Factory safetyReading time 11 min
ESD Damage Can Appear After Shipment
A component can pass final test and still carry electrostatic damage that fails later in service. Effective ESD control starts by understanding where charge builds up and how to verify the controls.
01How charge builds up
Contact and separation can transfer charge between materials. During handling, packaging or movement, that charge may build up without a visible spark. ESD control therefore starts with the actual contact points and paths to ground, not with whether an operator can feel a discharge.
| Motion | 10 – 20% RH | 65 – 90% RH |
|---|---|---|
| Walking across carpet | 35,000 V | 1,500 V |
| Walking on vinyl flooring | 12,000 V | 250 V |
| Rising from a work chair | 18,000 V | 1,500 V |
| Picking a PE bag off the bench | 20,000 V | 1,200 V |
| Peeling tape off a roll | over 15,000 V | a few thousand V |
02Three discharge models
| Model | Full name | Scenario |
|---|---|---|
| HBM | Human body model | A charged person touches the part. The most common case. |
| MM | Machine model | A charged metal fixture or piece of equipment touches the part |
| CDM | Charged device model | The part itself is charged and touches ground. Extremely fast discharge. |
03Inside the protected area
An ESD-protected area keeps people, tools and work surfaces at a controlled potential. Grounding and approved materials reduce the chance that a sensitive device becomes the discharge path; the area only works if its controls are checked in use.
- Wrist straps. The primary way to ground a person, with a 1 MΩ resistor in series to limit current. Test them at the start of every shift.
- ESD bench and floor matting. Surface resistance of 10⁶ to 10⁹ Ω, too low is a shock hazard, too high does not dissipate.
- ESD footwear and flooring. How you ground standing or moving operators.
- Ionizers. They handle charge on insulators, plastic housings, tape and packaging cannot be grounded, only neutralized.
- Packaging. Conductive (black), shielding (silver) and dissipative (pink) bags all serve different purposes; only a shielding bag blocks an external field.
04Humidity and environment
Humidity can help charge dissipate, but it is not a substitute for grounding, suitable packaging or process checks. Set an environmental range for the product and site, then verify that protection remains effective when conditions change.
- Below 30%: static risk climbs sharply.
- Above 70%: metal parts and PCBs risk oxidation and condensation.
05Checking the controls
| Item | Frequency | Tool |
|---|---|---|
| Wrist strap function | Every shift start | Wrist strap tester |
| Bench / floor mat surface resistance | Quarterly | Surface resistance meter |
| Ionizer balance voltage | Quarterly | Charged plate monitor (within ±35 V) |
| EPA ground resistance | Annually | Ground resistance tester |
| Charge on people and tools | Spot checks | Non-contact electrostatic fieldmeter |