Werner, A question that haunts me lately: the solubility of Ni in Sn increases with the temperature. At lead-free temperatures, the solubility of Ni in Sn is already at higher values than in SnPb. On top of it, there is more Sn, less "impurities", so it should not matter whether we solder to Cu or Ni. Therefore Liquidus + 20 should be enough for both. Where is the reasoning error? Thanks, Ioan -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Werner Engelmaier Sent: Friday, November 17, 2006 7:29 AM To: [log in to unmask] Subject: Re: [TN] BGA anomaly Hi Iain, Perhaps you have not seen some of my previous responses, but... For reflow soldering, the time-above-Solidus is not an important number for solder joint quality; you are not making solder joints at or just above Solidus. However, time-above-(Liquidus+20C [if soldering to Ni you need Liquidus+30C]) is very important and should be 3 to 5 seconds or longer. Unfortunately, paste vendors have been misleading their customers for a long time with this "time-above-183" nonsense, that is now spilling over into the LF-arena. Werner --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 1.8e 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 -----------------------------------------------------