Etching tank idea (Not a new idea)

[CodeMonk]

On those various "How It's Made" and the like tv shows, I have seen PCB's being etched via a spray.

While at the moment I HAVE NO PLANS TO DO THIS, I'M JUST CURIOUS,
I'm wondering if this drawing below would work.
Of course all pieces would be non-metallic, I am wondering if there would be enough of a vacuum created
by a small fish tank type air pump. This would be a sealed system so no evaporation.

I think those various liquid fertilizers that you hook up to your garden hose for your lawn or garden operate on the same idea...To draw a liquid from a tank via a vacuum.

[amptramp]

This looks like a number of air tools that use compressed air.  I have an air brush that could do this and there are larger paint guns, washing guns and undercoating guns available that operate by the same principle.  You would have to make sure the resist could withstand the impact of the spray.  In fact, you could use a rubberized pad for the resist and use a sandblasting gun and get a dry "etch" that would take about ten seconds to complete.  You may not be able to get the fine detail with a sandblaster, of course.

[EATyourGuitar]

insect sprayer example

Bottom versus Gravity Feed - In bottom feed airbrushes, the cup holding the paint is below the nozzle. The paint is sucked upwards by air pressure. In the gravity feed models, the cup is above the nozzle, so that gravity assists the paint in flowing out of the tip. The advantage to gravity feed is that lower pressures can be used for a given paint volume, which is great for fine line work. The disadvantage is that gravity feed models generally have the cup and brush body as one unit, not a plug-in as with the bottom feed; some people find the one unit slower to change colors and clean. There are also variations such as side feed and movable feed.

so with airbrushes you have to use more air if its siphoning from the bottom and it would have more velocity. why not check the patent office for some info on what they use.

[G. Hoffman]

On those various "How It's Made" and the like tv shows, I have seen PCB's being etched via a spray.

While at the moment I HAVE NO PLANS TO DO THIS, I'M JUST CURIOUS,
I'm wondering if this drawing below would work.
Of course all pieces would be non-metallic, I am wondering if there would be enough of a vacuum created
by a small fish tank type air pump. This would be a sealed system so no evaporation.

Probably not.  The VENTURI EFFECT takes more air flow than one of those little things will provide.  You might be able to come up with something using a larger air compressor, but you would probably be better off coming up with something using a plastic rotary pump, but its not really something I would bother with for a DIY thing.  Getting it completely sealed from the motor (which, obviously, MUST have some metal parts) would seem more work than it is worth if you aren't making an awful lot of boards.


Gabriel

[G. Hoffman]

Thinking just a bit more about it, I don't like any kind of Venturi effect setup for this, as the flow would almost have to be a fairly high pressure/low flow system, which would end up putting your etchant everywhere you don't want it.  A positive pressure pump plan providing plentiful proportions of product with puny pressure, perhaps.......  Sorry, I've got a thing for alteration....what was I saying.  Oh yes - a positive pressure pump would allow a low pressure, high volume supply of etchant, which would put the chemicals where you want them much easier than a negative pressure (i.e., Venturi type) solution.  You could maybe do it with enough pressure, you you'd want an awfully large etching tank, and a very big non-metallic area that you can clean easily.  And probably a Tyvex suit, at a minimum, and a full face mask.


Gabriel

[CodeMonk]

Thinking just a bit more about it, I don't like any kind of Venturi effect setup for this, as the flow would almost have to be a fairly high pressure/low flow system, which would end up putting your etchant everywhere you don't want it.  A positive pressure pump plan providing plentiful proportions of product with puny pressure, perhaps.......  Sorry, I've got a thing for alteration....what was I saying.  Oh yes - a positive pressure pump would allow a low pressure, high volume supply of etchant, which would put the chemicals where you want them much easier than a negative pressure (i.e., Venturi type) solution.  You could maybe do it with enough pressure, you you'd want an awfully large etching tank, and a very big non-metallic area that you can clean easily.  And probably a Tyvex suit, at a minimum, and a full face mask.


Gabriel

One reason why it would be a sealed system.
My air compressor goes up to about 150psi or so. Or maybe 275. Although its not really dry air

ATM, i just use this:


With the little pump blowing bubbles. It works well enough for my purposes.

Like I said I was just curious and just trying to educate myself.
If I ever got to the point where I needed to make massive quantities of PCB's, I would just farm it out.

Thanks for the replies and education.