PC Hardware —

Preventing ESD

Prevention is the best defense against ESD, and the first step of prevention is to understand the source. The number one cause of ESD damage is improper handling of electronic devices. A semiconductor device can be damaged by ESD during handling before it is installed.

The key to ESD prevention is to keep all electronic components-and yourself-at a common electrical potential. This usually means ground potential, or zero volts. Maintain a habit of "grounding" yourself to the computer chassis whenever you attempt a repair. There are times when it is not practical, or convenient, to wear a ground strap. At such times, touching a part of the metal chassis before removing devices will bring you and the computer chassis to a common voltage. Don't move around while installing or handling a part; doing so can generate additional voltages, negating any effort you have made to eliminate ESD.

All repair shops and workbenches should have proper ESD-suppression devices, and technicians should use them whenever working with exposed parts. These devices include:

  • Antistatic mats: Nonconducting pads placed on the work surface and on the floor in front of the work area.

  • Antistatic wristband: A wristband with a grounding strap connected to the chassis of the PC.

  • Antistatic pouches: A sealed, antistatic pouch used to store any sensitive electronic device, including hard disk drives, when they are not installed in a computer.

  • Antistatic pad: An insulating foam pad in which individual chips with exposed pins should be embedded when they are not installed in a computer.

CAUTION

  1. AC voltage can kill. Although the power used by the computer components is no more than 12 volts DC, many computers have 110 volts AC wired from the power supply to the on/off switch at the front of the computer case. This wiring can present a hazard. Never disconnect or remove boards from a computer with the power applied. This can damage the components.

  2. Safety precautions are different for computer monitors. Never work on a monitor with the cabinet removed, power applied, and a wrist strap on; a wrist strap coming in contact with the high voltage wire (30,000 volts) can cause electrocution.


Lesson Summary

The following points summarize the main elements of this lesson:

  • ESD damages computer components.

  • ESD can occur without detection.

  • ESD can be prevented.