Also, have you performed microsections (cross sections) to determine 
     what kind of material is at the core of the nodule?  Small nodules 
     usually require at least a few tries to get the small core.  Be 
     patient.
     
     
     Matt Byrne
     Hadco-Owego
______________________________ Reply Separator _________________________________
Subject: Re: COPPER  PLATING:Tiny nodules in plated through holes
Author:  [log in to unmask] at SMTPLINK-HADCO
Date:    5/22/97 01:21 AM


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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