Field guide · ESD & material selection
The science behind the spec.
Two questions worth answering properly: why do I need ESD control? and why pay for PEEK when aluminium is cheaper? Here's the reasoning — with the physics, not just the price.
Electrostatic discharge
A spark you can't feel can scrap a chip.
Contact and separation can create static charge. A discharge that a person cannot feel can damage a sensitive electronic component. Damage may be immediate or may reduce reliability without an obvious initial failure. The device sensitivity and the handling process determine the controls needed.
An insulating surface can retain charge in localized areas. A ground wire alone cannot reliably drain that charge; the process may require ionization and other ESD controls.
The resistance spectrum
Know the class and the test.
General EOS/ESD Association classes are shown below. They describe measured resistance, not a universal safe window. A worksurface requirement, a material resistivity value and a finished fixture test are different specifications.
Charge transfer is limited by resistance. Suitable grounding and the customer’s acceptance limits remain necessary.
e.g. Supplier ESD POM, PEEK and PEI candidates
Supplier labels are not test results. A CON grade reported at 10³–10⁵ spans the general conductive/dissipative boundary. Ask for the actual value, units, test method and environment.
A common mix-up
“But we already have ESD mats” — so why the plastic?
An ESD bench mat controls a work surface. A machined ESD plastic controls the material of a tray, fixture or other part. Each needs its own suitable grounding arrangement and verification.
The green/black ESD mat
A typical layered bench mat combines a dissipative surface with a more conductive backing. Test its resistance to ground as installed. Its colour does not establish performance.
ESD engineering plastics
A rigid tray or fixture can be machined from an ESD grade. Mechanical strength, thermal limits, cleanliness and electrical behaviour must all suit the part. The polymer name alone does not establish them.
A mat and a fixture address different contact points. Test the assembled workstation and part-handling path; neither material alone guarantees protection.
Particle requirements
Low particle generation is a separate requirement.
The local SKU list calls natural M6 POM an NFP grade. The supplier property table does not provide a particle-shedding test or a cleanroom classification. Confirm the formulation and request particle data after machining and cleaning before making a low-particle claim.
Material selection
Why an engineer picks PEEK over aluminium.
These are broad screening comparisons, not interchangeable design limits. Compare specific grades, part geometry and operating conditions before replacing a metal part.
| Property | ||||
|---|---|---|---|---|
| Density reference | 1.30 g/cm³ (K12) | About 2.7 g/cm³ | About 8 g/cm³ | 1.14 g/cm³ (A12) |
| Thermal limit | 250 °C reported long-term | Alloy / load dependent | Alloy / load dependent | Grade / conditioning dependent |
| Chemical compatibility | Check chemical and temperature | Alloy / chemical dependent | Alloy / chemical dependent | Check chemical and temperature |
| Electrical behaviour | Standard or modified grade | Conductive | Conductive | Standard or modified grade |
| Wear and lubrication | Grade / contact dependent | Surface / contact dependent | Surface / contact dependent | Grade / contact dependent |
| Structural stiffness | Below metals | Usually above polymers | Usually above polymers | Below metals |
| Moisture response | 0.07% air-conditioned (K12) | No polymer swelling | No polymer swelling | Moisture conditioning matters |
| Quoted part cost | Obtain a current quote | Obtain a current quote | Obtain a current quote | Obtain a current quote |
Where PEEK wins
PEEK can be a candidate when chemical exposure, low weight, electrical isolation or elevated temperature justify its cost. ESD or conductive PEEK changes the electrical behaviour. Its lower stiffness than metal and thermal expansion must be checked in the design.
When metal still wins
Metal often remains suitable for stiffness, structural loads and cost. Compare total part performance, machining, service life and qualification effort using the actual application.
Quick reference
Which material for the job?
Pick what matters most for the part, and see the material family that fits.
Start with ESD POM, PEEK or PEI and the customer’s electrical requirement. The supplier table reports 10⁶–10⁸, with units requiring clarification. ESD PET needs a separate datasheet.
Buy with proof
What to ask your supplier for.
Request documents for the exact grade, colour and supplied form. Surface resistance, surface resistivity, volume resistivity and resistance to ground are different quantities.
Electrical report
Method, units, electrodes, test voltage, conditioning, sample locations and measured results. Worksurface and material tests are not interchangeable.
Relevant declarations
RoHS and REACH documents address substances. They do not prove polymer identity, ESD performance or food/medical suitability.
Traceability
Grade code, supplier, lot number, document revision and any certificate of analysis for the supplied lot.
A technical datasheet supports screening. A current grade and lot-specific report supports a purchase decision.
The economics
Compare the whole part cost.
Compare the quoted part cost with machining, qualification, expected lifetime, rework, scrap and downtime. Use customer data to estimate the benefit of a better material; avoid promising an unmeasured reduction in failures.
The categories above are a discussion checklist, not measured costs or savings.
Still not sure what fits?
Send the part requirements and the failure you want to prevent. We will help identify candidate grades and the data needed to qualify them.
References: supplier datasheets and EOS/ESD Association fundamentals.
EOS/ESD Association · ESDin material reference (English PDF)