Homebrew PCBs

Simao Cardoso wrote:
> DJ Delorie wrote:
> 
>> IIRC you add a base (sodium hydroxide (drain cleaner) if you have it,
>> else baking soda) until the copper precipitates. That tells you the
>> pH has just passed neutral. Let the water evaporate, leaving a copper
>> salt "brick" at the bottom. Bring that to a hazmat place.
>>
> 
> Not really like that. I don't really know what chemistry things happens
> for sure but i can say that (since dumbly i try it once with a bit of
> used etchant) if you add NaOH until the thing starts to warm and get hot
> (or warm it by other means), after it cool and settle down you will end
> with a black fine powder mud at bottom that should be the complex
> Cu(FeO(OH)2)2 thing, above it a block of crystal NaCl in about the same
> amount of added NaOH, and all the remaining up top is clean transparent
> water. But it end even worst for disposal (etchant plus NaOH). SO DONT
> DO IT!! 
> There is no away i know to precipitate the copper on Cl based etchants.
> But i guess in my ignorance that FeCl3 etchants should be possible to
> expensively recover copper like CuCl with those DuPont ion membrane,
> large platinum anodes and ~1000A psu like some big pcb shops seem to do,
> ending with HCl and copper bars IIRC. 
> 
> Anyway nobody should use Ferric Chloride etchant this days,

I will use nothing else.

 > is a mess,

I haven't made a mess since using it the last 50+ times

> non recoverable,

It lasts forever. Just cover the container. Add a bit of HCl
every few months.

> not simple to disposal (pollutant if you dump it),

It's an excellent weed killer. There's rarely a reason to dispose
of it, so it's more enviroweenie friendly than most others.

> expensive, and in 2010 you have plenty alternatives available like
> Cupric Chloride.

Only expensive in retail shops. Buy it in bulk as "Profloc F" for $2/Lt.
Once you have a tank set up, there's little reason to buy much more.

Profloc F is a sewer treatment floculating agent iirc.
I got 30Lt of the stuff. Anyone in the local electronics clubs can
get it from me cheap.