Bubble Etcher

Hi,

Just in case some people here may be wondering how to speed up the etching
process for PCB's, one way to do it is to use a bubble etcher. Basically
all you
have to do is install a perforated plastic tube in the bottom of your
etching tank and force air through it. The bubbling action constantly
agitates the etchant and thus greatly speeds up the etching process. I'm
using some aquarium tubing with small holes drilled in it and I use an
airbrush compressor as an air source in my small tank. For a larger tank
you can use 1/2" ABS pipe and the exhaust of a canister style vacuum cleaner
such as a Shop Vac for an air source. You should use an adjustable valve in
the air line to regulate the flow so as not to spray etchant all over the
place. In this type of tank the circuit board must be hung vertically in
the etchant.
Heating the etchant is also recommended.
Have a good day.

Rod

 

some etchant can become airborne when it's bubbled, making breathing
rather dificult, proper ventilation will fix that.

depending on etchant formula it may be a good idea to heat it constantly
or not, i not then heating to operating temperature. some produce heat
when they work, constant heating could cause it to go exothermic, meaning
it would boil and perhaps cause fire or explosion, maybe a gaseous acid as
well. as long as you don't exceed a certain rate of copper absorbed in a
set timeframe things should be fine with preheating.

 

Good morning, Rodney. Someone who's interested in this type of etching
setup might want to look at the GC/Waldom Electronics Cat. No. 22-0394
"Professional" etching system. It uses a setup similar to the one
you're talking about, with an aquarium heater and a small aquarium
pump. I found it to be useful for small quantity ferric chloride board
etching.

A couple of caveats about using this type of setup. First, heated
etchant will emit fumes, which are corrosive. This kind of thing
should only be done in a well-ventilated area, and away from computers
or other electronics. Second, while the aquaruim controller provides
pretty good temp control (once you get the dial setting right -- use a
thermometer to get the controller to the right setting), the temp
control only works well with a constant etchant level. As etchant
evaporates, the level changes, and the temp control will be affected.
Not only that, but if the etchant level gets too low, the glass of the
aquarium heater will crack.

The aquarium heater itself hangs from the side of the etchant tank on
the inside. If the glass of the heater comes in contact with the
plastic tank, it can melt through, causing a disaster. GC now provides
an O-ring to slip around the side of the glass heater to help avoid
this problem. The O-ring should be used at all times. But, in order
to be safe, the whole tank should be placed in a large pan which would
catch the etchant in the event of a melt-through of the plastic tank
(voice of bitter experience here).

One other note -- it's very important to physically place the aquarium
pump over the level of the top of the etching tank. When power to the
pump is turned off (or in the event of a power failure) etchant can
back up the air tube into the pump. That's disastrous for the pump,
and will cause failure in the near term.

This type of hobbyist system is good for small quantity, single sided
boards where the minimum trace widths aren't too demanding. It's
difficult in this type of setup to get a double-sided board to etch
well. It can be of use to periodically flip the board over, turning it
around and upside-down, to try to even out the etch. This setup also
assumes you will have some scrap around your circuit, because the edge
of the board in the aerator/holder doesn't etch.

Anyone using this setup for real should obtain a spare O-ring and a
spare aquarium heater (which has been preset to the right temp) in case
of component failure.

Good luck
Chris

 

I've noticed that you can purchase a small check valve for aquarium pumps
which would prevent any back-flow of etchant in the lines.

If you hang the board vertically in the tank it should etch evenly on both
sides.

I would also add that placing a cover over the tank while etching would stop
and mist from escaping into the open air.

 

If you run the lines up and over the side of the tank there shouldn't be
any back-flow of etchant but the check valve might also be a good idea.
Keeping the air line fairly long might also be a good idea. I haven't seen
any problem with back-flow in my system so far but I'm not using an aquarium
pump.

Rod

 

Thanks for the input Chris

Rod

 

Thanks for the input Chris

Rod