RE: [SI-LIST] : ESD Smocks

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From: Paul Taddonio (ptaddoni@nortelnetworks.com)
Date: Wed Dec 20 2000 - 08:43:56 PST


I can see that. I suppose at some locations you have to wear a smock for
cleanliness... given that then a conductive smock is probably a good idea.
-Paul Taddonio

At 08:12 AM 12/20/00 -0800, Gaines, William wrote:
>But having an insulating layer will collect a charge! Especially a
multiple layer design with different materials inside (Clothing/Smock). The
insulated surface will have more area exposed to the circuit that the
(hopefully) grounded hands of the operator.
>(And no, I do not propose un-clad assemblers ;) )
>
>Bill Gaines
>Aerojet
>
>-----Original Message-----
>From: Paul Taddonio [mailto:ptaddoni@nortelnetworks.com]
>Sent: Wednesday, December 20, 2000 7:31 AM
>To: Michael Nudelman; si-list@silab.eng.sun.com
>Subject: Re: [SI-LIST] : ESD Smocks
>
>
>
>
>
>It sounds like a gimmick. The human body is already plenty conductive (its
the
>insulation on the bottom of our footwear that causes the body to build up
>charge). Adding a conductive cloth over an already conductive body sounds
>useless.
>
>
>
>At 09:59 AM 12/20/00 -0500, Michael Nudelman wrote:
>>Hail to you, people that know electricity.
>>
>>I have unrelated to SI question. And this question does not come from my
>>ancient animosity to ESD smocks. It comes but from the desire for pure
>>knowledge (and some distrust for businesses mongering ESD equipment).
>>
>>Now, somebody please explain me the principle of the ESD smock's
>>operation. It is a gown, laced through by carbon fibers, forming a cage.
>>(St. Mike Faraday is smiling in heaven reading this, I'm sure).
>>
>>As I remember from my Electricity course, any Faraday-cage-like device
>>(hollow metal object) is intended to protect inside from outside (a
>>static field inside the object is always zero if all the charges are
>>outside).
>>However any charge that is inside the object, upon touching the inner
>>surface will transfer ALL of its charge to the outside surface of the
>>object, thus
>>itself loosing 100% of the charge and the charge being distributed
>>evenly on the outside surface of the object. The object in our case is
>>the smock.
>>
>>BTW, the Van-de-Graaf generator (the one capable of developing few
>>million volts potential) works exactly on the same principle.
>>
>>For the smocks to work we need conductive floors and everybody wearing
>>straps. Otherwise, smocks are potentially harmfull. If you touch
>>something with it while not grounded, you may actually zap some poor
>>unsuspecting FET or a co-worker (unless he deserves it).
>>
>>(And as I know, lots of companies do not have those floors. And ESD
>>businesses do not really insist on them - otherwise they would loose
>>some business, admitting, that the smock itself is not the remedy).
>>
>>Unless there is some gimmick to the smock that I do not know of.
>>
>>Anybody can explain this ... phenomenon?
>>
>>Mike.
>>
>>
>>
>>
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>
>--------------------------------------------
>N. Paul Taddonio
>
>Nortel Networks, Optical Ethernet Switching
>600 Tech Park, Billerica, MA 01821, (mailstop E65-60-203)
>phone: 978-288-4611 fax: 978-288-0620
>email: ptaddoni@nortelnetworks.com
>
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>

--------------------------------------------
N. Paul Taddonio

Nortel Networks, Optical Ethernet Switching
600 Tech Park, Billerica, MA 01821, (mailstop E65-60-203)
phone: 978-288-4611 fax: 978-288-0620
email: ptaddoni@nortelnetworks.com

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