Homebrew PCBs

I'm also curious as to what the real use is for the bubblers.  Are we
trying to aerate the solution, or cause some movement in the solution
to get more even etches?

    What I wish to use is a clear acrylic, welded together with the
acrylic cement, and cause the liquid to move by using a small
propeller.  Obviously I can't run an electronic motor inside the tank,
and most gears and bands would probably fall apart after the first
board is done.
    So..  this is the idea I had.  Keep the motor outside of the tank,
and connect two magnets to the drive shaft.  For the propeller, use
the same material that the tank is made of, and seal matching magnets
or iron slugs into it, so that I can spin it using the magnetic force.
    Oh yeh,  I also cant run it at 50k rpms, so I will make a simple
gearbox to lower the speed and boost the torque.

    If the bubbles are still needed, I just want to run one single
line of bubbles, right near the prop so as to get things aerated.
    I haven't quite decided whether or not I want to submerge a heater
in the tank, or build in a heat pump.

Any ideas on this?  
-tommy

On Wed, 8 Dec 2004 03:36:03 -0800, dioxide <dioxide@...> wrote:

>
> I'm also curious as to what the real use is for the bubblers.  Are we
> trying to aerate the solution, or cause some movement in the solution
> to get more even etches?

I want to get the movement (to take spent etchant away from the brd  
surface and to mix
the etchant, because the spent settles on the bottom.
But with CuCl regeneration via air oxygen is an option, but you need to  
run the bubbler very long.

>
>     What I wish to use is a clear acrylic, welded together with the
> acrylic cement, and cause the liquid to move by using a small
> propeller.  Obviously I can't run an electronic motor inside the tank,
> and most gears and bands would probably fall apart after the first
> board is done.

well, it would be hard to use a prop. what could work is if you use the  
propshaft vertical
out of the tank, and a motor on top of it.
Doesn't work for me because the tank is only 2cm wide, no space for a prop.
it would generate a circular current in the tank.

>     So..  this is the idea I had.  Keep the motor outside of the tank,
> and connect two magnets to the drive shaft.  For the propeller, use
> the same material that the tank is made of, and seal matching magnets
> or iron slugs into it, so that I can spin it using the magnetic force.
>     Oh yeh,  I also cant run it at 50k rpms, so I will make a simple
> gearbox to lower the speed and boost the torque.

nt sure, sounds complicated. artificial hearts are made that way, but they  
use a electronic
drive instead of rotating magnets, like a magneti stirrer for chem. labs.

>
>     If the bubbles are still needed, I just want to run one single
> line of bubbles, right near the prop so as to get things aerated.
>     I haven't quite decided whether or not I want to submerge a heater
> in the tank, or build in a heat pump.

If aeration is a advantage depends on the etchant used, fo most it is no  
benefit other than agitation.

>
> Any ideas on this?
> -tommy

first decide on the etchant to use, then think very carefully how the tank  
is best built. i have the third
now and still much to improve.

ST

>     What I wish to use is a clear acrylic, welded together with the
> acrylic cement, and cause the liquid to move by using a small
> propeller.  Obviously I can't run an electronic motor inside the tank,
> and most gears and bands would probably fall apart after the first
> board is done.
Just got to thinking - In lab work years ago, a standard stirring 
mechanism was a motor (variable speed) driven magnet base for a liquid 
container (read: etchant tank) with a Teflon encapsulated magnet just 
dropped into the tank.  The base magnet would spin the teflon 
encapsulated magnet inside, stirring the liquid.  Higher speeds could 
generate a full whirlpool in a 8-10" deep flask.  I'd bet that the 
magnet s are still a common lab item - and should be cheap.  The only 
etchant contact would be teflon.  Might be an etchant agitator for PCB work.

Norm

about acrylic - the guys at TAP Plastics told me that it is not acid 
resistant.  I wouldn't use it for CuCl because of that.  It worked 
fine for AP and FeCl, though.

