etching printed circuit boards

[Allan Adler]

One of the problems with making your own printed circuit boards is the
difficulty of legally disposing of spent etchant. That might be easy in
some places, expensive or impossible in others.

It occurred to me that there might be less problematic alternatives for
dealing with printed circuit boards. For example, a few decades ago when
I wanted to try to synthesize copper acetate for myself, I dropped pennies
in vinegar and left them alone for a few weeks and copper acetate crystals
grew on the pennies. (I know that pennies are not pure copper, so this might
not have been pure copper acetate). The pennies never dissolved completely,
but I was after crystals and didn't worry about completely digesting the
pennies.

I was able hasten the process considerably by connecting the leads of a
battery to a cupful of vinegar with copper wire. In fact, the wire dissolved
completely. It produced a rich blue solution from which I obtained
broccoli-like dendritic growth, but it would probably have just as
well grown nice crystals under other conditions.

So, I was wondering what exactly would be wrong with dropping the printed
circuit boards in vinegar (or perhaps somewhat more concentrated acetic acid)
and trying to etch them that way. When you are done, you can just use the
resulting solution to grow nice copper acetate crystals. The battery idea
is also appealing, but it suffers from the obvious defect that once the
copper near the electrode is gone, the rest of the copper is no longer
connected to the battery. Maybe someone knows a clever way around that
inconvenience.

Alternatively, consider the problem of disposing of actual spent ferric
chloride or spent ammonium perchlorate. Some locales have no provision
for disposing of such chemicals at special waste sites, which are dedicated
to lists of specifically approved substances such as paint thinners, motor
fuel, used tires, etc. Instead, one has to contract with a company specializing
in toxic waste to get rid of it. That sounds like an expensive proposition and
they might simply refuse to deal with an individual and the tiny quantities
of spent etchant they generate.

Is there any reason why one can't simply try to use the spent etchant to
grow large single crystals and add them to one's crystal collection? In
fact, amateurs who etch their own printed circuit boards can have contests
for the largest and most perfect single crystals, or the most interesting
dendritic growth.

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[Garrett Mace]

I was able hasten the process considerably by connecting the leads of a
battery to a cupful of vinegar with copper wire. In fact, the wire
dissolved
completely. It produced a rich blue solution from which I obtained
broccoli-like dendritic growth, but it would probably have just as
well grown nice crystals under other conditions.

So, I was wondering what exactly would be wrong with dropping the printed
circuit boards in vinegar (or perhaps somewhat more concentrated acetic
acid)
and trying to etch them that way. When you are done, you can just use the
resulting solution to grow nice copper acetate crystals. The battery idea
is also appealing, but it suffers from the obvious defect that once the
copper near the electrode is gone, the rest of the copper is no longer
connected to the battery. Maybe someone knows a clever way around that
inconvenience.

Electro-etching is one way decent amounts of copper can be removed from a
board. Usually it's followed up by regular etchant to clean up the last
bits. This method allows you to use less etchant because you remove most of
the copper first, and don't wear out the etchant as quickly. I haven't tried
it.

 

[Harry Conover]

Allan Adler <ara@nestle.ai.mit.edu> wrote in message news:<y93llnaz4sf.fsf@nestle.ai.mit.edu>...

One of the problems with making your own printed circuit boards is the
difficulty of legally disposing of spent etchant. That might be easy in
some places, expensive or impossible in others.

It occurred to me that there might be less problematic alternatives for
dealing with printed circuit boards. For example, a few decades ago when
I wanted to try to synthesize copper acetate for myself, I dropped pennies
in vinegar and left them alone for a few weeks and copper acetate crystals
grew on the pennies. (I know that pennies are not pure copper, so this might
not have been pure copper acetate). The pennies never dissolved completely,
but I was after crystals and didn't worry about completely digesting the
pennies.

I was able hasten the process considerably by connecting the leads of a
battery to a cupful of vinegar with copper wire. In fact, the wire dissolved
completely. It produced a rich blue solution from which I obtained
broccoli-like dendritic growth, but it would probably have just as
well grown nice crystals under other conditions.

