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

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.