Homebrew PCBs

Markus Zingg <homebrew-pcb@...> writes:

> So, one would i.e. need to build 3l HCL/H2O2 and put in half a pound
> of copper into it? Correct?

Well, that's what I did.

> How many HCL and H2O2 to get to a 3l solution to start with? I mean
> what's the ratio of HCL to H2O2?

Assuming you're using 37% HCl and 3% H2O2, it's two parts H2O2 and add
one part HCl (always add acid to water, not the other way around).

> Any restrictions regarding the kind of copper? I do have copper left
> over that I use for the anodes in my through plating station. Would
> that do?

Any copper should do.  Any "tarnish" comes off really fast as it's
pre-oxidized.

> A hydrometer - when useing google - seems to be a device to measure
> humidity?

That's a hygrometer.  A hydrometer measures the density of liquids.

Alternately, just weigh 100ml of solution; it should weigh 120-130 g
when you're done (plain water weighs around 100g).

> Regarding the "air stone bubbler", I think I remember that one uses
> this to regenerate the solution. If so, does one have to do this
> every once in a while, or only during etching, or just before?

I run it during etching, because it also stirs the solution and helps
keep the etch even.  Otherwise, run it whenever the solution starts to
turn brownish.