ANSI/ESD S20.20 Requirements: Complete ESD Control Program Guide

Wrist Strap Grounding

Wrist straps are commonly used for seated operators and fixed workstations.

A wrist-strap system typically includes:

• Wrist band
• Ground cord
• Current-limiting resistor
• Connection point
• Grounding conductor
• Common-point ground

The wrist band should make reliable contact with the operator’s skin.

Daily or continuous testing may be used depending on the facility’s program.

Common wrist-strap failures include:

• Loose wrist band
• Dirty contact surface
• Broken ground cord
• Incorrect connection
• Damaged resistor
• Operator wearing the strap over clothing
• Unverified extension cables
• Disconnected common-point ground

A wrist strap should not be clipped to an unverified metal object.

It must connect to an approved personnel-grounding point.

Footwear-Flooring Grounding

A footwear-flooring system allows standing or mobile personnel to dissipate charge through:

Person
↓
ESD footwear
↓
Compatible ESD floor
↓
Ground

Possible footwear includes:

• ESD shoes
• Heel grounders
• Toe grounders
• Conductive footwear
• Static-dissipative footwear

The floor and footwear should be treated as a complete system.

Buying ESD shoes does not guarantee adequate performance on an ordinary insulating floor.

A qualified footwear-flooring system may be evaluated through:

• Person-footwear-floor resistance
• Walking body-voltage generation
• Routine personnel testing

For a commonly referenced footwear-flooring method, total system resistance below 3.5 × 10⁷ ohms is paired with walking body-voltage control below 100 volts. The actual method used by the organization should follow its adopted standard, qualification data and control plan.

Wrist Straps vs ESD Shoes

Operating condition	Preferred control
Seated bench work	Wrist strap
Standing production	Qualified footwear-flooring system
Mobile material handling	Qualified footwear-flooring system
Mixed seated and standing work	Combination defined by the ESD plan
Visitor access	Heel straps or approved visitor footwear
Continuous monitoring	Wrist-strap monitor where appropriate

A seated operator should not rely only on footwear because both feet may lose contact with the floor.

Step 7: Establish ESD Worksurface Controls

An ESD work surface provides a controlled area for handling ESDS items.

Typical work surfaces include:

• Rubber ESD bench mats
• Static-dissipative laminates
• Conductive work surfaces
• ESD shelving
• Grounded workbench surfaces
• Mobile-cart surfaces

An ESD work surface should:

• Be qualified before use
• Provide controlled charge dissipation
• Be connected to an approved ground
• Be verified periodically
• Be kept clean
• Remain free from insulating contamination
• Be clearly identified as part of the EPA

A commonly cited range for protective worksurfaces is approximately 1.0 × 10⁶ to 1.0 × 10⁹ ohms resistance to ground, although the organization must follow the limits and test methods defined in its adopted program.

Grounding an ESD Worksurface

A typical grounding arrangement includes:

ESD Worksurface
↓
Mat Grounding Snap
↓
Ground Cord
↓
Common-Point Ground
↓
Equipment Ground

Important requirements include:

• Use an identified grounding point.
• Avoid improvised grounding connections.
• Verify the common-point ground.
• Inspect cords and snaps.
• Prevent accidental disconnection.
• Test resistance to ground periodically.
• Document test results.
• Replace damaged grounding hardware.

The work surface should not be grounded through an unknown machine frame, painted metal, plumbing line or unrelated electrical structure.

Step 8: Control Conductors

Conductive objects can accumulate or transfer charge when they are not grounded.

Examples include:

• Metal tools
• Fixtures
• Shelving
• Carts
• Equipment housings
• Containers
• Machine parts
• Soldering equipment
• Test fixtures
• Metal trays

All conductors within the ESD-controlled process should be:

• Grounded
• Bonded to a common reference
• Removed from the area
• Otherwise controlled

Potentially dangerous isolated conductors should be identified during process assessment.

Common examples include:

• Ungrounded metal tweezers
• Floating metal fixtures
• Unconnected machine parts
• Metal trays on insulating surfaces
• Tools with insulating handles and exposed metal tips
• Unbonded carts
• Unsupported metal shelves

Grounding a workbench does not automatically ground every conductive object placed on it.

Contact resistance, coatings, feet, adhesives and insulating layers can interrupt the path.

Step 9: Control Process-Essential Insulators

Insulators do not readily lose charge through grounding.

Common insulators in electronics manufacturing include:

• Plastic bags
• Foam
• Adhesive tape
• Plastic trays
• Document sleeves
• Ordinary binders
• Styrene packaging
• Acrylic guards
• Plastic bottles
• Labels
• Clothing
• Machine covers
• Cable insulation

The preferred approach is:

1. Remove unnecessary insulators.
2. Replace them with ESD-control alternatives.
3. Increase distance from ESDS items.
4. Use ionization where removal is not practical.
5. Evaluate the electrostatic field or charge.
6. Document process-essential insulators.

