Mr. Khan,

Your problem would be difficult to address without additional details,
some questions and possible items to investigate are as follows:

How large/small are the nodules, and what sort of problem do they create
for the use or sale of the boards?  

Are they found in the holes only, or are they also on the surface?  Are
they found in all hole sizes? Are they found in all areas of the panels?
Is the problem constant or intermittent?

Have you tried a bright nickel flash to help make possible nodules in the
chemical copper more easily seen?  Lack of reflectivity can make them
hard to see.

You didn't mention the filtration on the electrolytic copper. Particles
in the electrolytic copper bath would be a prime suspect. The removal of
small particulates would require a large area of very fine (1 micron or
less) filters.

You mentioned control of the additive in the electrolytic copper by amp
hour, have you confirmed that the proper concentration is present via
Hull cells, CVS, and/or HPLC? 

High additive concentration, organic contaminants, high temperature,
and/or high copper concentration in the electrolytic copper bath can
contribute to dullness  or lack of leveling in the lower current density
areas (e.g. in the holes). 

To test for low current density problems, try plating in the Hull cell
(air agitated) at 1 amp for 30 min.  Low current density problems are
more easily seen in the Hull cell with the longer plating time.

If the problem is related to poor low current density performance of the
electrolytic copper, raising the current density (e.g. 3 amps/sq dm) may
provide a temporary fix. If this helps, the items above should be
investigated.  

Please feel free to contact me directly for more detailed discussions.

Regards,
Paul Galatis
Electrochemicals
E-mail:  [log in to unmask]



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