So, I was wondering what exactly would be wrong with dropping the printed
circuit boards in vinegar (or perhaps somewhat more concentrated acetic acid)
and trying to etch them that way. When you are done, you can just use the
resulting solution to grow nice copper acetate crystals. The battery idea
is also appealing, but it suffers from the obvious defect that once the
copper near the electrode is gone, the rest of the copper is no longer
connected to the battery. Maybe someone knows a clever way around that
inconvenience.

Alternatively, consider the problem of disposing of actual spent ferric
chloride or spent ammonium perchlorate. Some locales have no provision
for disposing of such chemicals at special waste sites, which are dedicated
to lists of specifically approved substances such as paint thinners, motor
fuel, used tires, etc. Instead, one has to contract with a company specializing
in toxic waste to get rid of it. That sounds like an expensive proposition and
they might simply refuse to deal with an individual and the tiny quantities
of spent etchant they generate.

Is there any reason why one can't simply try to use the spent etchant to
grow large single crystals and add them to one's crystal collection? In
fact, amateurs who etch their own printed circuit boards can have contests
for the largest and most perfect single crystals, or the most interesting
dendritic growth.

Allan, while I applaud your rather extreme level of environmentally
related political correctness, I really think you should get a closer
grip on reality and realize that the copper laden waste residue
created by amateur PC board etching wouldn't even create a glitch in a
graph of the copper salt residue released into the waste water
treatment systems by millions of copper pipe plumbed homes.

That said, you are correct in believing that you can electroplate or
precipitate crystals or salts from spent etchant. Large PC shops have
been since the early 1980s required to do just this, however the costs
involved in this copper reclamation process have driven most of the
industry into the use of additive copper PC fabrication processes
rather than etching away the majority of surface area on a copper foil
laminated panel.

The pollution produced by simply dumping small quantities of home
produced spent etchant into a municipal waste water collection system
is arguably no worse than that released into the same systems by
millions of home darkrooms and drugstore sited photo processors.
Simply neutralize the etchant by adding some lye or ammonia to it (in
well ventilated conditions) prior to pouring it down the drain.

Important note: Never dump spent etchant into a domestic system that
feeds into a residential septic tank for reasons that should be
obvious.

Harry C.

p.s., Allan, stay away from using a solder plated resist on your PC
boards, because lead salts present a far more serious disposal problem
than does copper.

 

[Muhammar]

Copper does not dissolve in vinegar. Zinc does. Since you had some
"insoluble stuff" left from dissolving pennies, you managed to get
some dirty zinc acetate and separate all copper (3% of it, used for
coating).

If you want to dispose spent etchant solution in a cheap and
enviro-friendly way, you can mix it into concrete slush and leting it
harden. While you are pouring your concrete mix, you can also include
your mother-in law for more satisfying monolith.

Allan Adler <ara@nestle.ai.mit.edu> wrote in message news:<y93llnaz4sf.fsf@nestle.ai.mit.edu>...

One of the problems with making your own printed circuit boards is the
difficulty of legally disposing of spent etchant. That might be easy in
some places, expensive or impossible in others.

It occurred to me that there might be less problematic alternatives for
dealing with printed circuit boards. For example, a few decades ago when
I wanted to try to synthesize copper acetate for myself, I dropped pennies
in vinegar and left them alone for a few weeks and copper acetate crystals
grew on the pennies. (I know that pennies are not pure copper, so this might
not have been pure copper acetate). The pennies never dissolved completely,
but I was after crystals and didn't worry about completely digesting the
pennies.

I was able hasten the process considerably by connecting the leads of a
battery to a cupful of vinegar with copper wire. In fact, the wire dissolved
completely. It produced a rich blue solution from which I obtained
broccoli-like dendritic growth, but it would probably have just as
well grown nice crystals under other conditions.

So, I was wondering what exactly would be wrong with dropping the printed
circuit boards in vinegar (or perhaps somewhat more concentrated acetic acid)
and trying to etch them that way. When you are done, you can just use the
resulting solution to grow nice copper acetate crystals. The battery idea
is also appealing, but it suffers from the obvious defect that once the
copper near the electrode is gone, the rest of the copper is no longer
connected to the battery. Maybe someone knows a clever way around that
inconvenience.

