Ioan, Two micro inches of Gold isn't very much. Is there a Nickel barrier layer? If not that is probably copper migrating up through your gold. Heat or time will do that to gold over copper. Chuck Charles W. Brummer | 3M Manufacturing Engineer 3M Electronic Solutions Division 3M Canoga Park, 8357 Canoga Ave. | Canoga Park, CA 91304 Office: 818 734 4930 [log in to unmask] | www.3M.com This message (including any attachments) may contain material, non-public information or proprietary information and is for the intended recipients only. If you are not the intended recipient, you should notify the sender and delete this message. Any disclosure, copying, or use of this information is strictly prohibited and may subject you to legal liability. From: Ioan Tempea <[log in to unmask]> To: <[log in to unmask]> Date: 10/21/2011 02:14 PM Subject: [TN] Discoloration on plated over vias Sent by: TechNet <[log in to unmask]> Dear Technos and Smarts, I got this issue, see http://ipc-technet.groupsite.com/gallery/21662 So 6 layer, 2oz Cu per layer PCB, epoxy filled vias and plated over. After assembly we see 4-5 vias having reddish stains, on most boards. Had it analyzed, no trouble with via integrity, no cracks in cover plating, no migration of fluids from inside out. FTIR does not detect any surface contamination. Au plating thickness stands at 2.09 micro inches. Nothing special detected in the stains, so the lab concluded what we see is an optical effect due to a certain roughness of the Cu. The logical conclusion is no issue, cosmetic defect. However, our end customer, high reliability, want to know what the stains are and want absolute confirmation that long term reliability is not affected. Also, we've been warned that no such issues will be tolerated on future lots. My questions to your infinite knowledge is: have you seen this before? How can I convince the customer everything is OK? What is the root cause and how can I get rid of the issue? Many thanks, Ioan Tempea, ing. Ingénieur Principal de Fabrication / Senior Manufacturing Engineer T | 450.967.7100 ext.244 E | [log in to unmask] <mailto:[log in to unmask]> W | www.digico.cc <http://www.digico.cc/> N'imprimer que si nécessaire - Print only if you must ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------