Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, garydeal <garydeal@...> wrote:
>
> 
>      This afternoon I finally got around to mixing up a small batch of 
> the 1/3 HCl + 2/3 H2O2. I've read the positive reviews on that recipe 
> here, but was really surprised/impressed at the results.

> 
>      Question:
>      The solution total was about 225 ml, and the brass sheet was
etched 
> one sided with an etch area of a couple of square inches. Afterward the 
> solution was quite hot and bubbling like soda pop on the stove. I
put it 
> in a cold water bath to cool it down, but I have to wonder - is
there the 
> possibility of a runaway reaction and what is the result?
> 
>

If you are going to use the 1/3 acid 2/3 peroxide use the 3% medicinal
grade peroxide you get at the drug store. The hcl is common pool acid
sold everywhere it is about 33-37% hcl. I add 2/3 cup of peroxide to a
plastic container dry the cup, add 1/3 cup acid. This is best done
outdoors as some fumes may be given off as the acid is added. After
all the acid is added the fuming if any will stop and it may be moved
indoors. (carefully, it is quite acidic) This makes one cup of etchant
(about 225 ml) and is for immediate use. It will etch about a 6x9inch
board with good results. Maybe more, this is as big as I have done at
one time. Once it sits for a hour or so the peroxide will bubble out
and it will not etch anymore. At that point I flush it down the drain
with plenty of water. If you are doing a lot of etching you may want
to go the full fledged cupric etching solution which may be
regenerated and used over and over.