Alternatively, consider the problem of disposing of actual spent ferric
chloride or spent ammonium perchlorate. Some locales have no provision
for disposing of such chemicals at special waste sites, which are dedicated
to lists of specifically approved substances such as paint thinners, motor
fuel, used tires, etc. Instead, one has to contract with a company specializing
in toxic waste to get rid of it. That sounds like an expensive proposition and
they might simply refuse to deal with an individual and the tiny quantities
of spent etchant they generate.

Is there any reason why one can't simply try to use the spent etchant to
grow large single crystals and add them to one's crystal collection? In
fact, amateurs who etch their own printed circuit boards can have contests
for the largest and most perfect single crystals, or the most interesting
dendritic growth.

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[Jamie]

Yup, i know the problem.
i my self don't have very much trouble in disposing of the
etching due to a local dump that handles those kinds of
problems.
i did how ever develop 2 different X,Y,Z scanning tables.
one is a sprayer that uses Blue Dye and sprays the protective
coating onto the clad..
the other is a EDM (electro discharge Machine) that actually
is using a plasma removable approach with the Clad submerged in
a oil that is very easy cleaning afterwards. i use a small little
fluid pump to circulate and filter the oil..
both work, i would rather use the EDM over my Blue Dye sprayer due
to the mess it some times makes..
P.S.
currently i am having noise emission problems with EDM but working
on it..




Allan Adler wrote:

One of the problems with making your own printed circuit boards is the
difficulty of legally disposing of spent etchant. That might be easy in
some places, expensive or impossible in others.

It occurred to me that there might be less problematic alternatives for
dealing with printed circuit boards. For example, a few decades ago when
I wanted to try to synthesize copper acetate for myself, I dropped pennies
in vinegar and left them alone for a few weeks and copper acetate crystals
grew on the pennies. (I know that pennies are not pure copper, so this might
not have been pure copper acetate). The pennies never dissolved completely,
but I was after crystals and didn't worry about completely digesting the
pennies.

I was able hasten the process considerably by connecting the leads of a
battery to a cupful of vinegar with copper wire. In fact, the wire dissolved
completely. It produced a rich blue solution from which I obtained
broccoli-like dendritic growth, but it would probably have just as
well grown nice crystals under other conditions.

So, I was wondering what exactly would be wrong with dropping the printed
circuit boards in vinegar (or perhaps somewhat more concentrated acetic acid)
and trying to etch them that way. When you are done, you can just use the
resulting solution to grow nice copper acetate crystals. The battery idea
is also appealing, but it suffers from the obvious defect that once the
copper near the electrode is gone, the rest of the copper is no longer
connected to the battery. Maybe someone knows a clever way around that
inconvenience.

Alternatively, consider the problem of disposing of actual spent ferric
chloride or spent ammonium perchlorate. Some locales have no provision
for disposing of such chemicals at special waste sites, which are dedicated
to lists of specifically approved substances such as paint thinners, motor
fuel, used tires, etc. Instead, one has to contract with a company specializing
in toxic waste to get rid of it. That sounds like an expensive proposition and
they might simply refuse to deal with an individual and the tiny quantities
of spent etchant they generate.

Is there any reason why one can't simply try to use the spent etchant to
grow large single crystals and add them to one's crystal collection? In
fact, amateurs who etch their own printed circuit boards can have contests
for the largest and most perfect single crystals, or the most interesting
dendritic growth.

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[Allan Adler]

muhammar@hotmail.com (Muhammar) writes:

Copper does not dissolve in vinegar. Zinc does. Since you had some
"insoluble stuff" left from dissolving pennies, you managed to get
some dirty zinc acetate and separate all copper (3% of it, used for
coating).

Chemists were fairly unanimous in telling me, before I tried it,
that it wouldn't work, muttering about oxidation potentials or
something like that. I admit that the presence of other metals in
pennies leaves that example inconclusive, but note that I also got
copper wire to be completely digested by vinegar when I used a battery.

