Compliance
Standard acrylic holds a charge of several kilovolts and will not let it go. Near exposed electronics that is a failure mode, and it is invisible until a board fails test.
Electrostatic discharge damages components that look fine and fail later, which makes it one of the more expensive failure modes in electronics assembly. Standard acrylic is a good insulator: it generates charge easily and holds it, so a guard panel or a cover near bare boards is a risk that nobody can see.
| Class | Surface resistivity | Behaviour | Typical material |
|---|---|---|---|
| Conductive | 10^2 to 10^5 ohm/sq | Charge drains almost instantly | Carbon-loaded plastics, metal |
| Static dissipative | 10^6 to 10^9 ohm/sq | Charge drains in a controlled time | ESD acrylic, ESD PVC, ESD PC |
| Insulative | Above 10^11 ohm/sq | Charge is held | Standard acrylic, glass, most plastics |
ESD acrylic sits in the static-dissipative band. Conductive material is not usually wanted for a window or a guard, because a fast discharge can itself damage a component; a controlled bleed is the objective.
Where a panel is outside the ESD-protected area, or where no bare components are exposed, standard acrylic is fine and costs far less.
An ESD surface works by a thin conductive layer or a dispersed additive. An ordinary glass cleaner leaves a film that insulates it, and the panel quietly stops being dissipative while still looking correct. This is the most common and least visible failure in service.
A panel that has been cleaned with the wrong product, or abraded, cannot be restored by cleaning it again. It has to be replaced, which is why the cleaning product belongs in the installation handover.
MATERIAL: STATIC-DISSIPATIVE PMMA, SURFACE RESISTIVITY 10^6–10^9 Ω/sqSUPPLY TEST REPORT FOR THE SHEET BATCHCLEANING: ESD-SAFE CLEANER ONLY (name the product, or state the prohibition)NO ABRASIVE CLEANING; RE-TEST SURFACE RESISTANCE AT INSTALLATIONWe supply the sheet manufacturer test report for the batch, stating the resistivity range and the test method. What we cannot do is certify the performance of an installed system: ESD protection depends on the grounding, the flooring, the operator and the whole workstation, and the panel is one element of it. Where a site needs certification, that is done by an ESD auditor against the relevant standard.
No. Standard PMMA is an insulator and holds charge. Anti-static treatments and coatings exist but are temporary; a genuine static-dissipative sheet is a different product with a documented resistivity.
With a surface resistance meter, following the standard test method for the material. A visual check tells you nothing, and a panel that has been cleaned with the wrong product can look perfect and be insulative.
It can, but it is slightly less clear and considerably more expensive. Unless the display is inside an ESD-protected area, standard acrylic is the better choice.
A static-dissipative panel bleeds charge to the frame if the fixing is conductive. Where the panel is isolated by plastic washers it has nowhere to bleed to, which is a detail to agree with the ESD auditor.
No. Conductive and dissipative surfaces are not repairable in the field. A damaged panel is replaced.
ESD is the one property where a part can pass on the day of delivery and fail six months later without anybody touching it wrongly. The reason is that two families of material behave completely differently, and only one of them is stable.
| Type | Resistivity | Behaviour over time | When to choose it |
|---|---|---|---|
| Surface-coated | 10^6–10^9 ohms | Decays with wiping, typically 6–12 months | Low handling, short-life fixtures, cost-sensitive |
| Volume-conductive | 10^4–10^6 ohms | Stable for the life of the part | Daily-wiped trays, production line fixtures |
| Standard PMMA | > 10^14 ohms | Holds several kV after a wipe | Never, near a bare board |
Verification is where specifications go wrong. A resistivity figure without a test method is not a specification: surface resistivity measured with a concentric ring probe at 500 V and 23 percent RH gives a different number from a point-to-point measurement at 12 percent RH, and both are legitimate readings. Write the method, the electrode geometry and the humidity into the drawing note, or accept that two labs will disagree.
In service, the two things that destroy an ESD property fastest are abrasion and solvent. A tray cleaned with an IPA wipe is fine; the same tray scrubbed with an abrasive pad loses its surface layer and its conductivity together. That is the practical argument for volume-conductive sheet on anything handled daily — not the resistivity number, but the fact that the number does not depend on a coating that can be worn off.
That single fact decides whether you need ESD sheet at three times the price, or standard acrylic at a fraction of it.