Question for the reliability guys... We use copper core PCBs, typically with an .060" core. There is some discussion on whether these edges should be left as copper OR finish plated. We use two finishes: ImAg and ImSn. We specify the edges to be plated, but the PCB vendor has requested to leave them as copper. To plate the edges, the PCBs must be depanelized, which creates excess handling and manual processing for the vendor. From a reliability standpoint, there are pros and cons. The silver and tin could be subject to electro-migration under temperature and humidity cycling conditions (all of our products are for avionics and therefore receive ESS testing and also an avionics environment in the end use). As for corrosion, none are safe: copper, tin, or silver, though the silver is most susceptible I believe? I was even forwarded a nice paper entitled "Galvanic Compatibility of Immersion Gold and Immersion Silver Printed Wiring Board Finishes with Aluminum, by none other than David Hillman and Matt Hamand at Rockwell... If I understand it correctly, looking at the Galvanic Series chart, tin, copper, and tin-lead (solder) are all about the same, and slightly closer to Aluminum (likely chassis material) than silver. This would suggest that leaving the copper edges vs silver plated may be better??? All the products are conformally coated with type UR coating. But it has been pointed out many times in this forum that given enough time, all conformal coatings will allow moisture through... Thoughts / opinions? As always, thanks in advance! Kevin Glidden Manufacturing Engineer Luminescent Systems Inc. --------------------------------------------------- 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 -----------------------------------------------------