The number of spray passes depends on what you want. Many times reducing the number of passes requires you to put down more material and if you take short cuts in drying, you may get imprefections in the coating. Increasing the number of passes lets you put down less coating and it is easier for the volatiles to flash off the surface. Also I have had problems with spider webbing. That is when the there is so much thinner in the coating it all flashes off when spraying and the resulting thicker material landing on the board doesn't coalese and forms spider's web. Control of the mixing ratios is more critical Also acrylic requires thinners so your facilities VOC emissions may go up. Some newer lower VOC materials are entering the market but a lot of people don't like them due to their odors. Also got to worry about post coating cleaning. About anything except for water will attack the acrylic surface- remember that is by design (for reworkability) Hope this helps Tom -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of - Bogert Sent: Thursday, February 15, 2007 7:24 PM To: [log in to unmask] Subject: [TN] Using Type AR Conformal Coating February 15, 2007 Folks, we have some military OEM'S that are switching from Type UR conformal coating to Type AR. The main reason for the switch is because it is hard to remove Type UR coating in event of a rework, and certain chemicals sold by the coating manufacturers for UR coating removal are highly conductive and have caused problems since the cleaning process did not adequately remove them. The other reason is we wanted a coating that could be easily removed in event product failed in the field so we could do ATE to quickly find the source of the problem. Our product is used in a military application but it is contained in a cabinet that is dust tight. We have some assemblies that are not coated at all with no known problems. Do any of you folks use Type AR for military product, and if so, what are your experiences using the coating? I have heard about problems using alcohol for coating removal since it goes where you do not want it to go. I have also heard that if a spray process is used, it takes 4 or more passes on each side of the board to achieve the minimum J-STD-001 thickness. At least one source indicated using AR may cause some solder joint reliability issues. Any info you have would be a help. Thanks. --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 1.8e 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 -----------------------------------------------------