PCB Etching (again!) - chemicals used

[Michael]

Hi everyone, again,

sorry to bother this group again -- it's just the most suitable I've
found for my questions.

Anyway, I'm a tad curious about the two different chemicals I use to
make PCBs - I never did much chem in high school, so I'm a bit weak in
that area.

1) I'm not sure what exact chemical I use to develop my boards, but
it's part of the Kinsten range of products for hobbyist PCB
manufacture, and it's called "Developer DP-50". Anyway, it says that it
only has an 8-hour life once combined with water, but I've read mixed
reports on the 'net as to if you can use it after that or not. Any
ideas? I'm just trying to save a bit of cash, because I don't want to
have to use up a new sachet of developer every time I make a PCB (even
though I've probably only used 5% of its potential).

2) I use Ammonium Persulphate to etch my boards, using (once again) a
Kinsten etching tank. Now, because this stuff is a lot more potent,
I've read that you're not supposed to store it at all, and discard
after use. Here, again, it's the same question -- can I store it and
re-use it? otherwise, I'm throwing out a lot of good etchant. I've
poured one lot that I used in a clear plastic bottle, and it's kept for
about a week - it was slightly blue when it came out of the tank, but I
think that's 'cos of the copper, right? Anyway, it seems to be the same
- any reason I can't reuse this?

3) again with the Ammonium Persulphate, when would I know to discard
the solution? I've read that it's when it goes blue, but how blue is
blue? Are there any other indicators I can use (besides it not
etching anymore? )

Oh, and if it's any help, here's the products I'm using, to give you an
idea:

http://www.computronics.com.au/kinsten/prices/

Cheers, thanks in advance for any help, and sorry if they're just
stupid chem questions that most people would know as basic knowledge.


Michael

 

[Nico Coesel]

Hi everyone, again,

sorry to bother this group again -- it's just the most suitable I've
found for my questions.

Anyway, I'm a tad curious about the two different chemicals I use to
make PCBs - I never did much chem in high school, so I'm a bit weak in
that area.

1) I'm not sure what exact chemical I use to develop my boards, but
it's part of the Kinsten range of products for hobbyist PCB

Save money and hassle. Buy pre-made developer in a bottle. If you ruin
one PCB by mixing the developer wrong you undo your savings. BTW,
you'll only need a little bit of developer every time.

2) I use Ammonium Persulphate to etch my boards, using (once again) a
Kinsten etching tank. Now, because this stuff is a lot more potent,
I've read that you're not supposed to store it at all, and discard
after use. Here, again, it's the same question -- can I store it and
re-use it? otherwise, I'm throwing out a lot of good etchant. I've

I use ferric chloride which can be re-activated by adding hydrochloric
acid (can be bought at any grocery store of pharmacist). I'm using the
same etchant for over 15 years now.

 

[John Woodgate]

I read in sci.electronics.design that Nico Coesel <[email protected]>

I use ferric chloride which can be re-activated by adding hydrochloric
acid (can be bought at any grocery store of pharmacist). I'm using the
same etchant for over 15 years now.

Where do you think all the copper went? Or do you make five boards a
year? (;-)

You can't get back ferric chloride by adding HCl. What MAY be happening
is that you are actually now using cupric chloride CuCl2 as the etchant.
That gets converted to cuprous chloride Cu2Cl2 and you CAN convert that
back with HCl.

 

[Nico Coesel]

I read in sci.electronics.design that Nico Coesel <[email protected]>


Where do you think all the copper went? Or do you make five boards a
year? (;-)

Probably less... But I etched quite a large amount of boards over the
years.

You can't get back ferric chloride by adding HCl. What MAY be happening
is that you are actually now using cupric chloride CuCl2 as the etchant.
That gets converted to cuprous chloride Cu2Cl2 and you CAN convert that
back with HCl.

This is an ongoing discussion. However, the fact is that it works (the
boards get etched).

Here is a snippet from an FeCl FAQ I put together almost a decade ago:

"
Regenerating FeCl
'Regenerating' Ferric Chloride is quite simple, just add HCl
(Hydrochloric acid).

Theory:
According to my sources the following happens:

4FeCl3 dissolved in water gives: 4Fe3+ and 12Cl-

When the etching starts the copper is converted by this reaction:

4Fe3+ and copper (2Cu) gives: 4Fe2+ and 2Cu2+

(The HCl is actualy supplied as 4H3O+ and 4Cl- because it's dissolved
in water)

When Oxygen is added to the etching bath the following happens:

4Fe2+ + 4H3O+ + O2 (atmospheric oxygen) gives 4Fe3+ + 6H2O

the last reaction shows that the 4Fe2+ ions are regenerated to 4Fe3+
(The ion which makes the etching process work.) As you can see the HCl
is used and the Ferric Chloride is regenerated.
"

 

[Jim Yanik]

[email protected] (Nico Coesel) wrote in

Probably less... But I etched quite a large amount of boards over the
years.


