Hi Wayne, Have you cross-sectioned one of the failed balls to look at the fracture path? If the failure doesn't look like BP, then I'd assume it didn't fail at the Ni-P/intermetallic interface. In such a case, a cross-sectional view would tell you where (which interface(s)) failure actually happened at. Regards, Vladimir -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne Sent: Monday, October 01, 2007 9:39 AM To: [log in to unmask] Subject: [TN] BGA Intermetallic failure 0.5 mm pitch BGA, board has via-in-pad. On 5 of 7 via-in-pad locations, the balls separated in the intermetallic zone at the substrate interface. All other balls look ugly, but not out of the usual ugliness when the BGA is SAC305 and we are attaching with Sn/Pb, and they seem well attached. The ugliness of the bulk of the balls is very uniform, indicating thorough mixing of the alloys. The separated intermetallic zone is lumpy gray, not like cases of black pad I've seen. Boards had ENIG, then had SnPb SIPAD done on them (requires 2 reflow cycles). After that, the BGA's were attached and then the other side was stenciled, populated, and reflowed. So the ENIG interface had been reflowed a total of 4X. The surface of the via-in-pad locations is fairly lumpy, like is common with CB100 via fill. Perhaps this lumpiness was responsible for too much gold in the joint? I can't think of any other reason why these locations are where the problems are. Additional insight would be very much appreciated. Thanks, Wayne Thayer --------------------------------------------------- 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 -----------------------------------------------------