Homebrew PCBs

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.