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May 2008

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Subject:
From:
"Douglas O. Pauls" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 27 May 2008 07:51:16 -0500
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Phil,
Most of the pure acrylic coatings are not that good in terms of chemical 
resistance.  We do not allow our conformally coated assemblies (Humiseal 
1B31) to go through saponified aqueous cleaning for just the reason you 
are seeing, the adhesion gets affected and the coating comes off. 

Doug Pauls




Phil Nutting <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
05/27/2008 07:46 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Phil Nutting <[log in to unmask]>


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Subject
Re: [TN] Conformal coating washing off






Brian,

I guess I should add that we have been using this conformal coating for 
about six years with "great success".  It has only been in this test of a 
new washing system that we are seeing the coating peel off.  The DI wash 
in my original post was the wash step after soldering with an OA flux. 
Maybe the detergent in the wash system is really good for cleaning 
conformal coating off the boards... if that was what I really wanted.

Phil

-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Saturday, May 24, 2008 2:04 AM
To: TechNet E-Mail Forum; Phil Nutting
Subject: Re: [TN] Conformal coating washing off

Some types of solder mask contain nasties that may prevent a decent
adhesion of a CC or they may not have been properly polymerised, leaving
insoluble monomers or other components on the surface. I suggest you
start looking in this direction.

Brian

Phil Nutting wrote:
> We are using Chemtronics Konform AR on some circuit boards.  The boards 
are batch washed in DI water and pre-baked prior to coating and then cured 
in a 60° or 77° C oven.
>
> In a recent test of a new washing system where we are removing slip ring 
dust (brass and carbon) on these boards and dielectric oil from other 
boards and aluminum castings, I noticed the conformal coating peeling off 
in sheets after both the wash and DI rinse cycles.  Both wash and rinse 
are between 140 and 150° F.
>
> Is this stuff peeling off because of the water temperature, poor 
pre-coating prep or possibly something else?
>
> Thanks in advance,
>
> Phil
>
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Note: All the information contained in this e-mail and its attachments is 
proprietary to Kaiser Systems, Inc. and it may not be reproduced without 
the prior written permission of sender.  If you have received this email 
in error, please immediately return it to sender and delete the copy you 
received.

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