The ASF is roughly the same regardless of location, but the mass transfer
(of copper ions) is going to be different due to concentration gradients
being different, and that depends on bulk solution concentration, agitation,
copper patterns on the board, hole geometry and probably a few other things
to lesser degree.
The PTH in the middle of a ground plane will plate slower than a isolated
one, due to lower Cu++ concentrations in the area right around the ground
plane hole.
I suppose what you are really asking is "how does one calculate the plating
rate in this hole or that hole?"
I don't think there's a simple formula, though I understand some CAM
software (we don't have) does look at copper distribution and recommend
adding thief areas to boards that need it.
One can reduce the plating variation in acid Cu by operating at the low end
on CuSO4 conc. and the high end on H2SO4 conc., maximizing agitation,
evening out anode distribution, and increasing anode-to-panel distance.
        But knowing all that hasn't helped me reduce copper thickness
variation much, so I'll be looking for better answers along with you!


> ----------
> From:         Robert Jordan
> Sent:         Tuesday, October 19, 1999 7:45 AM
> Subject:      ASF info...Super Plater
>
> Hello,
> Once again another question drawing in the vast talent and experience of
> Technet. Is there a way to calculate the ASF inside a through hole in a
> printed circuit board during the electroplate copper process? Is that ASF
> different if the pth is in the middle of a ground plane vs. an isolated
> area? If no formula exists please bend my ear with your opinion.
>
> Thanks,
> Bob Jordan
>

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