After I told some chemists about my experiences with it, they said
something about the presence of oxygen in the water being the reason
it worked when it shouldn't have. I don't know what reaction mechanisms
are involved, so I really can't comment on this. However, I got into a
conversation with someone specializing in the history of chemistry and
he referred me to something called the Stockholm manuscript, an ancient
Greek papyrus in which a process is described for making copper acetate
by heating vinegar and letting the fumes corrode the the copper lid of
the vessel.

Admittedly, a half remembered conversation from over two decades ago
about a work I haven't read is not an argument against what Muhammar
says. However, I happen to own a copy of a bilingual Greek-French
edition of the Stockholm manuscript that I acquired in Paris in 1985
for just this reason but which I've always been too busy to read. Now
that I have an excuse to do so, I'll start working through it. This
process is likely to generate some other questions about obsolete
chemical technology.

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[Allan Adler]

hhc314@yahoo.com (Harry Conover) writes:

Allan, while I applaud your rather extreme level of environmentally
related political correctness, I really think you should get a closer
grip on reality and realize that the copper laden waste residue
created by amateur PC board etching wouldn't even create a glitch in a
graph of the copper salt residue released into the waste water
treatment systems by millions of copper pipe plumbed homes.

Harry, thanks for all the suggestions. Regarding my motivations, it
is a matter of complying with the law and I don't know what the law is.
For example, in Jan Axelson's book, "Making printed circuit boards",
which I'm reading at the moment, it says on p.216, "Check with local
officials on how to dispose of used etchant." Her book is aimed at
amateurs and she still says that you have to find out the local regulations.

If I can find a local official who, in his/her official capacity, can tell
me that simply neutralizing the etchant with lye or ammonia and pouring
it down the drain is an acceptable way to dispose of it, then there is
no problem. So far, finding out the law is a lot harder than any of the
chemical issues.

Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[Allan Adler]

Jamie <jamie_5_not_valid_after_5_Please@charter.net> writes:

i did how ever develop 2 different X,Y,Z scanning tables.
one is a sprayer that uses Blue Dye and sprays the protective
coating onto the clad..
the other is a EDM (electro discharge Machine) that actually
is using a plasma removable approach with the Clad submerged in
a oil that is very easy cleaning afterwards. i use a small little
fluid pump to circulate and filter the oil..
both work, i would rather use the EDM over my Blue Dye sprayer due
to the mess it some times makes..

This is really useful information! I was wondering whether one could
do it with an EDM but I have so little knowledge about the devices
that I wasn't sure what one can or can't use it for. Everything I know
about EDM comes from the catalogue for Lindsay Publications, which sells
a book (24 pages, I think) on how to make your own EDM. Jamie, are you
familiar with this book or did you learn some other way of making an EDM?

More questions: What kinds of fumes does it generate? Also, do the electrical
discharges cause any damage to the underlying board itself? Was it your
own idea to use this for making printed circuit boards or did you read
about it somewhere and, in that case, where? If not, would you consider
writing a more detailed article about your experiences making printed
circuit boards this way? I think that that a sufficiently detailed and
protracted explanation could get published by Lindsay Publications, just
as they have published books (e.g. on how to cast your own pulleys) spawned
by the Gingery series on making your own metal shop. It doesn't have to be
500 pages: some of their books are only a couple of dozen pages, e.g. the
EDM book.

I guess this now also raises the following question, more pertinent to
sci.chem: how might one use an EDM in chemical experiments? I'm sure there
are lots of chemicals to try it on under various conditions, but just to
keep the discussion a little more self-contained, what would happen if
you grew a single crystal of spent etchant and applied an EDM to it?
What would be the chemical effects on the crystal and what would be
the products?

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[Chris R. Lee]

"Allan Adler" <ara@nestle.ai.mit.edu> a écrit dans le message de news:
y937jytn1bp.fsf@nestle.ai.mit.edu...

hhc314@yahoo.com (Harry Conover) writes:

Allan, while I applaud your rather extreme level of environmentally
related political correctness, I really think you should get a closer
grip on reality and realize that the copper laden waste residue
created by amateur PC board etching wouldn't even create a glitch in a
graph of the copper salt residue released into the waste water
treatment systems by millions of copper pipe plumbed homes.

