PCB Etchant Tank

Etchant Tank

Here are instructions on building a really good PCB etching tank.

Go to your local pet store and purchase the smallest and skinniest heating unit you can find, a cheap aquarium air pump, short length of flexible plastic tubing, stick on thermometer that measures up to 100 degrees, and a plastic bubbler hose to place on the bottom of your etching tank to provide a curtain of air bubbles.

Pick up some Plexiglass from your local hardware store and cut to size.

The dimensions of the etchant tank should be around 1" thick, 8 1/2" wide and 9" tall. This will provide the ideal volume for a single Radio Shack etchant bottle.

Make the bottom of the etchant tank oversize to provide a sturdy base. A 9" by 3" bottom plate should work fine. Buy silicone adhesive used for aquariums tanks or shower caulking to assemble the plexiglass pieces together. Roughing up the edges of the plexiglass with a bit of sandpaper will create a better bond for the silicone adhesive. You might want to glue very thin strips of silicone along the larger side panels to prevent your pc board from hugging the sides during the etching process, causing a non-uniform etch. Place the silicone in horizontal lines to provide a bumpy surface, this also enhances the bubbler action. I've been told using MEK (MethylEthylKetone) makes a very good adhesive for Plexiglass. I don't recommended using a hot glue gun since the aquarium heater may affect the bond over time.

Stick the thermometer near the heater. You should be able to pour the whole contents of a Radio Shack etchant bottle into the tank. The tank will be skinny enough to pour the etchant back for storage while using a funnel. The tank is also taller than the etchant liquid level poured in so bubbles won't splatter. Cut a piece of plexiglass to lay on top to further avoid any splatter. You can file a notch for the wire and air hose on one end so the top lays flat. Place the bubbler tube on the bottom. It must be secure enough not to float up once bubbles begin to form. You might also want to make it serviceable since the etchant and copper residue can plug up the holes in time. Try poking larger than normal holes to avoid this. Let the silicon adhesive dry then test everything including bubbler and heater using plain water. Seal up any leaks with a bead of silicon.

Once tested, you should be able to etch a board in about 4 minutes with the temperature of the heater set to around 100 degrees. Drill a small hole through your PCB and tie a string to it. You can then use the string to hang the PCB while etching. Always pre-heat the etchant solution before placing the PCB in. You may also want to get a air valve to help adjust the amount of bubbles created.

The above image is the etchant tank that I built, it was made out of plate glass at the time. I don't recommend using glass though. Always wear safety glasses when handling liquid etchant and in a well ventilated area since some fumes will form when the etchant is heated. Also wear rubber gloves, the etchant is pretty caustic.

Good luck and have fun creating your very own PC boards,

VKF

The building and use of the etchant tank is at your own risk. .

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