1,000 opinions on ESD!!!!

[Ian.M]

I fixed that for you:

Of course the traditional unpainted wooden pencil could have been designed for ESD safe environments - a resistive core and static dissipative outer.    Just don't break the lead.

Once its coated with a manufacturer's lacquer or varnish finish you risk undesirable triboelectric effects.

[KL27x]

Correction. After you paint it with the most tribolectric material possible, you spray it with conductive ESD-spray and sell it as ESD-pencil. Bare wood is natural, which you cannot call ESD-safe; that would just be a marketing ploy.

Before I retired, I worked with high value product where the consequence of failures was enormous.  Just about every ESD precaution you can think of was employed.

Yes, there is a time and place. I do not question all ESD safety practices. But I suspect some [products/practices/wisdom] are borderline questionable benefit, even where it does matter. General understanding maybe not 100% as straightforward to the general population or even to me. I just see some ideas out there and my own puny brain does not connect all the dots to know what the hell is the purpose. I suspect some of the generally accepted knowledge just might be misapplied or taken too far and/or used out of context. Since I don't have the tools to investigate, directly, I just speculate. When I find a dead FET taken from a metal container, I will be sure to make a post on this awesome forum.

ESD mat to protect from a wood bench and metal containers are two of the things I am not particularly impressed about. Maybe I'm dumb and won't know the sky is falling until I can either understand why it is falling or when it hits me on the head.

[Ian.M]

Freshly oven dried wood is an insulator.   Wood at a typical equilibrium moisture content to the air of 10% - 12% typically has a bulk resistivity of 10^10 Ohms/cm or less, which would put it at the upper end of the dissipative materials range.  If your building is air conditioned or you are in a desert climate, you'd better soak your pencils in calcium chloride solution for a week then rinse and air dry to decrease their bulk resistivity.

[KL27x]

Hehe.

I just had a thought. Yeah, that is rare for me.

Metal box has capacitance, and that is bad, right? If I solder a small value (smaller than gate capacitance) capacitor to one or other leg of a FET, is it more prone to ESD damage, now? The capacitance is in series with the gate. So the capacitance goes down, not up. And the voltage goes up? I mean, treating the FET gate as a capacitor.

Now I'm just confusing myself more, lol. And now I wonder if I can increase the max voltage and/or reduce the total capacitance of a FET gate by adding a series capacitor.

*Now I'm also wondering about what mike said. Grounded through 1megaohm resistor, the box can be dangerous through capacitance. The significant aside, I am now wondering if it deosn't makes a difference what metal. For instance, if human body has positive triboelectric effect, and aluminum has positive triboelectric effect, than aluminum cannot cause damage when it is so grounded. Or steel, which is close to zero. But maybe brass, going the other way (copper? who knows... it's a main alloying element in brass) can have some possible effect? Does any of this bare metal problem start sounding sorta trivial, to anyone else but me? (Of course when I saw trivial, this is assuming your bench is not made of bare metal, itself).

[Ian.M]

Sounds like a good way of FUBARing it.  Without a DC leakage path to the drain, any stray charge (e.g. from moving air) on the gate and your added cap will build up and shift the bias point.  Whichever way it shifts, the result is likely to be silicon shrapnel as not turning fully on is just as bad as not turning fully off.

[CatalinaWOW]

I suspect some [products/practices/wisdom] are borderline questionable benefit, even where it does matter.

I agree.  The various practices don't all have equal value.  And often the value lies more in the area of psychology than in physics.  The ritual of daily checking continuity of wrist-straps (or checking the continuity indicator on a continuous monitoring wrist strap each time you touch hardware) is a continual reminder of what can go wrong. Even though in many cases years passed between an observed failure other than forgetting to put the wrist strap on.  Same applies to other things like the anti-static ball point pen.

The problems are real though.  I used to plot product yield vs outdoor absolute humidity and see substantial correlation before appropriate indoor humidity control was installed.  There are many other examples that I and others here could provide.

[KL27x]

^ no doubt, they are real. When you consider the number of active semiconductors in a modern computer, it makes me wonder how many failed boards go in the trash heap to produce 100 working units.

The ritual of daily checking continuity of wrist-straps (or checking the continuity indicator on a continuous monitoring wrist strap each time you touch hardware) is a continual reminder of what can go wrong.

This reminds me of something I read about eastern pottery. Korean potters were at one time reknowned for a form of pottery that had a distinct greenish color. To produce this, the pottery had to be held to +- something like 15 degrees Celcius for a period of over 20 hours. Mind you this is somewhere in the 12th century AD, so this was something of a difficult feat. It was believed that this pottery could only be produced in times of peace and economic stability and spiritual harmony of the workers.

The culture of ESD is undoubtedly important to manufacturers of complex devices. W/e it takes to improve the yield and bottom line. I think some hobbyists cross that bridge just for the sake of crossing it, without having a destination on the other side.