Homebrew PCBs

Stefan,

Thanks for your information. Still some more questions :-)

- Can you give a ratio to at least start? I mean how much HCL and H2O2 
should I use for the first "run"?
- Do you have a link to the refractometer? Cause at that cost, I 
probably also would apreciate to avoid the mess involved with a hygrometer.
- what refraction coefficient or fluid density ranges would be good for 
etching?

Since I'm only makeing prototypes, I don't mind if cucl is not that 
fast. The Fe3Cl I used so far is also not that fast after a couple of 
boards. I'm more after a solution which etches evenly and where I don't 
have waste to dispose thereafter (or as few as possible).

Markus

Stefan Trethan schrieb:
>
> I can't actually give you the requested exact ratios since i built my
> etchant bit by bit and do not know them.
> However, i think you will have to do the same, since at least the H2O2
> must be added gradually. At first there would not be enough Cu2Cl2 to
> oxidise, so much of the H2O2 would dissipate.
>
> The copper should be thin pieces, like sheets or stranded wire.
> Electrode nuggets may take forever to dissolve.
>
> A hydrometer is not for measuring humidity, that is a hygrometer and
> many people are simply mistaken.
>
> A hydrometer is used to measure fluid density, it is a glass tube,
> with a weight at the bottom end and a scale at the top end. The higher
> the hydrometer floats the denser the liquid is and you can read this
> on the scale (the water line is the pointer). The ones sold to test
> car battery acid cost only like 2 eur and are just about sufficient.
>
> I recently bought a refractometer from china, for like 20eur. It is
> also designed to measure car battery acid, but it tried it with
> etchant and it seems to work. The refractometer is an optical
> instrument where you place a drop of liquid on a prism and the
> refraction coefficient is measured (Brechungsindex for you). You look
> into it like in a telescope. It is very quick, accurate, and less
> messy than the hydrometer in my opinion. But it does measure optical
> density, not physical density, as long as the two correspond there is
> no problem though. Also, of course, it is a measuring instrument and i
> just had to have one, no matter what.
>
> You only need the hydrometer to see how much copper there is in the
> etchant. There's an ideal density range for this etchant where you get
> the best speed.
>
> Another analysis tool you should have is a way to determine the HCl
> concentration in the etchant. This can be done by titration with NaOH
> and methylorange as indicator. That's actually quite easy to do, but
> not really needed that often.
>
> Bubbling, yes you can use it for regeneration but that is dead slow.
> H2O2 is more efficient. I just use bubbling to agitate the etchant so
> it is quicker and more even. You definitely want some form of
> agitation, CuCl is not the fastest etchant if you do not push the
> chemical parameters into the ideal range.
>
> ST
>
> On Tue, Jan 6, 2009 at 10:02 AM, Markus Zingg
> <homebrew-pcb@... <mailto:homebrew-pcb%40shdesign.info>> wrote:
> > I would like to switch to cucl for a while cause having a solution that
> > lasts virtually for ever seems to be very beneficial. Besides, I'm just
> > before building a new etching tank and thought that this would be a good
> > moment for a switch of the etchant too. Since english is not my native
> > language, I always felt a bit unsure if I understood things correctly if
> > you guys were talking about cucl in the past, and there were always some
> > open ends. In particular the following things are not yet clear to me:
> >
> > So, one would i.e. need to build 3l HCL/H2O2 and put in half a pound of
> > copper into it? Correct?
> > How many HCL and H2O2 to get to a 3l solution to start with? I mean
> > what's the ratio of HCL to H2O2?
> > 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?
> >
> > Then, Stefan wrote " If you want to measure this, you can get a
> > hydrometer. The ones sold for car battery acid checks will usually do. A
> > refractometer should work as well."
> >
> > A hydrometer - when useing google - seems to be a device to measure
> > humidity? Correct? What is a "refractometer", which of the two would be
> > easier to get and where, and how would one measure what? 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'm sorry if these are dumb questions, but since working with chemistry
> > might be dangerous I want to be very sure I understand things correcly
> > bevore I start to experiment.
> >
> > TIA
> >
> > Markus
> >
>
>