Homebrew PCBs

Ned Konz wrote:
> On Monday 03 March 2003 12:06 am, rolanyang <rolan@...> 
> wrote:
> 
>>I had a chance to play around with some CuCl2 (Cupric Chloride)
>>etching last Friday and performed a test etch with a small segment
>>of PCB created using the "cheap paper laser toner-transfer method".
>>The traces are 10 mil in width.
>>
>>You can see check out some pics at
>>
>>http://www.techfreakz.org/~rolan/mypics/cucl2/
>>
>>The neat thing about using CuCl2 is that the byproduct
>>of the etching process generates more CuCl2. And because of
>>this, the etchant solution can be used over and over.
> 
> 
> No, the etching reaction (a reduction reaction) generates CuCl . 
> 
> Cu + CuCl2 => 2 CuCl
> 
> People do regenerate the etchant using oxidizers (like chlorine gas or 
> hydrogen peroxide).
> 
> 2 CuCl + H202 + 2 HCl => 2 CuCl2 + 2 H2O
> 
> 2CuCl + Cl2 => 2 CuCl2
> 

Ordinary old air can regenerate the solution too. The cuprous 
chloride complex is quickly oxidized to the cupric state (Cu++) 
with dissolved oxygen. Air is widely available and doesn't cost 
anything. I don't know why more hobbyists are using this etchant.