Etching
Here are some common types of etchant solution that can be used:
● Ferric Chloride
● Ammonium Persulfate
● Sodium Persulphate
● Home-made mixture of 50% Muriatic Acid and 50% Hydrogen Peroxide.
The Ferric Chloride works very well, be careful, it leaves nasty stains on cloths and
work area. These stains are permanent. The Muriatic Acid/Hydrogen Peroxide
mixture is by far the least expensive alternative and works okay, but the fumes are
horrible and extremely corrosive. We highly recommend that, if you use this solution,
you do it outside, well away from the house or any tools. We noticed that after just
one usage on the work bench, some of my tools sitting nearby had a coat of
corrosion on them afterwards…just from the fumes from one session of etching! Two
gallons of this mixture cost about $10.00 (Muriatic from Ace Hardware, Hydrogen
Peroxide from Wal*Mart), compared to two gallons of Ferric Chloride cost of about
$30.00 (from Radio Shack). Two gallons is enough to etch about 500 or more
average size stompbox boards, so quart or litre bottles of Ferric Chloride is a good
choice for most home builders.
No matter which etchant you use, carefully follow the directions on the bottle and
always etch in a well ventilated area.
The etchant must be warm (100 to 120 degrees Fahrenheit) to work best. We use a
hot plate or a hot water bath. For the hot water bath, use two plastic containers to do
the etching. One is a small container with lid (not air-tight lid) that is just big enough
for one or two boards to fit in. The etchant and boards go in this container. Then get
a bigger plastic container that will be used for a hot water bath. Pour the etchant into
the small container, then boil some water on the stove. Pour the very hot water into
the larger container (just a few inches) and place the smaller container of etchant into
the hot water bath. This is a good simple way to keep the etchant very hot and makes
etching go very quickly. Keep the lid on while etching, if you have a lid, it cuts down
on the fumes and might keep the heat in better. If possible, place a goose-neck desk
lamp, with 60 or 100 watt bulb directly over the bath to keep it all warm longer.
Be careful not to get the etchant bath too hot. It may start melting the etch resistant
mask and the acid will eat way your circuit!