Homebrew PCBs

Stefan Trethan wrote:

> rotatig. Sometimes it oscillates "pulsing" the spray pressure, at other  
> times it doesn't. It is running way too loud and i'm sick of seeing it to  
> be honest. I do not see a point where the uniformity will be better than  
> with a bubbler in a somewhat reasonable timeframe and the eventual  
> increase in etching speed is long eaten up by construction time.

   Hadn't been following lately, sure there isn't more to the commercial 
systems?  What's the diameter of the tube?  Even 10K RPM isn't much if the 
diameter is small.  And water has a strong adhesion force, it could be very 
important that the tube is the right type of plastic so it's not sticking as 
it's coming out of the holes.  Still seems it would be problematic.  Also is it 
pressurized from the other end in commercial unit?  Etchant in a small closed 
tank, and pressurized with say a $10 car tire pump, basically a lower pressure 
pressure washer.

> I must draw a line somewhere how far i'm prepared to take this, and i have  
> reached it i think.
> I would much rather spend my time actually making PCBs (especially  
> following up on the silicone paper).
> 
> My plan now is to lay this project to rest, and use the existing materials  
> to build a bigger, better bubble-tank with all the flaws of the old one  
> corrected. The slightly uneven etch and longer times are something i must  
> live with i fear.
> 

   How are your bubble etches uneven?  More finer bubbles should make things 
fairly even in a local sense, if it's more etched at the top than bottom or vise 
versa then use more bubbles and slope the side of the tank away from or toward 
the board to even things out.

   Don't need one myself, but I'm thinking one of the long fine bubble aerator 
tubes for fish tanks and a sloped tank side to even things out against a 
vertical board should come out fairly even.  But bubbles do only travel one 
direction.


   Not sure that's even needed.  Use a rigid frame for the board, on a floating 
suspension over the tank.  Stick a medium sized massager vibrator motor on the 
frame and see if that doesn't work.  May need a small amount of pumped 
circulation for best effect, but a vibrating board should do fairly well just by 
itself.

Alan