Harry, thanks for all the suggestions. Regarding my motivations, it
is a matter of complying with the law and I don't know what the law is.
For example, in Jan Axelson's book, "Making printed circuit boards",
which I'm reading at the moment, it says on p.216, "Check with local
officials on how to dispose of used etchant." Her book is aimed at
amateurs and she still says that you have to find out the local
regulations.

It often happens that you can use simple common sense. If you add garden

lime you'll get a sludge of iron oxides/hydroxides that amount to no more
than one of the minerals the Earth is made of.

While I'm on the subject, the original posting referred to electrolytic
etching. This isn't really practical... because the objective is to create a
certain number of electrically isolated tracks.

Regards

If I can find a local official who, in his/her official capacity, can tell
me that simply neutralizing the etchant with lye or ammonia and pouring
it down the drain is an acceptable way to dispose of it, then there is
no problem. So far, finding out the law is a lot harder than any of the
chemical issues.

Allan Adler
ara@zurich.ai.mit.edu


****************************************************************************
*
*
* Disclaimer: I am a guest and *not* a member of the MIT Artificial
*
* Intelligence Lab. My actions and comments do not reflect
*
* in any way on MIT. Moreover, I am nowhere near the Boston
*
* metropolitan area.
*
*
*

****************************************************************************

 

[Jamie]

well thanks for your interest on the EDM.
no i wasn't aware of any published books on the
idea use of EDM on clad boards., i got the idea back
when i use to service some machine shop equipment. there
they had 2 EDM's, one for rough cut and one for the fine
cuts.
they would make carbit dyes use in various operations like
stamping out revits, nuts etc..
because the material is very hard it makes it difficult to
use common milling processes..
so what they did was make for example Hex brass stock and use that
for the quill (neg side) the stock material was placed in a holder at
the base of the tank and then the tank was filled with insolating oil.
after a short period of the brass probe inserting it self against the
stock material with regulated currents and servo's on the drive you
would have a nice near perfect hex hole of about 1 " in depth.
this unit simply used rectified DC at around 400 volts low current.
the second unit for the final was polishing used 400 cycles of
pulsed Dc on the probe. the unit had 4 banks of Push-Pull 3-400Z tubes
..
the whole theory is simply a plasma burn much like used today in
plasma cutters etc..
using the insolated oils it cuts down alot on the splatter and
carbon effects.
i call it plasma, some simply call it electro discharge burn.
i maybe miss using the terms but i think i get my point accross.

any ways i use 1 stepper motors to drive the X scan in bidirection
scans to speed things up and the Y motor to move down the clad board.
the head is a retractable hard point tip that is pulled in via a
electromagnet to skip over the area's not required to be removed..
i use a current shunt circuit so that i know when the copper is
fully removed. if a short out takes place the tip is retracted and
inserted again..
when the area is complete the X scan moves to the next possition.
this works well because low side of the board is clamped into the table
for the current path.
i need to remove the pin now an then and clean it up for better edges..
../.
my use of the blue dye actually works quite well too.
how ever that means i need to use etching.



Allan Adler wrote:

Jamie <jamie_5_not_valid_after_5_Please@charter.net> writes:


i did how ever develop 2 different X,Y,Z scanning tables.
one is a sprayer that uses Blue Dye and sprays the protective
coating onto the clad..
the other is a EDM (electro discharge Machine) that actually
is using a plasma removable approach with the Clad submerged in
a oil that is very easy cleaning afterwards. i use a small little
fluid pump to circulate and filter the oil..
both work, i would rather use the EDM over my Blue Dye sprayer due
to the mess it some times makes..


This is really useful information! I was wondering whether one could
do it with an EDM but I have so little knowledge about the devices
that I wasn't sure what one can or can't use it for. Everything I know
about EDM comes from the catalogue for Lindsay Publications, which sells
a book (24 pages, I think) on how to make your own EDM. Jamie, are you
familiar with this book or did you learn some other way of making an EDM?

