[Elecraft] potential of static damage

[Wallace, Andy]

> -----Original Message-----
> From: Ron D'Eau Claire [mailto:rondec@easystreet.com]
> 
> Still, I do not bother with one in my shop and don't have any trouble.
> Being "careful" as you said works for me. I DO use a grounded-tip
> soldering iron and I DO ground myself momentarily EVERY time before I
> pick up a static-sensitive device. 

Electrostatic Damage is like the Easter Bunny: some people believe
in it, some do not. 

Radio Shack has wrist straps for $5, which is something anyone building
an Elecraft should get. Unfortunately, they only seem to sell mats
in a service kit at $25. Perhaps an inexpensive mat and strap would
be something good to add at the Elecraft order page? An idea anyway.

Damage occurs because of potential differences. If the J310 is charged
to 300V and you're at 0V because you're grounded, when you pick
the part up, the discharge happens anyway. It doesn't matter
if you're high and the part is grounded or vice versa. 

But the thing to remember is that you don't have to feel or see a spark
to do damage. Some solid state parts can be damaged at less than 50V.

The damage is cumulative. Many small "hits" can kill a part in stages.
And it can be latent, too -- the part may fail much later, or die
in weird ways, causing troubleshooting headaches. 

Motion is what causes static, generally -- walking, getting up
from a chair, ruffling sheets of paper, pulling tape off a roll, etc.

Ground straps should have a 1 Megohm resistor in the cord. This allows
you to be safe - you're not tied directly to ground in case you touch
some voltage, and the 1M bleeds off static discharge slowly.

I've seen ESD films where they charge someone up to a controlled 
voltage and then have him touch a FET. The FET is in circuit and 
attached to a curve tracer oscilloscope. You can actually see the 
"knee" get worse and worse with each hit. They also showed electron
microscope shots of damaged parts -- the static discharge just blasts
through the fragile silicon.

The good news is, manufacturers DO design parts to minimize ESD risks
if possible. The fact that thousands of Elecraft rigs are working fine
says things are PROBABLY not a huge risk with the home builder. 

My recommendation would be to get a strap, and get a mat if you can.
They only work if they are grounded... Keep styrofoam cups and as
much paper as possible away from the transistors/FETs/ICs. When I
open a kit I stick any loose transistors into the black conductive foam.
It helps with inventory, too. Don't wear static-generating sweaters, etc.
Handle circuit boards by the edges. If you've bought cards for your PC,
save the silver anti-static bags and put your boards-in-progress inside
and fold over the opening when cleaning up for the day. 

Anyway, there are some tips. I generally try to be careful at home, because
the stockroom is not close by. :-)

Andy