Homebrew PCBs

On Wed, 8 Dec 2004 03:36:03 -0800, dioxide <dioxide@...> wrote:

>
> I'm also curious as to what the real use is for the bubblers.  Are we
> trying to aerate the solution, or cause some movement in the solution
> to get more even etches?

I want to get the movement (to take spent etchant away from the brd  
surface and to mix
the etchant, because the spent settles on the bottom.
But with CuCl regeneration via air oxygen is an option, but you need to  
run the bubbler very long.

>
>     What I wish to use is a clear acrylic, welded together with the
> acrylic cement, and cause the liquid to move by using a small
> propeller.  Obviously I can't run an electronic motor inside the tank,
> and most gears and bands would probably fall apart after the first
> board is done.

well, it would be hard to use a prop. what could work is if you use the  
propshaft vertical
out of the tank, and a motor on top of it.
Doesn't work for me because the tank is only 2cm wide, no space for a prop.
it would generate a circular current in the tank.

>     So..  this is the idea I had.  Keep the motor outside of the tank,
> and connect two magnets to the drive shaft.  For the propeller, use
> the same material that the tank is made of, and seal matching magnets
> or iron slugs into it, so that I can spin it using the magnetic force.
>     Oh yeh,  I also cant run it at 50k rpms, so I will make a simple
> gearbox to lower the speed and boost the torque.

nt sure, sounds complicated. artificial hearts are made that way, but they  
use a electronic
drive instead of rotating magnets, like a magneti stirrer for chem. labs.

>
>     If the bubbles are still needed, I just want to run one single
> line of bubbles, right near the prop so as to get things aerated.
>     I haven't quite decided whether or not I want to submerge a heater
> in the tank, or build in a heat pump.

If aeration is a advantage depends on the etchant used, fo most it is no  
benefit other than agitation.

>
> Any ideas on this?
> -tommy

first decide on the etchant to use, then think very carefully how the tank  
is best built. i have the third
now and still much to improve.

ST