More questions: What kinds of fumes does it generate? Also, do the electrical
discharges cause any damage to the underlying board itself? Was it your
own idea to use this for making printed circuit boards or did you read
about it somewhere and, in that case, where? If not, would you consider
writing a more detailed article about your experiences making printed
circuit boards this way? I think that that a sufficiently detailed and
protracted explanation could get published by Lindsay Publications, just
as they have published books (e.g. on how to cast your own pulleys) spawned
by the Gingery series on making your own metal shop. It doesn't have to be
500 pages: some of their books are only a couple of dozen pages, e.g. the
EDM book.

I guess this now also raises the following question, more pertinent to
sci.chem: how might one use an EDM in chemical experiments? I'm sure there
are lots of chemicals to try it on under various conditions, but just to
keep the discussion a little more self-contained, what would happen if
you grew a single crystal of spent etchant and applied an EDM to it?
What would be the chemical effects on the crystal and what would be
the products?

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[Garrett Mace]

"Jamie" <jamie_5_not_valid_after_5_Please@charter.net> wrote in message
news:102jm9d5d4uuj1e@corp.supernews.com...

Yup, i know the problem.
i my self don't have very much trouble in disposing of the
etching due to a local dump that handles those kinds of
problems.
i did how ever develop 2 different X,Y,Z scanning tables.
one is a sprayer that uses Blue Dye and sprays the protective
coating onto the clad..
the other is a EDM (electro discharge Machine) that actually
is using a plasma removable approach with the Clad submerged in
a oil that is very easy cleaning afterwards. i use a small little
fluid pump to circulate and filter the oil..
both work, i would rather use the EDM over my Blue Dye sprayer due
to the mess it some times makes..
P.S.
currently i am having noise emission problems with EDM but working
on it..

I am interested in this, might be a neat way to convert my mini CNC mill to
a quicker PCB maker. How fine of a cut do you get? What's the electrode made
out of, and the best angle for the point? Best working voltages and oils?
Any faster than milling?

 

[Steve Turner]

hhc314@yahoo.com (Harry Conover) wrote:

The pollution produced by simply dumping small quantities of home
produced spent etchant into a municipal waste water collection system
is arguably no worse than that released into the same systems by
millions of home darkrooms and drugstore sited photo processors.
Simply neutralize the etchant by adding some lye or ammonia to it (in
well ventilated conditions) prior to pouring it down the drain.

I agree with everything Harry wrote except for this bit about
"neutralizing" etchant. I have seen this advice before, and there is
no chemical basis for it. (ASSumption here: we're talking about
ferric chloride or ammonium persulfate etchants, NOT something like
nitric acid....) The mechanism of etching by these reagents is
oxidative, so to "neutralize" etchant you'd add a reducing agent.
Scrap iron would work. But it's probably unecessary anyway, as long
as you flush down the drain with lots and lots of water (which you
should do anyway). And most modern sewer pipes are PVC, which will
not be affected by etchants.

Steve Turner

 

[Steve Turner]

Allan Adler <ara@nestle.ai.mit.edu> wrote:

muhammar@hotmail.com (Muhammar) writes:

Copper does not dissolve in vinegar. Zinc does. Since you had some
"insoluble stuff" left from dissolving pennies, you managed to get
some dirty zinc acetate and separate all copper (3% of it, used for
coating).

Chemists were fairly unanimous in telling me, before I tried it,
that it wouldn't work, muttering about oxidation potentials or
something like that. I admit that the presence of other metals in
pennies leaves that example inconclusive, but note that I also got
copper wire to be completely digested by vinegar when I used a battery.

Copper does not dissolve to any great extent in non-oxidizing acids
without some help. That help can be in the form of atmospheric oxygen
or in the form of an electric current, either of which causes
oxidation of the copper to the ionic form, which does dissolve in
acids.

Copper does dissolve in nitric acid, but that's a special case --
nitric acid is a powerful oxidant.

