Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, Robert Hedan <robert.hedan@...> 
wrote:

> ...
> > aquarium pump and heater can be had at a pet store for those 
> > undertaking a similar but cheaper route.
> > 
> > http://www.web-tronics.com/lowcosetsysw.html
> > 
> 

I have found that any kind of vertical tank system, the area closer to 
the bottom of the tank will etch faster than the part near the top. 
This is made even worse with a tank with a bubbler. The bottom half of 
the board will be finished, while the top half will still have copper. 
So you have to flip the board around at the exact halfway point to 
make sure it etches evenly. Otherwise you'll have one side majorly 
undercut by the time the whole board finishes. The most even etch I've 
gotten is with a tank with the board face down towards the ground. 
This, of course, makes it difficult to check the progress without 
making a mess.

Even with a face down tank, if you use a bubbler, the board will etch 
faster where the bubbles directly hit the board. Unless you can build 
a system where the air is distributed evenly over the whole face of 
the board, a bubbler is generally a bad idea. A better system would be 
something that agitates the solution without bubbles so that the fluid 
circulates to let fresh etchant touch the board.