Most people who work in the electronics industry have heard of
ESD (Electro-Static Discharge). While some of them are familiar with the basics of personal grounding, others still have no clue. In this article, I’m going to cover the basics of personal grounding, electro-static discharge, the differences between conductive and dissipative materials, and finally, how to make yourself ESD safe when working on your PC.
Personal grounding has become a prime “must-have” in electronics
assembly plants and on smaller production lines. Operators who come
in contact with electronic components, primarily SMD and un-protected
EPROM technologies, are usually the primary cause of post-sale device
failure.
Remember that PCI card that died out after 3 days of use?
Normal quality control checks can not detect minor device damage due
to small ESD events. The device IS functional at time of testing, so
it goes on the market as a *doomed* 100% functional device. It could
be days, weeks, or even months before the thing dies. Call it a manufacturing defect or whatever you want, it’s usually ESD related.
ESD, or electro-static discharge, is a deadly occurrence in areas where sensitive devices are present.
Most people think of lightning or shocks when dragging feet on some carpet, when they hear static electricity. These events are on the 1000-1 Million+ volt scale, compared to 100-1000 volt events that happen all the time. An ESD event of 100 or so volts is not noticeable, but it can damage some components.
What causes an ESD event?
A tribo-electric charge is generated when two materials are rubbed together. Friction between the two pieces causes electrons to be rubbed off of one material and onto the other material. This creates a “high potential” energy field and a “low potential” energy field. As with lightning, the difference in potential has to be equalized.
When the high-potential field sees a way to shed some electrons,
it dumps them. This happens sometimes through your finger when you
grab that doorknob, or sometimes through a circuit board if you’re
holding it. When working with electronic devices, we have to use
static safe materials to prevent deadly discharges.
The two types of ESD safe materials on the market are conductive and dissipative.
Conductive materials have a resistance range of less than 10^5 ohms/sq. Dissipative materials have a resistance range of 10^6 ohms/sq to 10^10 ohms/sq. This means that conductive materials move the high potential electrons to ground very quickly, while dissipative materials slowly (but surely) drain any possible charges to ground.
You wouldn’t want conductive materials holding your board while you dragged it across the floor, you’d want dissipative. A quick discharge from the “carrier” would still jolt the board if it was in the drain path. You’d also want dissipative materials on a worktop where you’d solder or lay a device to physically work on. A jolt to ground from the worktop would ruin what you’re trying to fix!
So…How do I ground myself when I’m overclocking my parts?
Get a wrist strap!
Ground yourself before you get near that part. That way, all charges are drained to ground safely before, during, and after you’ve touched the device. But how do I actually GROUND myself?
Well…there’s several ways to establish an *earth* ground. Leave the PC power supply plugged in and clip your wrist strap to the metal case. This only makes *you* safe, not any parts you remove and lay on the *gasp* carpet. What if I’m taking out the Mobo? You’ll need a ground from the *grounded* power outlet. This is a bit more tricky.
If you aren’t confident around 120V or 220V AC, then you might want to invest in an Ideal ground tester/connector. It tests for a proper earth ground and also has a banana jack on the top for easy connection. If you know about AC wiring in your region, open up the outlet box. Check and see if there is a ground wire connected to the socket module.
If there is, you can use the cover plate screw as a ground terminal. Wrap some 18GA or 20GA wire around the screw and tighten it up (make sure you take it back off if the socket will be used – you don’t want a fire!). The best way to test for a ground is with a multi-meter. Check the black(hot) wire against the point you plan on grounding to. You should see voltage and amperage on the meter.
Once you have a good ground, set up a workstation with a dissipative work mat and a wrist strap. Most work station kits come with a grounding block that snaps onto the mat. This block has a ground cord which you’d connect directly to the earth ground. Now, you have a safe work area to place RAM, Mobo’s, chips, whatever.
You still can’t touch anything though!
Strap on a wrist strap and plug it into the grounding block on the mat. Now, *you* are grounded along with the work mat. ESD has no chance at getting to your components now. Get to work!
Visit All-Spec for a complete line of ESD equipment.
NOTE: I assume no responsibility for typographical errors or damage caused by use or misuse of information contained in this article. Electricity is no joke. I prefer that someone certified in electrical installation help you set up a ground to your workstation. Not only is tinkering with pre-inspected AC circuits dangerous, but it can also be unlawful. Check local electrical codes before attempting anything on your own.
Be the first to comment