Hi Dean,

After spending 20 years in the semiconductor industry (including FAB and
Probe & Test), I think that I can consider myself a bit of an ESD expert.

I think that the confusion here is being caused by the term "grounding".  In
this case, the term is not really being used properly (or maybe it's more
accurate to say that it is not being applied properly).  Grounding is
required when the potential of some part of an electronic or electrical
circuit must be set at the same potential as the planet Earth.  This is
accomplished simply by connecting (or "grounding") that part of the circuit
or component to the planet through a conductive piece of material with a
resistance of less than 1 ohm.

When dealing with ESD, the concern is not with the grounding of any element.
The concern is with maintaining anything that will touch, or anything that
will come close to each other, at the same electrostatic potential.  If you
are grounded through a wrist strap, and your case is sitting at a potential
of 5KV due to electrostatic build-up, then grounding is actually a bad thing
since you will definitely draw an arc as soon as you get close enough to the
case.  So, the focus here is to maintain all elements that come in contact
at the same potential:

Connect your wrist strap to the object that you are working on.  In the case
of a computer, clip the strap to a bare piece of metal that is part of the
case.  If you have a number of objects that you are working on (e.g. a hard
drive that is to be mounted in the case, new memory, etc.), then place all
objects on a conductive mat and connect your wrist strap to the mat.  It is
NOT necessary to ground any part of this setup.  Remember that the object is
simply to bring all elements to the same potential.  We never recommend
using any part of a live circuit (including house wiring) for any purpose
other than providing power to an electrical instrument or appliance.  NEVER
connect a living thing to your house wiring.  This includes the cat, the
fish, the canary and, oh yes, YOU!  If you require a ground reference,
install a separate ground bus that is not part of, or near, your house
wiring.  NEVER remove, install or replace components on a device that is
connected to a source of power (i.e. ALWAYS unplug the power supply before
doing any component work).

Follow these simple rules and you and your components will live to see
another day.

Regards,
Steve Collins
AlternateRealities - High Performance Computers, Clusters and
Infrastructures
Phone: (819)669-8885
Fax: (819)669-8887
e-mail: [log in to unmask]
URL: http://www.AlternateRealities.ca


> -----Original Message-----
> From: PCBUILD - Personal Computer Hardware discussion List
> [mailto:[log in to unmask]] On Behalf Of Dean Kukral
> Sent: Thursday, January 01, 2004 9:45 AM
> To: [log in to unmask]
> Subject: [PCBUILD] Grounding yourself; Was: Adding memory -
> grounding yourself
>
> What if you have a faulty device in your house with a short
> (fault) to ground?  It is **possible** for the ground wire to
> be hot, isn't it?  I know it is not likely, and even if you
> got shocked, it would not likely be serious, but for the
> average guy who works on his computer only now and then, I
> think that a wrist strap connected to the case is the better choice.
> The problem is ESD.  On a case with many sharp corners and
> edges, electrostatic charge is quickly dissipated.
>
> Are there any electricians out there who can tell us if I am
> being anal about this?
>
> Dean Kukral

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