Loan Is there any chance that the BGA package is warping? The thinking here is that if the package is warping enough to keep the spheres above the paste during liquidous, then as it the profile cools and the package returns to its "normal" state, the solder will have also cooled, and entered that pasty region where it cannot wet to the spheres, even if they reestablish contact. The spheres would then sit on top of those "pillows". If this is the case, my guess it that most of these would occur away from the center - and more toward the corners of the perimeter. This also fits in with your description that this same part is having similar problems on other boards, where no other problems are apparent. Bruce Tostevin Benchmark Electronics Hudson, NH -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan Sent: Wednesday, November 15, 2006 10:58 AM To: [log in to unmask] Subject: Re: [TN] Separation in BGA joints George, Victor, foot-in-the-mud, head-on-pillow. It seems that you two are talking about the same thing, but what is it and why is this happening? The stencil is 6 mils thick with square apertures, the dimension equal to the diameter of the pad. ENIG finish. Time above liquidous is 65s. Due to pressures from our customers we run many lead-free BGAs on leaded paste at 220C. If this forms joints, why LF on LF would not form joints at 246C, or let's say 230C if I am really off in my temp measurements? Thanks, Ioan ------------ --------------------------------------------------- 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 -----------------------------------------------------