Just so everyone is clear...The copper dissolution is not specific to OSP but the effect of soldering to the base copper. The same affect occurs with HASL, immersion Tin, immersion Silver and DIG for the same reasons. Thanks, Ryan -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Drew meyer Sent: Friday, January 04, 2008 5:36 AM To: [log in to unmask] Subject: Re: [TN] OSP w selective gold Genny, I'm pretty sure that you already know what Tan Geok Ang means but thought I'd mention it to you as well. We just encountered an issue with this on an OSP finish board used in a lead-free process. The term used here was copper dissolution. An intermetallic layer is formed between the copper and the solder during the soldering process. This layer is part of the bond that makes the wonderful soldering process work. The layer is combination of the available metals. In the case of OSP the available metal on the PCB is copper. Intermetallic thickness is dependent upon time and temperature. Higher temperatures and or long soldering times, the more intermetallic will be formed. Copper readily forms an intermetallic layer and will continue to form it at each soldering step including repairs. With the higher lead-free soldering temperatures more intermetallic will be formed than with lead based eutectic soldering. So, if repeated soldering or prolonged soldering operations occur it is possible to simply consume all of the copper into intermetallic. A board that reaches such a state is scrap. A carefully controlled soldering process should not lead to this problem. With lead-free you want solder wetting to be the best possible to avoid long dwell times that can induce copper dissolution. If you want to see some images let me know and I can send them to you. It's not very pretty. Drew Meyer --------------------------------------------------- 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 -----------------------------------------------------