Homebrew PCBs

On 3/05/2011 10:30 PM, Mark Lerman wrote:
>
> If I add 3% H2O2 to regenerate my etchant, I'm adding a lot of
> water to the mix, so I'm wondering if there's any advantage or
> disadvantage in bubbling oxygen rather than air through CuCl2 etching
> solution? Or does the air itself regenerate the solutionadequately in
> addition to agitating it?
>
> Mark
>
I've had the same brew of cucl2 for about 5 years now, and haven't found 
I ever needed to add h2o2. The only advantage of h2o2 would be very 
quickly regen it if it's over used (brownish look to fluid) and you need 
to etch something quickly right now. Air bubbling will take a few hours 
at least to clear up a well used batch of fluid.

These days I don't do a lot of etching, and other than the bubbler and 
heater running while etching I haven't had to do anything to regen it, 
the contact with air above the vertical tank (one of the basic off the 
shelf types) is enough to clear up the liquid. The fluid lives in the 
tank, which lives in the shed. And I don't have any kids of pets that 
could get into it, so haven't worried about its safety too much.

Back when it was getting much heavier use (previous job) I did bubble it 
overnight a couple of times, and eventually when saturated with copper 
it'd precipitate out as a grey sludge on bottom of tank I simply 
filtered that out with coffee filter paper and add a little hcl to top 
up the chloride ions. Make sure you filter it before the hcl, adding hcl 
will dissolve the sludge. Chances are you may never het to the 
precipitate stage, that only happened after a long time of a lot of use, 
without adding hcl.

Andrew


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