Mornin' Steve & All

There's some correspondence in TechNet archives about 6-8 months ago about
the Navy's findings relative to polyimide insulated wiring in the wing and
landing gear sections of carrier based aircraft.  The material is
susceptible to alkalines and was heavily degraded by aircraft cleaning
compounds.  In my recollection, this was detected back in the early 1980's.
Secondly, NASA detected problems with polyimide film sensitivity to atomic
oxygen in selected space applications and limited the usage of the material
in that respect.  Neither of these issues produced a "ban" on Kapton or any
other polyimide.  Like any other materials, the polyimides do have design
limitations.

Regarding use of a Kapton insulator as noted in your query: BAD NEWS!!  Two
reasons - first, the adhesives on most of the tapes and films (save the new
all polyimide materials) aren't that great from a process durability
standpoint.  I've had similar applications where the film moved to a
different location when the adhesive failed.  Second, what happens to the
adhesive bond when the solder on the via reflows?  Goodbye bond!!  I restate
my case for filled/tented vias.

Good luck and have a fun day.

Regards - Kelly
-----Original Message-----
From: Stephen R. Gregory <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Monday, November 01, 1999 10:45 PM
Subject: [TN] Kapton (Tm) materials...


>Hi ya'll,
>
>Not to start another thread about something that will upset people, but
>lately in the media there has been some talk about Kapton (tm) materials
>being somewhat unstable at elevated temperatures...there's stories about
this
>with the recent crash of Egypt Air flight 990...
>
>I, as undoubley as possibly many of you, have always understood that Kapton
>(tm) tapes are what you should use when high temperatures are encountered.
>I've used it on numerous assemblies to in the past to prevent such things
as
>a metal connector body connecting to a via that was mistakenly laid-out
>without mask beneath the footprint. As a big as a pain in the butt as it
was,
>we would cut a teeny piece of kapton (tm) tape to cover a via so that there
>was no chance of a via to short to the connector. This is just one
>example...there have been many other instances in the past (crystals,
>oscillators, etc..) or with other components where I've used Kapton (tm)
tape
>to do similar things...the tape needed to stay with the assembly as a
finshed
>product.
>
>Should I, or designers who specify the use of Kapton (tm) in this manner be
>concerned about this? Or is this just media hysteria?
>
>-Steve Gregory-
>
>##############################################################
>TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
>##############################################################
>To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in
>the body:
>To subscribe:   SUBSCRIBE TECHNET <your full name>
>To unsubscribe:   SIGNOFF TECHNET
>##############################################################
>Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
>information.
>If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
>847-509-9700 ext.5365
>##############################################################

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################