Getting bent (ON topic if not thread)

From: Thorhallur Ragnarsson <thorh_at_ismennt.is>
Date: Sun Mar 15 19:46:51 1998

At 07:26 15.03.1998 PST, Max Eskin wrote:

>Actually, I find most precautions such as anti-static and so forth to
>be baloney.......

No, unfortunately this can be a real problem, some years ago when working
as test engineer for DNG Electronics, we suddenly had skyrocketing failure
rates in assembly of equipment containing CMOS logic. Everybody involved
was grounded with a 1Mohm wrist strap so this was quite a mystery until we
noticed that when carrying the boards from the test bench to the final
assembly, the lead from the strap was too short and the carrier had to
disconnect it for the 6 feet trip across the floor, this zapped approx. 30%
of the boards. His shoes must have been something!!

>...................... When I was upgrading RAM in the machines in
>my school's MacLab, the person in charge of it constantly looked over
>my shoulder and bleated, "Touch the case again, Max. I want to SEE you
>touch the case. OK, now gently, gently, now. Oooh! Yeesh! DON'T touch
>those chips!",etc.etc. I didn't damage anything, ......

Well, we have no way of knowing that. Static damage may just weaken the
chips so they fail later.

>.............. but he thinks there
>is a problem even with touching the actual plastic case of the chip.

That may also be a problem, the _voltages_ involved can be very high, in
fact several kV, so the sparks jump easily 1/4-1/2" across insulated
surfaces. When handling small items like SIMM?s or DIMM?s the _current_ in
the discharge is way below what we normally can feel or see, so one tends
to think no harm is done, but we have no way of knowing.

>I don't discharge static all over chips, mind you, I just think most
>precautions are waay overblown. Or have I just been lucky?

Yes, I hope we are lucky. I do not normally wear an antistatic wrist strap,
I just try to wear cotton clothes, "touch the case" often and avoid rubbing
against all those synthetic surfaces (table, chair, carpet etc.).
When dealing with old equipment I try to be even more careful as it may be
more static sensitive and spares harder to find.

??rhallur.

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Thorhallur Ragnarsson Electronics Technician
Bjarmastig 1 Verkmenntaskolinn Akureyri
IS-600 AKUREYRI Box 280
Iceland IS-602 AKUREYRI
E-Mail: thorh_at_ismennt.is Iceland
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Received on Sun Mar 15 1998 - 19:46:51 GMT