Paul,

Manganese will accumulate in the solution with time as it does not plate
out and at a certain concentration (depending on the additive system) may
start to interfere with plating.  Some additive systems are more resistant
to it than others.  At least one major Acid Copper supplier used to prefer
permanganate treatment, which seemed to work better than peroxide/carbon
with their system.

One of the reasons that peroxide/carbon treatment was not effective enough
for you might be fairly low peroxide concentration/temperature that you
were using.  Try 2-3 ml/l 30% or 1.5-2 ml/l  50% peroxide if you can.
Although not too many tanks will withstand the temperature above 140°F that
you are using, generally at about 160°F peroxide breaks down the long chain
leveller polymer molecules (which makes them adsorbable by carbon) much
easier.  Let the solution cool down  before adding the carbon.  Adsorption
on activated carbon is much more effective at room temperature.  The
effectiveness of your treatment can be easily tested by TOC (total organic
carbon).  The actual adsorption process is very fast, in just a few minutes
the reaction equilibrium starts to shift toward desorption so you might
want to keep it short.
After successful treatment you should be able to plate a uniformly matte
pink Hull cell panel with no traces of brightness in low current density
area at 1 Amp/5 min (microetch the anode and leach the cell/anode in 10%
sulfuric prior to plating).  Make sure to use high quality activated carbon
(contact your Acid Copper supplier for recommendations).  Microetching the
film from all the anodes and washing/replacing anode bags helps as well.
Good treatment should bring your TOC from several thousand ppm down to
about 100 -- 300 ppm range.

The effectiveness of your treatment depends a great deal on the particular
Acid Copper process that you are using.  Some of them are more easily
treatable than others.  No matter how you might choose to treat your
solution, it is always a good idea to simulate the treatment in the lab
using a few hundred ml of solution, checking TOC before/after, in order to
optimize it.

Eric Yakobson
Alpha PC Fab





Paul Gould <[log in to unmask]> on 10/12/98 02:32:06 AM

To:   [log in to unmask]
cc:    (bcc: Eric Yakobson/AlphaPCFabUS/Cookson)
Subject:  [TN] Copper ductility






Does anyone have information regarding the treatment of copper sulphate
plating solutions for organic contamination.

We do this approximately once a year on all solutions and have been using
the following method:-
0.5-1.5gm/litre  of Potassium Permanganate depending on level of organics
Agitate for 2 hours
0.5 ml/litre of 35% Hydrogen Peroxide
Agitate for 1 hour
Heat to 60 C (140F)
Add 2gm/litre of activated carbon
Continue with heat and agitation for 2 hours
Allow to settle and filter pump to storage tank as soon as possible to
prevent organics leaching back into solution from carbon.

Conversion factors ( g/l x 0.134 = 0z/US gal) & (1 litre = 0.264 US Gals)

This method is very effective at removing the organics but I would like to
know more about how this works. My concern is the level of Manganese left
in the solution after treatment. We recently tried using peroxide only and
carbon but this did not reduce the organics sufficiently. We are told there
is a finite number of times where permanganate can be used before the bath
has to be replaced.

Is this method likely to cause a build up of manganese and is there any
alternative?

Many thanks for any information
Paul Gould
Teknacron Circuits Ltd