Francis,

Your plating thickness will depend largely on your cathode current density,
not your anode area. However, if you try to force too much current through
your anodes and you have insufficient anode area, then you can create a
condition known as anode polarization.
The best remedy for plating pwbs with different areas on each side is to
have separate rectification. In  this manner, you can control the amount of
current for each side separately.

However, make sure your agitation on both sides of the cathode is as uniform
as possible, that is no dead spots. Another possible remedy here is to
outfit your plating cell with eductors, ratheer than air spargers. Eductors
use pumps to cause a solution movement across the face of the cathode. thus
you are getting a laminar flow, rather than a turbulent flow. I have
performed controlled experiments where the distribution is improved up to 20
%.

Best regards,

Michael Carano

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