Jim Higgins

#36884

At 5/1/2022 13:13 UTC Nuno Yahoo wrote:

If you look for the reactivity series of metals, you'll find out that the silver in the silver nitrate will exchange places with the copper in the PCB.
The concept of the reactivity series isn't applicable because... long before the silver nitrate can contact the copper to plate out silver, the silver nitrate will react immediately with chloride in the etching solution to precipitate silver chloride. The solution will immediately turn cloudy and is likely to be slow to settle.

Since that silver will not be part of the PCB, but will be a fine elemental silver powder, will fall to the bottom along with the rest of the copper etched.
No... but if it could form fine elemental silver it would immediately, and very rapidly, catalyze the decomposition of the hydrogen peroxide in the solution. There would be a lot of foaming unless the amount of peroxide were very small.

If you're not after the silver, this isn't a concern. Actually speeds up the process.
Won't speed up anything because copper won't be removed by the silver in the first place. The silver nitrate will immediately react with chloride in the solution to form a precipitate of silver chloride, which won't react further because it's essentially insoluble.

The problem comes from the silver chloride that will form once the silver nitrate gets in contact with the chloride acid.
Silver chloride is a white solid substance that will create A BIG MESS everywhere. Sticks to everything and is a pain to clean.
Yes!... at least for some definition of a "BIG MESS." I'd guess big mess, but others might find it not so bad. Couldn't say until actually seeing it... but would rather not find out with my own solution. Even tho the silver concentration is low, for sure the precipitate will heavily cloud the solution. A little silver will look like quite a lot when precipitated as silver chloride.

Not sure if the amount mentioned is, or not, enough to be a problem. Maybe try first with a small sample?
For sure!

Seems to me that the AgNO3 concentration is really low. I would give it a try.
I wouldn't, but if tried the result at worse will just be annoying... requiring settling to remove the silver chloride... and perhaps boiling for some time to grow larger particles of precipitate that will settle faster. At best I can't imagine adding enough peroxide that I couldn't just avoid the precipitate by adding it in the form of 3% or 6% peroxide containing no silver.

JimH

#36883

Another peroxide question: how long can unopened peroxide be stored? Does it deteriorate? Some time ago I got a quart of 35%, then got sidetracked. Is it still usable??

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People who have the most seem to live longest . . . . .
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On Sun, May 1, 2022, 11:29 AM Jim Higgins <HigginsJ@...> wrote:

At 5/1/2022 11:30 UTC Morris Odell wrote:

>Hi all,
>
>I've been using the regenerated copper chloride method for etching PCBs for
>years and have had very good results. One problem I do have though is
>getting adequate supplies of hydrogen peroxide which I use to give the
>solution a boost while etching a board.

If your solution needs a boost during etching, perhaps the volume of solution
used is too small. Or perhaps I'm misunderstanding and all you're looking for
is overall faster etching than you would get with a decently large volume
that doesn't get appreciably weaker as etching progresses. If the latter, I'd
tend to be more patient before resorting to a peroxide boost containing
silver nitrate... which will react with the solution to give insoluble silver
chloride which may be difficult to remove without boiling the solution for a
while to clump the silver chloride, then filtering. It's not much silver, but
it may look like a lot of precipitate if it remains suspended.

If you can buy 35% peroxide, you should also be able to get it without
silver... tho maybe not in a pool store.

>The local pharmacies only sell it in 100 ml bottles of 6% and even then they
>keep it behind the counter and give you the third degree when you ask for
>it. I thought I could get larger volumes from a hairdressing supply place
>but it turned out to mixed into a gel.

If pharmacies keep it behind the counter, I'd guess you don't live in the
USA. Here the typical peroxide that some use for wound cleaning (bad idea
despite such use by many) is 3%. The 6% strength is better suited to
bleaching hair... it's way too strong for application to skin and definitely
to wounds... where it was never a very good idea anyhow.

>However I was at the swimming pool shop yesterday and was surprised to find
>1 litre bottles of "chlorine free pool sanitizer" that contains 35% H2O2 and
>0.33 g/L of silver nitrate which is 1.9 millimoles/litre. My question is,
>can this be used instead of pure H2O2? Should I be concerned that the AgNO3
>would interfere with the etch or have a detrimental effect on the stock
>CuCl2 solution that I have built up over the years especially as it would
>accumulate?

Silver will accumulate, but it will do so in the form of a precipitate that
you will hope settles to the bottom of the container... but it might not...
or at least slowly. Silver nitrate will react immediately with the chloride
in the solution to form insoluble silver chloride, which I wouldn't want in
my etch tank... just because it's going to be "messy" - at least for my
definition of messy. It's will form a precipitate that probably won't settle
readily unless the solution is boiled to "clump" the precipitate. If you can
buy 35% peroxide, you should be able to also buy it without silver. Any pool
stores selling the stuff you're describing are catering to folks who don't
want chlorine in their pools and thus don't have problems with precipitation
in their pools. Both peroxide and silver nitrate are powerful germicides. I'm
wondering if this is used as the normal disinfectant, or as a shock
treatment, but none of that is really important for your purposes.