Phil

On Wed, 08 Dec 2004 18:55:01 -0000, Phil <phil1960us@...> wrote:

>
> about acrylic - the guys at TAP Plastics told me that it is not acid
> resistant.  I wouldn't use it for CuCl because of that.  It worked
> fine for AP and FeCl, though.
> Phil
>

had a acrylic pcb holder for some time, saw no adverse effects.
Have a glass tank now, with silicone seams.

ST

Phil wrote:
> 
> about acrylic - the guys at TAP Plastics told me that it is not acid 
> resistant.  I wouldn't use it for CuCl because of that.  It worked 
> fine for AP and FeCl, though.
> 
> Phil
> 
The three above mentioned etchants normally have acid and pH will be 
very low (< 1). Acrylic (PMMA) is ok for acid. I made a small 
electrochemical test cell out of this stuff and have had 20% sulfuric 
acid in it for weeks at a time and see zero effect to date.

Nylon is the common plastic you must avoid contact with acid for long 
periods, even vinegar.

Of course there is always www.google.com

On Thu, 09 Dec 2004 07:35:26 +1100, Adam Seychell  
<a_seychell@...> wrote:

>
> The three above mentioned etchants normally have acid and pH will be
> very low (< 1). Acrylic (PMMA) is ok for acid. I made a small
> electrochemical test cell out of this stuff and have had 20% sulfuric
> acid in it for weeks at a time and see zero effect to date.
> Nylon is the common plastic you must avoid contact with acid for long
> periods, even vinegar.
> Of course there is always www.google.com


And the links section, where you will find links to chemical compatibility  
pages.
(tank construction folder)

ST

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:
> Phil wrote:
> > 
> > about acrylic - the guys at TAP Plastics told me that it is not acid 
> > resistant.  I wouldn't use it for CuCl because of that.  It worked 
> > fine for AP and FeCl, though.
> > 
> > Phil
> > 
> The three above mentioned etchants normally have acid and pH will be 
> very low (< 1). Acrylic (PMMA) is ok for acid. I made a small 
> electrochemical test cell out of this stuff and have had 20% sulfuric 
> acid in it for weeks at a time and see zero effect to date.
> 
> Nylon is the common plastic you must avoid contact with acid for long 
> periods, even vinegar.
> 
> Of course there is always www.google.com

Nylon is definitely no good in a FeCL3 etch bath.  

Years ago, I had the brilliant idea that, instead of moving the 
etchant, I'd move the board instead (Think of this as sort of a 
Mohammed and the Mountain analogy.).  So, I used one of the index
holes in the board to tie a section of nylon monofilament fishing 
line to the board, and could jiggle the board with that, thus 
achieving agitation (Think clock drive or something like that 
eventually.).  Only, the nylon monofilament line didn't 
even last for one etch before it broke.  Oh, well, back to the 
drawing board.

Dave

>From: "Dave" <wa4qal@...>
>Reply-To: Homebrew_PCBs@yahoogroups.com
>To: Homebrew_PCBs@yahoogroups.com
>Subject: [Homebrew_PCBs] Re: Etch safe materials for etch tank
>Date: Thu, 09 Dec 2004 16:01:00 -0000
>
>
>
>--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
>wrote:
> > Phil wrote:
> > >
> > > about acrylic - the guys at TAP Plastics told me that it is not acid
> > > resistant.  I wouldn't use it for CuCl because of that.  It worked
> > > fine for AP and FeCl, though.
> > >
> > > Phil
> > >
> > The three above mentioned etchants normally have acid and pH will be
> > very low (< 1). Acrylic (PMMA) is ok for acid. I made a small
> > electrochemical test cell out of this stuff and have had 20% sulfuric
> > acid in it for weeks at a time and see zero effect to date.
> >
> > Nylon is the common plastic you must avoid contact with acid for long
> > periods, even vinegar.
> >
> > Of course there is always www.google.com
>
>Nylon is definitely no good in a FeCL3 etch bath.
>
>Years ago, I had the brilliant idea that, instead of moving the
>etchant, I'd move the board instead (Think of this as sort of a
>Mohammed and the Mountain analogy.).  So, I used one of the index
>holes in the board to tie a section of nylon monofilament fishing
>line to the board, and could jiggle the board with that, thus
>achieving agitation (Think clock drive or something like that
>eventually.).  Only, the nylon monofilament line didn't
>even last for one etch before it broke.  Oh, well, back to the
>drawing board.

