Homebrew PCBs

On Fri, 25 Apr 2008 20:13:22 +1000, you wrote:

>
>I was looking at an easier and more reliable way to etch PCBs. I know 
>from experience that bubble etching never produces acceptable uniformity 
>and often needs manual brushing to finish it off.

Depends on where the bubbles go, I think.  The more agitation the
better the etching.  Getting them even is the trick.
>
>I though maybe the bubbles could be released on one side of the tank 
>causing etchant to flow in a circular path around the tank.
>The PCB is held vertically in a frame that pivots by two small shafts at 
>either side. The moving fluid should continuously rotate the PCB around 
>thus guaranteeing uniform concentrical etching. I'm not sure how uniform 
>the etch rate would be radially.
>

I think you might have the same difficulty.  Etching on the leading
edge will be better than the trailing edge.  Think wing vortex for my
reasoning.  

You might try etching only one side at a time.  That might give you a
bit better control.  I'd also suggest rotating the board halfway
through, or making sure that the bubble stream is the right size.

Harvey


>Has anyone tried making such a contraption ?