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PCB Etching (again!) - chemicals used

J

John Woodgate

I read in sci.electronics.design that Glenn Ashmore <[email protected]>
Takes about half a 1kg bottle of MG Chemicals amonium perulphate
crystals to mix enough to fill the tank and it is FAR cleaner than
feric chloride.
Click to expand...

If you could please give the volume of water you use in the tank as
well, we could work out the concentration, which would be valid for
other tanks.
 
M

Michael

Glenn said:
I use Amonium Persulphate in a Kinsten etching tank and it works great.
Made a couple of modifications though. Bought a higher wattage aquarium
heater at the pet store so I can get the tank up to working temperature a
lot faster and made a cover from 1/2" acrylic to reduce evaporation between
sessions. I use the same solution for about a month etching 8 to 10
Click to expand...
boards.

Ha -- I actually broke my heater for the Kinsten tank on Friday. (Left
the water level slightly lower than 1000ml, and the top of the heater
got too hot and cracken when [much] colder water splashed up on it.)
I've ordered 2 more heaters for it -- I'll probably put one either side
of the tank, to heat it twice as fast. ;-)

I was surprised you got an aquarium heater to get it to the
temperatures required, though -- all the ones I've seen have
thermostats which would limit the temperature to a much lower range.
Did you get one and modify it? Or do you just etch at a cooler
temperature? How much did it set you back?

Cheers,
Michael
 
M

Michael

Nico said:
I bought the stuff I use from Farnell.
Click to expand...

Ahhh, fair enough. I don't actually check RS and farnell, much - their
prices depress my poor uni student budget too much. ;-)

If it is too strong or too warm, it will strip all the resist of the
board (happened to me once). If it is not strong enough, it won't
strip all the exposed areas. Temperature is also important. I always
use the developer at room temperature. I usually use around 25cc of
developer for a small board.
Click to expand...

Hrm, that's interesting -- mine's definately not too strong, but I'm
thinking it could be too weak. Some areas didn't develop properly, and
I just presumed it wasn't exposed enough in my light box. Shouldn't it
be the sort of thing that I can just leave it in the developer for
longer if it isn't concentrated enough?

Ta,
Michael
 
N

Nico Coesel

Michael said:
Ahhh, fair enough. I don't actually check RS and farnell, much - their
prices depress my poor uni student budget too much. ;-)
Click to expand...

I think I paid 7 euro for 1 liter. Seems expensive, but you'll only
need a little every time.
Hrm, that's interesting -- mine's definately not too strong, but I'm
thinking it could be too weak. Some areas didn't develop properly, and
I just presumed it wasn't exposed enough in my light box. Shouldn't it
be the sort of thing that I can just leave it in the developer for
longer if it isn't concentrated enough?
Click to expand...

Tough question. If the exposure time is right, you can cut some
corners with the developer and vice versa. I think you can leave it in
the developer for a longer time. I recall I tried to strip the resist
after etching using the developer used to develop the PCB again. This
didn't seem to work, nowadays I expose the etched PCB and develop it
again to strip the resist (beats sanding, alcohol or acetone by
miles).

If you mix your own developer, you can make a stronger developer
solution (with hot water) which will strip the resist without exposing
it to UV. I discovered this trick when I was working as a stagiaire at
a hospital. Again, this shows the strength and temperature of the
developer is quite critical.
 
B

Barry Lennox

Ahh, fair enough -- any idea where to get stuff like that? I've just
never seen it, although I do restrict all my google searches for PCB
product purchases to "site:.au".

Also, you mention mixing the developer 'wrong' -- what ill effects does
that have? I understand that if it's too strong it'll strip the stuff
off too quickly, and potentially damages copper (is that right?), but
most hobbyist sites say that the exact mix isn't really that important
-- as long as it's about 1:20 or so. (50g for 1L of water)


ahh, excellent. Yeah, I've read that some people use FC, but a lot of
other places recommend AP as it seems 'easier' to use. But if FC can be
stored properly, I might make the switch... Is there anything important
to know about storage? ie. a tightly sealed plastic bottle would do?
Click to expand...

Many years ago, I bought a largish qty, may have been 20Kg, of FeCl
from a Dairy supply house, diary farmers used to use it to clean
stainless steel vats. I don't know if it's still used for this, but as
I had to buy such a large qty as a minimum, and it was very cheap, I
just finished the last of that a couple of years ago. So, it may be
worth asking around in these circles.

Anyway, they supplied it to me in a metal tin, but the FeCl was in a
heavy-duty plastic bag inside.

When mixed ready to use, I stored it in a plastic 1/2 gal jar, I
understand it's made from PET.
 
G

Glenn Ashmore

I bought a "Top Fin" 150watt heater at PetsMart for about $12.00. The
normal full on is about 95F but if you pull up on the knob you can get past
the stop and the next full turn will bring it up to 120F. The 150 watt size
also goes deeper into the tank than the 100 watt heater that comes with the
tank so you can get the whole tank up to working temps before turning on the
air.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Michael said:
Glenn said:
I use Amonium Persulphate in a Kinsten etching tank and it works great.
Made a couple of modifications though. Bought a higher wattage aquarium
heater at the pet store so I can get the tank up to working temperature a
lot faster and made a cover from 1/2" acrylic to reduce evaporation between
sessions. I use the same solution for about a month etching 8 to 10
Click to expand...
boards.

