Hi Gary,

I'd love to see that spec, can you post it? If not, send it to me (mailto:
[log in to unmask]) Are you sure you're not seeing a via-in-pad (blind) via
on the BGA side, and a via-in-pad (blind) via on the cap side, both only
going to the next layers down? I haven't seen a spec that shows the BGA
via going directly thru to the cap pads. That's a new one on me.

Secondly, unless you're going some incredible SPEED on your board (over
2GHZ?) you might not even need to do what they're suggesting. I've seen a
few current specs, written by chip app engineers that 'suggest' an ungodly
amount of bypassing. Normally if you breakout a BGA pattern correctly, you
should be able to get a good amount of 0402 caps directly under the BGA,
then sprinkle many more around the perimeter.

Send the spec if you can. Good day.

Mitch
>
> Hi All,
>
> I'm looking at a spec for a new processor we may be using. They
> recommend using via in pad and show a diagram of how to place 0402
> bypass caps right on the vias under the chip. Has anybody done this?
> This brings up a few questions. Since 2 adjacent vias will form the
> footprint for the caps, should I make the bottom pad of the via a square
> that approximates the pads I normally use on these caps? How do I place
> the caps without creating DRCs? Will our assembly house be completely
> dumbfounded when they see this? Is this whole idea just a figment of
> some engineers imagination with no basis in reality?
>
> Thanks for all help
>
> Gary Boccoleri
> Bivio Networks
> 925-924-8621
> www.bivio.net
>
>
>
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