Homebrew PCBs

Hi Stefan,

I am glad it worked for you. I would have thought a fly screen would
tend to collect the bubbles rather than breaking them up. I haven't
actually tried this so I could be completely wrong of course...

I have noticed my tank also etches slightly unevenly. To get around this
I usually turn the board over half way through.

Les

Stefan Trethan wrote:

>hi
>
>bubbler is working fine already.
>Aginst better knoweledge i decided to try cutting corners and did not test  
>the bubbler with water.
>I just took a plastic hose, made 5 holes with a hot needle, put a isolated  
>copper wire (seal the ends)
>in the hose. Also selaled one end of the hose. the wire inside allows for  
>shaping and holds it down and in place.
>
>The bubbles are maybe 6mm dia. and all holes work equally well.
>The bubbles create a mad circular current, up in the center and down the  
>sides. Also along with the
>big bubbles there are thousands of tiny bubbles, which you only see after  
>stopping the pump, when
>they rise slowly to the surface.
>
>The mixing is of course homogenous, i am sure 1/10 of the bubbles or less  
>would already ensure complete
>mixing.
>
>when the bubbles rise they spread, so that at the top of the tank they  
>already cover the whole area,
>but on the bottom they do etch streaks where they rise. i think about  
>adding two more holes
>to create a more even etch. Also it could be that some obstruction above  
>the air holes might
>help to spread the bubbles over the entire length, i was thinking about a  
>roll of plastic fly screen,
>what do you think?
>
>i had to modify the pump to get a suction input, but it wasn't much of a  
>problem.
>the closed circuit seems to work from what i can tell, but long-term  
>rusting will show the truth..
>
>So, at the end of the day it seems bubbling is really a good method to mix  
>the etchant.
>
>Thanks for the suggestion of a hot needle to punch the holes.
>
>ST
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