On Wed, 18 Feb 2004 08:46:02 -0500, Jeremy Taylor <
jt@...> wrote:
> You are not going to get near the needed pressure/volume from a
> peristaltic
> pump to use spray nozzles. (unless it's HUGE)
we've had all this before.
i too do not think it is the ideal choice.
>
> Most commercial units use magnetic drive centerfucial pumps. The closest
> your going find on the cheap end is a submersible (saltwater style)
> aquarium
> pump. And that may or may not be compatible with your etchant. The ones
> that
> have high pressure, use a ceramic shaft.
must be a mighty big aquarium pump (for big fishes i guess).
but then there is seaworld and such stuff - they have big fish...
>
> You can get 100% plastic spray nozzles, that screw right on to threaded
> PVC "T"s, Usually used for small decorative fountains.
>
> A 300Watt submersible aquarium heater (again saltwater safe all
> plastic/glass) will get a few gallons of etchant up to temp fairly
> quickly.
>
>
Look at the rotrary spray etchers from bungard and similar.
it is nothing but a vertical pipe with holes in the side and a motor on
the top.
the etchant sprayed out of the holes creates the suction which lifts
the etchant from the bottom. centrifugal force and so on.
maybe you need a "propeller like wheel" in the bottom end.
(for additional pressure and startup).
the motor on the top is nothing special, needs not to be sealed.
maybe you want to add a ceramic bearing on the bottom end for stability.
(you need some rpm). the pictures i have seen for the bigger sprayers
use a motor looking like a off-the-shelf ac motor.
(to give you an idea of the speed).
the small units use thinner pipes and brushed dc motors (and more rpm i
think).
I believe if you really want to go with a spray etcher (which i wouldn't
do)
then you might very well make a array of such roatating tubes on each side
of the
pcb and it will work fine.
I still have no idea how much "a lot of pcbs in big numbers" is.
You also have to rething twice if you will use ferric cloride.
i think this depends on availability and the local laws (what you do with
it when it is spent).
if you have a hard time disposing of it then you might consider the
sulphuric acid / h2o2 thing.
there you can get out the copper by cooling (you get copper sulphate which
you can use for
other funny stuff like electroplating). you wouldn't need to dispose of
this etchant often.
ST