Hi Gaby, I think that you're right - this is certainly unusual and interesting - and a good chance to learn! Did you have a chance to look at this in the SEM? - like some of the other folks, I believe that this would be really helpful in determining what has caused the features which you've seen. It's difficult to see why it would have failed electrical test, another layer of mystery? Seems like there is still sufficient solder volume to carry signal, and interfaces at BGA and PCB look normal. Is this device/joint carrying high frequency signals? (could the electrical fault then be noise through this joint - some kind of skin-effect perhaps?) Be really great to see this section in the SEM, we would be happy to take a look for you free of charge, purely for the learning opportunity and the greater good! Another thought, did you have a chance to examine the pad-track connection on PCB and device? We've examined joints which are fine in the bulk but have suffered fracture at the connection between track and pad. Look forward to hearing how things progress. Kind regards, Stewart Stewart McCracken MCS Ltd. Centre House Midlothian Innovation Centre Roslin Midlothian EH25 9RE m. +44(0)7711 541735 t. +44(0)131 440 9090 f. +44(0)131 440 9085 e. [log in to unmask] w. www.themcsgroup.co.uk -----Original Message----- From: Gabriela [mailto:[log in to unmask]] Sent: 06 July 2009 17:16 To: 'TechNet E-Mail Forum'; Stewart McCracken Subject: RE: [TN] Weird solder joints I am really impressed about you people, being ready to help so much. Thank you all from all my heart. No, these specific feature is not due to handling. I think that the continuation was due to outgassing from the "open" in the solder into the mold. Also, the feature stayed there through all the polishing steps. Seems to me that this is a first for many of us. Forgot to tell you: This specific ball failed during ELECTRICAL test. The exact location-row and ball was given to me. Two other balls had similar features, but not through all the width. I don't know if they passed the electrical test. Gaby -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Stewart McCracken Sent: Monday, July 06, 2009 5:28 PM To: [log in to unmask] Subject: Re: [TN] Weird solder joints Hi Gaby, Just a thought, are you 100% certain that the features which you have shown are not caused by scoring/scratching/handling on the surface of the section? Could be some contact on the delicate sample surface between final polish and observation, perhaps during etch or rinse steps, or even during mounting onto a slide for viewing (dirt of the sample press)? This could explain the continuation of a feature from the solder joint into surrounding mould resin or soldermask. Would be worth ruling out and again SEM inspection of the sample would clarify. Would also be happy to take a quick look at them in the SEM for you if you don't have access. Kind regards, Stewart Stewart McCracken MCS Ltd. t. +44(0)131 440 9090 f. +44(0)131 440 9085 e. [log in to unmask] w. www.themcsgroup.co.uk -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Gabriela Sent: 04 July 2009 08:01 To: Administrator Subject: [TN] Weird solder joints Dear all, By cross sectioning BGA solder joints on a failed assembly, I found that the suspected joints are not uniform and that they contain unusual separation areas. I suspect mixed assembly and/or bad reflow profile. Steve was so kind and enabled me to send the links. Please may I have your opinion? http://stevezeva.homestead.com/files/small.jpg <http://stevezeva.homestead.com/files/small1.jpg> http://stevezeva.homestead.com/files/small1.jpg <http://stevezeva.homestead.com/files/small2.jpg> http://stevezeva.homestead.com/files/small2.jpg http://stevezeva.homestead.com/files/small3.jpg <http://stevezeva.homestead.com/files/small4.jpg> http://stevezeva.homestead.com/files/small4.jpg Gaby --------------------------------------------------- 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 -----------------------------------------------------