Steve Turner

 

[Garrett Mace]

I am interested in this, might be a neat way to convert my mini CNC mill
to
a quicker PCB maker. How fine of a cut do you get? What's the electrode
made
out of, and the best angle for the point? Best working voltages and oils?
Any faster than milling?

My experiment with a 24V supply, piece of copper-clad, blob of motor oil,
and fine drill bit was rough but successful enough to warrant further
investigation and experimentation. I'll go look for more information on EDM
and see if I can convert my little mill to use this. I'll most likely use
point-to-point outline removing (G code) instead of the scanning method you
outlined below. I wonder what it will take to monitor the electrode current
and modify TurboCNC to adjust Z accordingly...really this looks like a great
application of hobby EDM, removing a foil of copper is going to be much
faster than cutting a hunk of steel. The only thing I'm doing right now is
wondering why I didn't think of it before, just last week I was discussing
how to use continuity on copperclad to zero a Z axis very accurately. Never
occurred to me to just increase the testing voltage and put a little acrylic
tank on the mill.

 

[Allan Adler]

Acid Test writes:

You could try etching in dilute HCl.

What would you recommend using for the resist?

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[CBarn24050]

you could try a mixture of sulphuric acid and hydrogen peroxide.

 

[Michael A. Terrell]

Muhammar wrote:

While you are pouring your concrete mix, you can also include
your mother-in law for more satisfying monolith.

What? that would ruin a perfectly good batch of concrete!

--
We now return you to our normally scheduled programming.

Michael A. Terrell
Central Florida

 

[Allan Adler]

CBarn24050 writes:

you could try a mixture of sulphuric acid and hydrogen peroxide.

Thanks. At this point, I think the question of what can etch the copper
has been abundantly answered. What hasn't been touched is the question of
what is a suitable resist for use with the other proposed etchants. Can
one use the same resists one uses with ferric chloride or are different
resists required? Or, even better, is there a household substance one
can use for a resist instead of the usual commercial resists?

E.g. assuming one can in fact use vinegar for the etchant, with either
bubbled air or hydrogen peroxide to provide oxygen, what can one use for
the resist? For example, might some kind of paint or ink be ok that one
can apply through a mask? Or some kind of wax?

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[Dale Trynor]

Allan Adler wrote:

CBarn24050 writes:

you could try a mixture of sulphuric acid and hydrogen peroxide.

Thanks. At this point, I think the question of what can etch the copper
has been abundantly answered.

Dale Trynor wrote:
I could add one. I have etched PC board on occasion and have used a dilute
nitric acid. Use it pure and its so fast it heats up and is likely to cause ones
resists to lift off and also can produce a lot of noxious NO and NO2 gas. Reason
I mention it is because its so easily made especially if you don't need it very
concentrated and in hat case mixing sulfuric acid with nitrates will usually
result in enough nitric acid for this type of thing. I have on occasion mixed
sulfuric acid solution with ammonium nitrate fertilizer solution as a way of
dissolving the base metals from old electronics so that I could recover the gold
and it did work, although it was a bit slow.

What hasn't been touched is the question of
what is a suitable resist for use with the other proposed etchants. Can
one use the same resists one uses with ferric chloride or are different
resists required? Or, even better, is there a household substance one
can use for a resist instead of the usual commercial resists?

I think I had used a resist pin when I did this myself using the dilute nitric
acid but I am not really sure now. I think the nitric acid was less than 10% but
could only guess now. Why don't you just try a small piece of PC board with
different things you can find around the house and just draw or paint a line
with each sample to see what works best. I have even tried tape at one time but
it was a bit too time consuming to cut it into circuit patterns, it did work
alto not really very well as in some places it had started to lift off the tape
etching a bit more than I waned in some places, although it was still usable.
The tape is a common type but I don't remember what its called.

I think I remember seeing kits with stick on patterns that one could use for
this sort of thing alto its been so long ago that I am not sure anymore. I do
still have a photocopy and then iron on type of paper for PC board resists that
I never got around to using. Do note that you can buy special pins that contain
electrically conductive silver powder that can even be soldered onto. I bought
one of these for a little more than 10.00 long ago but never used it either as
once its opened I didn't figure it would keep very long, now its probably
spoiled anyhow.

