At 12:14 PM 4/24/2002 -0700, Afshin Salehi wrote:
>Hello all,
>         Currently on PCB's I flood the top and bottom layers with a 
> ground plane after routing.

I've started doing that on certain boards, particularly fine-pitch SMT 
boards. It can make a good 6-layer stackup, with power and ground planes 
separated by 5 mils or so in the middle, for good distributed capacitance, 
layers 2 and 5 for most routing, and only fanouts and occasional or extra 
power routing on the top and bottom.

covering the top and bottom -- except for component pads and fanouts -- 
with ground *may* improve noise behavior. It might also cause impedance 
discontinuities, it depends....

>   I have it remove the dead copper then I manually place via's where 
> there was no flood to connect those area's to ground.

One might want to place extra vias anyway, for better return paths.

>   I then repour
>the planes and continue this process until I am satisfied with the coverage.
>This can't be the most efficient way.  Is anyone else doing something like
>this that has a better way or a trick I am unaware of?  I look forward to
>reading your replies.

The only thing I can suggest is that you place as many vias and ground them 
before pouring. There is very little harm, if any, in having extra vias.

I received a board here, done in OrCAD Layout, where the designer had used 
a pour, top and bottom, and had not removed dead copper. Worse than useless....

The pours that I made as described above did not need many additional vias, 
if any, for simple connection, because the only islands were inside QFPs or 
the like, and there was always at least one ground via already in there....

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