Mark-
2oz internal layers is not a problem. We do a lot of smd's on 2oz, but not
fine-pitch. You have to watch very narrow traces with heavier weights. We
try not to go below 12mil though I'd guess you can go smaller without
problems. I'll leave the EMC/planes stuff to the smart guys here, but
generally speaking, putting gnd on one side, power on the other, and all
your traces inside, places all your signals in the middle of a loop.
-Chris

>Hello all,
>
>I am currently working on a very interesting board which has quite a few
>high current carrying tracks (around 10A). The scheme suggested by the
>engineer is to have the planes on the outer layers (for EMC reasons) and
the
>tracking on the inner layers. There are surface mount components on both
>sides.
>
>Is EMC performance improved by having planes on outer layers? Are there
any
>problems are associated with mounting surface mount parts on 2oz copper
>pads? Can I have 2oz copper as inner layer? All the trace width
calculators
>I have seen use copper weight for the calculations, but PCB manufacturers
>often talk of "plating up" and "finished weight" presumably this it not
the
>same as 2oz of copper - any advice?
>
>My view is I could get a more complete plane using the inner layers
(because
>of the surface mount pads) and I am concerned that high current tracks on
>the inner layer, being much wider than if the were on the outer layers,
may
>be difficult to route.
>
>Any advice or comments on the above would be most appreciated!
>
>Regards,
>
>Mark.
>
>Mark Holmes