap-to-2025-website.pdf) section 2.5.1. This was done at a few different locations.
If you have any other questions, feel free to post.
Hi, John, thanks for your answer! I also have another question. Since the resistance control of the personnel wrist band system should be < 3.5×10E7 ohms to control the voltage of the human body below 100V, the grounding point of the ESD floor and ESD shoes should be < 1×10E9 ohms for the personnel grounded through the floor-shoe system in the EPA area. The walking voltage of personnel is required to be less than 100V, which is not in conflict with the technical parameters required by the personnel wristband system (in other words, should all be controlled at less than 3.5×10E7 ohms)? Or what is the technical difference between a wristband system and a floor-shoe system?
The wrist strap system will maintain that resistance while moving, walking or sitting. The study showed that no matter what the charging mechanism of a person is, a wrist strap with a resistance of less then 3.5x10e7 ohm resistance will keep a person below 100 volts.
A flooring/footwear system has two requirements, the system resistance of less than 1x10e9 ohms and a walking voltage of less than 100 volts. The difference between the flooring/footwear system is the charge generation process. While a wrist strap system can use any floor/footwear combination, a controlled flooring/footwear system uses specific floors and footwear so that not only does the system discharge the person, the system may not charge a person.
There are flooring/footwear system with resistances that exceed 3.5x10e7 ohms that do not charge a person above 100 volts when doing the walking test. Of course there are also flooring/footwear system that do charge personnel above 100 volts that have a resistance of less then 3.5x10e7 ohms. The material combination of the shoes and floors matter. That is why there are two tests to qualify flooring/footwear systems.
Hi John, thank you very much for your answer! Wish you a happy life!