ESD

[Mercutio]

One of the students in the A+ class I'm teaching at the moment suggested that I might be just a touch too cavalier about ESD. He does some kind of electronics work, so I suppose he may be right but at the same time, I can honestly say I've never out-and-out killed any PC hardware via static.

Basically my standard precaution is to ground myself somehow before I start working inside a case. Most often, the metal of the chassis is the best available candidate.

I know that static can cause damage that often lead to intermittant failures or a problem down the road but, again, the machines I build and sell tend to be pretty damn reliable.

So... am I not taking things seriously, or is ESD really not that big a deal?

 

[Tea]

I could have made the exact same post. I will be interested to see what answers pop up.

 

[Clocker]

Nothing of interest here. I've built about 20 systems or so ( can't compare to how many you have built) and I've never run into any problems I could blame on ESD. Of course, I don't hold anything by the electrical contacts and drag my feet across the carpet, either.

C

 

[Buck]

Electro-Static Discharge is a big deal. Your body is an excellent conductor of electricity because of the high water and salt content (pure water is an insulator, not a conductor). As we create friction, free electrons are just itching to leave our body. Once that moment arises, they leave at an enormously high rate of speed. Depending on the amount of electrons leaving your body, you can easily discharge 20,000 Volts (usually the zaps that you feel; smaller amounts are discharged without you even knowing) and one time. Having that surge of electricity on any circuit designed for 5 or 12 Volts is never a good idea.

Having worked with different computer component manufactures, I’ve seen the high product failures resulting from ESD issues. Besides mis-handling (dropping, banging), ESD is one of the top reasons for component failure.

Nevertheless, most people take this subject rather lightly because immediate destruction is rare. Grounding yourself to the case of a system (metal to skin contact) with the system plugged in (earth ground connectivity) is one of the easiest ways to minimize ESD damage.

 

[P5-133XL]

I think ESD is a really big deal. My observation is that stuff that I built without paying attention to ESD had much shorter lifespans and a high return rate 6 months+ from building. before instituting the controls, I was getting around a 35% return rate for some HW failure within a year. After I instituted ESD controlls the reliability of the stuff sky-rocketed. After the ESD controlls, it is signifigently less than 5%: I don't keep track anymore because it isn't very common.

I don't think I can ever identify a specific ESD event that actually destroyed equipment either. That does not surprise me though because ESD does damage at a voltage level that there are no sparks of other detectable events. I do note that the risk of ESD damage varies alot depending upon the geographical local and how much humidity is in the air: High humidity prevents static from building-up.

In my shop I actually did alot to control ESD. I put in a humidifier. replaced all my tables with metal tables and grounded them. Because I didn't like working on the metal, I covered the tables with Anti-ESD padding too. Then I permanently attached multiple wrist straps to the tables and then tried to apply some discipline and actually use them. It wasn't really very expensive and what I gained were far fewer long-term returns. I actually encourage others to do the same.

I can understand a technician point of view that they needn't bother because they've not seen the damage that ESD causes. However, ESD damage occurs, is cumulative, and often destroys the equipment: just not necessarily immediately. Also, they may be in an area with high humidity and theyby have a natural immunity to ESD. thus they don't associate their behavior to returns and even when the return occurs one can't easily trace the failure to an ESD event. All I can say is the reliability of my HW went up drasticly upon instituting ESD controls during the building of my computers.

 

[flagreen]

We don't have that much of problem given the climate here in Florida. Or is ESD present even though you can't feel it?

 

[Mercutio]

Well, the standard as I hear it is...

2000 volts is enough to feel - a good jolt.
200 volts is enough to see arc if it's really dim (some people can feel charges this small, but if you've ever felt 110VAC you realize it takes a second to actually sense the shock).
20 volts is enough to cause some damage to electronics.

It's pretty common to build up a 1000 volt charge just walking across 20 feet of carpet.

So yes, it's there. You don't feel it.

 

[Cliptin]

High humidity prevents static from building-up.

Odd. I was just noticing how the incidences of me shocking myself on my car has gone up drasticly since the hot weather hit. Humidity comes with the hot weather.

The only incidence of SSD damageing equipement that I am aware of is the case where a friend of mine grasped the top of the car door while exiting the vehicle and shocked himself. He also nuked the Palm he was holding in the same hand.

 

[Clocker]

High humidity prevents static from building-up.