Ionization is not a substitute for grounding conductive objects or personnel.

It is used mainly where charge cannot be removed effectively through grounding, especially on insulating materials and isolated objects.

Step 10: Use Ionization Correctly

Ionizers produce positive and negative ions that help neutralize charge on insulating materials and isolated objects.

Common ionizer types include:

• Benchtop ionizers
• Overhead ionizers
• Ionizing air guns
• Ionizing nozzles
• In-tool ionizers
• Cleanroom ionizers

Ionizer qualification and verification may include:

• Offset voltage
• Positive decay time
• Negative decay time
• Test distance
• Airflow setting
• Environmental conditions
• Electrode condition
• Installation position

A factory should not assume an ionizer is working because the fan is operating.

Ionizer performance can deteriorate because of:

• Dirty emitter points
• Incorrect distance
• Obstructed airflow
• Poor positioning
• Electrical faults
• Incorrect settings
• Maintenance problems

Ionizers require scheduled cleaning and verification.

Step 11: Establish an ESD Protected Area

An ESD Protected Area, or EPA, is a defined area where ESDS items can be handled under controlled conditions.

An EPA may be:

• A single workbench
• A repair station
• A production line
• A storage area
• A laboratory
• A cleanroom
• An inspection station
• A complete production room

Typical EPA controls include:

• Grounded work surfaces
• Personnel grounding
• ESD flooring
• Approved footwear
• Ionization
• Grounded tools
• ESD-safe storage
• Approved packaging
• ESD signs
• Access control
• Training
• Compliance verification

Unprotected ESDS items should be handled inside an EPA unless appropriate protective packaging or covering is being used.

ESD Protected Area Checklist

Area Identification

• EPA boundaries are clearly defined.
• ESD warning signs are visible.
• Entry requirements are posted.
• Visitors are controlled.
• Unauthorized materials are restricted.

Personnel

• Operators are trained.
• Grounding devices are worn correctly.
• Personnel testing is completed.
• Failed tests trigger corrective action.
• Records are retained where required.

Workstations

• ESD work surfaces are grounded.
• Ground cords are intact.
• Common-point grounds are identified.
• Wrist-strap points are available.
• Work surfaces are clean.
• Ground connections are verified.

Materials

• Ordinary plastic bags are removed.
• Approved ESD packaging is used.
• Process-essential insulators are identified.
• Conductive containers are grounded where required.
• Documents and labels are controlled.

Equipment

• Metal equipment parts are grounded.
• Carts and racks are verified.
• Tools are approved for EPA use.
• Ionizers are positioned correctly.
• Test equipment calibration is current.

Documentation

• ESD Control Program Plan is current.
• Qualification records are available.
• Verification records are complete.
• Training records are available.
• Failed tests have corrective-action records.
• Audit findings are closed.

Step 12: Select and Control ESD Packaging

Packaging requirements depend on whether the ESDS item is inside or outside an EPA.

Inside an EPA

Packaging should:

• Avoid generating damaging charge
• Prevent direct discharge
• Maintain suitable electrical properties
• Be compatible with the process

Possible materials include:

• Static-dissipative bags
• Conductive containers
• ESD trays
• Conductive foam
• Dissipative foam
• ESD bins
• PCB racks

Outside an EPA

Additional protection may be required against:

• Electrostatic discharge
• External electrostatic fields
• Triboelectric charging
• Direct contact with charged objects

Static-shielding packaging is commonly used when sensitive devices leave the controlled area.

A pink anti-static bag and a static-shielding bag do not necessarily provide the same protection.

Packaging selection should be based on:

• Device sensitivity
• Transportation environment
• Handling process
• Mechanical protection
• Moisture requirements
• Reuse conditions
• Cleanliness requirements

Step 13: Control ESD Garments and Gloves

ESD garments and gloves should be evaluated as part of the process rather than selected only by appearance.

ESD Garments

Garments may help reduce:

• Charge generation from clothing
• Electrostatic fields from underlying garments
• Contamination
• Uncontrolled contact with sensitive products

Groundable garments may also form part of a personnel-grounding system when properly designed, worn and verified.

ESD Gloves and Finger Cots

Gloves may be selected for:

• ESD control
• Contamination control
• Fingerprint prevention
• Grip
• Cleanroom use
• Chemical compatibility
• Mechanical protection

Glove performance should be evaluated in the actual use configuration.

A glove marked “anti-static” should not automatically be assumed to provide an acceptable person-glove-grounding path.

Step 14: Establish Training Requirements

Training is a fundamental part of an effective ESD control program.