>Any advice from someone who knows more chemistry than I can remember from
>half a century ago would be most welcome.

I majored in chemistry the same half century ago that you mention... but
having been retired a long time I've forgotten a lot of my more specific
chemistry. From what I recall I'd tend to steer clear of silver in PCB
etching solution... not because silver will plate onto the board as someone
said... but because it will precipitate as silver chloride immediately - well
before it has any real chance to plate out. And the precipitate has a pretty
good chance of being annoying if it doesn't settle so you can get rid of it
by decanting periodically. Boiling will make it settle far better, but that
seems like a pain in the backside as well as likely to result in rapid loss
of any remaining peroxide... with loss not being a big problem, but *rapid*
loss could be if the solution suddenly foams up.

I've never had any problem etching using a proper strength well rejuvenated
(by air bubbling) cupric chloride solution. Lots of air bubbling - even to
great excess - also has the benefit of removing some of the water that gets
added if you regularly add a bit of 3% peroxide... tho I've never thought
that was necessary either. More than a touch of peroxide might even tend to
cause some undercutting, which could matter if the traces are thin to begin
with.

All in all I recommend at most very minimal added peroxide when etching and
no added silver.

Good luck.

JimH

Jim Higgins

#36882

At 5/1/2022 11:30 UTC Morris Odell wrote:

Hi all,

I've been using the regenerated copper chloride method for etching PCBs for years and have had very good results. One problem I do have though is getting adequate supplies of hydrogen peroxide which I use to give the solution a boost while etching a board.
If your solution needs a boost during etching, perhaps the volume of solution used is too small. Or perhaps I'm misunderstanding and all you're looking for is overall faster etching than you would get with a decently large volume that doesn't get appreciably weaker as etching progresses. If the latter, I'd tend to be more patient before resorting to a peroxide boost containing silver nitrate... which will react with the solution to give insoluble silver chloride which may be difficult to remove without boiling the solution for a while to clump the silver chloride, then filtering. It's not much silver, but it may look like a lot of precipitate if it remains suspended.

If you can buy 35% peroxide, you should also be able to get it without silver... tho maybe not in a pool store.

The local pharmacies only sell it in 100 ml bottles of 6% and even then they keep it behind the counter and give you the third degree when you ask for it. I thought I could get larger volumes from a hairdressing supply place but it turned out to mixed into a gel.
If pharmacies keep it behind the counter, I'd guess you don't live in the USA. Here the typical peroxide that some use for wound cleaning (bad idea despite such use by many) is 3%. The 6% strength is better suited to bleaching hair... it's way too strong for application to skin and definitely to wounds... where it was never a very good idea anyhow.

However I was at the swimming pool shop yesterday and was surprised to find 1 litre bottles of "chlorine free pool sanitizer" that contains 35% H2O2 and 0.33 g/L of silver nitrate which is 1.9 millimoles/litre. My question is, can this be used instead of pure H2O2? Should I be concerned that the AgNO3 would interfere with the etch or have a detrimental effect on the stock CuCl2 solution that I have built up over the years especially as it would accumulate?
Silver will accumulate, but it will do so in the form of a precipitate that you will hope settles to the bottom of the container... but it might not... or at least slowly. Silver nitrate will react immediately with the chloride in the solution to form insoluble silver chloride, which I wouldn't want in my etch tank... just because it's going to be "messy" - at least for my definition of messy. It's will form a precipitate that probably won't settle readily unless the solution is boiled to "clump" the precipitate. If you can buy 35% peroxide, you should be able to also buy it without silver. Any pool stores selling the stuff you're describing are catering to folks who don't want chlorine in their pools and thus don't have problems with precipitation in their pools. Both peroxide and silver nitrate are powerful germicides. I'm wondering if this is used as the normal disinfectant, or as a shock treatment, but none of that is really important for your purposes.

Any advice from someone who knows more chemistry than I can remember from half a century ago would be most welcome.
I majored in chemistry the same half century ago that you mention... but having been retired a long time I've forgotten a lot of my more specific chemistry. From what I recall I'd tend to steer clear of silver in PCB etching solution... not because silver will plate onto the board as someone said... but because it will precipitate as silver chloride immediately - well before it has any real chance to plate out. And the precipitate has a pretty good chance of being annoying if it doesn't settle so you can get rid of it by decanting periodically. Boiling will make it settle far better, but that seems like a pain in the backside as well as likely to result in rapid loss of any remaining peroxide... with loss not being a big problem, but *rapid* loss could be if the solution suddenly foams up.

