electrostatic discharge (8)

8/10/2019 Electrostatic Discharge (8)

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ESD Elect ro s ta t ic Disc harge


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Defini t ion

Electrostatic Discharge: Thetransfer of an electrostatic chargebetween bodies at different electricalpotentials Also referred to as staticelectricity.

The electrostatic charge is mostcommonly created by the contact andseparation of two materials whichresults in Tribocharging .


3/23

Larg e Charg es Generated A ll The Tim e

Walking across a carpet:1,500 - 35,000 volts

Walking over untreated vinyl floor:250 - 12,000 volts

Vinyl envelope used for workinstructions: 600 - 7,000 volts

Worker at a bench:700 - 6,000 volts

Unwinding regular tape:9,000 - 15,000 volts


4/23

Typed o f Mater ials th at Charg e

Conductors Materials that easily transferelectric charge

Can be used to transfercharge to earths ground

Examples MetalsWaterCarbonPeople

Insulators Materials that hold an electriccharge and can not easily transfer

the chargeCan not be grounded to earth bycommon means

Examples PlasticGlassDry Air


5/23

Sourc es of ESD The following items are examples of materials that generate and

hold electrostatic charge.

Vinyl binders

Equipment covers

Plastic documentholders/sheet protectors

Post-It TM notes

Plastic pens

Bubble wrapPlastic housings onequipment

Paper, schematics, etc.

Plastic work travelers

Plastic spray bottles

Personal items

Purses

Sweaters/jacketsInsulated lunch totes

Combs/brushes

Lotion bottles


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7/23

Com m on Causes o f ESD

Opening a common plastic bag

Removing adhesive tape from a roll or container

Walking across a floor and grabbing the door knob

Transporting computer boards or components

around in their trays on non-ESD carts

Sliding circuit boards on a work bench


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9/23

Examp le of ESD Dam age

Optical photo of alarge IntegratedCircuit which has

experienced ESDdamage to the pinnoted by thearrow.

Highermagnificationphoto of pin notedby the arrow in theprior slide Thistaken at 400 timesmagnification on a4" X 5" photo. Thedamage is noted

as the "fuzz" at theend of the arrow.

Overlyingglassivation hasbeen removed andthe surfacedecorated to showthe ESD damageat 5,000 timesmagnification inthis scanning

electronmicrograph.


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Why is ESD Im po r tant?

Electrostatic Discharge (ESD) can damage sensitive

electronic devices, resulting in:Higher manufacturing costs

Rework

Repair

Scrap

Lower production yields

Unhappy customers

Shorter product life

Reduce product reliability

Estimates of actual cost of ESD damageto the electronics industry = $$$ Billions

annually


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How to c on t ro l ESD?

ESD Training

ESD Control Areas

Ground Conductors

Ionization

ESDS Component Handling and Storage

ESD Contro l Program


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ESD Cont ro l Prog ram

Any area where unprotected ESD sensitive parts and

assemblies may be handled shall be designated anESD Control Area, and must meet the followingrequirements;

The area is free from non-essential staticgenerators, and the risk from process-essential staticgenerators is minimized

All personnel must be grounded and groundingequipment must be tested daily

All movable carts, racks, etc. are grounded

The area is labeled as an ESD control area, and theboundaries are clearly marked


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Create an ESD Control Area

Any area where unprotected ESDS parts and assemblies may be handled

ESD areas must be labeled with posted signs and their boundaries marked


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All Conductors within the EPA mustbe grounded

Personal Grounding: All personnel,including visitors

Work surfaces and flooring

All equipment in EPA


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Person al Groun ding

Wrist Straps and Coil Cords Wrist Straps ground personnel atworkstations

Heel Grounders Ground mobile personnel in areas wherethere are ESD floors

Smocks

Smock sleeves should be incontact with the skin, clothingunderneath should not show


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Equipm ent Groun d ing

Work Stations and Tables

Must have static dissipative surfaces connected to the

building ground source.

Must have wrist strap ground connections (2

recommended), preferably banana jack receptacles,

connected in parallel to the bldg ground source

Should be cleaned daily with an antistatic cleaner


19/23

Equipm ent Groun d ing

Shelving and Cabinets Must provide a grounded surface unless the

parts remain fully enclosed within shielding-

type packagingStorage Bins

All parts bins and containers must be

static dissipative or antistaticWhenever practical, sensitive parts

should remain in the original container

until assembled


20/23

Ionizat ion

Many times, equipment or objects(insulators) are unable to begrounded in which case air ionizers should be used.

What is Ionization?

Air Ionizers use a process called "neutralization" to remove static

charge from insulators that cannot be grounded.

Ionizers produce positively and negatively charged ions and floods

ESD area with Ions.

Ions are charged particles that are present in the air, and as

opposites attract, charges will be neutralized over time.


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Typ es o f Air Ion izers

Bench Top

Ionizing Nozzles

Air Guns

Overhead Ionizers
http://www.transforming-technologies.com/ionizers-overhead.htmlhttp://www.transforming-technologies.com/ionizers-blowers.htmlhttp://www.transforming-technologies.com/ionizers-guns.htmlhttp://www.transforming-technologies.com/ionizers-nozzles.html


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23/23

ESD B asics Review

Things to remember about an ESD protection plan.

Only allow trained or escorted people in EPA

Ground all conductors including people at ESD workstation

Test wrist straps at least daily, or use continuous monitors

Test ESD footwear at least daily, if used

Visually check all grounding cords

Keep wristband snug, foot grounder grounding tab in shoe,and ESD smocks buttoned

Ionizers are maintained and air flow directed at ESDS

items Use shielded packaging for shipping or storing ESDsensitive items outside the ESD Protected Area

Handle unpacked ESDS items only when grounded

electrostatic discharge (8)

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