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pcb etching tank

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Wp100

Well-Known Member
Hi,

With a new kitchen soon to be delivered I have been told, in no uncertain terms, that etching pcbs in there will not longer be tolerated - or risk untold personal damages !

So I'm going to knock together a vertical style etching tank from an old fish tank, heater and air pump.

Wondered if the Ferric Chloride solution I use needs to be drained off and stored in a sealed container every time I use it - not sure if it oxydizes quickly ?
Thought putting a cover on the top of the tank might suffice ?

Also wondered how much the bubble size from the air pump matters - can I just let it bubble from the airline tube or does it need an airstone, fine or course - although concerned they might fall to pieces in the etchant ?

thanks
 

Boncuk

New Member
Also wondered how much the bubble size from the air pump matters - can I just let it bubble from the airline tube or does it need an airstone, fine or course - although concerned they might fall to pieces in the etchant ?

thanks
The bubble size matters a lot with two respects:

1. If the bubbles are large they won't do a proper job removing the already etched copper off the surface of the PCB evenly.

2. Large bubbles will also take up a lot of etchant and spill it around the tank.

I've never tried an airstone as used in aquariums. There are perforated hoses on the market producing very small air bubbles. They should be alright for etching.

You might want to get away from bubbling etchant and use either the whirl or spray method.

Boncuk
 

Wp100

Well-Known Member
Originally Posted by Boncuk
There are perforated hoses on the market producing very small air bubbles. They should be alright for etching.
Forgot about that kind of plastic hose, just the job - thanks

You might want to get away from bubbling etchant and use either the whirl or spray method.
Although highly desirable, for my small useage they are a bit expensive - unless you know of any cheap pumps that have an all plastic head like the Iwaki pumps.
Could use a cheap motor with remote impellor but thats getting a bit beyond my idea of simple !
 

unclejed613

Well-Known Member
Most Helpful Member
or if the tank were sturdy enough, put it on a "wobbler" table. this would be a flat surface big enough to hold tha tank. the table would be floated on springs or pieces of inner tube. bolted to the table would be a motor with an offset weight on it's shaft (kind of like the vibrator motor in a cell phone but bigger). as the motor spins, it creates a wobbling motion in the table, which would agitate the liquid in the tank. there's no pumps or tubing that can get clogged or leak.
 

Sceadwian

Banned
From 10 years in a metal finishing plant there are more ways to agitate a chemical tank than you can shake a stick at. Including using the stick to stir the tank, believe me that works better than you think..

I recommend, air agitation. Fish pump silicon tubing, want a strip.. punch holes in it along it's length. If the silicon tubing isn't compatable find one that is, tubing is dirt cheap.

The air bubbles go up relatively randomly caotic flow (good for a chemical tank) as long as the chemistry itself isn't hyper air sensitive it's all good.
 

Wp100

Well-Known Member
Thanks guys for all those suggestions - sure I will be able to get something good working.

Bit surprised that the wife seemed very interested in UncleJed613's reply though ?? !! ;)
 

Boncuk

New Member

Sceadwian

Banned
A fish tank bubbler air compressor run from cheap plastic tubing will have a variable control on it. No micro controller required for something that simple. Come to think of it, between the tank the heater and the air pump you can get pretty much a complete etch system at a pet store.
 
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Rolf

Member
A fish tank bubbler air compressor run from cheap plastic tubing will have a variable control on it. No micro controller required for something that simple. Come to think of it, between the tank the heater and the air pump you can get pretty much a complete etch system at a pet store.
Question.......
Has anyone any thoughts on using an rotating agitator on a long shaft, with an impeller close to the bottom of the vertical etching tank?
I am thinking about something similar to a paint steerer driven by a small slow motor.
 

Sceadwian

Banned
Rolf that's right up there with a 'wobbler'. Nothing can beat air agitators for chaotic gentle mixing. All industrial setups that require heavy mixing use air agitators, no reason you shouldn't. Your idea would work though, just not nearly as well.
 

Rolf

Member
Rolf that's right up there with a 'wobbler'. Nothing can beat air agitators for chaotic gentle mixing. All industrial setups that require heavy mixing use air agitators, no reason you shouldn't. Your idea would work though, just not nearly as well.
I would think that bubbles rising up and bursting would put a mist of corrosive aerosol in to my shop. :-( Even if I cover the tank up, the air has to escape and then I need to make a trap of some kind. So the whole setup will become more cumbersome than the tray setup I use now.

I do mostly very small boards and a turkey baster is all I need to agitate the etching solution. I can do a board in less than 15Min.

Edit: I just read where someone used a inexpensive ultrasonic cleaner tank. I am going to look into that.
Seems like all the tanks are SS, how can I overcome that problem?
 
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Sceadwian

Banned
If you feel worried about the chemical mist use a multi-layer cloth filter, a few coffee filters will do fine. If you think a heated tank isn't already going to be emitting these vapors without an air agitator you're wrong. All you have to do with an air agitator is physically prevent the bursting bubbles from exploding fluid outside of the tank.
 

Rolf

Member
If you feel worried about the chemical mist use a multi-layer cloth filter, a few coffee filters will do fine. If you think a heated tank isn't already going to be emitting these vapors without an air agitator you're wrong. All you have to do with an air agitator is physically prevent the bursting bubbles from exploding fluid outside of the tank.
Who said any thing about a heated tank? Room temp is fine.
To use air you have to have a compressor of some sort, that requires a power cord and a air hose, it all gets to be too cumbersome, I will stay with my plastic tray and turkey baster for now. Making only enough etching solution for the job on hand eliminates having to store used etcher and gives you the advantage of a fresh batch for each job. And I do it outside when temperature permits.
 
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Sceadwian

Banned
Almost all enchant tanks are heated, decreases etch time.
 

Boncuk

New Member
A fish tank bubbler air compressor run from cheap plastic tubing will have a variable control on it. No micro controller required for something that simple. Come to think of it, between the tank the heater and the air pump you can get pretty much a complete etch system at a pet store.
Something to be mentioned about using aquarium heaters for the etchant:

Natriumpersufate works nicely at temperatures between 40 and 50 deg/C. It starts crystallizing at temperatures ≥55deg/C and builds up a solid layer (as tough as concrete) at the bottom of the etchant tank.

It will already start crystallizing if the glass encapsulation of the heater exceeds that temperature.

Boncuk
 

Sceadwian

Banned
How many hobbyists do you think use that chemistry?
 
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