Bob, Wouldn't mid-chip solder balls in SMT display slightly flat bottoms as well? Leland -----Original Message----- From: Bob Willis [mailto:[log in to unmask]] Sent: Wednesday, October 28, 2009 8:54 AM To: 'TechNet E-Mail Forum'; Leland Woodall Subject: RE: [TN] Birth of a Solderball You can only really tell from the shape. Trying to microsection balls is fun, you get a great section then the ball comes out during polishing. I use these images as how not to do sections in my microsection class at college. Next time I am doing some sections I have a board with some nice balls from selective that I have vacuum coated. In selective and wave if the solder ball is still in a liquid state during contact with the mask it can have a flat bottom. This is normal in air but not nitrogen Bob Willis 2 Fourth Ave, Chelmsford, Essex, CM1 4HA England Tel: (44) 1245 351502 Fax: (44) 1245 496123 Mobile: 07860 775858 www.ASKbobwillis.com www.SolderingStandards.com New Package on Package Workshops 24th November www.ASKbobwillis.com/PoPWorkshops.pdf PCB Inspection & Quality Control Workshop 3rd November www.ASKbobwillis.com/faworkshops.pdf Book Bob's "Step by Step Failure Analysis Workshop"4th November www.ASKbobwillis.com/faworkshops.pdf Package on Package Assembly & Inspection Workshops 21th January ITRI www.ASKbobwillis.com/PoPWorkshops.pdf -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall Sent: 28 October 2009 11:54 To: [log in to unmask] Subject: [TN] Birth of a Solderball TechNetters, Is there any possible way to determine the origin of a solder ball? We've had a failure because of one, and we're trying to determine whether it came from our SMT or wave soldering process. We use SAC305 at both, so using the SEM to determine alloy composition is not really helping. The ball itself is spherical with no "tails" and quite shiny in appearance. If we cross section the ball, will we see a difference in grain structure due to the differences in cool down rates? Is there anything else we can use or do? Thanks in advance for your help! Leland --------------------------------------------------- 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 -----------------------------------------------------