ESD prevention

[RC-16]

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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[michael taylor-3]

On 2/15/07, RC <[hidden email]> 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?

While I don't know if the KX1 is more sensitive to electrostatic
damage, as far as I do know your anti-static wrist strap and/or mat
should be tied to earth or AC mains ground via a 1-Megaohm or higher
resistor (to prevent a shock risk). Some wrist straps and mats have a
resistor built into the cable for this purpose. You can check with
your DMM / VOM.

I believe this connection via the resistor essentially "drains" the
static voltage to ground.

-Michael Taylor, VE3TIX
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[dave.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
[hidden email]



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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> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>

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[Ron D'Eau Claire-2]

RC asked:

> 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?

-------------------------------------------------

Here's the scoop from the KX1 manual. It's typical of the Elecraft manuals:

Preventing Electro-Static Discharge Damage

Problems caused by Electro-Static Discharge (ESD) may be very
difficult to troubleshoot because damaged components may still
operate somewhat rather than fail completely. We strongly recommend
you take the following anti-static precautions (listed in order of
importance) to avoid trouble:

. Leave ESD-sensitive parts in their anti-static packaging until
you install them. The packaging may be a special plastic bag
or the component's leads may be inserted in conductive foam.
Parts which are especially ESD-sensitive are identified in the
parts list and in the assembly procedures.

. Wear a conductive wrist strap with a series 1 megohm
resistor. If you do not have a wrist strap, touch a ground
briefly before touching any sensitive parts to discharge your
body. Do this frequently while you are working. You can
collect a destructive static charge on your body just sitting at
the work bench. DO NOT attach a ground directly to
yourself as this poses a serious shock hazard.

. Make sure your soldering iron is ESD-safe and has a
grounded tip

. Use a grounded anti-static mat on your work bench.

------------------------------------------

"Grounded" means connected to ground. The mains ground is normally used for
this. In general it's a bad idea to have a ground connection separated from
the mains ground. (In many places it's a violation of the electrical codes.)
It *is* a good idea to make sure your mains grounds are connected! A very
simple tester is available in almost any hardware store that plugs into an
outlet. It tells you if the mains hot and neutral are connected to the right
sides of the outlet and whether the ground is connected. It's rather
astonishing to me (and un-nerving) just how many outlets in new homes and
recently re-wired homes have no ground connection at all!

Your carpet is not conductive. That's why you can develop a huge static
charge on it. Connecting a wire to it won't do much. The idea of the wrist
strap is to bleed off any charge you do accumulate so that even if you have
a 'killer' carpet in the room, your body will be safely at ground potential
when you touch the ESD-sensitive parts. You can accomplish this just as well
without a wrist strap by briefly touching a known good, unpainted ground
before touching the parts, but be aware of the warning to do this
*frequently*. Squirming around on a cloth seat or sliding our foot on the
floor can produce a killer static charge in an moment, so keep touching that
ground before picking up each part.

Finally, be aware that it's not just individual parts that need protection.
Normally parts in a circuit will have a dc path to ground through resistors,
coils and other components that protects them from most ESD dangers but,
when you pull a board out of the rig, some circuits are opened by
disconnecting the cables and connectors. It's rare to damage the assembled
rig unless there's a huge pulse such as a near strike by lightning, but
individual boards should be treated with the same respect you'd give the
most sensitive individual component.

Ron AC7AC

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