Well then,
 
Work as distances. Why didn’t you say that from the beginning. Like we use sometimes: we remove some corner balls and replace with somewhat higher temperature.  I understand now. Thanks.
 
Inge
 
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Skickat: den 17 april 2007 19:10
Till: [log in to unmask]; [log in to unmask]
Ämne: Re: [TN] Tacking corners of BGAs
 
Hi Ingemar,
The corner epoxying serves not so much a mechanical fixation in the x/y-directions, but a way of preventing the solder balls from collapsing, and thus improving thermal cycling creep-fatigue reliability by (1) increasing h [with N h**2.2], and (2) improving the solder joint shape from squashed collapsed spherical to near-hour-glass. I also rather doubt that the 4 epoxy corners would be anywhere near strong enough to prevent the warping of superBGAs that thermally asymmetrically designed. 


Regards,
Werner Engelmaier
可靠性先生
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com


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