Homebrew PCBs

On 06/14/2010 12:12 PM, James wrote:
>    
>> Wondering that myself.  I suppose the easy answer is "when it stops
>> etching to your expectatins".  Also is probably a reason bubbling air is
>> better than H2O2, but bubbling creates corrosive aerosols.
>>
>>      
>
>
> They both work fine. Once it's turned into cupric chloride, it doesn't matter of the peroxide breaks down. You just add a capfull prior to etching if you don't want to wait around for air to regenerate it. It's cool, it almost instantly changes from very dark brownish-green to light green.
>    

This is my understanding of the process, I could be terribly wrong.

Etching produces

2 Cu + 2 HCl -> 2 CuCl + H2.

Adding the H2O2 gives the following:

H2 + 3 H2O2 -> 4 H2O + O2

You also wind up with this one if there is any "head space" in the 
container:

2 H2O2 -> 2 H2O + O2.

Adding H2O merely regenerates the source of quickly available Oxygen 
molecules.

I can't make the H2O2 produce HCl, but it's been a while.

:)

Hence, my assumption that sooner or later, you're gonna need to dump the 
stuff and start over.

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