Hello, I have a copy of the 'Head-in-pillow' document by Alpha Metals. Is there any way I could send Steve a copy and he could post it on his site? Thank you, David -----Mensaje original----- De: TechNet [mailto:[log in to unmask]] En nombre de Kane, Joseph E (US SSA) Enviado el: Friday, April 20, 2007 1:07 PM Para: [log in to unmask] Asunto: [TN] BGA Head In Pillow Steve was good enough to post some pictures of one of our recent failures: http://stevezeva.homestead.com/files/solder_ball_fracture_site_115x.jpg http://stevezeva.homestead.com/files/solder_ball_SEM_photos_4-13-07_003. jpg These are pictures of the underside of the same failed BGA connection, and I believe this illustrates a phenomenon discussed here a while back, called variously "foot in mud" or "head in pillow" or "ball in socket". Looking back through the archives I couldn't figure out why sometimes the divot appears on the underside of the ball, and sometimes the depression is in the solder remaining on the land. I take it that sometimes the BGA ball doesn't melt as fast as the solder paste, and the intact ball may be pulled upward out of the paste when the BGA warps. When things begin to cool, the ball descends into the pasty solder on the pad, resulting in the "ball in socket". But if everything does melt together, and the corner warps upward, most of the solder can be pulled up and away by surface tension, leaving a smaller solder deposit on the pad. When things begin to cool, this smaller mass freezes first, and the pasty mass attached to the underside of the BGA settles onto this hard mound, creating "head in pillow". Like in this case. Is this fair? I also saw a number of citations of this link: http://alphametals.com/products/solder_solutions/pdf/pillowhead.pdf ..which might have led to some good information, but the link appears to be broken. Anyone have a copy of this file, or know a valid shortcut? Joe Kane BAE Systems Johnson City, NY --------------------------------------------------- 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 -----------------------------------------------------