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Thursday, 19 June 2014

How Electrostatic Discharge ( ESD ) Damages ICs?

by realfinetime  |  in IC at  08:59

Electrostatic Discharge is an important fact that should be considered while packaging and assembling ICs. For the longer life of ICs, electrostatic discharge must be considered at the construction stage itself. Main cause of Electrostatic discharge is Static Electricity.


What is Static Electricity ?.

Static electricity is the electricity at rest. Static electricity is generated due to friction and seperation. Friction generates heat, that excites the molecular particles in the materials. When these materials are seperated, a transfer of electrons from one material to another will takes place, generating static electric fields. Amount of static electric field depends on the nature of materials, friction and seperation between materials and the relative humidity of the environment.

Many of the human activities in our daily life will generate static electricity on our body.

Some of the activities include:

a) Walking across a carpet will generate 1,500 to 35,000 volts
b) Walking over untreated vinyl floor will generate 250 to 12,000 volts
c) Worker at a bench will generate 700 to 6,000 volts
d) Vinyl envelope used for work instructions will generate 600 to 7,000 volts
e) Picking up a common plastic bag from a bench will generate 1,200 to 20,000 volts

What is Electrostatic Discharge ?.

Electrostatic discharge (ESD) is the sudden flow of electricity between two electrically charged objects caused by contact, an electrical short, or dielectric breakdown. A buildup of static electricity can be caused by tribocharging or by electrostatic induction.

How Electrostatic Discharge affects the ICs ?.

If a person having static electricity on his body touches the IC Chip, then electrostatic discharge will takes place. Electrostatic Discharge is an important problem since the beginning of production of ICs. Chips works on small voltages whereas Electro-Static Discharge will be thousands of volts. Chips should be capable for absorbing these high voltages and handling them harmlessly without damaging the chip.

If ESD is incorrectly handled, discharge will reach the gates and will damage the thin oxide underneath the gate. This may make entire IC inoperable. Electro Static Discharge can also occur during packaging, assembling and testing of the ICs.  Internal charge build-up from in-package capacitors and on-chip memories will also results in Electrostatic Discharge.

How to protect ICs from Electrostatic Discharge ?.

ICs can be protected from ESD by placing Clamp circuits in appropriate locations. Clamp circuit provides a low impedance discharge path for the ESD and clamp the signal voltage at a level that avoids dielectric breakdown.

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IMPORTANT NOTICE

All the circuits, published in this blog is only after testing and getting proper results in my private lab. When you try these circuits, you should check the supply voltage, polarity of components, presence of childrens nearby and shorts in the circuits. This website will not be responsible for any harm happened to you or your components caused by your carelessness.

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