No personal experience, but here is a link to building a bubble tank
http://www.thinktink.com/stack/volumes/voliii/equipmnt/bubltank/bubltank.htm
Tim
[Denver, CO]
> -----Original Message-----
>
>
> Hi all,
>
> I'm trying to make a bubble etching tank that can etch
> uniformly. I've
> spend lots of my time experimenting with different designs
> and can't get
> uniform etching of double sided circuit boards. I tried
> large bubbles
> from 2 mm holes drilled in PVC pipe. They never go evenly on
> each side
> of the PCB. The bubbles also have a tendency to group
> together on one
> side of the tank and circularliquid downward on the opposed
> side. I also
> tried increasing tank width (from 50 mm to 200 mm) so the
> solution down
> flow does not interfere rising bubbles. This helped but the bubbles
> still don't flow evenly enough for my liking. I even tried using two
> rows of bubbles on each side of the PCB. All this makes the etching
> terribly non uniform. I was going to look into spray etching
> but I heard
> spray equipment design must deal with all the same problems.
> Has anyone
> tried putting stuff like plastic beads in the solution ?
> this may even
> up distribution. How about very small bubbles ?
>
> The only other method I've seen is to pump the etchant over
> the PCB like
> a river bed.