Homebrew PCBs

> To work for 
>spray etching you will probably need a fairly large diameter tube 
>(50mm?) and a reasonable speed.

Uhm.. My memory aparently was not that bad. Back home, I measured the
tube of the etcher I have here. The outer diameter is 2.5 cm. The tube
consist of 2mm thik material.

I was wrong with how the drills for the etchant to spray out of the
tube were were made. They are NOT in spiral form. However, I heard
from Mr. Bungard that their system uses a spiral form since it gives a
smother spray effect. The diameter of those small holes is ~1mm.

The three holes at the bottom plate definately do not have an angle,
but the holes are hmmm - don't know the propper english term for this
- wider on the out side. They are 5mm diameter on the inner end and
~9mm on the outer. The three holes are evenly spreaded around the
center and they seem to be centered in the radius of the bottom plate.

Stefan, I can't tell at what RPM the tube is turning since I have no
equipment to measure. It must be fairly high since the tube is
directly driven by a very powerfull motor. The motor is in a plastic
housing and I can't look into it, but I have the impression that it's
one of those parts used with bigger scale electro RC car models. When
running it consumes about 5amps at 12 Volts.

I hope this gives you guys some ideas.

I would like to add that I have one of those Radix etchers. Radix used
to have a very bad reputation and I must say that there were good
reasons for it. However they are now under new management and they
seem to make things now a lot better. Anyways, you can see details of
the etcher under http://www.radixgmbh.de Go to "Hobby Line" and scroll
down. There you see some details of the device (replacement parts)
including the motor unit and the tube.

The disadvantage of their etcher is that the spray is not smoth/even
enough. That said you get a wave kind of pattern on the PCB which is a
bad thing in that you hardly get reproducible results. I think for
through hole hobby work with not too thin tracks etc. it's ok. It's
not sufficient however for SMD kind of work or work with 10mil tracks
etc. Personally I stoped using the device for these reasons. I do
however strongly belive in the principle used and I'm sure it's
possible to manufacture such an etcher which works fine. You can also
see Bungard devices on the very same page if you look under "Pro
Line". I never had a chance to use one of those etchers but they are
said to work really well.

Markus