Homebrew PCBs

One of the variables affecting etch time in CuCl is etchant
temperature. However, you have to be careful not to melt or soften
your etchant tank. And, the amount of HCl in the tank is another
variable - I'm not sure how it is related to etch time. 

But, if you heat a high enough concentration of HCl, it will "fume".
These are a health hazard if breathed in, or if they get in your eyes. 
And the fumes will corrode metal it comes in contact with; steel for
sure as I learned the hard way.

I don't know the concentration of HCl which I got fuming. However, it
was 20 Baume (31.5%) before I diluted it; I started with one part HCl
to 2 parts water. Later I added more HCl. I had not heated it very
much- I was running air from a large vacuum pump exhaust into the
sparger. The pump got very warm to the touch, and so did the air. I
think the heat was what provoked the fuming. I use a less powerful
pump now and have not had a return of the fuming problem.

Anyway, you would either have to have a pretty close control over your
process (amount of acid, ?amount of copper, ?amount of air,
temperature of etchant) to be sure fuming would not be a problem, or
at least supervise the process closely. The other option is to provide
ventilation to get rid of the fumes. One list member suggested a
simple vent such as an ABS pipe going from your etchant tank to the
outside of your house would do the trick. So far I don't think that
will be necessary.

But my basement is about 60 deg. F at present. That may change in the
summer so I will have to keep an eye out for fumes.

As far as an even etch rate - I don't know what all goes into getting
it even. Anyone know? My first board etched fastest at the top (it was
vertical); it was in the bubblestream. I don't know how the bubbles
were placed since I just put the small bubble sparger in the bottom
under the etchant. Maybe a uniform exposure to bubbles is an element
in getting it even. I want to try my large sparger (the Think and
Tinker version) with another PCB because it provides a great deal of
etchant movement. It's bubbles are fairly large, by design, to agitate
the etchant.

Grant

--- In Homebrew_PCBs@yahoogroups.com, "Mike Putnam" <circuit@g...> wrote:
> Even the Ferric Chloride etchant will etch unevenly and take some
time in
> cold etchant. Is CuCl the same? I have always heated the Ferric but am
> wondering if this is the thing to do with the CuCl.
> -Mike
> 
> ----- Original Message -----
> From: "Francisco Peña" <mute@i...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Tuesday, May 06, 2003 10:00 AM
> Subject: Re: [Homebrew_PCBs] First pcb etched with CuCl
> 
> 
> > I have experienced uneven etching using CuCl too. I etch my boards
> horizontally facing up, and the etching happens from the edge to the
center
> of the board, and takes about 30minutes to have an 8x6" board done.
The end
> result is perfect and the traces look fine, although I'm a bit concerned
> about the time too. I think my mix needs more oxigen too.
> >
> > Fp
> > www.tonepad.com