Homebrew PCBs

What effect does heat have on the HCl etchant? My Ferric Chloride tank uses
aeration as well as heat for a fast etch. Can you get a faster reaction by
heating the HCl or is there an inherent danger to doing this?

-Mike

----- Original Message -----
From: "Adam Seychell" <adam_seychell@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, April 28, 2003 11:59 PM
Subject: Re: [Homebrew_PCBs] CuCL too much effort ?


> I cannot pinpoint why its slow. As I posted ealier I got a piece
> of clean copper in fresh 20% HCl and completely dissolved it in
> little over 3 hours to end up with deep green colored solution.
> You can see from the picture that air supply was extremely
> vigorous so the test dosn't represent a practical situation. It
> became warm (20\ufffdC above ambient) during its peak because of the
> heat generated by the reaction. Unfortunately its been a slow
> week with your setup, and I can understand your frustration.
>
> I haven't yet done a direct comparison between the use of large
> bubbles and fine bubbles and how it effects the reaction rate.
> Maybe there is a 100:1 difference ???. On a more theoretical
> thought, the surface area/volume ratio of a bubble (assuming
> perfect sphere) is proportional to 1/r. For equal volume of air 1
> mm bubbles would give 10 times surface area than 10 mm bubbles.
> Any foaming on the surface would also dramatically increase air
> contact area. Small bubbles are much more effective at creating
> foam than large bubbles.
>
> Its expected for splashes to jump out of the tank, you should
> have a lid on. Virtually all the oxygen source is from the air
> bubbles, not the surrounding air.
>
> Adam
>
> grantfair2001 wrote:
> > To put the HCl fume problem in perspective - I had been bubbling the
> > etchamt solution with an open tank for over a week without any HCL
> > damage, even on steel a few feet away.
> >
> > It was only when I started aerating with a much higher volume pump
> > that the problem appeared. The etchant surface was so agitated that it
> > was spitting some etchant out of the tank - and into the air. And the
> > bigger compressor got warm enough that the air was being warmed, and
> > increasing the temperature of the etchant. I understand a higher
> > temperature alone may cause fuming.
> >
> > I believe the CuCl approach can be used without any fume damage, even
> > without a fume exhaust.
> >
> > As to the slow process, this is in part due to my air sparger making
> > largish bubbles. If I got an aquarium air stone the process would
> > probably be much faster.
> >
> > Grant
> >
> > --- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan
> > <stefan_trethan@g...> wrote:
> >
> >
> >>i really believe with this cost / etch i won't start the bubbling
> >
> > campaign.
> >
> >>this seems much to high effort (concerning the corrosive fuem
> >
> > discussion also).
> >
> >>regards
> >>st
> >
> >
> >
> >
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