I've never had any problem etching using a proper strength well rejuvenated (by air bubbling) cupric chloride solution. Lots of air bubbling - even to great excess - also has the benefit of removing some of the water that gets added if you regularly add a bit of 3% peroxide... tho I've never thought that was necessary either. More than a touch of peroxide might even tend to cause some undercutting, which could matter if the traces are thin to begin with.

All in all I recommend at most very minimal added peroxide when etching and no added silver.

Good luck.

JimH

#36881

You can also just bubble air through it. My understanding is that oxygen is the thing that hydrogen peroxide adds to the mix.

Have it far away from anything affected by the solution, though, as bubbling will atomize some of the mix.

--
Steven Greenfield AE7HD

#36880

Have you been regenerating it by bubbling air through the solution? I've bee using it for years as well and have never found a need to add any hydrogen peroxide. I use a fish tank bubbler and bubble it for a couple of days or until it returns to a clear emerald green. Works as good as it did the day I originally made it.

#36878

Morris,
I was curious why the stuff contained silver nitrate, looks like the sliver must form nano particles when used for disinfection purposes and the metallic silver likely reacts with the peroxide releasing its extra oxygen as part of its disinfection process.? There are numerous articles on Google.? Back to the question, the silver content is relative low so not likely to mess up the etching though I am not a chemist. ? ? Silver and for that matter most finely divided metals will cause the decomposition of hydrogen peroxide but so as long as the silver stays as a salt it's likely to be a non issue.?

I suspect that once you add the peroxide with silver nitrate? to your HCl the silver ions are going to react with the chloride and form an insoluble silver chloride precipitate that will settle out as sludge.
? ? ?

#36877

开云体育

Hi Morris,

?

If you look for the reactivity series of metals, you’ll find out that the silver in the silver nitrate will exchange places with the copper in the PCB.

Since that silver will not be part of the PCB, but will be a fine elemental silver powder, will fall to the bottom along with the rest of the copper etched.

If you’re not after the silver, this isn’t a concern. Actually speeds up the process.

The problem comes from the silver chloride that will form once the silver nitrate gets in contact with the chloride acid.

Silver chloride is a white solid substance that will create A BIG MESS everywhere. Sticks to everything and is a pain to clean.

?

Not sure if the amount mentioned is, or not, enough to be a problem. Maybe try first with a small sample?

Swimming pool chemicals are used, among other things, in precious metals refining. But there, the silver, and other elements, are the end goal.

?

Seems to me that the AgNO3 concentration is really low. I would give it a try.

?

Good luck

?

Nuno T.

?

From: [email protected] [mailto:[email protected]] On Behalf Of Morris Odell
Sent: domingo, 1 de Maio de 2022 12:30
To: [email protected]
Subject: [homebrewpcbs] Question re peroxide

?

Hi all,

I've been using the regenerated copper chloride method for etching PCBs for years and have had very good results. One problem I do have though is getting adequate supplies of hydrogen peroxide which I use to give the solution a boost while etching a board. The local pharmacies only sell it in 100 ml bottles of 6% and even then they keep it behind the counter and give you the third degree when you ask for it. I thought I could get larger volumes from a hairdressing supply place but it turned out to mixed into a gel.

However I was at the swimming pool shop yesterday and was surprised to find 1 litre bottles of "chlorine free pool sanitizer" that contains 35% H2O2 and 0.33 g/L of silver nitrate which is 1.9 millimoles/litre. My question is, can this be used instead of pure H2O2? Should I be concerned that the AgNO3 would interfere with the etch or have a detrimental effect on the stock CuCl2 solution that I have built up over the years especially as it would accumulate?

Any advice from someone who knows more chemistry than I can remember from half a century ago would be most welcome.

Morris

Virus-free.

#36876

Hi all,

I've been using the regenerated copper chloride method for etching PCBs for years and have had very good results. One problem I do have though is getting adequate supplies of hydrogen peroxide which I use to give the solution a boost while etching a board. The local pharmacies only sell it in 100 ml bottles of 6% and even then they keep it behind the counter and give you the third degree when you ask for it. I thought I could get larger volumes from a hairdressing supply place but it turned out to mixed into a gel.

However I was at the swimming pool shop yesterday and was surprised to find 1 litre bottles of "chlorine free pool sanitizer" that contains 35% H2O2 and 0.33 g/L of silver nitrate which is 1.9 millimoles/litre. My question is, can this be used instead of pure H2O2? Should I be concerned that the AgNO3 would interfere with the etch or have a detrimental effect on the stock CuCl2 solution that I have built up over the years especially as it would accumulate?

Any advice from someone who knows more chemistry than I can remember from half a century ago would be most welcome.

Morris