This is late but as once said... You may have more of an issue than CC blisters if you don't repair this correctly. If the cc bubbles up and the product is in a moist dirty area you can have the contamination pass through the cc as a gas and then form as a chemical soup inside the blister. eric -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Phillip Bavaro Sent: Friday, November 23, 2007 11:50 AM To: [log in to unmask] Subject: Re: [TN] RTV contamination and conformal coating In a former position, I had the benefit of being able to still use a freon vapor degreaser to easily strip the acrylic 1B31 from any board that needed better prep (non-adhesion qualifies as that), but I don't know if there is a equivalent stripping method these days. My recommendation is to locally scrub the area that has the problem, IF it is flat and easily rubbed with a cotton swab. The RTV can be rubbed off using a suitable solvent (but be very careful not to drip the solvent onto any good areas). Adhesion of the touch up 1B31 to the "clean" surface will be just a good as the rest of the board has long as you do a good job cleaning. Don't forget to bake the board before reapplying the 1B31. Covering up the spots (that you are no doubt seeing under ultraviolet light) with more 1B31 is not recommended as you are right, you have not fixed the problem. However it depends on what the environment is that you are using the 1B31 for. Typically such an environment is not one which would bubble up an area like you are mentioning (if the pull-aways are in fact only due to RTV). I am just curious, are you applying the RTV after prepping the boards for the 1B31? Is it possible to coat the board and then apply the RTV afterwards. Typically the RTV is applied to external surfaces which could be easily locally stripped and then covered up with RTV. It would seem obvious that you don't have a requirement to put 1B31 on top of the RTV. Hope this helps. Phil At 02:31 PM 11/22/2007 -0500, Ioan Tempea wrote: >Dear Technos, > > > >I am having a few boards that have spots of Dow Corning 3-1744 RTV where >they should not. We need to CC with acrylic 1B31 from Humiseal and, >guess what, the CC does not catch on the silicone. > > > >If the problem spots are touched up with CC thinner or CC, after 2-3 >passes we manage to cover the problem. Now, there will probably be no >adherence under the touch-ups, since there was no adherence in the first >place and on the long run, or maybe not so long, the CC will bubble and >peel off. Do I see it right? > > > >I would appreciate an idea on how to work this out, have never been >involved with CC before. Will patching work? Should I strip and clean >locally? What to clean with and how, and so on? Any post-cleaning >cleanliness worries? > > > >Thanks for your input, > > > >Ioan > > > > >--------------------------------------------------- >Technet Mail List provided as a service by IPC using LISTSERV 15.0 >To unsubscribe, send a message to [log in to unmask] with following text in >the BODY (NOT the subject field): SIGNOFF Technet >To temporarily halt or (re-start) delivery of Technet send e-mail to >[log in to unmask]: SET Technet NOMAIL or (MAIL) >To receive ONE mailing per day of all the posts: send e-mail to >[log in to unmask]: SET Technet Digest >Search the archives of previous posts at: http://listserv.ipc.org/archives >Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 >for additional information, or contact Keach Sasamori at [log in to unmask] or >847-615-7100 ext.2815 >----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ********************** ** LEGAL DISCLAIMER ** ********************** This E-mail message and any attachments may contain legally privileged, confidential or proprietary information. 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