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

[John Griessen <john@xxxxxxxxxxxxxx>]

DJ Delorie wrote:
  laser
>> cutter seem like a prudent investment :D
> 
> More like $90k.  I've checked. 

I have some old experience with lasers and a YAG laser with no practical pump.
If anyone sees some 807-nm laser diodes that output a line of light,
or are coupled to a fiber, tell me.  I can use them to pump the
Nd:YAG 5 inch long rod of my 60 Watt formerly lamp pumped basket case laser.




>> HCl/H2H2 (and the CuCl I use) do not give as sharp an edge as
>> FeCl3. 
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.

> The problem with brass is that it's *thick*. 
This is maybe the root of why pros use a laser for stencil making.
Optimum stencils even need thickness variations across them done
by etching zones before cutting.

What would vary thickness zones of plastic stencil media before cutting?

John Griessen
-- 
Ecosensory   Austin TX



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