Homebrew PCBs

On Fri, 15 Apr 2005 18:33:54 -0400, Alan King <alan@...> wrote:

>
>    Well I was thinking make more bubbles.  If you have enough bubbles  
> 1/4" or
> 1/2" shouldn't be a problem, more like a circulating foam..
>

Well, too much foam will not be good, if it overflows the container ;-)
So far i have noticed foaming is not a problem, the CuCl readily releases  
the air and one can safely assume the increase in volume is only dependent  
on air flow. I don't know if other etchants foam more, FeCl is used in  
foam etchers but i dunno if there is a foaming agent used.
The whole thing meaning, in CuCl the foam doesn't circulate because the  
bubbles only go up, but it isn't a problem as with more air the same  
effect can be achieved.

>   Yep test plates in a normal tank to figure the angle.  May be easier  
> to have
> a straight tank and insert type plates anyway..
>   If you've got 2 bubble tubes one on each side with enough bubbles, and  
> enough
> slope forcing the bubbles in, the board should stay fairly centered as  
> long as
> about the same amount of bubbles are on each side I think..
>   Hmm two bubble tubes touching and the board sitting in the groove  
> between
> them should do it.  Bottom 1/4" or 1/2" may over etch but that's a small  
> price
> to pay for simplicity.
>   Hard to keep the tubes aerating evenly in a fishtank but I think  
> nothing will
> grow in etchant.  Still may clog over time but I think they're cheap..
> Alan


What i do not know is if bigger or smaller bubbles are better.  
think/tinker is sure big bubbles are good, 'cause small bubbles are not  
causing enough scrubbing action. OTOH i have tried big bubbles, and it is  
hard to get them evenly distributed over the board and they tend to form  
vertical streaks on the board that are 2 to 3 times faster etched than  
other places. I will rather have smaller bubbles, and slightly longer  
etch, if it is even.

ST