Hi Technet! Pbfree component finishes - a very cool subject that gives all of us ulcers! I have no doubt there will be a Dilbert strip some day showings an engineer rambling about the "old days" when all we had were tin/lead surface finishes. It is easier to cover the topic of Pbfree component finishes if we break it up into a couple of segments. Area Array Components (BGAs, CSPs, FCs) - there are a couple of industry camps: those folks who solder a Pbfree BGA in a tin/lead solder process with a reflow temperature that achieves good solderpaste/solderball mixing and those folks who rebump the BGA with tin/lead solderballs. There is plenty of industry data which shows that a nonhomogeneous area array solder joint has poor integrity so the industry folks has been focused on getting a uniform solder joint. The industry camp that raises the reflow temperature has to deal with the potential temperature impact on the other components on the assembly. The industry camp that rebumps the BGA has to deal with the potential impact on the BGA integrity. Great discussion topic to exchange beers over! Other Components - there is a persistent myth that Pbfree component surface finishes can not be used in a tin/lead solder process. I wish we could put that myth in the ground and forget about it sometime in the near future. In a tin/lead solder process we diffuse a non tin/lead surface finish into the solder joint, we don't melt them into the solder joint. The industry is very good at doing this - we have utilized gold, nickel/palladium/gold, tin, palladium silver, etc., for many years making solder joints with good integrity. Due diligence is needed on understanding that you don't have some weird metallurgical issue result from a component surface finish/solder joint combination but combining Pbfree component finishes with a tin/lead soldering process is very simple and not rocket science. As for Ken's question: What about a SAC component surface finish? Well, its a Pbfree surface finish that has a high tin content. Hummm, sounds like a matte tin finish with a little bit of silver added and the industry solders matte tin surface finishes all of the time. There will be a pretty decent industry data set on this topic by APEX. The gang at CALCE has SAC surface finishes under test, the NASA DoD consortia (formerly the JCAA/JGPP group) has SAC surface finishes going into test and a number of other organizations/investigators are chasing the topic. My opinion is that a SAC component surface finish is not a solder joint integrity issue if the reflow solder process uses adequate time/temps. If the industry is competent with soldering matte tin surface finishes, then a SAC finish should not be any greater issue (and yes, I didn't mention tin whiskers on purpose!). Enough said - time to find a Diet Coke and harass Doug! Dave Hillman Rockwell Collins [log in to unmask] Gerald Bogert <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 08/14/2007 05:23 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Gerald Bogert <[log in to unmask]> To [log in to unmask] cc Subject Re: [TN] SAC Soldered With SnPb August 14, 2007 Good question. I also need info in this regard for SAC for all type of component leads/terminations that may be finished with SAC. Is it better from a reliability standpoint to just live with a SAC finish for SnPb assembly level soldering, or otherwise re-work the components to replace the SAC with SnPb? Are we at the point yet where we can reliably predict equipment life in the field for SAC alloy as compared to SnPb alloy? I have need seen any widely accepted industry papers yet that equate accelerated life testing results to expected product fieldlife using SAC alloy. On a related issue, for pure tin, I understand that NEMI is not endorsing it unless there is a nickel under-plate. Just annealing after plating for pure tin plated parts is not acceptable per NEMI recommendations. I believe Dave Hillman of Rockwell published some data regarding soldering to SAC with SnPb solder. If you get any info on SAC or pure tin plated leads/terminations, I would appreciate it if you could forward to me. Thanks. Seems like when I post a question to Tech-Net, I get very few answers. Could be my questions are difficult to answer. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bloomquist, Ken Sent: Tuesday, August 14, 2007 4:51 PM To: [log in to unmask] Subject: [TN] SAC Soldered With SnPb We are a Class 3 manufacturer and are looking at the different lead finishes that can be soldered successfully with SnPb. One that we are having a hard time finding information on is SAC lead finish soldered with SnPb. I know that it's not good practice for BGA's but what about SMT and through-hole parts? Thanks in advance, KennyB --------------------------------------------------- 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 -----------------------------------------------------