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Electrostatic discharge (ESD)

by Parm Mann on 14 June 2008, 00:00

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Electrostatic discharge – The invisible menace

We’ve all been victims of static electricity at some point. Perhaps somebody’s used a balloon to make your hair stand on end, or you’ve walked across the office and been ‘shocked’ by a metal door knob? That’s electrostatic discharge at work.

While it’s annoying for us, it can be fatal for computer components and unfortunately that means whenever we handle computer parts, we could be endangering them.

What is static electricity and ESD?

This isn’t a physics lesson, but here’s static electricity explained at a fairly basic level.

Static electricity is the presence of a charge in an object. When an object possesses a charge, it has an imbalance of electrons to protons in its atoms. When there are extra electrons, there is a negative charge. Fewer electrons mean there is a positive charge.

It just so happens that electrons are the parts of an atom that can move freely in some elements. When this is the case, the element is a conductor; the electrons can flow through it, and an electrical current can exist. The opposite of a conductor is an insulator; electrons cannot move freely.

Rubbing two different insulators together can cause electrons to move from one to the other, creating a positive charge in one object and a negative charge in the other. If one of these then comes into contact with a conductor, that charge equalizes. If there’s enough of a charge, it can actually overcome the insulation of air over short distances, resulting in a visible spark, clicking sound and shock feeling you get when touching a door knob. This is electrostatic discharge.

Why is it bad?

An ESD that we can notice takes place at high voltages… in the thousands of volts. The charge must be great for the discharge to occur through air. We all know how easy it is to create enough charge… just walk across a length of carpet.

Computer chips usually operate in the range of 1 to 5 volts, depending on their design. If a higher voltage difference were to be present across part of a chip, then that chip could become damaged. So, if an ESD occurs through a computer component, there’s a chance that harm has will be done.

If an ESD we can feel is in the thousands of volts, then what about those we can’t feel? Any voltage above a chip’s designed operating threshold could damage it, which is what makes ESD an invisible enemy; we need not know we ever did any damage.

Sometimes ESD won’t harm a component. Sometimes it’ll kill it outright. However, sometimes it will damage the component in such a way that it continues to work, without error, but will fail prematurely some time in the future.

The fact is you could be using an ESD damaged computer right now, and never know about it.

Protecting against ESD

ESD is a concern from the very start of a microchip’s existence. Workers in places handling microchips work at specially designed workstations which stand on floors that are grounded to prevent any charge building up. Special clothing must be worn to avoid the body or clothing building up a charge too.

When components are transported, they are kept within special anti-static packaging to prevent them getting in harm’s way.

Finally, when a component gets to you, it’s important that you take care of it too. If components are part of a complete PC, then the big hulk of metal around them does a pretty good job of keeping them protected. However, if you’re self-building, more care should be taken.

The easiest way of protecting components is to be careful how you handle them, and stay grounded. If you plug a PC into a socket, but don’t turn it on, then it’s grounded, but there’s no electricity present so you’re safe. If you’re in contact with the metal of the case when dealing with components, then you’re always grounded, greatly reducing the chances of ESD damaging anything.

When placing components down outside the case, don’t put them on a carpet, or in your pocket; try to put them in an anti-static bag, or a worktop if you can’t find out.

For the seriously ESD conscious, special wrist bands which attach to leads can be purchased. The end of the lead can be clipped to something that’s grounded. This was the user is always free of charge (in theory).

Final words

Modern computer components are a lot more robust than those of days gone by and this includes their robustness against ESD. However, it’s important not to get complacent. You wouldn’t want to kill that new £200 graphics card by being careless, now!

Be careful how you handle stuff, where you put stuff and make sure you’re grounded when dealing with computer internals. If you’re going to leave a computer plugged in to keep it grounded, make sure it’s turned off at the wall… no point avoiding killing components if you’re going to risk killing yourself!

A little care will go a long way towards making sure your components don’t fail unexpectedly.


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