Homebrew PCBs

Here is an idea for a spray etcher, inspired by Steven's project:

  http://www.instructables.com/id/The-Etchinator-low-cost-spray-etcher/

Lets say we have some PVC glueable tube such as 8mm to 10mm outside
diameter with 1mm to 1.5mm thick walls.  I am not sure where to get this.

Have the motor connected to a straight, rigid vertical section of this
(or perhaps something else thicker, such as wider PVC tube) with the
bottom end either free-floating and self-balancing or running into a
bearing of nylon or similar at the bottom of the tank.

Then, have two straight or somewhat outwardly curved sections of the 8
to 10mm OD pipe, glued to the bottom of this shaft, and rising on either
side like a narrow V shape.  The top ends of the two outer pipes are
sealed shut, such as by heating them and crimping them in a vise.  The
top ends need to be held firmly to the central shaft by some means, such
as more pipes and glue.

The bottom ends of both side pipes are open and perhaps slightly angled
so as they rotate, they are like shallow scoops into the liquid etchant
at the bottom of the tank.  These ends only need to go 5 to 8 mm below
the top surface.  If they go deeper, then they will create unnecessary
disturbance in the etchant at the bottom of the tank.

If the shaft is rotating clockwise, when viewed from above, the right
side-tube is joined to it on our side of the central shaft and the left
side-tube is joined at the far side.

Once the etchant is in the bottom of the tube, it will be forced up the
tube by centrifugal force, due to the V-shaped angle of each tube.

The side tubes have holes drilled in their outer edges, so there are two
rows of spray holes in the entire rotor.  These would be suitably
staggered to achieve a reasonably even set of jets.  Then we modulate
the motor speed with longer slower periods of a few seconds ramping up
to a shorter period of faster speed, so the impact points of the jets
are raised a little due to a faster travel time to the PCB and so
falling less due to gravity.

With sufficient turbulence in the container, this may disperse the
pattern of sprays.

Alternatively, to achieve an even spray pattern, the holes can be more
numerous and smaller, such as 0.7mm or so, so that they don't make such
distinct spray patterns on the PCB.

 - Robin  http://www.firstpr.com.au/pcb-diy/