[Elecraft] ESD prevention

[David Wilburn]

When you walk across carpet in the winter, and touch a door handle and 
generate a spark, you are producing in excess of 3000 volts.  It takes 
significantly less than that to damage many silicon circuit elements. 
The damage can be done without and indication of the event.

A ground strap with a built in mega-ohm resistor provides a path to 
ground for the charges that build up on your body.  If you have an EDS 
mat, that is grounded (to home electrical ground) that is even better. 
I tend to work on a wood service, and wear an anti-static strap that is 
connected to a computer chassis, or the earth ground coming into my shack.

You have to be aware of areas where you lay the card, how you hold the 
card when you walk with it, and where you work on the card.  Most the 
time I have the card laying on something, I have it laying on the black 
ESD foam pieces that come with the kits.

Do not take the chips off of these foam pieces and put in plastic boxes 
(unless they are ESD rated boxes).  I leave my chips on the foam, inside 
the ESD bags (the ESD protection is on the inside of the bags, not the 
outside) until I use all the items.  My control boards and front panel, 
when I am not using them, stay in their ESD bags and in a box.

No floating allowed.  You should be grounded, to bleed off any charge 
that happens to build up on you.  In the Elecraft manual, it tells you 
to touch a ground before doing certain work.  This assumes you are 
sitting still, and not generating any charges.  A somewhat safe 
assumption, but not always the case, depending on what you are wearing, 
what you are sitting on, and other factors.

I have not heard of connecting the ESD mat to carpet.  The ESD mat needs 
to be connected to a ground.  I don't have a call to go by, so I don't 
know what to tell you considering you house electrical ground.  In the 
US it is the third prong below the other two, you can also connect a 
small wire to the screw that holds the electrical cover plate on the 
outlet, as this is grounded.

All of this is worth verifying at least once with a meter and 
periodically depending on how much work you do in this environment.  I 
hope I have cleared it up a bit, and not added too many other questions.

David Wilburn
dave.wilburn at verizon.net



RC wrote:
> Hi Gang
> I am slightly confused! When using ESD protective measures you should use:
> 1) a wrist strap connected to
> 2) an anti-static mat.
> 3)You should build/work on the anti-static mat to be certain that all 
> components (and you)are at the same electrical potential there by 
> minimizing any ESD damage.
> 4)should you connect the anti-static mat to the carpet with a long clip 
> lead?
> 5)or house electrical ground?
> 6)or should the mat/yourself/components voltage FLOAT at the same 
> potential.
> OF the several Elecraft kits I've built I don't believe that I've had 
> any ESD damage by using steps 1,2,3 & 6.
> I'll soon be starting a KX1 tribander which I believe is more sensitive 
> to ESD and my new seniors residence has carpet instead of a concrete 
> slab/tile floor
> RC
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