Electrostatic Discharge (ESD)

1.) Electrostatic
It is the study of electrical charges at rest.

A charged object is created by the separation of charges:

- An atom is electrically neutral; it has the same number of protons (positive charges) as it does electrons (negative charges).

- Objects are charged by adding or removing electrons.

- A positive charge occurs when there are fewer electrons than protons; its classical definition is the charge accumulated by a glass rod rubbed with silk or wool.

- A negative charge occurs when there are more electrons than protons; its classical definition is the charge accumulated by a hard, rubber rod rubbed with fur.

2.) How is static charge generated?
Static charges are produced whenever there is friction between 2 materials or between human and material, for example touching or rubbing material, touching a plastic bag, clothing, foam coffee cup, or vinyl traveler. Demonstrate generation of static charges using a comb, small pieces of paper, a mylar  tape or balloon.

3.) What is Electrostatic Discharge?
ESD is a sudden discharge of the stored up of static charge. This sudden discharge can cause rupture on material inside devices. ESD sensitive devices therefore can be damaged when in contact with skin.

4.) What are ESD sensitive components?
Class 1 (0kV to 1kV)
- MOS IC
- VLS IC
- Linear IC, voltage regulators
- MOS capacitor
- FET, SCR
- Microwave, VHF transistors
- Thin film resistors

Class 2 (1kV to 4kV)
- MOS IC (CMOS)
- High speed bipolar logic IC
- Monolithic ceramic
- Schottky deiode

Class 3 (4kV to 15 kV)
- Small signal diodes
- Transistor
- Low speed bipolar TTL, DTL
- Quartz piezo-electric crystals

5.) ESD Safety Devices
The following safety precautions are used to prevent damages by ESD:

Handle static sensitive devices and PCB assemblies only at an anti-static workstation.

Discharge human body by wrist or heel straps.

Keep away static generators such as common plastic, tapes, and static generating tools away from work stations.

Use ionizers to reduce charge.

Store and transport sensitive devices in ESD protective packaging, (e.g. anti-static/conductive magazines, conductive bags/tote boxes) which are labeled clearly with a 'CAUTION" message.

Use treated plastics.

6.) Ionisers

An ioniser is a device that is used to clean the air of dust particles.

The ionisers uses a minute amount of electricity to generate billions and billions of negative ions (charged air molecules). These negative ions shoot down dirt particles that are circulating in the air by electrostatic action.

7.) How Static electricity is generated?

Examples:
- Pulling a tape from a reel.
- Clothing rubbing against a chair.
- Walking across a carpeted floow.
- Separating.rubbing 2 foils.
- Combing your hair.