This is an ongoing discussion. However, the fact is that it works (the
boards get etched).

Here is a snippet from an FeCl FAQ I put together almost a decade ago:

"
Regenerating FeCl
'Regenerating' Ferric Chloride is quite simple, just add HCl
(Hydrochloric acid).

Theory:
According to my sources the following happens:

4FeCl3 dissolved in water gives: 4Fe3+ and 12Cl-

When the etching starts the copper is converted by this reaction:

4Fe3+ and copper (2Cu) gives: 4Fe2+ and 2Cu2+

(The HCl is actualy supplied as 4H3O+ and 4Cl- because it's dissolved
in water)

When Oxygen is added to the etching bath the following happens:

4Fe2+ + 4H3O+ + O2 (atmospheric oxygen) gives 4Fe3+ + 6H2O

the last reaction shows that the 4Fe2+ ions are regenerated to 4Fe3+
(The ion which makes the etching process work.) As you can see the HCl
is used and the Ferric Chloride is regenerated.
"

How do you get the REMOVED COPPER(that came off your etched PCBs) out of
your FeCl when "reactivating" it?

Where does it go?

 

[Leon Heller]

[email protected] (Nico Coesel) wrote in


How do you get the REMOVED COPPER(that came off your etched PCBs) out of
your FeCl when "reactivating" it?

It forms cupric chloride, eventually, which is an etchant in its own right.

Leon

 

[John Woodgate]

I read in sci.electronics.design that Nico Coesel <[email protected]>

When Oxygen is added to the etching bath the following happens:

4Fe2+ + 4H3O+ + O2 (atmospheric oxygen) gives 4Fe3+ + 6H2O

the last reaction shows that the 4Fe2+ ions are regenerated to 4Fe3+
(The ion which makes the etching process work.) As you can see the HCl
is used and the Ferric Chloride is regenerated.

You didn't mention the oxygen before. I'm still not convinced, because
FeCl2 is not likely to reduce molecular oxygen, but that is more
plausible.

 

[Chris]

Hi everyone, again,

sorry to bother this group again -- it's just the most suitable I've
found for my questions.

Anyway, I'm a tad curious about the two different chemicals I use to
make PCBs - I never did much chem in high school, so I'm a bit weak in
that area.

1) I'm not sure what exact chemical I use to develop my boards, but
it's part of the Kinsten range of products for hobbyist PCB
manufacture, and it's called "Developer DP-50". Anyway, it says that it
only has an 8-hour life once combined with water, but I've read mixed
reports on the 'net as to if you can use it after that or not. Any
ideas? I'm just trying to save a bit of cash, because I don't want to
have to use up a new sachet of developer every time I make a PCB (even
though I've probably only used 5% of its potential).

2) I use Ammonium Persulphate to etch my boards, using (once again) a
Kinsten etching tank. Now, because this stuff is a lot more potent,
I've read that you're not supposed to store it at all, and discard
after use. Here, again, it's the same question -- can I store it and
re-use it? otherwise, I'm throwing out a lot of good etchant. I've
poured one lot that I used in a clear plastic bottle, and it's kept for
about a week - it was slightly blue when it came out of the tank, but I
think that's 'cos of the copper, right? Anyway, it seems to be the same
- any reason I can't reuse this?

3) again with the Ammonium Persulphate, when would I know to discard
the solution? I've read that it's when it goes blue, but how blue is
blue? Are there any other indicators I can use (besides it not
etching anymore? )

Oh, and if it's any help, here's the products I'm using, to give you an
idea:

http://www.computronics.com.au/kinsten/prices/

Cheers, thanks in advance for any help, and sorry if they're just
stupid chem questions that most people would know as basic knowledge.


Michael

Hey Michael, I used to use Ammonium Persulphate but Ferric Chloride is much
better. I got 4L from a PCB maker but you can get it here
http://www.altronics.com.au/index.asp?area=item&id=H0800 . I practice the
same procedure as outlined here http://www.geocities.com/pdmtr/ but with
the slight distinction that I warm up my FC to bath temp on the BBQ. Use the
Press-n-Peel from Jaycar http://www1.jaycar.com.au/ and the main point is
clean the board thoroughly with a cream cleanser like Jif or Ajax before
ironing. The whole process from printing to drilled board is less than an
hour.

Cheers.

 

[Michael]

Save money and hassle. Buy pre-made developer in a bottle. If you ruin
one PCB by mixing the developer wrong you undo your savings. BTW,
you'll only need a little bit of developer every time.

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)

I use ferric chloride which can be re-activated by adding hydrochloric
acid (can be bought at any grocery store of pharmacist). I'm using the
same etchant for over 15 years now.

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?

Cheers!

