Jean-Francois

Silicone coatings do not generally exhibit high Mar resistance - that is to
say you can rub them off relatively easily. This is largely due to them not
being receptive to anything sticking to them.

Now when you consider doing a X-Hatch or other "peel" type testing, this
involves sticking a particular adhesive tape to the "scored" area and
removing it to count how much / many areas (squares) have been removed.

This should be an easy test for a silicone to pass, because the tape doesn't
stick to it!

You should NOT be concerned about the materials low Mar resistance. You
should rather, test your final assembly through accelerated aging that is
representative of the anticipated environment the end product will see and
thus establish if it survives.

Yes? Good coating - but it peels off! So?
Of course if it fails the test, then you have another problem - as outlined
by Jim McGuire (Hello Jim!) this will very probably be inter-related to poor
surface cleanliness.

I hope this helps but if you need more, let me know

Regards,
Graham Naisbitt

[log in to unmask]

WEB: http://www.concoat.co.uk

CONCOAT Ltd
Alasan House, Albany Park
CAMBERLEY GU15 2PL UK

Tel: +44 (0) 1276 691100  Fax: +44 (0) 1276 691227
----- Original Message -----
From: Jean-Francois Bissonnette <[log in to unmask]>
To: <[log in to unmask]>
Sent: 03 December 1999 15:26
Subject: [TN] Conformal coating pelling off


> Hi!
>
> We use silicon conformal coating on some boards and some of these
> show a lack of adhesion of the coating.  It peels off very easily
> with gently scratched.  I also heard of some peeling test that could
> be done, can it be done with any kink of tape?  The same coating on
> the other boards wont peel if I try to scratch it off.
>
> Can anyone shed some light on this?  I tought that it would be a
> cleaning problem but the supplier says that they do clean it.  Can
> the board material be the source of that problem?
>
> Thank You!
>
> JF
>
> ##############################################################
> 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
##############################################################