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How Serious is Static Electricity?
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?"
I worked for many years as a contractor at a large US-based defense company. They make lots of neat useful things, and some nasty things.
One thing was always stressed, in the hardware departments, in the software departments, in the finance departments, wherever. If you go into a lab, you must have ESD training. At least 3 levels of training existed. Level 1 was little more than awareness training. If something had an ESD warning label, stay clear of it. Don't touch. Etc. Why? The training also emphasized the costs associated with ESD damage to components. A great deal of effort was spent making sure that we all understood that ESD damage to components might not be visible or even detectable at test / QA time, HOWEVER, in the field, the defect rate over time was dramatically lower when ESD controls were in place on the assembly and test / QA lines. This was serious stuff, the examples ranged from deployed PCs going inop after years of reliable service up to air-to-air missiles not functioning due to static damage. In the end, a very large sum of money was spent investigating the effects of ESD on the reliability of components in the field and it was determined that the benefits far out paced the costs of training everyone and taking precautions in the labs.
I now work somewhere much smaller and have a really hard time getting people to believe that ESD is real. I even had to fight a bit to ESD mats at the workstations where we do assembly.
There are a lot of myths and misperceptions surrounding ESD incidents, and I think that people would be well served by understanding that damange to electronic devices is not either fatal or non-fatal. A FET device might have it's gate region severely weakened by an ESD incident, but it would appear to function normally for an extended period of time. Perhaps the thermal efficiency has been compromised because the gate has partially broken down. The added thermal stress on the part over time will lead to early failure. The reason, naively, would look like a bum part or a thermal problem. The ESD problems don't always reach out and slap you across the face with a sign that says: "Zapped by poor assembly / handling techniques".