Re: gEDA-user: PCM making methods - was - Re: alarm clock update

[andrewm <andrewm@xxxxxxxxxxxxxxx>]

John Griessen wrote:
> I'm liking the transparency and low hassle and low toxicity of HCl/H2O2,
> and mostly want to do prototypes or circutis that go on low cost
> substrates so don't need to be teeny
> as possible to save board area.  I like the low tolerance approach --
> don't want to be a commercial fab.
>
> I got pretty good results etching DJ's lines test pattern for choosing amount of bloat to use
> in making postscript masks.  8 or 9 mils was the limit with my laser printer and toner transfer.
> I didn't see much morphing of shapes from etching.  I etched with good stirring action.
>
> My   HCl/H2O2 recipe is:  250 ml 35% Hcl, 35% H2O2  500ml distilled water,  do all the acid precautions,
> work under a shade tree, use 1000ml Erlenmeyer flask,
> add half the acid to the water, stir and add the rest slowly,
> heat on hot plate to 105 deg C, add 3 5 inch lengths 12 Ga Cu wire,
> stir occasionally till dissolved,
> Next add 20 ml of H2O2 and 40ml of HCl at a time according to appearance.
> Aim for yellow green solution, if blueish needs more HCl, add H2O2 carefully, and if you see
> bubbles starting to evolve much, stand back since it's chlorine.
>
> Now to use for etching, just observe colors:  If dark and starting to be hard to see
> your board from too much dissolved copper, add some H2O2 to clarify.  If getting to
> be forest green or blue green, it needs more HCl.   The solution volume grows.  Neutralizing with Na-OH
> gives copper oxide precipitate and fairly pure slightly salty water you can dump on the ground.
>
> That's what I like about it compared to FeCl.  No bright orange stains (on everything),
> and easier to neutralize and the remains
> of neutralizing can be sold even.
>   

If you let the HCl H2O2 just keep going to emerald green you will get 
CuCl etchant.  You never again need
to add H2O2 and can regenrate it by bubbling air through it.

I have been using CuCl for a bit over a year now and all I ever need to 
do is measure the acid levels and
density and then top up with HCl or water to keep it in spec.

Will still stain like FeCl, but you never need to neutralise it or throw 
anything away.




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