We can do it John. That is what we do for leaving. Vladimir SENTEC Testing Laboratory Inc. 11 Canadian Road, Unit 7. Scarborough, ON M1R 5G1 Tel: (416) 899-1882 Fax: (905) 882-8812 www.sentec.ca -----Original Message----- From: John Parsons <[log in to unmask]> Sender: TechNet <[log in to unmask]> Date: Fri, 19 Nov 2010 13:17:07 To: <[log in to unmask]> Reply-To: [log in to unmask] Subject: Re: [TN] BGA Falling off PCA Thanks Werner for you input. I had suspected that definitive answers might only be obtained through SEM analysis and the like. Can anyone recommend a good lab? We have used Microtek before but I don't think that they have an SEM. Regards John _____ From: Werner Engelmaier [mailto:[log in to unmask]] Sent: Friday, November 19, 2010 12:49 PM To: [log in to unmask]; [log in to unmask] Subject: Re: [TN] BGA Falling off PCA Oh boy, John, There are a number of possible root causes-also, remember that those BGAs are the heaviest components and the thermally most massive ones. (1) this being ENIG, there is always 'Black Pad;' (2) when soldering to ENIG, you are soldering to nickel-it is possible you had an insufficient peak reflow temperature to cause adequate 'wetting' of SAC solders to Ni; (3) given SMD (solder mask defined) PCB pads, it could be a combination of stress concentration and weak interface due to either 'Black Pad' or insufficient reflow T's; Full root cause determination will take cross-sections and SEM. Werner -----Original Message----- From: John Parsons <[log in to unmask]> To: [log in to unmask] Sent: Fri, Nov 19, 2010 3:31 pm Subject: [TN] BGA Falling off PCA I am not seeing a lot of the usual Friday quiz traffic so I know you guys-n-gals are just itching for some real work :o). We are a PCB fabricator and one of our customers has returned some assemblies to us for feedback. What they noticed when someone accidentally dropped an assembly is that the BGA (352 pin Cirrus Logic EP9312-CBZ) popped off the board. They then proceeded to drop a few more from a height of about a foot with the same results. All the other components on this Pb-free assembly stay fast. We have received three PCA's and 5 BGA's. On one of the BGA's a single ball has remained on the PCB. The rest of them all the balls have broken cleanly from the PCB leaving a very flat (under x10 magnification) dull gray surface. I sure wish that I could take photo's but lighting is critical and I don't think that I have the resources to get photo's that would do justice to what the naked eye is seeing. Also of note is that the BGA lands are mask defined with a 31mil circuit pad and 26mil solder mask relief. Does anyone have any ideas as to how we can determine the root cause of this failure. This part has been built for some time but previously the surface finish on the PCB was a solder finish. This is the first run of the boards that has an ENIG finish. This doesn't look to me like a raw board issue but that is where everyone looks first isn't it ;o). Regards John Parsons ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- 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 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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