Hi, I am looking for some clarification to the S20.20 section on Qualification:
Section 7.3 For ESD control items that were installed by the Organization before the adoption of this standard, on-going compliance verification records can be used as evidence of product qualification.
We have an ESD floor already in the facility from some time ago and there is no specification data available - reading the above leads me to believe that as long as we continue to carry out verification testing (which we do, and it’s within limits) that satisfies the qualification standard.
Hi, your understanding may be correct. For the floor itself, ongoing compliance verification records can be used as objective evidence for product qualification. If in addition, the floor is used as part of a footwear/flooring system, then system resistance and body voltage measurements must be done per ANSI/ESD STM97.1 and ANSI/ESD STM97.2. That data will be needed no matter how much resistance data you have on the floor. Ensure that you take data during the lowest humidity time of the year as proof.
Start taking body voltage measurement as soon as possible if none exists. Continue a few times during the year to ensure the environment does not impact the measurement.
Thanks JohnK, I hadn’t defined the flooring as a system - that makes much more sense from a qualifying perspective. It does go into it further in TR53 and note 6 of S20.20.
this is also related to product qualification. my question is if prior adoption of S20.20, the organization is implementing these TDS and TDS was based on ASTM D257. is this also acceptable in present? and they set limits was at ohm/sq? please advise.
Thanks for the additional question. The issue with specifications set by ASTM D257 is that without knowing the measurement electrode configuration you have no idea how they would compare to ANSI/ESD STM11.11 measurements or the resistance to ground measurements of the other referenced test methods in ANSI/ESD S20.20. They could be close or they could be several orders of magnitude different. D257 is designed for measurement of insulators and there have always been issues with measurements below about 1 x 10E10 ohms/square. The reason STM11.11 exists is because of the issues of reproducibility (between organizations) when D257 was used to measure materials used in an electrostatic control program. D257 allows the use of a variety of electrodes and it has been shown that the results can vary significantly depending on the set of electrodes used on the same material.
It would be best to verify that the surface resistivity specifications in ohms/square from D257 are equivalent to the surface resistance values in ohms as made by STM11.11 (the STM11.11 values being a factor of 10 lower). Since the program is now using ANSI/ESD S20.20 as the basis, it will be necessary to convert to resistance values based on the currently referenced test methods.