I believe that the problem is to low a Tg for the coating.  Routing can cause some extreme temperatures at the point of contact which might preclude even changing coatings. I'm sure your aware of all this, but you might try changing coatings to higher Tg's and once you find it, spec it in. The other possibility is to find a coating which doesn't exhibit viscous flow when heated.  The Tg's may still be similar but the stringiness might be avoided. One suggestion is to look into the silicone conformal coats.
    -----Original Message-----
    From: Graham Naisbitt <[log in to unmask]>
    To: [log in to unmask] <[log in to unmask]>
    Date: Friday, September 11, 1998 8:25 PM
    Subject: [TN] Routing conformal coatings
    
    
    Hi TechNetters,
     
    I hope you can help. We have a customer who needs to route (de-panellise) his assemblies after Conformal coating. The coating is an acrylic.
     
    The problem is that when he does this routing operation, the coating (not surprisingly) goes into a state of partial melt so that the coating is stringing on the underside making a problem for clean-up which is costly.
     
    He cannot route from the other side. He has tried chilling the assembly but this is impractical because of the time constraints. He cannot selectively NOT coat the affected area because his selective coating system then takes too long for the operation.
     
    Does anyone have any suggestions? 
     
    Regards, Graham Naisbitt
     
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