|MICRO CENTER: COMPUTERS AND ELECTRONICS|
|In The Lab
I was rummaging around my storage closet the other day trying to find an extra power cord. I found a spare cord, and something else. One of the bags I found in the shadowy recesses to the closet had several ring-shaped cold cathode lights pulled from some computer fans. What caught my attention was that every time I shifted around in the bag, these ring lights flickered! The static electricity generated by the plastic bag was causing the gas within the fluorescent tube to glow either from the induced charge or through the shielded wires connected to the bulbs.
Besides the obvious concerns about keeping my spare parts in plastic bags, it started me thinking about ESD (electrostatic discharge). In my opinion, ESD is one of the most common causes of premature failure of electronic components. Other causes would have to include power surges and sags (brown-outs), heat, and improper configuration or installation. I continue to hear stories about someone installing their new motherboard directly into a system case without installing the standoff posts first. And people wonder why the system won't power on when numerous solder points on the bottom of the motherboard are shorting out against the case.
Static discharge can occur any time there is an imbalance of electrical charge between two objects. How severe the discharge can depend on a number of conditions. The most common cause occurs through friction, or more specifically tribocharging. Tribocharging describes the build up of electrical potential as two surfaces are brought into contact and then separated. For example, moving around on a chair or car seat, walking across a rug, and pulling a piece of tape from a dispenser are actions that cause tribocharging. Similarly, when the cold cathode fluorescent tubes rubbed against the plastic bag, they created a difference of electrical potential, and triggered the visible flashes.
Static discharge can also be induced. Induced charge during a lightning strike can create a counter-charged bolt to discharge upward from the ground, trees, power lines, etc. and can be the cause of many "near-strike" lightning-related failures. With cloud-to-ground lightning strikes, there is often a ground-to-cloud discharge that rises to meet the downward strike.
As a charged object, like your finger, comes close to another surface, an equal but opposite charge can build up on that surface. Even though the balance of the existing charge of the object may be unchanged, electrical charge can migrate across the surface, at least until the difference between your finger and the new video card is greater than the resistance in the air gap between the two. At that point "an arc of death" can occur between the two, and destroy your video editing hopes, game playing dreams, and the video card circuitry in a tiny, unnoticed event. Throughout the day, you are constantly picking up or losing electrical charge by touching things that have more or less charge than you do. Most of the time this charge is "small," perhaps only a couple of hundred volts. You usually won't notice anything until your charge potential builds up to a couple of thousand volts, and you get zapped. But your electrical stuff will be affected by even those "small" voltages.
How does an anti-static wrist strap help? ESD straps actually do two things: First, they provide a conductive connection between you and the electrical ground point. This connection constantly discharges excess static charge to the ground, preventing it from reaching a level that can damage your components. Static can be generated by friction between your shoes and the floor, clothing, furniture, or just touching objects that may have a static charge already such as a plastic bag or foam cup. Second, static straps have a resistor between the strap and the wired connector. Most are inside the small plastic block that the cable attaches to, but some may be at the other end of the cable. The resistor limits the current that can pass through the strap in either direction. This makes it unlikely that you could receive a shock by touching unshielded or improperly wired electrical equipment. (Touching the live power connection while grounded is still a bad idea - don't try this at home, or work for that matter...)
Did you hear the spark? What you don't see, hear, or feel can be just as catastrophic to your electronics as one you do. Most of your current components operate on a couple of volts. Where thousands of volts from a noticeable discharge (a spark) can immediately kill your product, the unnoticed discharge can still destroy or will at least degrade the circuitry enough to shorten its life to a fraction of normal span.
Plastic static bags and clamshells help protect your components, but only as long as they are inside. This type of packaging acts as an insulator to prevent static from being conducted through the material to the sensitive electronics inside. They also may have a special coating that helps conduct electricity over the surface, allowing excess static charge to dissipate into the air or nearby conductive surfaces. Removing your part from the bag and then using the sack like an oven mitt is likely to do more harm then good, since you now have a path from you to the component over the conductive surface of the bag. To protect your memory during transport or while storing it, save your old static bags and clamshells. Don't substitute sandwich bags or other containers not designed for ESD shielding as it is a very good way to shorten their life.
Tips to protect yourself and your parts:
© Micro Center