Okay, starting to make some sense. But, finding and buying
chemicals isn't the easiest thing to do these days.
So, a couple of follow up questions.....
hydrogen peroxide (H2O2), is this the same as what I can purchase at
the local drug store? Or, is there a stronger solution or something
I have to get at a specialty supplier?
hydrochloric acid (HCl), I know I have seen this for some purposes
but can't recall common uses - toilet bowl cleaner perhaps? Again,
where would I purchase this, and is there a certain strength I
should look for?
With this chemical make up, do you still want to use a heater?
Does anyone know which plastics will be okay to use as a tank for
this type of etching? I was thinking of using Acrylics, but that
stuff can be a pain in the ass to glue up good. Then I thought
about polystyrene which you can get translucent and I believe it can
be glued up more readily.
TIA, I am getting closer to understanding it :-)
Chris
--- In
Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
> On Sat, 20 Aug 2005 02:38:22 +0200, <JanRwl@A...> wrote:
>
> > Can someone here PLEASE outline the procedure and chemistry to
use for
> > this
> > etch-method? I have never seen ANYWHERE a list like,
> > "1. Boil the bare blank in swamp-water;
> > 2. Incant;
> > 3. Swish the board around in a 30% CuCl solution over 80°C
for 15
> > minutes;
> > 4, Etc. etc."
> > With FeCl, you can omit steps 2. and 4., and the result is
fine, but
> > messy.
> > Please?
>
>
> I'll try.
> Let's divide that into 3 parts:
> Etching boards, maintainance, and first "brewing" of CuCl.
>
>
> For normal etching, you'd need to do nothing much. You'd just put
a board
> in, and add H2O2 if the etchant is too dark in color. a few ml is
enough
> to oxidize it. The color is all you need to determine if it is ok
or needs
> something. Then you turn on the bubbler and simply wait until
done.
> Nothing needs to be done after etching.
>
> The adding of hydrogen peroxide (H2O2) takes the hydrogen away
from some
> of the hydrochloric acid (HCl). That means the chlorine is freed
and can
> "take" one copper from Cu2Cl (the dark brown stuff) to form more
CuCl
> (light green), and water. CuCl is now prepared to take a second
copper
> again, thus etch the board. You can also introduce the oxygen from
other
> sources, like pumping air through it (takes long), or even
chlorine gas
> directly, but that's poisonous.
>
>
> maintainance:
> From time to time you might want to measure the molarity of the
HCl in
> there. That is, how many hydrochloric acid is still "free" (not
carrying
> copper) and can be used to form CuCl. Because every time you add
H2O2 some
> of the HCl is converted into CuCl. At some point, if all HCl is
used up,
> adding H2O2 will not bring on the expected brigtening of the
etchant and
> increase in etch speed. Also, the etchant will have a bluish color
ad
> deposit a blue sludge on boards. This is a sure indicator there is
not
> enough HCl, but you sould have added some by then.
>
> To measure the HCl molarity, you need 4 things. A alkaline
solution of
> known molarity (NaOH), some indicator (like methylorange), and
two
> eyedroppers. You can get your NaOH solution by solving a weighed
amount of
> developer in water. It should be a 1 molar solution. How much you
need to
> weigh is said in one of the pages in the links section. When you
have that
> the procedure is simple. Put 10 drops of etchant in a small
container, add
> some water if you like, and one drop of indicator. It's now
orange. Then
> add the alkaline solution drop by drop, all the time swishing the
> container to mix it. When it turns green stop and your number of
alkaline
> solution drops added is your molarity after dividing by 10.
> I don't do that often, and usually only add HCl by feel. A wide
range of
> molarity will be ok. I keep it around 1. Still every few months i
feel
> like checking the molarity.
>
> There's also the density to be measured. Adding the copper makes
the
> etchant more "heavy". In a away this is good - because you'll have
more
> CuCl do do the etching. But if it gets too much you need to remove
some
> etchant and add water. I have never encountered this, i guess the
water in
> the HCl and H2O2 added is enough. You can measure the density with
a
> hydrometer, which you can simply by in a car parts store, as a
tool for
> checking car battery acid. It comes in a neat huge "eyedropper" in
which
> the hydrometer swims.
>
>
> First brewing:
> Some tutorials call for adding copper in some form.
> I have found you can start just as well with only HCl and H2O2,
and water.
> At first, you don't have any CuCl, but those two chemicals will
etch all
> by themself. You can make etchant up by diluting HCl to about 10%
and
> adding a swig of H2O2. Then put in the board and go by color.
> At first there is none or little CuCl, so you have to add some
H2O2 each
> time you etch. As copper content increases you get more and more
CuCl,
> which does the etching and must only be re-oxidized from time to
time. I'm
> now at a stage where i need to add H2O2 maybe each third or fourth
board.
>
> Here you go.
>
> ST