There was a design in the ARRL Handbook a few years back for an etching 
arrangement that simulated hand agitation by using an eccentric cam on the 
shaft of a geared-down motor to rock the container. The etchant was kept hot 
with a heat lamp positioned above the container.

Leon

In message <opsipjgycjmg0lsf@...>
          "Stefan Trethan" <stefan_trethan@...> wrote:

> And the links section, where you will find links to chemical compatibility  
> pages.
> (tank construction folder)

Heh - I only just noticed that :)
My etchtank is a modified polypropylene cereal storage tub. I drilled three
holes in the cover (one for the heater's power cable, one for the bubbler
hose, one for a thermometer). The only problem is, when the bubbler is
running, it produces a fair bit of FeCl3 mist. Plugging the holes with
Blu-Tack and kitchen paper (and careful setting of the air pressure) seems
to lessen the effect though.
The only major problem is the loss of etchant when the tank gets drained and
cleaned. I seem to be losing about 10mL each time I use the tank. Not a big
problem, 'cos I can always top the etchant up, but it gets annoying when you
need to etch a Eurocard and the etchant level is a bit too low to etch the
board properly :-/

Later.
-- 
Phil.                              | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB,
philpem@...              | ViewFinder, 10BaseT Ethernet, 2-slice,
http://www.philpem.me.uk/          | 48xCD, ARCINv6c IDE, SCSI
... PARENT: Don't you understand English? HONEST CHILD: No, not fully!

In message <cp9srs+8mns@...>
          "Dave" <wa4qal@...> wrote:

> Only, the nylon monofilament line didn't 
> even last for one etch before it broke.  Oh, well, back to the 
> drawing board.

PVC insulated wire works quite well. Get the thinnest stuff you can get your
mitts on - there is some available that will go through a 0.8mm hole.
I normally drill one hole on each side of the top edge of the board, then
suspend the board using PVC-coated wire. It seems to work quite well, and
makes it easier to remove the board after it's finished etching.

Later.
-- 
Phil.                              | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB,
philpem@...              | ViewFinder, 10BaseT Ethernet, 2-slice,
http://www.philpem.me.uk/          | 48xCD, ARCINv6c IDE, SCSI
... It's not in the manual !!!!!

On Fri, 10 Dec 2004 00:32:43 GMT, Philip Pemberton <philpem@...>  
wrote:

>
> Heh - I only just noticed that
> My etchtank is a modified polypropylene cereal storage tub. I drilled  
> three
> holes in the cover (one for the heater's power cable, one for the bubbler
> hose, one for a thermometer). The only problem is, when the bubbler is
> running, it produces a fair bit of FeCl3 mist. Plugging the holes with
> Blu-Tack and kitchen paper (and careful setting of the air pressure)  
> seems
> to lessen the effect though.
> The only major problem is the loss of etchant when the tank gets drained  
> and
> cleaned. I seem to be losing about 10mL each time I use the tank. Not a  
> big
> problem, 'cos I can always top the etchant up, but it gets annoying when  
> you
> need to etch a Eurocard and the etchant level is a bit too low to etch  
> the
> board properly :-/
> Later.

I have solutions for both problems:
Mist: put the inlet of your pump in the tank too. Make sure the pump is  
made completely of plastic/rubber.
This causes the mist to be recycled and not expelled.

Losses: Don't empty your tank. i leave the etchant in all the time, but i  
have a homebrew tank.

ST

In message <opsir6p1wrmg0lsf@...>
          "Stefan Trethan" <stefan_trethan@...> wrote:

> I have solutions for both problems:
> Mist: put the inlet of your pump in the tank too. Make sure the pump is  
> made completely of plastic/rubber.
> This causes the mist to be recycled and not expelled.

Not gonna happen - it's an aquarium air pump.
That and the mist doesn't seem to be mist at all - it's more like droplets of
FeCl3 condensing on the inside of the tank lid.