Ha -- I actually broke my heater for the Kinsten tank on Friday. (Left
the water level slightly lower than 1000ml, and the top of the heater
got too hot and cracken when [much] colder water splashed up on it.)
I've ordered 2 more heaters for it -- I'll probably put one either side
of the tank, to heat it twice as fast. ;-)

I was surprised you got an aquarium heater to get it to the
temperatures required, though -- all the ones I've seen have
thermostats which would limit the temperature to a much lower range.
Did you get one and modify it? Or do you just etch at a cooler
temperature? How much did it set you back?

Cheers,
Michael
Click to expand...
 
G

Glenn Ashmore

The ratio is 250 grams to the liter. It takes 2 liters to fill the tank so
a 1Kg container will make two batches. In my experience AP is a lot better
than Feric Chloride. Beside much less mess, at about 120F with the bubbler
running it will etch a 2oz board in 14-16 minutes.

I am about to put it to the ultimate test. The current batch of AP has been
in the tank for a month and etched about 400 sq. in. of 1 oz and 100 sq.in
of 2oz board. Tonight I am etching a two sided 2 oz panel with 24 1x2"
boards for my solid state light switches. I will time it and report back.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com
 
M

Michael

Glenn said:
I bought a "Top Fin" 150watt heater at PetsMart for about $12.00. The
normal full on is about 95F but if you pull up on the knob you can get past
the stop and the next full turn will bring it up to 120F. The 150 watt size
also goes deeper into the tank than the 100 watt heater that comes with the
tank so you can get the whole tank up to working temps before turning on the
air.
Click to expand...

Ahh, ok -- but that's only about 50 degrees celsius, right? I'm looking
at something like 80 degrees, which I assumed most aquarium stuff
wouldn't get anywhere near. :)

Anyway, I've now got 2 of the Kinsten heaters -- putting one each side
should do a good job, I think.
 
M

Michael

Glenn said:
The ratio is 250 grams to the liter. It takes 2 liters to fill the tank so
a 1Kg container will make two batches. In my experience AP is a lot better
than Feric Chloride. Beside much less mess, at about 120F with the bubbler
running it will etch a 2oz board in 14-16 minutes.

I am about to put it to the ultimate test. The current batch of AP has been
in the tank for a month and etched about 400 sq. in. of 1 oz and 100 sq.in
of 2oz board. Tonight I am etching a two sided 2 oz panel with 24 1x2"
boards for my solid state light switches. I will time it and report back.
Click to expand...

Hrm - and you just leave the etchant in the tank, right? doesn't go off
at all, or affect the tank (such as blocking the air holes at the
bottom)?

Thanks!

Michael
 
J

John Woodgate

I read in sci.electronics.design that Michael
Ahh, ok -- but that's only about 50 degrees celsius, right? I'm looking
at something like 80 degrees, which I assumed most aquarium stuff
wouldn't get anywhere near. :)
Click to expand...

No. Think 'bain marie'!
 
G

Glenn Ashmore

So far so good. I just leave it in the tank. I do remove the heater and
put my homemade cover on top. It turns blue with use and there is a very
slight precipitate but unless you are making a whole lot of boards I don't
think it will be a problem.

I see no sign of it loosing potency. My solutionhas been in the tank for
over a month and last night I etched a 60 sq. in. double sided 2 oz board at
110F and it took right at 20 minutes.


Now I need to lay off the coffee today so I can place all these 0805 caps
tonight. I thought I had a pretty steady hand but under the microscope it
looks like I have Parkinsons. :-(
--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com
 
A

Aubrey McIntosh, Ph.D.

Nico said:
^^^^^^^^^
Wrong word, it should read 'impossible'. I drove my mother mad with
FeCl stains :)
Click to expand...


Has anyone tried citric acid for the stain cleanup?
 
M

Michael

John said:
No. Think 'bain marie'!
Click to expand...

....

*scratches head*

as far as google can tell me, it's some sort of cooking thing - heating
something in water... do youm mean that fish tanks are heated with,
er... ok, I'm lost. :)

suggestions? :p

Cheers,
Michael
 
M

Michael

M

Michael

J

John Woodgate

I read in sci.electronics.design that "Aubrey McIntosh, Ph.D."
Has anyone tried citric acid for the stain cleanup?
Click to expand...

It doesn't work very well. Oxalic is better.
 
J

John Woodgate

I read in sci.electronics.design that Michael
...

*scratches head*

as far as google can tell me, it's some sort of cooking thing - heating
something in water... do youm mean that fish tanks are heated with,
er... ok, I'm lost. :)
Click to expand...
If your aquarium tank reached 80 C or whatever it was, you would have
poached fish. A bain marie is like a double saucepan in action, but not
in shape, with water in the lower part, for heating things very gently.
 
J

John Woodgate

I read in sci.electronics.design that Michael
Hrm, that's weird -- the bottle of AP crystals I have recommends a
temperature of about 75-80ºC for etching -- it's from dick smith's in
Australia.
Click to expand...

Typical room temperature in Oz!
 
O

OBones

John said:
I read in sci.electronics.design that "Aubrey McIntosh, Ph.D."



It doesn't work very well. Oxalic is better.
Click to expand...

But does it leave the colouring of the fabric alone or does it make a
white spot instead of a orangish one?
 
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