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

I have an etcher suggestion for you.

Many years back I build a spray etcher for a college class, it never really worked all that well. Spray holes would get plugged, never enough pump pressure, plumbing used too much enchants and it was hard finding a pump that would take the hot etchant.

A few years I was doing more and more boards in my garage and got tired of rocking the glass tray back and forth to do the etching. I was looking for a better way to etch, I knew a spray tank was not the answer. Then a friend suggested a splash tank, at first didn't think it would work but it turned out to be the best etcher. At the time I was using heated Ammonium Persulfate and would take up to two 8 x 10 board. With fresh etchant it would etch a single sided board in 20 to 30 seconds but usually it took 1 to 5 minutes.

The tank was built from 3/4" plywood a little over 12" x 12" x 12" with an open top. The interior surfaces were fiber glassed with polyester resin and glass cloth the outside just resin. Makes a nice strong waterproof chemical resistant tank. At each end of the tank there were some guides formed in the sidewalls similar to guides in a card cage. Two board holders, build from pieces of 11" x 11" x 1/4" acrylic slipped down the guides from the top. Boards to be etched were fastened to the face of the holders using rubber suction cups stuck to the holders, the board edges wedged between the upper section of he suction cups. It would hold any shape board or multiple boards and worked very well.

The tank top was three pieces, two removable end covers about 3" x 11" built from acrylic that allowed access to the board holders and a 6" wide center secton from fiber glassed plywood that was screwed down to the sides of the tank. On top of the center section I mounted a 1/16 hp motor salvaged from a squirrel cage blower. A stainless steel shaft extended down to the bottom of the tank into an acrylic block used as a bearing. Near the bottom of the shaft there was a paddle blade sort of like what you see in a blender. The top edge of the tank was formed that no splashing could get out between the covers and the side walls.

In operation the hot persufate was filled just to about the middle of the paddle blade, boards attached to the holders and sliped down into place and the covers installed. When the motor was turned there was a very aggressive splash hitting the boards attached to the holders.

IIRC the bottom of the tank was sloped to the center so as to minimize the volume of etchant, which I think was less than a quart. I posted a sketch in the files section called SplashEtcher.pdf

Craig