Electrostatic discharge materials
Plastics that reduce static electricity
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Electrostatic discharge materials (ESD materials) are plastics that reduce static electricity to protect against damage to electrostatic-sensitive devices (ESD) or to prevent the accidental ignition of flammable liquids or gases.
Materials
The properties relevant to a material in an ESD context are:[1][2]
- Conductivity: how well it passes electricity. When dealing in thin sheets, sheet resistance is used, describing the resistance of a square of the material for a current flowing from one edge to the opposite edge. The value is depends on the thickness of the material.
- Antistatic: whether rubbing can cause dangerous electrostatic buildup (> 1000 V) on the material via triboelectric effect.
- Static-dissipation: whether any existing static charge can be gradually removed by conducting through the material.
- Shielding: whether the electromagnetic field due to an electrostatic discharge from the outside results in a non-dangerous amount of voltage on the inside.
- Isolation: whether the two sides of the material are electrically isolated enough, so that any discharge that happens across the material is weak enough.
| Material | Ohms per square | Shielding | Antistatic | Dissipation | Isolation | Purpose |
|---|---|---|---|---|---|---|
| Metals | < 10−3 | Yes | Yes | Too fast | No | Used as shielding layer in some moisture-barrier laminates (ESD bag). |
| Metalized film | 10-1 to 102 | Yes | Yes | Too fast | Yes | Used as part of shielding laminates and some moisture-barrier laminates (ESD bag). Always appears silvery-translucent. |
| Carbons (graphite powders and fiber) | 1 to 103 | Yes | Yes | Too fast | No | Not used in pure form as it generates powder easily. May be incorporated into composite materials. |
| Conductive plastic (carbon-loaded) | 103 to 105 | 30%[1] | Yes | Yes | Low | Used as a film to make ESD bags. Also used to make solid plastic pieces (e.g. boxes), foam, and bubble-wrap. Always appears opaque black. Carbon-loaded elastomers such as rubber and Ethylene-vinyl acetate are also used. |
| Dissipative plastic | 107 to 1011 | < 10% | Yes | Yes | Yes | Used as a film to make ESD bags. Also used as a part of shielding laminates. Also used to make foam and bubble-wrap. Typically translucent pink due to added coloring. |
| Insulators and base polymers | > 1013 | No | No | No | Yes | Not an ESD material: charges will build up. |
