Rich: I agree with everything said so far, and further remind you that having Copper and Tin exposed and connected promotes corrosion dramatically because of the Galvanic effect. Covering the lead completely with Tin should minimize or eliminate this issue. Rudy Sedlak RD Chemical Company Rich Lasko <[log in to unmask]> wrote: Good morning all, I have a customer who is having problems with a couple of their assemblies. It appears that the conformal coating (Dow Corning 1-2577) is reacting with the untinned copper portions of an IC (MC68HC908AZ60A). The untinned portion is on the sides of the lead right near where the lead enters the package body. It seems that the copper is leaching out into the conformal coating and lowers the resistance between the two pins. (When the two pins are measured they read approx. 80K ohms - 150K ohms). Without the conformal coating the resistance is much higher (> 1M). This lower resistance is causing some erratic failures from time to time. When my customer sliced through the conformal coating between the pins with an exacto knife the resistance returned to a more normal reading and the unit worked fine. They have sent this unit to a lab and the lab report stated that they found traces of copper in the conformal coating. So my questions are as follows: 1.) Is it common to have untinned portions of a SMT IC such as the one identified above? Or should the lead be completing tinned? 2.) Has anyone else seen this type of problem with copper in the conformal coating? If so, what did you do about it? 3.) Is there a concern from a solder paste position and how the flux in the paste reacts with the copper and then is ultimately conformal coated in a later process? (This question applies to both an aqueous SMT process and a no-clean SMT process) Need a little help and insight here. Thanks! Rich Lasko --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------- Do you Yahoo!? --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- New and Improved Yahoo! Mail - Send 10MB messages!