Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Randy,

You could also try using hydrogen peroxide and sulfuric acid as an
etchant. The mixture is 10% hydrogen peroxide (35% grade) and 15%
sulfuric acid (technical grade) with the balance made up of water.
This mixture will heat up and be ready for use upon make up. You can
replenish the etchant with small additions of peroxide when the etch
time is too long. When the bath is saturated with copper let it cool
down for a day or so and copper sulfate crystals will precipitate to
the tank bottom. Scoop out the crystals, replenish the acid and
peroxide and you can start etching again after heating the solution
to 100-120 degrees F.

You will need a good ventilation system or do this outdoors since
there will be some fumes produced. Also, the peroxide breaks down
into water and most of this will leave the tank as vapor which is why
you need the vent system. If solution growth becomes a problem, just
turn up the heat for a while and the water will evaporate bringing
the solution volume back down to normal.

The same solution can be used for many years without having to dump
it. I used this method in a commercial shop and didn't change the
solution for seven years. We processed many thousands of square feet
through this tank and sold all of the copper sulfate crystals to a
recycler for cash. If you are going to do lots of etching this is a
good way to get the job done with a minimal investment.

Tom