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March 1998

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Subject:
From:
Bev Christian <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 10 Mar 1998 11:09:23 -0500
Content-Type:
text/plain
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text/plain (92 lines)
Christine,
In the past the problem with silicones has been their breakdown during
electrical arcing in crossbar (mechanical) switches and the formation of
nonconducting silicone dioxide (sand) on switch surfaces.

The other problem with silicones is that they are themselves incredibly
good electrical insulators. So you do not want them on conducting mating
surfaces; like inside mating connectors, inside dip switches, etc.  This
is further complicated by the fact that silicones have a tendency to
creep and if they get on a circuit pack it is quite possible to find
that the material has moved considerable distances across the circuit
pack.  As a result of these problems, liquid silicones and solid
silicones containing a certain % of liquid silicones are not allowed for
use in Nortel products.

So if you are going to be putting product in an environment where these
materials are prevalent it would be nice if all your connectors make
gas-tight connections and that they are not going to have to be
removed/reinserted once the packs are in the field, that all your dip
switches are sealed and that you use a silicone impermeable conformal
coating (if there is such a thing, Nortel doesn't generally have to use
coatings so I can't offer much there.) Hopefully other Technetters can
give you more info.

regards,
Bev Christian
Nortel
> ----------
> From:         Christine Cleveland[SMTP:[log in to unmask]]
> Sent:         Tuesday, March 10, 1998 9:40 AM
> To:   [log in to unmask]
> Subject:      [TN] Silicone oil environments
>
> Hello, everyone.
>
> I am new to the forum and have a question; hopefully, you can help me.
> My question is regarding an application where a printed circuit board
> (polyamide) will be operating in a "silicone oil" environment. Are
> there
> any reliability standards or other information available on PCB
> environments and their long term reliability?
>
> Any information you can provide will be greatly appreciated.
>
> Best regards,
> Christine
>
> --
> Christine Cleveland
> Custom Standards Services
> Engineering Documents and Information Services
> Phone: (800)699-9277 (734)930-9277 Fax: (734)930-9088
> e-mail: [log in to unmask]  On the Web: www.cssinfo.com
>
> **Ask me about
> --IEC Standards on CD-ROM
> (http://www.cssinfo.com/iec.html)
> --PERINORM - The new International Standards Database
> (http://www.cssinfo.com/perinorm.html)
> --The new 1998 ASME Boiler and Pressure Vessel Code
> (http://www.cssinfo.com/BPV1998.html)
> These are all available now at great discounts!
>
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