Odd. I was just noticing how the incidences of me shocking myself on my car has gone up drasticly since the hot weather hit. Humidity comes with the hot weather.

The only incidence of SSD damageing equipement that I am aware of is the case where a friend of mine grasped the top of the car door while exiting the vehicle and shocked himself. He also nuked the Palm he was holding in the same hand.

Are you running your air conditioning in the car? It not only cools the air but dehumidifies it.

C

 

[Mercutio]

Do remember that a car is basically building up a big ol' static charge just in the change of potential between tires and pavement while it's rolling around. People zap themselves all the time getting in and out of cars.

As I understand things, cool, dry environments are worst for ESD. I hear ESD problems are worse in Arizona than Indiana. Maybe because they run air conditioning all the time?

 

[Handruin]

I noticed since purchasing my car that having leather seats has reduce the number of zaps I get when exiting my car. I used to get them all the time, now I never do...

 

[time]

Mmmmm, leather ...


Some people are more susceptible than others, but clothing and floor coverings have a lot to do with it. Basically, anything synthetic is ESD poison, and unfortunately that's increasingly common.

Hence leather seats, wool carpets and cotton clothing minimize static electricity buildup. I've seen suppliers with bare concrete slab floors take a few liberties, but they're at much lower risk to start with.

I don't wear a wrist strap any more, but that would get one fired from some places who very probably know better. But I do ensure I regularly ground myself on earthed equipment or whatever is available. Especially before handling a component after carrying it across the room.

I think Mark's approach is best.

 

[GIANT]

Electrostatic discharge used to be a hell of a problem for handling CMOS electronics back in the late 1970s and early 80s. When one was handling newfangled CMOS devices back then, you never *ever* walked around with a CMOS device in your bare hand -- it was that bad. Of course, this would have been inside a building that was air conditioned or heated, so the relative humidity was low (40% ~ 50%).

Expensive (then) CMOS devices always stayed inside their anti-static tubes until it was time to mount them into PCB for soldering or into sockets. At that point, you would already have your ground strap on your wrist and likely working on an anti-static mat. This is still the practice at any decent manufacturing facility that is working with CMOS devices, even though modern CMOS can take voltage transients better than CMOS circa 1979.

 

[Buck]

As I understand things, cool, dry environments are worst for ESD. I hear ESD problems are worse in Arizona than Indiana. Maybe because they run air conditioning all the time?

Yes Mercutio, dry air is bad. They get especially bad around my area in the fall when we get particular weather systems that blow in hot air from the desert and drop our humidity down to 20% or less. You can put a sheet of paper on the desk and watch it curl as the humidity slowly leaves. There is usually a high rate of return during this time in my area.

 

[Fushigi]

I normally use a wrist strap that I clip to the PC case. However, the PC itself is usually unplugged since ATX supplies some mobo power even when it's turned off. I suppose it's sort-of grounded because a charge could travel from the case to the mobo to the AGP card up to the monitor and through it to it's power plug, which stays plugged in.

I generally don't take parts out of the anti-static bag until I'm ready to use them and don't walk around with them.

Beyond that, though, I can't say I take too many other precautions. I mostly work on carpeted areas and my chair mat is not grounded. And, the obvious, I try not to handle stuff by the connectors & exposed metal bits (unless it's a drive).

Cars .. Yeah, I rarely shick myself with the leather in my car, but will get hit all the time in my wife's car, which has cloth seats. My old Mazda had a neat feature on the door: a little plastic button that said "Touch". Touch it before getting out and your static buildup was drained away; no shocks. Too bad that car needed a new AT every 36K miles...

- Fushigi

 

[GIANT]

...My old Mazda had a neat feature on the door: a little plastic button that said "Touch". Touch it before getting out and your static buildup was drained away; no shocks. Too bad that car needed a new AT every 36K miles...

You can add electrostatic discharge capability to any motorcar, by attaching a discharge strap to the undercarriage. The discharge strap is simply a strip of heavy rubber with a heavy aluminum wire conductor embedded inside. The discharge strap drags along the surface of the roadway as you drive, sending static electrical buildup to earth ground. The best place to attach this discharge strap is at some point roughly in the middle of the undercarriage so that it is not particularly visible. They will usually last about a year or so of driving. The aluminum wire does not make sparks and is not scoured away by friction because the fairly hard rubber that surrounds the wire takes most of the wear