Bob, You are correct that the solder mask/resist and the conformal coating should be chosen to be compatible with each other. I have generally found that if the mask qualifies to IPC-SM-840 and the coating qualifies to IPC-CC-830, and are processed correctly by the fab house and assembler, respectively, then they will be compatible. Unfortunately, the part about the materials being used correctly has a bigger impact on material compatibility than the material itself. You are also correct that defining "compatibility", testing for it, and interpreting the results are an art form in themselves. If you get a lack of adhesion and ask the solder mask vendor the problem, then the problem is that darn conformal coating. If you ask the coating vendor, the problem is that darn solder mask. The present IPC philosophy, as shown in J-STD-001, is that it is the responsibility of the OEM to determine that the materials they use are compatible with each other and to generate objective evidence of that compatibility. There are many ways to do this, from lab tests to life test on product. The easy way is to put on the drawing that the solder mask must be qualified to IPC-SM-840 and the coating qualified to IPC-CC-830, and do a J-STD-001 qualification on the combination. Doug Pauls Bob Wilson <[log in to unmask] M> To Sent by: TechNet [log in to unmask] <[log in to unmask]> cc Subject 12/14/2004 01:00 [TN] LPI and conformal coating AM Please respond to TechNet E-Mail Forum <[log in to unmask]> ; Please respond to Bob Wilson <[log in to unmask] M> Hi, I'm studying for the CID+ test and, among other things, I've discovered there is a bunch of things I don't know or didn't realize that were important in the fab/assy world, even after 20+ years in the biz. I had boards that needed to be conformal coated. I used one fab house and a different assy house and a 3rd conformal coat house. Now that I'm studying, I see it is pretty important that the LPI and conformal coat "match" in compatibility. Has anyone run into this (potential) problem? How do I specify a compatibility between disparate disciplines? Sigh...I swear my fab and assy notes take up more room on the drawings than the biggest boards I've ever done, by far. Regards, Bob http://www.cstone-design.com/home.html --------------------------------------------------- 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 -----------------------------------------------------