RE: [SI-LIST] : Some issues about fineline BGA ..

Andrew Ingraham (Andrew.Ingraham@digital.com)
Wed, 25 Nov 1998 10:20:21 -0500

>Also - I believe - that in normal situations, as long as decoupling
caps
>and supply pins have their connections to PWR/GND planes made with very
>short trace lengths, it is not very important to get the cap really
>close to the supply pins - the inductance of the power planes is so low
>it doesn't matter much - better to make routing life easier by shifting
>them away a bit if needed.

Not necessarily. It does matter. We see situations where we just can't
get enough capacitance, close enough to the active components, around
things like SRAMs, DRAMs, and even some simpler ICs, to hold down the
PWR noise right at the IC pads.

Regards,
Andy

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