How Serious is Static Electricity? 95
seanadams.com asks: "My company is considering the purchase of a small surface-mount assembly line so we can do our manufacturing in-house, and the issue of static control has come up. We've all been told to take ESD precautions when handling electronics, but how much precaution is enough? Obviously we plan to do the easy stuff like making sure that equipment and work surfaces are properly grounded. However, many shops go even further - conductive shoe straps, wrist staps, special flooring, humidity control, etc. The SMT equipment vendor says that it's unnecessary, and I would tend to agree. I've handled tons of electronics over the years and have never been able to attribute a single failure to ESD damage. Granted, Silicon Valley is a fairly humid area so that may be a contributing factor. Has the ESD threat been blown way of proportion by the guys who sell those little grey bags?"
Explanation of failure (Score:5, Interesting)
Just a note here... unless you can actually explain, with 100% certainty (or something close to it) the causes of all the other hardware failures, then you can't say for certain that any of the failures that you have observed are due to damage done from ESD. Just because a failing component doesn't sit up and shout "you shocked me with static three months ago and now I'm on my death bed" doesn't mean that a damaging static discharge didn't occur.
Additionally, note that what might be explained at a higher level as the failing of a certain component doesn't mean that the root cause wasn't a static discharge. Moreover, what if there was a ESD that you didn't notice. Just because you don't see a spark or feel one, it doesn't mean that there wasn't an ESD.
just some thoughts... -tcp
If anything, it's gotten more serious (Score:2, Interesting)
The bottom line is potential differences (Score:4, Interesting)
This means, in practice, that there must be a conductive, resistive path between them prior to this happening.
This is easiest to achieve if you just connect everything together, the wrist straps, the conductive shoes, the whole 9 yards.
For example of what can happen. I have a component in my hand- but that's fine, I have my strap on, and the component is at the same voltage as me. I take off my strap with the component in my hand, and walk across the floor and touch someone on the shoulder with my other hand.
Zap! That component is now toast! The problem is that myself and the component built up a few thousand volts when I walked across the floor, and the person I touched instantly discharged me, and a large current came out of the component too... 90% of such components work for a while before failing.
You don't have to have all of these gadgets, but if you don't; you have to move very deliberately, and even then you can screw up sometimes.
Re:ESD is a real problem (Score:3, Interesting)
But it's unlikely that the shock did absolutely no damage. Shocks don't necessarily destroy electronics completely. But severely reduced lifetime and sporadic malfunctions are not desirable either. On the contrary, these are hard to detect and therefore even more problematic.
Everybody who thinks "I'm always touching the circuit board of my PCI cards when I install them and I'm never grounded" should think again: The traces on the board are covered by a protective coat. In assembly, raw and unprotected electronic devices are much more at risk of being negatively impacted by electric shock.
Well as an IO designer (Score:2, Interesting)
If your setting up a production line that will move a lot of material it only makes sense to take precautions.
Real-world ESD precautions (Score:4, Interesting)
The floors have conductive particles embedded in them, all employees are required to wear either two ESD sole straps or take advantage of the conductive-sole shoe discount program. In addition, all employees venturing onto the production floor are required to wear an ESD smock. All handling equipment is grounded, conductive rubber used for conveyors, and many transport mechanisms are wire brush rollers. The environment is rigidly temperature and humidity controlled.
It's easy to develop huge static potentials when you have equipment running for a long time. Look at devices intended to generate high voltage static electricity: Wimshurst generators, Van de Graaf generators, etc work with simple components such as a rubber belt or rotating disk. Even dropping components can generate electricity; one high voltage generator works by dripping water from two tin cans.
Since the effects of static electricity may not show up until later, when the operating limits of a gate or two are much lower than necessary, it makes no sense to manufacture any electronic devices without rudimentary ESD protection.
Humidity is the cheapest answer. (Score:3, Interesting)
We tried conductive floor materials, jumpering all the machines in the room together, stringing tinsel across all the paper trays, etc. etc. etc. ad nauseum but we kept frying motherboards every time a jumper wire slipped off or a floor mat got insulated by shoe crud.
Eventually I put a bunch of spider plants in the room and watered them every day. Humidity in the room went up to a reasonable level immediately from aspiration of water through the plant leaves.
Never burnt a single board after that. The plants were still on the job five years later when I visited the site again.