Homebrew PCBs

At 09:18 PM 4/14/03 -0700, luther m stroud wrote:
>I tried verticle etch with cucl and it was't even faster near the bubbles
>from the bottom that at the top . stainless steel may not last in the
>etchant .

The PCB holder arrangement I described has been working well for at least 
15 years - that is about the age of the holders I described.  However, I 
use ammonium persulphate catalyzed with sulfuric acid as my etch solution - 
clean and effective.  My etch tank is welded stainless steel, as is the 
immersion heater used to heat the etchant - both of these have been in 
regular use for about 20 years.  We used to just hang the boards in the 
etcher before I made the holders.

Vertical bubble etch is somewhat slower than a spray etcher but there is a 
lot less mess and it was cheap to build.  This was a very important 
consideration back when we built our PCB etch system.

The air source is a very compact blower (something like a vacuum cleaner 
motor) obtained from a local surplus outlet (Princess Auto) years ago.  The 
sparging tubes are drilled PVC - 2 tubes that form a "U" in the bottom of 
the tank.

I've been told that the reason bubble etch works so well with ammonium 
persulphate is the constant agitation and the continuous addition of oxygen 
to the etch solution.  We pretty much followed Clyde Coombs PCB Handbook 
and it just works.

dwayne

-- 
Dwayne Reid   <dwayner@...>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

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