Desco - Questions And Answers

What is the difference between conductive and dissipative matting? - Anonymous, ., ., CA,

Materials are either conductors or non-conductors. Non-conductive material is also called insulators and have a resistance of over 1 x 10^11 ohms. Dissipative material refers to a range of conductive material; greater than 1 x 10^4 ohms and less than 10^11 ohms which has the ESD control benefit of more slowly removing electrostatic charges to ground. So for ESD control purposes conductive refers to material less than 10^4 ohms.
The minimum recommended technical requirement of ANSI/ESD S20.20 for ESD worksurfaces and floors is less than 1 x 10^9 ohms (see Table 1). The reason for this is that if a worksurface material resistance is too high (>1.0 X 10^9 ohms RTT and/or RTG) it will not provide a surface that is sufficiently ‘conductive’ to provide an effective surface to ‘ground’ conductive or dissipative items or materials placed on the surface.
However, typically, we recommend dissipative ESD Mats for worksurfaces, specifically 10^6 to 10^8 ohms. This is in accordance with ESD Association ESD S4.1 and ESD-ADV53.1 Electrical Requirements, ‘Worksurfaces - Resistance: Between 1 x 10^6 ohms and 1 x 10^9 ohms’ If the ESD worksurface is too conductive (<1.0 X 10^6 ohms RTT and/or RTG), it can discharge charged ESDS devices too quickly and possibly cause device damage via the Charged Device Model (CDM).
Typically, we recommend more conductive mats for floors; most of the ESD Systems.com Statfree® conductive mats are 10^3 to 10^5 ohms (in the upper conductive range or low dissipative range). Since dirt and other contaminant are typically insulators, the flooring will measure less than 10^9 ohms throughout the maintenance cycle.

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