There are several things to consider when selecting an ESD control floor. The first and foremost is whether to opt for a conductive or static dissipative system.
Which control technique to use largely depends on the application. In a general office environment, a coating with antistatic characteristics that reduces triboelectric charging on contact surfaces will normally be sufficient.
However in an area where any significant charge accumulation may damage sensitive components or create a spark risk, the emphasis is on dissipating electrostatic charge before it has chance to build up to dangerous levels.
In practice, this is usually achieved by a combination of static dissipative personnel footwear and flooring, where there is an adequately low resistance path from the person, via footwear and flooring to ground (zero/earth potential). In many cases dissipative floor is the most cost-effective option.
ANSI/ESD S20.20 (S20.20) requires a system resistance of a person through the floor and to ground of less than 3.5 x 107 ohms (35 megohms) when the floor is to be used as the primary ground. Many dissipative floors have resistance ranges above 35 megohms before considering operator resistance.
ANSI/ESD S20.20 revised in 2014, comprises the latest parameters for ESD workplace compliance. There are 3 standards within the specification relating to flooring materials; all 3 standards are required for compliance.
ANSI/ESD STM 7.1 Floor Materials ‘Resistive Characterization of Materials’ states that any flooring material must measure below 1.0 x 10E9 ohms to ground.
ANSI/ESD STM 97.1 Floor Materials and Footwear ‘Resistance in Combination with a Person’ states 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’ suggests the recommended maximum voltage allowed is 100 volts.
The selection of an effective ESD floor covering system should always begin with a thorough evaluation of the intended use and possible future use. Intended use should include the evaluation of the devices or processes in the environment that are most sensitive to ESD events, chemical resistance and aesthetic requirements.
Understanding the need for and importance of ESD compliant footwear is also critical in the performance of the ESD flooring chosen. Personnel grounding requires effective ESD footwear that is appropriate to the application, properly worn and in good repair.