Homebrew PCBs

I have been pondering the false walls idea for a while. I would 
experiment with driving the bubbles up the tank walls to cause the 
return flow of 'Unbubbled' etchant to flow down the surface of the 
PCB. -This should take away the etching issues caused by the 
incorrect bubble size or rate of bubbling.

The spacing between the false walls and the PCB should be kept small 
to ensure there is a decending flow at the surface of the PCB. As the 
etching by-product is heavier, having a decending flow makes sense. 

The bubble bar/hose should be a little way up in the bubble channel. 
I suspect the greater the column height of the bubbles the greater 
the etchant flow rate will be. Bubbling may need to be much stronger 
with this arrangement to induce the desired flow 

It would be good if the etch by-products could stagnate on the bottom 
of the tank and not be involved in a new etch cycle. This would 
probably be achieved by having the false walls rest on the bottom of 
the tank but have slots or a row of holes 15cm up the walls for the 
etchant to flow back into the bubble channels during etching. 

If the false walls are thick, then less etchant is required in the 
tank. 

The etchant decent rate over the PCB surface could be tested with 
water and food colouring.

Regards


 
> 
> How about false walls and have the bubble flow
> up the PCB and the fluid flow down the side in
> a seperated channel behind the false walls
> 
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