June 19, 2007 Folks, we have an OEM who designed a laminated bus/power plane that has "boss" connections brazed to copper bus bars within the assembly. Basically, the construction is similar to a PWA since it uses FR4 and copper conductors laminated together under heat and pressure similar to a PWA, except the "boss' terminations serve the purpose of a PTH. The OEM inserts a helicoil insert into a tapped hole in the "boss". However, when doing this, there are small areas of the top of the "boss" where the matte tin-plating is scraped off (when the helicoil insert is compressed, the first several threads go in easily, but toward the end, the diameter is not compressed as much and this scrapes off some of the plating). Electrical connections to the "boss' are made via ring type terminal lugs (MIL-T-7928) and a screw that threads into the insert. However, the electrical connection is made directly to the top surface of the "boss', and does not rely on the threads of the insert, nor does it come in contact with the exposed copper surface. My question is, if we left the copper areas exposed, is there any technical concern having exposed copper. If there is, would conformal coating (Type UR) be acceptable to cover the exposed copper areas, using caution to make sure none of the coating comes in contact with any electrical mating surface. --------------------------------------------------- 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 -----------------------------------------------------