Werner,
How big were the rectangular pads? Were they of the same area as the
circular pads they replaced on the PWB? Presumably the failures with
both circular and rectangular were at the PWB side of the solder joint,
not the device side?
Regards,
Werner Engelmaier /* wrote:
> Hi Joe,
>
> In the '80's, we at Bell Labs tries round, and rectangular pads. The ATC results showd a slight reliability advantage for solder joints resulting from rectangular pads. I have a paper in SMI sometimes in the early '90's [Bell Labs management would not let it be published at the time] with the data. The reason for the rectangular pads , by the way, was smaller possible pitch.
>
> Werner
>
>
> -----Original Message-----
> From: Joe Fjelstad <[log in to unmask]>
> To: [log in to unmask]
> Sent: Thu, Sep 3, 2009 8:10 pm
> Subject: [TN] BGA/LGA land shape versus assembly yield reliability
>
>
>
>
> Greetings folks.
>
> I did a quick check of the archives on the subject and drilled a dry well
> (maybe drilled in the wrong place?).
>
> That said, in design and lay out we all tend to match pad shapes on the
> board with their mates on the package (round hole - round peg , square hole -
> square peg)
>
> My question is has anyone looked at (or know of) round with square and
> vice versa and collected assembly efficacy/results and/or reliability data?
>
> Finite Element Modeling data would be of interest as well.
>
> Thanks in advance for any responses
>
> Joe
>
> Since its Friday in some place of the world (or soon will be) I was looking
> over the period table recently and afterwards was wondering if anyone had
> ever mentioned that this little forum has it very own element, TechNetium,
> the first man made element. (the upper case N is my suggestion for future
> spelling... ;-)
>
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--
Eric Christison Msc
Mechanical Engineer
Consumer & Micro group
Imaging Division
STMicroelectronics (R&D) Ltd
33 Pinkhill
Edinburgh EH12 7BF
United Kingdom
Tel: +44 (0)131 336 6165
Fax: + 44 (0)131 336 6001
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