Dave, Echoing Denny's input, I would repair Lead Free (SAC) with Lead Free (SAC) and Tin Lead (SnPb) with Tin Lead (SnPb). I would keep the two technologies separated. Just a warning, there are several papers out there that indicate that you could do first piece production mixing technologies (SAC BGA / SnPb paste or SnPb BGA / SAC paste), and some might imply that you can do rework in the same manner. I am very skeptical on this since I work in the aerospace arena and the test data documented does not come close to what I have to deal with. One more thing - your soldering temperatures with SAC are about 20C higher than Tin Lead (SnPb). This means that you have to control your processes better so you do not disturb the neighboring solder joints. Hope this helps. Good Luck. Lee Whiteman, PMP Senior Member Engineering Staff L-3 Communications East Telephone: (856) 338-3508 FAX: (856) 338-2906 E-Mail: [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Schaefer Sent: Tuesday, October 27, 2009 11:53 AM To: [log in to unmask] Subject: [TN] Reworking LF(SAC) Assemblies with SnPb Solder Working on a product that is exempt from RoHS requirements but does require LF(SAC) processing because of BGA ball solder composition. Most other products are standard SnPb process, and rework is performed with SnPb solder. Am I correct to question the use of SnPb solder to rework the LF(SAC) assemblies? It would seem that mixing SnPB and SAC solder would result in an unknown solder composition. --------------------------------------------------- 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 -----------------------------------------------------