E.g. assuming one can in fact use vinegar for the etchant, with either
bubbled air or hydrogen peroxide to provide oxygen, what can one use for
the resist?

If you have ever taken a tarnished copper item and put it into hydrochloric acid
you would note just how good the acid is at removing tarnish. Acetic acid will
similarly brighten a bit of tarnished copper. Because tarnish is copper oxide
you will instantly realize that the acid is probably not really dissolving the
metal but rather its oxide coating and if you remove this protective coating
then another will quickly form only to also be dissolved off. I don't know if
the acid might speed up this tarnishing rate somehow but its a good guess that
hydrogen peroxide would help. Even ammonium hydroxide will dissolve copper and I
believe its due to the same sort of reaction because of the way it will also
dissolve copper oxide. You should have seen the amount of corrosion I
accidentally caused to a brass lock by spilling ammonia near by.

Long ago I have even tried cutting holes in hardened steal using nitric acid as
this is a bit to hard to drill. It was doing a great job except that the tape
always failed when the acid got about 1/4 or so inches into the metal. Its
amazing how fast this acid is when its nearly concentrated and gets warmed up
and going. What's bizarre is that the really concentrated acid will pasivate
iron so well it will even resists rusting for some time after treatment so you
need to weaken it a bit with water to get it really vicious on iron. Cutting
steel cable with this stuff or with a bit of hydrochloric acid added is so fast
that its at least almost the sort of exaggerated stuff one would only expect to
see on tv, but it for real. Yes I have had lots of entertaining times showing
this to my friends. When using the concentrated acid on a small metal object it
helps to astonish the audience as the very heavy and dark reddish brown nitrogen
oxides tend to flow like water and are so toxic they can knock the fly's of a
window when you hold the beaker up to them. Do these types of demonstrations out
doors. You shouldn't have much trouble with very dilute solutions on small
pieces of pc boards but its wise to place the container in a well ventilated
area anywise if you chose to try this method.

Don't forget silver nitrate solution will rapidly deposit silver while it also
dissolves copper and gives no gases or vigorous reactions to deal with and you
can recycle your silver.
The reduced silver particles should be easily removed.

Dale

 

[Mohammed Farooq]

Allan Adler <ara@nestle.ai.mit.edu> wrote in message news:<y93llnaz4sf.fsf@nestle.ai.mit.edu>...

I'm still trying to understand how copper gets etched and am still
confused. I don't think it would take much to lift that confusion.

What I've been doing is looking in the CRC Handbook for
electrochemical
potentials. For example, whereas Steve Turner writes that Cu(II)
oxidizes
Cu to Cu(I), I find in the CRC book that

Cu(I) + e -> Cu with E0=0.52 V and Cu -> Cu(II) + 2e with E0=-0.64,

so that indeed Cu(II) + Cu -> 2 Cu(I) with E0 = 0.68 V. So far, I
haven't
found any way to use that. Just working on my own, using the formulas
in
the CRC book, I've done the following:

Water always has some hydroxide ions in it. The CRC book says that
Cu(OH)2 + 2e -> Cu + 2OH- with E0=-0.222 V and that
2 Cu(OH)2 -> 2e -> Cu2O + 2OH- + H2O with E0=-0.80 V, so I conclude
that
2 Cu + 4OH- -> Cu2O + 2OH- +H2O + 2e with E0=0.364 V.

The electrode potentials given in CRC are for the standard conditions
.. If you are considering water as a source of hydroxide ions which is
approximately about 10^-7 mole/liter in water at 25 C, , you will need
Nernst equation to get the correct electrode potential for the
conditions you are applying and then check the possibility of the
reaction between copper and hydroxide ions.
Though the reaction under standard conditions seems to be
thermodynamically possible, but I never heard of copper being attacked
by common alkalis except ammonia, which perhaps dissolves copper by
the forming a blue complex rather than forming a oxide.