Employees should understand:

• What ESD is
• Why ESDS devices can be damaged
• Which products are sensitive
• Where the EPA begins and ends
• How to wear grounding devices
• How to test wrist straps or footwear
• Which packaging is allowed
• Which materials are prohibited
• How to report failed ESD controls
• How to handle ESDS items safely

Training should be provided:

• Before personnel perform ESD-sensitive work
• After procedure changes
• When new equipment is introduced
• After repeated nonconformities
• At intervals defined by the organization

Training effectiveness should be evaluated.

Possible methods include:

• Written test
• Practical demonstration
• Supervisor observation
• Competency checklist
• Refresher assessment

A training attendance sheet alone may not demonstrate that employees can correctly perform the required ESD procedures.

Step 15: Maintain Records

An ANSI/ESD S20.20-based program depends heavily on documented evidence.

Important records may include:

• ESD Control Program Plan
• Product qualification reports
• Compliance-verification logs
• Personnel grounding results
• Floor-test results
• Worksurface-test results
• Ionizer-test records
• Grounding verification
• Equipment calibration
• Training records
• Internal audits
• Corrective actions
• Supplier documentation
• Environmental records
• Packaging approvals
• Change-control records

Records should be:

• Legible
• Traceable
• Dated
• Approved
• Protected from unauthorized changes
• Retained for the defined period
• Available during audits

Step 16: Manage Failed ESD Tests

A failed test should lead to a controlled response.

A practical process is:

Detect failure
↓
Stop use or isolate affected area
↓
Protect exposed ESDS items
↓
Identify the failed control
↓
Investigate the cause
↓
Repair, clean or replace
↓
Retest
↓
Assess potentially affected product
↓
Document corrective action
↓
Return to service

Possible failure causes include:

• Broken ground cord
• Dirty work surface
• Worn footwear
• Incorrect cleaning chemical
• Disconnected floor ground
• Contaminated ionizer emitters
• Failed tester
• Incorrect test voltage
• Low humidity
• Operator misuse
• Unauthorized material changes

Do not simply retest repeatedly until a passing result appears.

Repeated failure may indicate a process problem requiring investigation.

Step 17: Conduct Internal ESD Audits

Internal audits help determine whether the ESD control program is both documented and effectively implemented.

An audit should review:

Program Management

• Is there an approved ESD Control Program Plan?
• Is the scope clear?
• Is a responsible coordinator identified?
• Is device sensitivity documented?
• Are changes controlled?

Product Qualification

• Are new control items qualified?
• Are reports complete?
• Are applicable test methods used?
• Are low-humidity conditions considered?
• Are model numbers traceable?

Compliance Verification

• Are all required items included?
• Are frequencies defined?
• Are tests completed on time?
• Are instruments calibrated?
• Are failed results investigated?

Personnel

• Are operators trained?
• Are wrist straps and footwear tested?
• Are grounding devices worn correctly?
• Are visitors controlled?

EPA

• Are boundaries clearly marked?
• Are unapproved materials present?
• Are work surfaces grounded?
• Are conductors controlled?
• Are process-essential insulators managed?

Packaging

• Is packaging appropriate inside and outside the EPA?
• Are opened or damaged bags controlled?
• Are reusable containers verified?
• Are ESDS labels used correctly?

Records

• Are records current?
• Are signatures and dates present?
• Are corrective actions closed?
• Can the organization trace a product to its qualification data?

ANSI/ESD S20.20 Audit Checklist

Use this abbreviated checklist before a customer or certification audit.

Program Documentation

• Current ESD Control Program Plan

• Defined program scope

• Identified ESD coordinator

• Documented lowest device sensitivity

• Product Qualification Plan

• Compliance Verification Plan

• Training Plan

• Packaging Plan

• Tailoring statements where applicable

• Corrective-action procedure

Product Qualification

• Worksurface qualification

• Flooring qualification

• Wrist-strap qualification

• Footwear qualification

• Ionizer qualification

• Packaging qualification

• Garment qualification

• Seating qualification

• Glove qualification where applicable

• Supplier reports linked to exact product models

Compliance Verification

• Worksurface testing current

• Floor testing current

• Wrist-strap testing current

• Footwear testing current

• Ionizer testing current

• Ground-point testing current

• Cart and rack testing current

• Test instruments calibrated

• Failed tests investigated

• Corrective actions documented

EPA Inspection

• EPA signs displayed

• Boundary defined

• Ordinary plastic removed

• Unprotected ESDS items handled only in EPA

• Workstations grounded

• Personnel grounded

• ESD packaging available

• Conductors grounded

• Insulators controlled

• Ionizers positioned correctly

Training

• New employees trained

• Refresher training completed

• Practical competency evaluated

• Training records retained

• Visitors instructed

• Supervisors understand failure response