Steve/Alcon: - Re exposed copper. Not a problem per 600, A-610. Exposed copper just turns green and as soon as the surface is protected from the environment by the coating, the oxidation/tarnishing stops. There has been some conjecture that exposed copper would lead to metal migration, but as far as I know neither DOD or anyone else has found a smoking gun to indicate that this has ever caused or contributed to a field failure. - History Lesson: Once upon a time DOD had a bad problem with exposed Kovar/Alloy-42 (it kept oxidizing and eventually would result in an open circuit when the lead rusted away from the solder (bad things happen to a Naval or Marine Corp. airplane and onboard systems in a perpetual salt-fog environment). Consequently, DOD prohibited exposed Kovar/Alloy 42. During one revision of the Mil-Specs the DOD contractors cried hard times and got the requirement for optimum inspection lighting (centered at 3000K, e.g. quartz halogen) deleted (cost too much to have a good light). Without the broad color spectrum available with optimum lighting it is difficult or impossible to differentiate between exposed Kova/Alloy 42 and exposed copper, so DOD simply said "no exposed basis metal", and didn't really worry about exposed copper. For a while industry standards/specifications mimicked the DOD requirement for no exposed basis metal. Eventually someone figured out why the Mil-Stds said no exposed basis metal and then the requirement was dropped. Recent industry specifications and standards require neither optimum lighting or (in some cases) magnification aids. - Exposed copper (on lead ends and the vertical sections edges of circuit traces/pads/etc.) should not be considered a problem (as far as I know no failure mode is/has-been associated with exposed copper). Exposed copper due to mechanical, thermal, or chemical attack is another kettle of fish and must be examined on a case-by-case basis to determine if it constitutes a defect. Cheers, Jim Moffitt, Technical Director, Electronics Training Advantage, Indianapolis IN ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################