ESD FUNDAMENTALS

What is ESD?Known as ElectroStatic

Discharge

It is the release of static electricity when two objects come into contact.

ESD first requires a build-up of an electrostatic charge. This occurs when two different materials rub together. One of the materials becomes positively charged; the other becomes negatively charged. It also occurs when there’s an imbalance on the electrons on the surface material.

How does ESD occur?All matter is made up of atoms, and atoms are made up of smaller particles. The three main particles making up an atom are the proton, the neutron and the electron.

NEUTRONS - NEUTRALPROTONS – POSITIVE CHARGE ( + )

ELECTRONS – NEGATIVE CHARGE ( - )

Behavior of Electrons

Static electricity is the imbalance of positive and negatively charge particles. It commonly occurs when to object have contact and separation which is also known as Tribocharging.

ESD EVENT• When a charge

comes into contact with the right material, it is transferred and we have an ESD event. The heat from the ESD event is extremely hot, although we do not feel it when we are shocked.

• When the charge is released onto an electronic device such as an expansion card , the intense heat from the charge can melt or vaporize the tiny parts in the card causing the device to fail.

Samples of ESD Events• Damaged Circuit board

• Sometimes an ESD event can damage a device, but it continues to function. This is a called a latent defect, which is hard to detect and significantly shortens the life of the device.

Samples of ESD Events• Damaged Circuit part

ESD DAMAGE CLASSIFICATION1.Catastrophic

Failure - Device is totally

damage2. Latent Defect

- Device is partially degraded.

Example of static generations

Typical Voltage LevelsMeans of Generation

10-25%RH

65-90%RH

Walking across carpet

35000V 1500V

Walking across vinyl tile

12000V 250V

Worker at bench 6000V 100V

Poly bag picked from bench

20000V 1200V

chair with urethane foam

18000V 1500V

Practices to prevent ESD events

These first few pertain to your environment:

• DO NOT place your computer on carpet, fabric, or any other fibrous surface but DO place it on a clean and table.

• DO NOT stand on carpet, especially if you are wearing socks. If you have no other option, try not to move around a lot. Moving around (especially with socks on) will build up static.

• DO NOT hold on to metal objects after you had contact or hold the fur of your furry pets because static charge is already existing.

How to prevent ESD events in a Cleanroom?

• Groundingprevents the generation of static charge and removes it from isolated conductive or static dissipative materials that have become charged.

Practices to prevent ESD events• Many electronic

devices are susceptible to low voltage ESD events. For example, hard drive components are sensitive to only 10 volts. For this reason, manufacturers of electronic devices incorporate measures to prevent ESD events throughout the manufacturing, testing, shipping, and handling processes.

Practices to prevent ESD events• Wearing of wrist

strap to control the static charge on the personnel.

• Installing anti-ESD floor mats or tiles.

• Wearing of anti-ESD shoes/grounders to provide electrical contact between person or object and the floor material.

• Wearing of anti-static apparels to minimize the effects of electrostatic fields or charges that may be present on a persons clothing.

Practices to prevent ESD events• Use of anti-static

packaging materials to protect the products when it leaves the facility, usually when shipped to customer.

• Use or installation of ionizers in the cleanroom neutralize the static charge on insulated and isolated objects.

BASIC PRINCIPLES OF STATIC CONTROLS

- design and immunity

- define the level of control

- eliminate and reduce generation

- dissipate and neutralize

- protect products

Typical Facility Areas Requiring ESD Protection

Receiving Inspection

Stores and warehouses Assembly

Test and inspection Research and development

Packaging Field service repair

Offices and laboratories Clean rooms

ELECTRICAL CHARACTERISTICS OF MATERIALS1. Conductive materials are defined as those having a surface resistivity less than 1 x 105

Ω/sq or a volume resistivity less than 1 x 104 Ω-cm.1 With a low electrical resistance, electrons flow easily across the surface or through the bulk of these materials. Charges go to ground or to another conductive object that the material contacts or comes close to.

ELECTRICAL CHARACTERISTICS OF MATERIALS2. Dissipative materials have a surface resistivity equal to or greater than 1 x 105 Ω/sq but less than 1 x 1012 Ω/sq or a volume resistivity equal to or greater than 1 x 104 Ω-cm but less than 1 x 1011 Ω-cm.2 For these materials, the charges flow to ground more slowly and in a somewhat more controlled manner than with conductive materials.

ELECTRICAL CHARACTERISTICS OF MATERIALS

3. Insulative materials are defined as those having a surface resistivity of at least 1 x 1012 Ω/sq or a volume resistivity of at least 1 x 1011 Ω-cm.1 Insulative materials prevent or limit the flow of electrons across their surface or through their volume. Insulative materials have a high electrical resistance and are difficult to ground. Static charges remain in place on these materials for a very long time.

100 Ω/sq 105Ω/sq 1011 Ω/sq

SURFACE RESISTIVITY SPECTRUM

Conductive Dissipative Insulative

106Ω/sq

1012 Ω/sq and above

• END OF SLIDE SHOW..

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