> Losses: Don't empty your tank. i leave the etchant in all the time, but i  
> have a homebrew tank.

Probably not a good idea around here. Things tend to get tipped and bumped
quite a lot and the idea of having to clean up the mess caused by three
litres of heated, concentrated FeCl doesn't appeal to me.

Later.
-- 
Phil.                              | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB,
philpem@...              | ViewFinder, 10BaseT Ethernet, 2-slice,
http://www.philpem.me.uk/          | 48xCD, ARCINv6c IDE, SCSI
... James Dean taught Marc Bolan to drive.

>
>Not gonna happen - it's an aquarium air pump.
>That and the mist doesn't seem to be mist at all - it's more like droplets of
>FeCl3 condensing on the inside of the tank lid.

Recycling corrosive vapor through one of these would be a very short-lived 
project.

On Mon, 13 Dec 2004 12:46:31 -0500, Dave VanHorn <dvanhorn@...>  
wrote:

>
> Recycling corrosive vapor through one of these would be a very  
> short-lived
> project.


disagree, i have an aquarium pump and it is made of rubber and plastic. no  
worries here.

ST

>
>disagree, i have an aquarium pump and it is made of rubber and plastic. no
>worries here.

The copper winding in the vibrator has been replaced by rubber and plastic?
The steel electromagnet core also?

Very interesting technology.

On Mon, 13 Dec 2004 14:03:09 -0500, Dave VanHorn <dvanhorn@...>  
wrote:

>
> The copper winding in the vibrator has been replaced by rubber and  
> plastic?
> The steel electromagnet core also?
> Very interesting technology.


Haha, of course not.

There is no need at all for the gas to ever reach the parts you described.
I just attached a hose directly to the inlet valve of the pump.

ST

P.S.: it would be very easy to coat the e-magnet in thick epoxy, same for  
the magnet.
There is a gap several mm between them so it would't be a problem. but it  
isn't required.

>
>There is no need at all for the gas to ever reach the parts you described.
>I just attached a hose directly to the inlet valve of the pump.

Must be a different sort of pump.
The ones I'm familiar with, have no inlet valve as such.
They are a small blue or green box, with just an outlet.

On Mon, 13 Dec 2004 16:40:13 -0500, Dave VanHorn <dvanhorn@...>  
wrote:

>
> Must be a different sort of pump.
> The ones I'm familiar with, have no inlet valve as such.
> They are a small blue or green box, with just an outlet.
>


well, mine had no port for a hose, simply a hole in the pump mechanism.  
but nobody can prevent me from simply attaching a hose there with the aid  
of glue.
In normal (fish) operation the hole in the mechanism sucks the air in form  
the inside of the pump housing.

ST

>
>well, mine had no port for a hose, simply a hole in the pump mechanism.
>but nobody can prevent me from simply attaching a hose there with the aid
>of glue.
>In normal (fish) operation the hole in the mechanism sucks the air in form
>the inside of the pump housing.

Ok, in mine, when you open the box, there's exposed copper and steel parts.

On Mon, 13 Dec 2004 17:14:27 -0500, Dave VanHorn <dvanhorn@...>  
wrote:

>
> Ok, in mine, when you open the box, there's exposed copper and steel  
> parts.


yes, and that's why you attach the hose to the pump mechanism inlet and  
not to the housing.

ST

On Mon, 13 Dec 2004 17:14:27 -0500, Dave VanHorn <dvanhorn@...>  
wrote:

>
>
>>
>> well, mine had no port for a hose, simply a hole in the pump mechanism.
>> but nobody can prevent me from simply attaching a hose there with the  
>> aid
>> of glue.
>> In normal (fish) operation the hole in the mechanism sucks the air in  
>> form
>> the inside of the pump housing.
>
> Ok, in mine, when you open the box, there's exposed copper and steel  
> parts.
>

by the way a cover over the tank would probably solve the problem. add a  
outlet with a filter
of cloth. you can add some NaOH or something, dry, to neutralise any mist  
droplets.

ST