Doug, De-wetting occurs all over the assembly and pools in roughly the same pattern. I am pretty sure the consistent pattern is due to the spray pattern from our coater. SMT is the process prior to coating all operators use gloves throughout the process from start to finish due to coating and the assembly. I just recently read about surface energy and I am in the process of ordering a dyne pen. This was the first time I ever heard that surface tension had a direct impact on coating. Here is what we know 1. We do know that boards from the same lot code might coat fine while others show signs of de-wetting 2. Populated and un-populated arrays have the same problems 3. We sent out sample arrays to the coating supplier who cleaned them in a vapor degreaser and when returned they coated fine. The material used was Leksol AL 4. completed a Zestron flux and resin test and they came back negative 5. There is no way to tell if the board is going to coat until coating is applied, nothing looks different between boards that will coat and ones that wont. 6. We have sent samples to a lab, ones that coated and ones that didn't for comparison. This is the second time we have sent boards out for evaluation. The first tests came back with nothing but only one array was sent and that was prior to knowing that we had variation in our lots. 7. Today we changed the coating and the carrier from 1B73AP to 1B73 and had better results. We think it is because of the Methyl Ethyl Ketone in the 1B73 and it is lifting what ever is on the board allowing the coating to wet better. Or because MEK is just at good at killing brain cells then it is for thinning coating, we are hallucinating and seeing what we want to see. Oh look a bunny Thank you, Ted _____ From: [log in to unmask] [mailto:[log in to unmask]] Sent: Thursday, February 05, 2009 4:33 PM To: TechNet E-Mail Forum; Ted Tontis Subject: Re: [TN] Coating material Ted, Where do you see the dewetting and what processes come before coating? In my experience, dewetting comes three general sources: 1. A problem with the surface energy of the component or solder mask. This may be due to mold release agents or the slick nature of the plastic itself. You want surface energies in excess of 40 dynes/cm. Surface energies of 30-35 dynes/cm are a problem. I use Dyne Pens as a quick check. Has there been a change in process or part supplier? 2. A problem with a barrier material. Again, it may be a mold release agent, many of which are Teflon or sulfur based, or it may be a process residue. Could be silicone residues, could be fingerprints, could be any number of things from second or third shift. 3. Dewey Whittaker. Doug Pauls Rockwell Collins --------------------------------------------------- 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 -----------------------------------------------------