Static electricity is an imbalance of charge; ESD is the discharge event. When that charge transfers through a sensitive electronic component, the resulting current can damage internal structures.
The small shock you sometimes feel when touching a metal door handle is a familiar example of ESD. In electronics work, damaging events can occur without a visible spark or a noticeable shock. The goal is to control charge before a sensitive part provides the discharge path.
What Causes Static Electricity and ESD?
One common source is triboelectric charging: two materials contact and separate, leaving an imbalance of charge. Film peeling from a roller and plastic packaging being opened are everyday production examples. Charging can also occur through electrostatic induction.
- People moving on insulating floors
- Plastic bags, foam packaging, and ordinary plastic bins
- Film unwinding or separating from conveyor rollers
- Ungrounded tools, fixtures, and other isolated conductors
Material properties, contact and separation, and humidity affect charge buildup. Dry conditions can increase charging, but there is no single humidity threshold that makes every process safe.
Background: EOS/ESD Association — Introduction to ESD.
How Much Voltage Does an ESD Event Involve?
People and materials can acquire thousands of volts during ordinary handling. That does not mean every discharge has the same energy or causes the same damage. Voltage, the discharge path, and the component’s construction all matter.
There is no universal failure voltage for all CMOS chips. Check the specific part’s ESD ratings and the test model used. A voltage measured on production material is not directly interchangeable with a component’s laboratory test rating.
Texas Instruments describes damage occurring below the level a person can notice. Rely on verified controls and measurements, rather than an operator’s ability to feel a discharge.
Texas Instruments — Electrostatic Discharge application note (PDF).
ESD Discharge Models: HBM vs. CDM
HBM and CDM are two component-level test models used to characterize ESD sensitivity.
| Model | What it represents | Component test standard |
|---|---|---|
| Human Body Model (HBM) | A charged person discharging through a component. | ANSI/ESDA/JEDEC JS-001 |
| Charged Device Model (CDM) | A charged component discharging when it contacts a conductor at a lower potential. | ANSI/ESDA/JEDEC JS-002 |
CDM discharges can be extremely brief, often under one nanosecond, with high peak current. Their behavior differs from HBM, so the two voltage ratings should be assessed separately. Neither rating replaces an evaluation of the actual handling process.
Source: EOS/ESD Association — Device Sensitivity and Testing.
How ESD Damages Electronic Components
A discharge can damage junctions, insulating layers, or interconnects inside a device. The effects may appear immediately or be harder to detect.
- Catastrophic failure: the device no longer meets its electrical specifications. Testing may reveal a functional failure or an out-of-limit parameter, leading to scrap or rework.
- Latent damage: a device may initially function despite degradation that can lead to premature failure. A standard functional test alone may not reveal that history.
A later field failure is not, by itself, proof of ESD. Failure analysis is needed to establish the cause. Effective handling controls help avoid damage before it becomes a reliability problem.
Further reading: Texas Instruments — ESD and latent defects (PDF).
Industries Affected by Static Discharge
- PCB and SMT manufacturing. Receiving, placement, inspection, and rework involve repeated handling of sensitive components. Evaluate carriers, feeders, tools, and operator workstations.
- Semiconductor assembly and test. Bare die and packaged ICs require controls matched to their documented sensitivity. Review charging and discharge paths in automated handling equipment as well as manual operations.
- Display panel manufacturing. Charge on glass and polarizer films can attract particles; a discharge into sensitive circuitry can also cause electrical damage. Contamination and ESD need separate acceptance checks.
- Printing, packaging, and plastics. Static can disrupt feeding, stacking, labeling, and cleanliness even without a damaging discharge through an electronic component.
For production examples, see the five practical benefits of an ionizing bar.
How to Prevent ESD Damage
Start by identifying the most sensitive parts and the steps where they are exposed. Then build controls around three practical principles:
- Ground people and conductive items. Use an appropriate personnel grounding system, grounded work surfaces, and bonded equipment. Test wrist-strap systems and other controls according to the verification plan; do not assume a connected strap is functioning.
- Remove unnecessary insulators and ionize essential ones. Ordinary plastic and glass cannot readily discharge through grounding alone. Where those materials must remain near sensitive parts, use suitable ionization and verify its performance at the work location.
- Protect parts during handling, storage, and transport. Handle exposed sensitive parts in an ESD protected area (EPA). Select appropriate low-charging, dissipative, and shielding packaging for the journey, especially when parts leave the EPA.
Guidance: EOS/ESD Association — Basic ESD Control Procedures and Materials.
Where ionizing bars fit
Industrial static eliminators and ionizing bars provide positive and negative ions to reduce charge on nearby materials. A bar suits linear coverage over film or panels; an ionizing blower can suit a workstation. See how an ionizing bar works.
Select equipment against your required discharge time and offset voltage (ion balance), then verify it at the installed distance and process speed. There is no single residual-voltage target that establishes protection for every component and production line.
Train staff in handling and packaging procedures, the checks required before work, and what to do when a monitor or ionizer reports a fault. For a broader checklist, read how to prevent static electricity.
ESD Standards and Routine Verification
ANSI/ESD S20.20-2021 and IEC 61340-5-1:2024 address ESD control programs for handling electronic parts and assemblies. Use the standard and edition required by your organization or customer, with limits appropriate to the parts you handle.
Program requirements go beyond buying equipment. Document the controls, qualification, training, and compliance verification. More sensitive devices can require tighter limits or additional measures.
- Check personnel grounding systems and ground connections.
- Measure work-surface and flooring performance using the applicable methods.
- Verify ionizer discharge time and offset voltage under the relevant test procedure.
- Review packaging, handling changes, and records of corrective action.
Inspect ionizer emitters for contamination and follow the manufacturer’s cleaning instructions with power isolated. Set maintenance intervals using the environment and measured performance. Recheck after cleaning or moving the unit.
Shidike Static Control Products for ESD Applications
Shidike offers ionizing bars for inline processes and ionizing blowers for localized work areas. Match the model’s documented performance to your process before specifying it for an EPA.
- ST-G Intelligent Ionizing Bar — a pulsed AC bar for general inline static control.
- ST-E Intelligent Ionizing Bar — a high-frequency pulsed DC model for wide-span applications.
- ST-S200 Mini Ionizing Air Blower — a compact blower for localized static control.
- ST101A Desktop Ionizing Air Blower — a desktop option for assembly, inspection, and rework stations.
Compare formats in our ESD control products guide.
Frequently Asked Questions About ESD
Why can ESD damage electronics even when the operator does not feel a shock?
A discharge can exceed a component’s tolerance without being noticeable to a person. Sensitivity varies by device and discharge model. Use the manufacturer’s HBM and CDM ratings to plan controls, rather than relying on whether an operator feels a shock.
What is the difference between HBM and CDM ESD events?
The Human Body Model represents discharge from a charged person through a component. The Charged Device Model represents a charged component discharging to a conductor at a lower potential. CDM events can be much faster. These are separate component test models, so their voltage ratings are not interchangeable.
Why is latent ESD damage harder to detect than catastrophic failure?
Catastrophic damage causes a device to fail its electrical specifications. Latent damage can leave a device functioning at first, with degradation that may lead to premature failure later. A passing functional test alone does not establish that the device has never experienced damaging ESD.
When should ionization be used instead of grounding?
Use ionization for essential insulating materials, such as plastic film or glass, whose charge cannot readily drain through a ground connection. Continue grounding people and conductive equipment. Ionization complements those controls; it does not replace personnel grounding or protective packaging.
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