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

-----Original Message-----
From: Francis Lai <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Saturday, November 14, 1998 5:45 PM
Subject: [TN] Copper plating Anode ratio


>1/ In our copper bath, there are 3 anodes in the front side and 3 anodes
>
>   on the back side with the panel immersing in copper sulphate agitating
>
>   between the front and back anodes. Say, if I get X mil in an hour of
>
>   copper plated.
>
>2/ If for pattern plating, the front to be plated is only half of the area
>
>   to be plated at the backside. If I used 2 anodes in the front and 4
annodes
>   at the back, do I still get X mil of copper plated on both the front and
>
>   back sides of the panel?
>
>3/ What is the theory of the ratio of anodes to cathode in copper or tin
>
>   lead plating?
>
>4/ If the front and back side anodes are not equal, will this affect the
>
>   shape of the plated trrough hole?
>
>Could somebody help me with this? I work in copper plating for 2 years but
>
>I do not know the theory behind it. I am just curious to know.
>
>Thanks in advance!!!!!!
>
>my e-mail: [log in to unmask] (this is text base pls do not send
>                                      graphics)
>
>Thanks again
>
>Francis
>
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