Hi Paul. 1. Can copper dissolution change the tin/lead ratio of the solder that is above the intermetallic? A: Of course, it becomes Pb-rich unless replenished. 2. Is copper dissolved throughout the solder or only at the intermetallic layer? A: Cu3Sn stays at the Cu surface; Cu3Sn5 can migrate if there is a lot. 3. Would this be a significant concern for assembly? A: Not any IMC migration, but the Pb-rich regions frequently are those where the fractures run through. Connection? Werner -----Original Message----- From: Paul Reid <[log in to unmask]> To: [log in to unmask] Sent: Tue, Jun 16, 2009 11:09 am Subject: [TN] Copper Dissolution Questions continued To continue my quest to understand copper dissolution. I have a coupon where the copper in the PTH is dissolved by the solder during thermal excursions. I notice a metallic interface against the copper. I assume the interface is a tin copper concentration but then again I don't know. Understand that this is thermal excursions on a coupon without any solder paste, component etc. The solder volume consists of the solder associated with a surface finish. In other words a low fixed solder volume. 1. Can copper dissolution change the tin/lead ratio of the solder that is above the intermetallic? 2. Is copper dissolved throughout the solder or only at the intermetallic layer? 3. Would this be a significant concern for assembly? Sincerely, Paul Reid Program Coordinator PWB Interconnect Solutions Inc. 235 Stafford Rd., West, Unit 103 Nepean, Ontario Canada, K2H 9C1 613 596 4244 ext. 229 Skype paul_reid_pwb [log in to unmask] <mailto:[log in to unmask]> --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------