Dissipative or Conductive
Which is right for electronics manufacturing?
Let's start with the concept of "meeting S20.20." ANSI/ESD S20.20 is a process document - not a specification. Flooring does not meet S20.20; it meets recommended parameters derived from standard test methods referenced in S20.20. For example, S20.20 references not one but 3 standard test methods:
ANSI/ESD STM 7.1
Floor Materials—Resistive Characterization of Materials. Any flooring material must measure below 1.0 X 10E9 ohms to ground. However, the flooring must also comply with the 2 parameters listed below:
ANSI/ESD STM 97.1
Floor Materials and Footwear—Resistance in Combination with a Person. The recommended maximum system resistance is 3.5 X 10E7.
ANSI/ESD STM 97.2
Floor Materials and Footwear Voltage Measurement in Combination with a Person. The recommended maximum voltage allowed is 100 volts.
Many flooring manufacturers state that their floors will meet ANSI/ESD S20.20. What they actually mean is that their floors will measure less than 1.0 X 10E9. That fact has nothing to do with using a floor in a program that must meet the 2007 revision of S 20.20 because the floor is one part of a bigger picture. The full picture involves the combination of the floor, people, ground connections and controlled footwear. Hence the need for recommendations 2 and 3 referenced above.
Needless to say, it would be very difficult for a flooring material measuring in the upper end of the static dissipative range (> 1.0 X 10E8) to be part of a total system measuring less than 3.5 X 10E7. The math just doesn't work. Measuring the resistance through a person and footwear (as opposed to two five pound weights) will yield a lower resistance value than you would get with just the 5 pound NFPA probes. But, once the floor RTG exceeds 1.0 X 10 E8 by itself, it is likely that the system including the person and footwear will not compensate for the high resistive properties of the floor. Furthermore, it has been demonstrated that most static "dissipative coatings" are often incapable of keeping body voltages from exceeding 100 volts. Since the premise of ANSI/ESD S20.20 is preventing body voltages above 100 volts, it is impossible to categorically state that all static dissipative floors measuring less than 1.0 X 10E9 will meet ANSI/ESD S20.20-2007. You need to do your homework.
A warranty stating "This floor complies with ANSI/ESD S20.20" is not sufficient.
A floor should never be evaluated in isolation. It must always be qualified as part of an overall system that includes all variables: The floor, the person, and the controlled footwear. When the system is evaluated, the only way to confidently meet the recommended parameters of ANSI/ESD S 20.20-2007 is to install a floor measuring less than 100,000,000 ohms to ground.