Skip:You should not be getting dewetting on the plastic parts and it 
is not an accectable condition in most cases.It's possible there are release 
agents on the parts.Since I don't know what your flux/clean processes 
are I don't know how "clean" your assembly is prior to coating.I would try a 
bipolar cleaner on the assembly prior to the conformal coating application or 
you could preclean the problematic parts before assembly.In all cases make 
sure everything is thoroughly dry before apply the coating.Urethanes are 
typically susceptible to moisture which can form blisters an also give a 
dewetted appearance.							
									
	Another option would be to mask off these areas,coat the assembly 
than install the parts.	Good Luck!					
									
					Regards 			
					Michael Barmuta			
					Staff Engineer			
					Fluke Corp.			
					Everett Wa.			
					(206)356-6076			
						

On Wed, 23 Oct 1996 04:12:53 -0700 CINDY KEMP ORLANDO ISC *8-306-6873 wrote:

> From: CINDY KEMP ORLANDO ISC *8-306-6873 <[log in to unmask]>
> Date: Wed, 23 Oct 1996 04:12:53 -0700
> Subject: FWD: pwb-cca : conformal coating
> To: [log in to unmask]
> Cc: [log in to unmask]
> 
> Technet,
> 
> I'm forwarding this from a colleague.
> 
> Cindy Kemp
> Lockheed Martin
> Orlando, FL
> 
*****************************************************************************
**
> 
> From: [log in to unmask]
> Date: Tue, 22 Oct 96 16:35:22 EDT
> Message-Id: <[log in to unmask]>
> To: [log in to unmask]
> Subject: pwb-cca : conformal coating
> Sender: [log in to unmask]
> Precedence: bulk
> 
> hi group;
> 
> We are finding that in designs using conformal coating (UR) over plastic 
parts
> that the cc is dewetting on the parts.
> 
> Question - is this seen as a problem ?
> 
> I am proposing that a note should be added to our designs as follows:
> 
> 	CONFORMAL COAT DEWETTING ON PLASTIC ENCAPSULATED MICROCIRCUIT
> 	COMPONENT BODY IS ACCEPTABLE.
> 
> If there is a better way please let me here from you.
> 
> What is the real would doing ?
> 
> 
> 			thanx; Skip Greb
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