Homebrew PCBs

On Fri, 11 Mar 2005 11:33:42 -0500, Earl T. Hackett, Jr.  
<hacketet@...> wrote:

>
> The objective in any etching system is to replace the spent etchant at  
> the
> surface of the board with fresh.  The speed of the etchant moving doesn't
> contribute to the etch rate other than to bring fresh etchant to the
> surface.  Friction between the etchant and the board surface makes this
> quite difficult.  This is why spray etching is the best - if you have  
> enough
> of the right spray nozzles to produce a uniform spray pattern.  In a  
> spray
> etch 1 oz copper foil will etch in a little over a minute.  If you look
> inside you'll see why.  The etchant is rushing over the board surface at
> about a thousand feet per minute.  In a bubbler system your lucky to get  
> to
> 50 feet per minute.  In an ultrasonic cleaner there is almost no  
> movement so
> all the etchant does is sit there and shake.


so that means what? big bubbles are better? spray etchers are awfully  
complicated to build and i have yet to hear of someone building one that  
works. Has anyone tried toner transfer with a sprayer? and what about CuCl?

ST