[Elecraft] potential of static damage

Don Brown [email protected]
Fri Mar 14 08:15:01 2003


Hi

Although static is not usually a problem in my lab/shack because of the
concrete floor and high humidity in East Texas I am still careful about
handling electronic parts. One handy way I deal with it is I have mounted a
aluminum yard stick to the front edge of my work bench and connected it to
ground through a 1 meg resistor. This makes it easy to touch a ground before
handling any sensitive parts. The yard stick is also useful for measuring
wire for toroids. A wrist strap and mat is still the best but this was
worked for me.

Don Brown
KD5NDB


----- Original Message -----
From: "Wallace, Andy" <[email protected]>
To: <[email protected]>; <[email protected]>
Sent: Friday, March 14, 2003 6:55 AM
Subject: [Elecraft] potential of static damage


> > -----Original Message-----
> > From: Ron D'Eau Claire [mailto:[email protected]]
> >
> > 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
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