Hi Werner, I'll take a look at the phase diagrams tomorrow for Sn-Pb-Cu system, but I don't see why a pair of metals (Cu and Sn) which forms a chemical bond can be "influenced" the third party element (Pb) which doesn't form any phases (but predominantly mechanical mix) with either of those two metals. In a short word, I don't see why all Sn can not be ultimately consumed by Cu to form intermetallics. Regards, Vladimir SENTEC 11 Canadian Road, Unit 7. Scarborough, ON M1R 5G1 Tel: (416) 899-1882 Fax: (905) 882-8812 www.sentec.ca -----Original Message----- From: [log in to unmask] Date: Tue, 16 Jun 2009 20:14:10 To: <[log in to unmask]>; <[log in to unmask]> Subject: Re: [TN] Copper Dissolution Questions continued Hi Vladimir, 1. If all Sn is consumed to form intermetallics, then you end up with only Pb in the former solder. A: Not so, what you end up with is the Pb-rich phase of the SnPb alloy. Werner -----Original Message----- From: Vladimir Igoshev <[log in to unmask]> To: [log in to unmask] Sent: Tue, Jun 16, 2009 11:56 am Subject: Re: [TN] Copper Dissolution Questions continued Paul, What you are saying sounds "strange", as more details would require. You can contact me off line if you wish, as I'm in GTA area. Regarding your questions, then; 1. If all Sn is consumed to form intermetallics, then you end up with only Pb in the former solder. 2. Intermetallics formation occurs only at the interface, BUT once Sn at the interface is consumed, the one from the rest of solder "rush-in" 3. It's a problem if instead of ductile Cu you have a brittle material as a wall of a PTH. Regards, Vladimir SENTEC ------Original Message------ From: Paul Reid Sender: TechNet To: [log in to unmask] ReplyTo: TechNet E-Mail Forum ReplyTo: Paul Reid Sent: Jun 16, 2009 11:09 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 ----------------------------------------------------- SENTEC 11 Canadian Road, Unit 7. Scarborough, ON M1R 5G1 Tel: (416) 899-1882 Fax: (905) 882-8812 www.sentec.ca