It depends. (Thanks, Doug).

If your ESD program has all 6 major components working:

1. All personnel inside the ESD zone are grounded with either ESD shoes
or wristrap, and a smock with conductive elastic sleeves to transfer
charge from clothing to ground through the operator. 
2. ESD flooring is in place, tested quarterly. 
3. All benches and worksurfaces are properly grounded (individually
where possible, no daisy chains), Faraday cages are used for sensitive
components, etc. 
4. Environmental controls are in place for humidity. 
5. You have an ESD training program in place and all of the personnel
are trained and certified. 
6. All of the above is checked and documented on a regular basis.

Then there is not so much danger if an operator's footstrap fails. The
other 5 components of the ESD program will help ensure that no damage is
done to the hardware as a result.

But why throw something like not testing footstraps in front of you to
stumble over? It does not cost anything to require personnel to re-test
upon re-entry. 

A better solution is to forget about the footstraps and require ESD
shoes. Operators often wear footstraps home and forget them, and they do
not last very long. Replacement of ESD footstraps can become more costly
over time than providing the operator some type of allowance towards ESD
shoes once every two years or so. The shoe data shows better results
than the footstraps.
 
A comprehensive 6-component program is the basis for not having to worry
if a single bench is found to have a broken ground wire, or a single
operator was found to be carrying an ESD device with a footstrap loose,
or whatever. It is also the basis for not having to perform segregation
and analysis of any hardware that may have come in contact with the
ungrounded bench or operator during the time it was technically not
grounded. If one or more of the components is missing (no ESD flooring,
for example), then strict compliance to items such as how often the
footstrap should be tested becomes much more important.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Joseph E (US
SSA)
Sent: Tuesday, March 07, 2006 5:06 PM
To: [log in to unmask]
Subject: [TN] ESD Heel Strap Testing

I'm trying to get an idea about industry practice, how often heel strap
testing is performed.

An outside auditor has questioned our practice of testing heel straps
just once a day.  Operators wear a strap on each foot, and test each
individually.  We require operators to remove the straps if they leave
the building, but we don't require them to retest when they put them
back on, and there lies the objection.

Our position is that the primary purpose of testing is to verify the
integrity of the equipment, to make sure that the straps haven't worn
out.  It does matter how the straps are put on, but in our experience,
operators usually get it right, and we don't see a lot of failures when
footwear is tested.  Of course, most of our people wear conductive
shoes, not heel straps.

We operate to MIL-STD-1686 and ESD S20.20, which do not speak to this
issue, so what we have is a difference of opinion.
I've seen shops that require testing every time a heel strap or wrist
strap is put on, and this is certainly defensible.  But I think there
should also be some tolerance for considerations of practicality and
general effectiveness of the ESD program.

Any comments?

Joe Kane
BAE Systems
Johnson City, NY

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