Homebrew PCBs

On Sat, 12 Feb 2005 09:50:24 +1100, Adam Seychell  
<a_seychell@...> wrote:

>
> All references I've seen for hobby etching with CuCl2 is S.G < 1.2,
> which in my experience found to be almost useless as an etchant.  If
> H2O2 is present then etching rate is fast regardless of S.G even with no
> CuCl2 present! It seems the etch rate is very sensitive to CuCl2
> concentration if and only if the mechanism of regeneration is from
> dissolved O2 alone. In other words people seem to be running
> HCl+CuCl2+O2 at far lower concentration than what they should. So I'm
> wondering who uses HCl+CuCl2+O2 and at what S.G and what are their
> experiences ?
> Adam


Yes, i understand that the same way. when i started with my etchant it  
took long until the S.G. was high enough to allow etching without H2O2. I  
don't know how much different the etch rate now is, between H2O2 added and  
not added. It is har to say because i got my bubbler only a while ago, so  
i don't have much experience with the much shorter times now. Also, i only  
add enough H2O2 to achieve a color change, so it migh not be much "free"  
after regenerating the bath.
But remember, if the S.G. gets too high it stops working properly too.


I would only consider going with air oxygen alone if there is really no  
way to get your hands on H2O2. A liter lasts years for my use, and it is  
"instant". So if i need 5 boards at once i have no problems...


I have suggested that before, but aquarium guys use a reactor to solve  
CO2. it is a vertical tube where the water is pumped downwards, and the  
CO2 added at the bottom. The stream holds the CO2 in for a long time, and  
there are obstacles in the reactor (balls). They say one can set it so  
that all CO2 is solved.
Such a setup would surely not solve all air ('cause only 20% oxygen), but  
i bet one could increase the effectiveness of a oxygenating system  
dramatically with such a reactor.
The aquarium guys pay for pressurized CO2 (or make it chemically) so they  
sure want to use every last bubble. If the added complexity of using a  
pump is worth the gain for cucl, i dunno.

ST