Michael

 

[Michael]

Hey Michael, I used to use Ammonium Persulphate but Ferric Chloride is much
better. I got 4L from a PCB maker but you can get it here
http://www.altronics.com.au/index.asp?area=item&id=H0800 . I practice the
same procedure as outlined here http://www.geocities.com/pdmtr/ but with
the slight distinction that I warm up my FC to bath temp on the BBQ. Use the
Press-n-Peel from Jaycar http://www1.jaycar.com.au/ and the main point is
clean the board thoroughly with a cream cleanser like Jif or Ajax before
ironing. The whole process from printing to drilled board is less than an
hour.

Hrm, that's good to know... do you know if it will work fine with the
kinsten etching tank that I have (referenced in the link in my first
post)? I don't see why it wouldn't, as it's all plastic (and glass, for
the heater), I'm just led to believe that it's pretty nasty stuff
(worse than ammonium persulphate) and I don't want to end up with nasty
results.

Cheers!

Michael

 

[John Woodgate]

I read in sci.electronics.design that Michael

I'm just led to believe that it's pretty nasty stuff (worse than
ammonium persulphate) and I don't want to end up with nasty results.

Both are medium-soft oxidizing agents. I suspect that the only thing
'worse' about FeCl3 is that it stains everything orange-brown, and it's
difficult to get rid of the stains, especially on some materials where
the iron attaches chemically to the molecules of the material.

 

[Nico Coesel]

I read in sci.electronics.design that Nico Coesel <[email protected]>


You didn't mention the oxygen before. I'm still not convinced, because
FeCl2 is not likely to reduce molecular oxygen, but that is more
plausible.

Well, in order to make ferric chloride etch fast, you need to add
oxygen. That's one of the reasons ferric chloride is used in foam or
spray etching machines. Lots of oxygen in the air.

 

[Nico Coesel]

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".

I bought the stuff I use from Farnell.

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)

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.

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?

Any glass or plastic bottle will do as long as it is not made from
nylon.

 

[Nico Coesel]

I read in sci.electronics.design that Michael


Both are medium-soft oxidizing agents. I suspect that the only thing
'worse' about FeCl3 is that it stains everything orange-brown, and it's
difficult to get rid of the stains, especially on some materials where

^^^^^^^^^
Wrong word, it should read 'impossible'. I drove my mother mad with
FeCl stains

Anyway, I've been etching boards since I was a teenager. My father
(who has a degree in chemistry) decided ferric chloride the safest
stuff for me to use.

 

[John Woodgate]

I read in sci.electronics.design that Nico Coesel <[email protected]>

Well, in order to make ferric chloride etch fast, you need to add
oxygen. That's one of the reasons ferric chloride is used in foam or
spray etching machines. Lots of oxygen in the air.

I suspect it's more an effect of the turbulence clearing away the CuCl2
from the etch site. It would be interesting to see if N2 or CO2 bubbles
would increase the etch rate or not.

 

[John Woodgate]

I read in sci.electronics.design that Nico Coesel <[email protected]>

Wrong word, it should read 'impossible'. I drove my mother mad with
FeCl stains

You snipped the bit where I said it's impossible to get it off SOME
materials. Oxalic acid works pretty well on things that don't combine
chemically with the iron. But that's not nice stuff, anyway.

 

[Chris]

Hrm, that's good to know... do you know if it will work fine with the
kinsten etching tank that I have (referenced in the link in my first
post)? I don't see why it wouldn't, as it's all plastic (and glass, for
the heater), I'm just led to believe that it's pretty nasty stuff
(worse than ammonium persulphate) and I don't want to end up with nasty
results.

Most likely, I use a plastic ice-cream container to do my etching in as my
boards are usually small. Fingers I find don't fall off when inserted in the
FC, I may go out on a limb here but I'm sure it would take a while to feel
any effect from leaving any FC on your skin for a while. Water cleans up OK.

BTW, if you go down this road with the Press-n-Peel, I think a laser printer
is the go.

Cheers.

 

[John Woodgate]

I may go out on a limb here but I'm sure it would take a while to feel
any effect from leaving any FC on your skin for a while.

Just try it with a small cut on your finger! It won't kill you, but for
a minute or two you may wish it would.

Water cleans up OK.

Water won't get FeCl3 stains off my fingers. Only the passage of time
does that.

 

[Glenn Ashmore]

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 boards.

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.

--
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]

Most likely, I use a plastic ice-cream container to do my etching in as my
boards are usually small. Fingers I find don't fall off when inserted in the
FC, I may go out on a limb here but I'm sure it would take a while to feel
any effect from leaving any FC on your skin for a while. Water cleans up OK.

BTW, if you go down this road with the Press-n-Peel, I think a laser printer
is the go.

Yeap, I've actually made a nice UV light box from scrap bits of wood,
with 4 x 15W UV tubes. Combined with my 1200 DPI laser printer, I can
get 20mil spacings (8mil tracks with 12mil between) out pretty easily
-- it's just etching it that's the problem.

Cheers!

Michael