Hi Fred,

Thanks very much for the suggestion. Sounds like a great method. I take it
you use carbon filter packs instead of adding bulk carbon to the solution?

Best Regards

Paul Gould
Teknacron Circuits Ltd

-----Original Message-----
From: Fred Johnson <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 12 October 1998 15:05
Subject: [TN] Copper ductility -Reply


ooh - permanganate bad!  This was the industry standard many years ago, but
people got away from it for precisely the reason you mentioned, i.e. buildup
of manganese in the solution.  The industry standard for many years has been
hydrogen peroxide followed by heating to drive off (destabilize) the
peroxide and followed by adding granular or powdered carbon to absorb the
organics.  Like you, I have seen situations where peroxide alone has been
insufficient to remove all organics.

I have been quite successful by adding 1/4 ml/liter of common household
bleach (a solution of 5.25% v/v sodium hypochlorite; NaOCl) in 3 increments
(add 1/3, wait 20 minutes, add the next 1/3, wait 20 minutes, and then add
the last 1/3) followed by carbon polishing.  All of these methods utilize a
strong oxidizer to "break up" the organic chains into portions which can be
then attached to the carbon; the bleach is another strong oxidizer which has
the advantage of not requiring heat treatment or adding bulk carbon to the
solution and adding only a few ppm of chloride to the bath.  I promise, it
really works very well and is much, much easier to do.

While you're at it, the next time you pump your copper bath out of the tank,
if you have a polypropylene or polyethylene tank you might fill up the tank
with a solution of 10% sodium hydroxide and 1/4 pound/gallon (120 g/l) of
trisodium phosphate.  Use hot water to make this up if it's available; after
an hour or so the solution will be brown from all of the soaked-in organics
it will remove from the plastic tank.  Drain and neutralize with a weak
sulfuric acid solution.

Regards,
Fred J.

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