ESD - Electrostatic Discharge

    ESD is simply the discharge of built up static electricity. Electrostatic discharge however, should not be taken lightly when working with computers. ESD has the capability of causing enough damage to the components inside your computer to render it completely inoperable. It's important to use an anti-static strap and/or a grounding mat whenever working on the inside of your computer. Being aware of ESD precautions can significantly reduce the chance of damage to your computer due to static electricity.

   Static electricity is a fact of Life. You're producing it and discharging it constantly. Moisture in the air can help it to dissipate, and raising the humidity in your workplace is another very good measure you can take to reduce the chance of damage caused by ESD. ESD is bad for computers and electronic components. If you are opening the case or working inside a computer, always take ESD precautions.

WARNING:
There are capacitors inside a computer's monitor and power supply that store enough electricity to stop your heart, even when they are unplugged. You should not be grounded if you are working inside a monitor or a power supply.
    But then, you shouldn't even open a monitor or a power supply unless you know what you're doing.

How Much is Too Much?
    Have you ever walked across a carpet on a dry winter day, touched somebody, and heard the snap of electricity as a small blue spark jumped from your fingertip to the edge of your victims ear?

    If the discharge was felt, it was probably more than 2000 volts. If you heard it, then it could have been between 3000 - 5000 volts. If you actually saw a small blue spark, it was more than likely in excess of 10,000 volts.

    So do I have to walk on a shag rug? Does it have to be a dry winter day? No! Your body is building up and discharging static electricity all the time. Just shifting in your chair can produce up to 150 - 200 volts! You can't completely eliminate this problem but it can be controlled.

ESD and Your Computer
    The ICs (Integrated Circuit chips) on the various circuit boards in your computer use between 2 - 5 volts. They can be damaged by less than 200 volts. Some may be damaged by as little as 30 volts. This means that ESD can cause damage to the various components inside your computer and you won't feel it, hear it, or see it. In fact, the discharge voltage could be 1000 times less than what the human body can feel!

     When they started replacing the tubes in radios with transistors, people were amazed at how small radios were getting. You could get a transistor radio that boasted 7 transistors and was about the size of a brick! …Today, some of the individual chips on your computer's circuit boards contain millions of transistors. Advancements in technology allowed for entire circuits to be etched onto a single chip. These are called Integrated Circuit Chips.

     One technology for producing ICs is called TTL (Transistor Transistor Logic). These chips are actually more tolerant of ESD and even faster than the newer technology. However, they're also larger, use more electricity or power, and their resistance causes them to run very hot. As computer technology advanced and the number of transistors in the chips increased, heat and power consumption became a huge problem.

     TTL ICs are still used in computers today, but the newer CMOS chips (Complimentary Metal-Oxide Semiconductor) have all but replaced them entirely. These chips have a semi-conductive metal oxide layer that allows for less resistance, reducing the power consumption and the generated heat.   Unfortunately, the very technology that makes these CMOS chips more efficient also makes them very susceptible to electrostatic discharge.

    Wait a minute! If you can discharge 10,000 volts of static electricity into somebody's ear, how come it doesn't kill them? Well, the amperage is very low. The human body is very tolerant of voltage, it's the amperage, or a current's strength, that will kill you. The chips inside your computer however, are highly sensitive to any kind of voltage, even at very low amperages.  ...By the way, all of today's CPUs (Central Processing Units) and system memory chips on your RAM SIMMs or DIMMs are CMOS chips.

ESD Damage
    So what kind of damage can be caused by ESD? Anything from a simple system interruption, causing your computer to reboot with no further problems, to complete destruction of a chip that will make your system unusable until the chip is 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:

Immediate Failures (Direct Failures, Catastrophic 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 (or worse yet, someone else's) to install more memory. Without using an anti-static strap or a grounding mat (you've done it lots of times before and never had a problem), you take a brand new DIMM from its anti-static tube, install it, and now the computer won't even finish its boot sequence. Not a good situation, but you do know the computer worked before you installed the RAM, so you should have an idea where to start looking for the problem.

Latent Failures (Upset Failures, Delayed Failures) - Sometimes a chip can be damaged by electrostatic discharge and the results aren't immediately noticeable. 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 track down.

Continued....