That's the post I've been waiting for :-) 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: "David D. Hillman" <[log in to unmask]> Date: Tue, 27 Jan 2009 10:45:30 To: <[log in to unmask]> Subject: Re: [TN] SnPbAg solder and Immersion Silver PCBs Hi Werner! I don't believe that there is an silver embrittlement issue with the use of ImAg PCBs. Rockwell Collins has been using ImAg PCBs for over 10 years with no issues of silver embrittlement. We have also conducted several lead-free assembly studies using the SAC305 solder alloy and have found no issue with silver embrittlement. And, the IPC 4-14 Plating committee did not find any silver embrittlement issues with a test assembly that was excessively silver loaded - ImAg PCB finish and silver in the solder paste - and we did not find any evidence of silver embrittlement. The 4-14 committee will be publishing that study as an IPC Technical Report in the near future after completing the necessary committee reviews. As a general rule of thumb, I think silver embrittlement is on a much lower risk register than gold embrittlement. However, I have seen the PLCC study data and it indeed was a case of silver embrittlement so I think that each situation needs to be understood to avoid having an embrittlement issue. Dave Hillman Rockwell Collins [log in to unmask] Werner engelmaier <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 01/27/2009 10:30 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Werner engelmaier <[log in to unmask]> To [log in to unmask] cc Subject Re: [TN] SnPbAg solder and Immersion Silver PCBs Hi Kevin, That "thin (?) silver finishes...prevent the dissolution of the component lead into the solder joint" is a Red Herring. All you may be getting is AG-embrittlement which is just as bad as Au-embrittlement. It was just such 'silver finishes' on TI PLCCs that caused those PLCCs to fall off PCBs during bed-of-nail testing in 1982 at IBM-Austin and resulted in the formationof the IEEE Compliant Lead Task Force. Also, how would an Ag-finish prevent the formation of IMCs with the lead metal? Werner -----Original Message----- From: Kevin Glidden <[log in to unmask]> To: [log in to unmask] Sent: Tue, 27 Jan 2009 8:35 am Subject: [TN] SnPbAg solder and Immersion Silver PCBs Morning all, Question today about SnPbAg solder. We have always used Sn63Pb37 solder alloy for all products, with exception of some high temp solders for special cases. The lion's share of our PCBs are ImAg finish, 5 to 12 micro-inches, per IPC-4553. In reading about SnPbAg solder, it appears to be recommended for use on SMT components with thin (?) silver finishes. This is to prevent the dissolution of the component lead into the solder joint. Drawbacks appear to be only that the joint is not as shiny and reduced mobility of the solder. Is it also considered good practive to use an SnPbAg alloy for immersion silver PCBs for the same reasons? Any tech articles available on this? Thanks (again!) Kevin Glidden Manufacturing Engineer Luminescent Systems Inc. --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------