I am currently using Dow 3-1753 over no clean in high volume 
     production. There are no adhesion problems related to the flux 
     residues. There is an adhesion problem related to residues at one 
     particular PCB supplier, while identical laminates and solder 
     mask/finish have excellent adhesion from our regular PCB supplier.
     
     Prior to that, we used a high VOC acrylic with very few adhesion 
     problems, all related to the bare PCB as arrived.


______________________________ Reply Separator _________________________________
Subject: Re: ASY: Conformal Coatings
Author:  [log in to unmask] at internet
Date:    8/12/96 8:44 AM


     We presently use parylene. It is a very good, but expensive cvoating 
     system. The main problme you will have with the no-clean residues is 
     that SCS will try to clean those residues off in their precoat clean. 
     That could create problems depending on the noclean flux in question.
     
     Another coating you might consider is Dow's 3-1753.
     
     
______________________________ Reply Separator _________________________________
Subject: ASY: Conformal Coatings
Author:  [log in to unmask] at internet 
Date:    8/8/96 8:18 PM
     
     
   I'm doing a background search on various conformal coatings but, I was
wondering if anyone has experience with parylene.  From my literature search 
it seems that there is a question of how well it adheres to flux residues. In 
particular, I'm interested in parylene's interaction with no-clean flux 
residues or other related problems.
   I know that SCS uses a patented system to apply a gaseous adhesion-enhancer
before actually applying the parylene but, it there any equally-good 
alternative?  An immaculate board does enhance adhesion but, cleaning with an 
alcohol (isopropanol) is not desired because the flux residue may become 
activated and cause severe ion migration and subssequent corrosion of the 
board.
     
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