Homebrew PCBs

Stefan Trethan wrote:
> I see...
> 
> Thanks for the explaination.
> I already had the idea that basically the same might happen after writing the post.
> 
> But i don't fully understand why all of these 3 parameters must be adjusted.
> I only adjust one, the color. If to brown it doesn't work and H2O2 (obviously regeneration) is added.
> 
Color is a good way of checking if too much cuprous ions are 
  presents. Cuprous is not very soluble and will form film 
on copper being etched and slow down the reaction.

a hydrometer is very easy and quick way of knowing when too 
much copper has been dissolved and water must be added. I 
think a copper content of 150 to 200g/l is ok.

> The density: I don't monitor at all. But my H2O2 and HCl guide did say if there is any brown mud 
> settling on the bottom simply filter it through filter paper to get it out.
> from the page you mentioned: "Etch rate will slow down and sludge may form with increasing density" - 
> has this experienced one of you? is this really happening?
> Is the homebrew Hydrometer enough for normal work? but how to start if not bying the cucl but rather 
> starting with etching solid copper (or using my now in use fluid)? How exact has this to be?
> Isn't there another method of getting the copper out (electrolytic deposition?)?
> 
> Acid concentration:
> I also don't monitor it, but it is too high, get fumes i think.
> I don't like the titration, i don't like buying a buret and a stirrer and indicator etc.
> But i believe this is quite important if bubbling...
> 

 From what I've been told, the free acid of commercial 
cupric chloride etchers can range from zero to 15% (wt). The 
acid doesn't have a large effect on etch rate, but for 
bubble etchers it should  not be zero. Say 0.5% to 2%


> 
> Also if only 3% HCl:
> 
> Don't you get a lot of fumes from bubbling attacking any nearby oxidizeable material?
> 
no, at 2% acid there isn't any problems.

Adam