Homebrew PCBs

Stefan Trethan wrote:
> On Tue, 06 Sep 2005 05:46:55 +0200, Adam Seychell  
> <a_seychell@...> wrote:
> 
> 
>>Dull green is ok, only when it becomes brown is the problem. If you
>>dilute a bit of it and it turns bright green then its pretty much
>>regenerated. But, this doesn't necessarily mean it'll etch ok.
>>I here a lot of people on this group that cannot get air re-generated
>>cupric chloride to work, simply because they run their solutions too
>>damn week. I have done a side by side comparison with fresh full
>>strength ferric chloride (sp.gr 1.47), under exact same conditions and
>>the cupric chloride (without any H2O2, ever) is only fractionally slower
>>(7.5 minutes for FeCl and 9 minutes for CuCl for bubble etching, 35um
>>thick copper at 15\ufffdC).
>>Adam
> 
> 
> 
> i agree, you need a strong solution to do air-regeneration.
> For H2O2, anything works, but as it grows denser the time between H2O2  
> applications can be extended, wile at the beginning with a very weak  
> solution you need to add it each time you etch, at least. Density, and a  
> enough volume, are the key to air regeneration i think.
> 
> 

Yes, the more copper the faster, and the more acid the faster. You are 
only limited by solubility, and HCl fuming. A good compromise I found is 
to run at sp.gr 1.38~1.45 and acid at 2~3 Molar. This will be almost 
fast as fresh undiluted ferric chloride. Unfortunately you have to 
invest in a hydrometer, and perform titration (using a 1 ml syringe) to 
determine acid concentration about every 20~30 PCBs or so etched.


Adam