Classifying materials by resistance
The ESD Association classifies materials by surface resistance.
| Class | Surface resistance | What it does |
|---|---|---|
| Conductive | Below 1 x 10^4 ohm | Charge flows away very quickly. Used for shielding and grounding paths. |
| Static dissipative | 1 x 10^4 up to below 1 x 10^11 ohm | Charge flows away in a controlled way. Used for worksurfaces, mats, trays and flooring. |
| Insulative | 1 x 10^11 ohm and above | Charge stays where it is. Ordinary plastics, paper and rubber. |
Anti-static is not the same as dissipative
- Anti-static (low-charging) means a material makes less charge when rubbed. It may still be an insulator, and it does not guard against outside fields.
- Static dissipative and conductive materials move charge away, and can be grounded.
- Static shielding goes a step further: it protects the contents from external fields and discharge. See the bags guide.
What to ask a supplier
- Which class is the material: conductive, dissipative or low-charging?
- What test method and conditions gave the result, and what is the value?
- Does the value stay the same at low humidity?
Ranges follow the commonly used ESD Association definitions. Always confirm against the current standard and the product datasheet.
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