Module 5: Digital Techniques and Electronic Instrument Systems

5.12 Electrostatic Sensitive Devices

Electrostatic discharge

ESD: Electrostatic Discharge. The sudden flow of electricity

between two objects. Caused by imbalance of

electrons between the 2 objects. A field created by tens of volts

between the 2 objects is enough to damage a RAM module.

Walking on a vinyl floor can generate up to 12,000V of static electricity.

ESD abbreviation can also mean “Electrostatic Sensitive Device”

Common Electrostatic Sensitive Devices & actions causing ESD. Devices prone to ESD:

MOSFETS CMOS ICs (Chips) Computer cards (CPU, GPU, etc.) LED, Diodes

Actions causing ESD: Opening a plastic bag. Removing a tape from a roll or a container. Transporting computer components around with trays

or carts. Dry environments (non-humid) increase the possibility

of ESD.

ESD Prevention of working personnel Methods to remove

charge from the human body: Touching metallic objects. Wrist band. Antistatic garment.

Other methods to prevent ESD when working with electronic equipment Avoid touching connections

or pins. Ground all test equipment. Use Antistatic mat:

Made a low resistance material (10ΚΩ to 100ΜΩ) that is grounded. It allows slow discharging.

Use Antistatic Agent: A compound used that makes

the surface of a material conductive, thus reducing or preventing ESD. Usually absorbs moisture from the air.

They are often added to jet fuels.

ESD Preventing Materials Conductive Materials:

Materials with resistance between 1ΚΩ & 1ΜΩ/m2

Dissipative Materials: Materials with resistance between 1ΜΩ /m2 & 1ΤΩ /m2

Shielding Materials: Materials that attenuate current and electric fields.

Static electricity on the aircraft

The aircraft picks static charges from rain, cloud, snow etc. (precipitation static)

• Strong charges developed between different parts of the plane can break down the insulator between them.

• Problems caused by static electricity on the aircraft:Material damage, Corrosion, Electromagnetic interference etc.

Corona Threshold and Static electricity control

The Corona Threshold: High velocity gasses exiting the engine Static electricity dissipates surrounding atmosphere from sharp edges EMF.

Solutions to control static electricity: Bonded (i.e. interconnection) of electronic

equipment. Wickes (to eliminate static electricity dissipation

from sharp edges).

Wicks

ESD signs