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Reply To: | TechNet E-Mail Forum. |
Date: | Tue, 29 Oct 2002 15:19:56 EST |
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Hi Glenn!
Don't have a real concrete answer for you, but as you probably already know,
everything I've read recommends NSMD pads over SMD pads. I found figures of
ball collapse that range from 20-25%, but those figures were all referencing
NSMD pads.
Sorry I couldn't be more help...
But during my search, I found this excellent *.PDF file regarding PBGA's,
covers just about everything...
http://e-www.motorola.com/brdata/PDFDB/docs/PBGAPRES.pdf
-Steve Gregory-
> Technetters,
>
> There is a proposed design here that incorporates Solder Mask
> Defined (SMD) and Non Solder Mask Defined (NSMD) BGA pads on the same part.
> Solderable area on the pad is the same for both as is the solder ball
> diameter to place. I'm concerned about coplanarity, but I don't have any
> data to back it up. I know the SMD balls will be higher off the substrate
> than the NSMD balls, but by how much? The reason for this design is
> electrical performance.
>
> What do you think? Is the amount of variation in height too small
> to be concerned about?
>
> Thanks,
>
> Glenn
>
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