Hi Dehoyos, Most Kapton tapes have a silicone based adhesive. Silicon is a contaminant for AR and UR coatings and will not allow the coating to stick! We have different coating rooms for this purpose. One sprays AR and UR, while the other sprays only SR Also we use a non silicone based adhesive for the masking we use with AR and UR Amol Kane M.S (Industrial Eng.) Process Engineer Harvard Custom Manufacturing, Inc. 941 Route 38 Owego, NY 13827 Phone: (607) 687-7669 x349 [log in to unmask] www.harvardgrp.com -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon Sent: Thursday, June 22, 2006 11:47 AM To: [log in to unmask] Subject: Re: [TN] Conformal Coat Voids You are having a case of dewetting. It happens with some kapton dots. I have tried to cover them with UR coating and the coating pulls away from the dot leaving the dot untouched no matter how many times I brush the dots. There is also a ring around the dots where there is no coating. It could be static build up or a chemical that rejects the coating. Suggestion: after the board is totally cleaned, rinse it one more time with DI. Submerge it in alcohol and brush the concerned areas. Rinse it again with DI water, bake and then try to coat it. Second suggestion: Place board in front of an Ion Generator for a few minutes. Ramon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bloomquist, Ken Sent: Thursday, June 22, 2006 9:19 AM To: [log in to unmask] Subject: Re: [TN] Conformal Coat Voids Hi Graham, I have not noticed any dewetting anywhere else on these boards. There is always a possibility that something could be coming out of the holes but I'd think that it would get cooked away during wave solder or washed off during cleaning. Hi Amol, We are doing some tests right now to see if there might be something in the cleaning process. The flux is water soluble and the board gets run through an inline washer two to three times during the process. The board goes through one final saponified wash in a batch washer before coating. We have not seen any residues on these solder joints after all this cleaning. What brought this to our attention was a test failure during a dust test. It's a very difficult test with materials that are conductive. We can apply a drop of water on the via's and create a failure of the board so we know there's not much coating over the solder. Is there any possibility that the really smooth slick domed surface is allowing the coating to be pulled off of it? Thanks, KennyB -----Original Message----- From: Graham Naisbitt [mailto:[log in to unmask]] Sent: Thursday, June 22, 2006 4:15 AM To: [log in to unmask] Subject: Re: [TN] Conformal Coat Voids Hi Kenny Clutching at straws here - any chance you have "drilling" residues before the via is plated? Can it be something from the via plating operation that has changed? Have you noticed de-wetting anywhere other than the via's? Regards Graham Naisbitt [log in to unmask] Phone: +44 (0)12 5252 1500 Mobile: +44 (0) 79 6858 2121 ______________________________________________________ Hi, How are the boards cleaned before coating? For a test sample of boards, take a Q-tip with a solvent like Xylene and manually scrub the problem areas and then try the coating process. That way you can change the cleaning procedure if necessary for those particular boards. Amol Kane M.S (Industrial Eng.) 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