Homebrew PCBs

grantfair2001 wrote:
> Hi Adam -
> 
> My etchant continues to slowly progress. It seems that some variable
> at this end differs from your approach. Nevertheless, the solution has
> slowly changed in the same ways you described.

Good point. I'm certain there is probably some very 
important variable(s) that I do not know of yet, and maybe I 
just happen to fluked upon it. I suspect air/copper/liquid 
interface has an important part in the initial reaction.
Maybe the copper should be positioned above the acid, and 
the sparger turned on so it continuously wets the copper 
with fine droplets. That way the lid can remain on.

I know that the reaction accelerates as more CuCl2 is 
produced. Once the solution goes dark brown and copper is 
well on its way to etching, then the limiting factor becomes 
the amount of air that the solution can absorb to continue 
the reaction of copper(I) to copper(II).  As I said earlier 
the copper(I) is the main etchant inhibitor.



> 
> At present it is a dark coca cola brown, and it is difficult to see
> much of the wire under the etchant, although maybe the top inch of
> solution is somewhat translucent. Overall, the solution has become
> darker and less translucent over time.
> 
> I had recently placed a piece of PCB in the solution. It took about 2
> days, but all the copper is now gone - so clearly, the etchant is etching.
> 

yep, its etching. But don't let 2 days worry you. If there 
white film of the copper when you pull copper out of 
solution then its saturated with copper(I).

> My tire air compressor failed. 

These machines are *not* designed for continuous use, and 
I'm not surprised it keeled over. I use a largish aquarium 
pump, which are designed for continuous use (and quiet). 
I've just been searching for a larger air pump, and found 
that they are used in hydroponics, along with all the 
necessary airstones accessories for creating lots of fine 
bubbles. DIY hydroponics seems quite popular in Australia, 
enough to have a dozen or so shops to choose from in my city.

> 
> I am hoping that although the process is slow, it will succeed in the
> end. I will keep the list posted.

I know this process of mine to make CuCl2 etchant is far 
from optimum so I'll keep chipping away at the problem. I'm 
certain its possible to be made without a drama , but just 
need to do a bit more learning to get there.

Thanks for keeping us updated.

Adam