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What is Electro Static Discharge (ESD)?
Published Date : 05 Nov 2001   Last Updated : 31 Oct 2018   Content Ref: TEC6899  


What is ESD?

ESD (Electro Static Discharge) is an invisible enemy of computer components, such as motherboards, CPUs, memory, graphics, network and sound cards, hard disk, CD-ROM and floppy drives.  The build up of static charge can seriously affect the function of a device that is sensitive to electro static shocks.  Static electricity is created when you rub two non conducting materials together.  The friction causes a charge to build up on the surface of the material.  You will not damage your computer just by using the keyboard or mouse because keyboards and mice are made of plastic, a nonconductive material.  If you feel a ‘shock’ then you have just transmitted at least 3,000 volts, many PC components (i.e.CMOS chips) will be damaged with charges less than 1000 volts.  Many common daily activities will cause a build up of static:

  1. Walking across a carpet, 1,500 to 35,000 volts.
  2. Picking up a plastic bag 1,200 to 20,000 volts.
  3. Brushing your hair, 1,200 to 27,000 volts.
  4. Picking up a common plastic bag from a work bench, 1,200 to 20,000 volts.


So What Kind of Damage can Static Cause?

ESD damage can cause anything from a simple glitch that requires a reboot, and no more problems are experienced, to total chip destruction that will cause the computer not to work until the chip has been replaced.  Also, you won't find any discoloration, burn mark or physical indication whatsoever as to which chip has been damaged.

There are 2 types of damage that can occur:

  1. Immediate Failures - These are failures that occur immediately after the chip has been damaged and usually aren't recoverable until the chip has been replaced.  Say you open your computer to install more memory.  Without using an antistatic strap or a grounding mat, you take a brand new DIMM from its anti-static bag, install it, and now the computer won't even finish its booting, but you do know the computer worked before you installed the RAM.
  2. Latent Failures - Sometimes a chip can be damaged by electrostatic discharge and the results aren't immediately noticeable.  Days, weeks or months later the chip could finally fail completely, or you may end up with intermittent failures that occur sporadically.  These are usually difficult to attribute to any specific cause, and very hard to trace as a fault.


Helpful Guidelines
Here are some simple guidelines to help prevent damage caused by a static discharge:
  1. The use of an anti-static wrist strap is the ideal way to prevent damage, these can be purchased from your high street computer shop.  They simply plug into a wall socket (switched off) or attach to an unpainted metal part of the computer casework.
  2. Do not attempt to carry out any PC internal upgrades with the power cable plugged in.  If you do not have access to an anti-static wrist strap, then some precautions maybe taken to reduce the risk of ESD damage.
    1. Remove monitor, unplug monitor mains cable and then the signal cable from the PC.
    2. Disconnect any other mains powered peripheral that is connected to the PC (e.g. Printer parallel cable, Scanner USB cable, etc).
    3. Remove mains lead from PC or unplug PC.
    4. Remove lid of PC.
    5. Locate DIMM socket.
    6. Touch PC chassis with one hand and the new DIMM (inside packaging) with the other.
    7. Remove DIMM and hold by edges.
    8. Touch PC chassis with one hand briefly.
    9. You may now use both hands to fully insert the DIMM.

    These precautions will only reduce the risk of ESD damage,  but will not eliminate the risk completely.  RM always recommend the use of an anti-static wrist strap, and cannot be held responsible for components that have been fitted without the use of a wrist strap.

  3. Keep any components that are not fitted to the computer, in the special ESD bags that the component is supplied in. Only remove the component from the ESD bag when you are ready to fit it, and place the replaced component into the ESD bag as soon as its removed from the computer.

Warning: Monitors and components, like power supply units, should never be opened. They hold enough charge, even when switched off, to cause an electric shock!

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Document Keywords: anti-static, precautions, electro, sensitive, device, wrist, strap, discharge, shock, electricity, friction, charge, build up, volts, component, cmos, chips, immediate, latent, failure, failures, damage, cpu, memory, graphics, network, sound, cards, hard disk, cd-rom, floppy, glitch, failed, dimm, chip, help, guidelines, library

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