RST Engineering wrote:
I just got a very good "homebrew" PCB process set up using gloss photo paper
printed in a laser printer ironed onto the board for the resist and muriatic
acid / hydrogen peroxide for the etchant. Is this the way you are making
boards?


No, I use conventional UV exposure and FeCl3. With artwork printed on
an inkjet printer I can reliably do 8 mil tracks.

Leon

Leon wrote:
No, I use conventional UV exposure and FeCl3. With artwork printed on
an inkjet printer I can reliably do 8 mil tracks.
=========================
Leon , How do you dispose of spent ferichloride?
Do you take it to the local Council waste yard ?

Frank GM0CSZ / KN6WH

Highland Ham wrote:
Leon wrote:
No, I use conventional UV exposure and FeCl3. With artwork printed on
an inkjet printer I can reliably do 8 mil tracks.
=========================
Leon , How do you dispose of spent ferichloride?
Do you take it to the local Council waste yard ?

Frank GM0CSZ / KN6WH

I just flush it down the toilet. I think that ferric chloride is used
for water treatment and I can't see the small amount of copper doing
any harm by the time it has been diluted millions of times. It's only a
litre ot so every six months - it's negligible.

73, Leon

In article .com,
Leon wrote:

I just flush it down the toilet. I think that ferric chloride is used
for water treatment and I can't see the small amount of copper doing
any harm by the time it has been diluted millions of times. It's only a
litre ot so every six months - it's negligible.

By the time you dump it in this way, you aren't dumping pure ferric
chloride by any means! You're dumping a residual amount of ferric
chloride, plus a bunch of copper chloride.

The waste-treatment authorities in this area are very much against
having soluble copper dumped into the sewage system. The copper
eventually ends up in San Francisco Bay (after having caused some
amount of interference to the biological sewage-digestion/treatment
system). Multiplied by a large number of potential sources, the
copper load can have an injurious effect on the Bay ecosystem... it's
toxic to algae and to many other natural microorganisms.

This problem can be prevented, quite easily, by simply titrating some
sodium hydroxide (lye) or sodium carbonate (washing soda, soda ash)
into the exhausted etchant. It may bubble a bit, with the bubbling
ceasing as the pH rises to the point of being mildly alkaline (pH of 7
to 8... use pH paper to monitor). The copper remaining in the
solution will precipitate out as an insoluble solid. Allow it to
settle and pour off the remaining liquid... MG says that the liquid
can now be poured down the toilet safely. The solid (copper hydroxide
or copper carbonate, I believe) should be disposed of according to
local requirements.

I've used the same precipitate-with-soda-ash trick when using sodium
monopersulphate as an etchant (it's surely work with the somewhat
faster-acting ammonium persulphate). It's quite striking in this
case... the clear blue-green copper-loaded etchant turns a milky
green, the precipitate settles out, and you're left with a clear
near-colorless liquid which contains little or no copper.

I've heard of people disposing of copper-loaded used etchant by mixing
in some Portland cement powder. This raises the pH, converts the
copper to an insoluble form, and then binds it into (in effect) solid
rock which can be disposed of in a landfill without causing
significant leaching of copper. The same trick could no doubt be used
to solidify the precipitated copper from a lye or soda-ash
neutralization of spent etchant.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Dave Platt wrote:

In article .com,
Leon wrote:

I just flush it down the toilet. I think that ferric chloride is used
for water treatment and I can't see the small amount of copper doing
any harm by the time it has been diluted millions of times. It's only a
litre ot so every six months - it's negligible.

By the time you dump it in this way, you aren't dumping pure ferric
chloride by any means! You're dumping a residual amount of ferric
chloride, plus a bunch of copper chloride.

The waste-treatment authorities in this area are very much against
having soluble copper dumped into the sewage system. The copper
eventually ends up in San Francisco Bay (after having caused some
amount of interference to the biological sewage-digestion/treatment
system). Multiplied by a large number of potential sources, the
copper load can have an injurious effect on the Bay ecosystem... it's
toxic to algae and to many other natural microorganisms.

This problem can be prevented, quite easily, by simply titrating some
sodium hydroxide (lye) or sodium carbonate (washing soda, soda ash)
into the exhausted etchant. It may bubble a bit, with the bubbling
ceasing as the pH rises to the point of being mildly alkaline (pH of 7
to 8... use pH paper to monitor). The copper remaining in the
solution will precipitate out as an insoluble solid. Allow it to
settle and pour off the remaining liquid... MG says that the liquid
can now be poured down the toilet safely. The solid (copper hydroxide
or copper carbonate, I believe) should be disposed of according to
local requirements.

I've used the same precipitate-with-soda-ash trick when using sodium
monopersulphate as an etchant (it's surely work with the somewhat
faster-acting ammonium persulphate). It's quite striking in this
case... the clear blue-green copper-loaded etchant turns a milky
green, the precipitate settles out, and you're left with a clear
near-colorless liquid which contains little or no copper.

I've heard of people disposing of copper-loaded used etchant by mixing
in some Portland cement powder. This raises the pH, converts the
copper to an insoluble form, and then binds it into (in effect) solid
rock which can be disposed of in a landfill without causing
significant leaching of copper. The same trick could no doubt be used
to solidify the precipitated copper from a lye or soda-ash
neutralization of spent etchant.


I've also heard of putting steel wool into spent ferric chloride etchant,
which I think gets the copper out in a metallic form and probably replaces
it with iron. Whether that would be better I don't know.

Chris

Since ferric chloride is another name for iron chloride, I'm not sure how
that would work, since there is already an abundance of iron in the
solution, but I've never tried it so I'm not going to say it won't work.
However, I'd like to hear from somebody who HAS tried it, for better or for
worse.

Jim




I've also heard of putting steel wool into spent ferric chloride etchant,
which I think gets the copper out in a metallic form and probably replaces
it with iron. Whether that would be better I don't know.

Chris

RST Engineering wrote:

Since ferric chloride is another name for iron chloride, I'm not sure how
that would work, since there is already an abundance of iron in the
solution, but I've never tried it so I'm not going to say it won't work.
However, I'd like to hear from somebody who HAS tried it, for better or
for worse.

Jim




I've also heard of putting steel wool into spent ferric chloride etchant,
which I think gets the copper out in a metallic form and probably
replaces
it with iron. Whether that would be better I don't know.

Chris

It's possible that I have confused myself and it might have been spent
ammonium persulfate etchant instead, that the steel wool was to be put
into. I don't enough about chemistry to say which would make more sense.

The one thing I have learnt about etchant is: Don't store ammonium
persulfate etchant in a sealed (airtight) container. My bottle of etchant
burst and went everywhere.

Chris

Chris Jones wrote:

I've also heard of putting steel wool into spent ferric chloride etchant,
which I think gets the copper out in a metallic form and probably replaces
it with iron. Whether that would be better I don't know.


I recall hearing this method used for recovering
silver from spent photographic developer.

Dave Platt wrote:
In article .com,
Leon wrote:

I just flush it down the toilet. I think that ferric chloride is used
for water treatment and I can't see the small amount of copper doing
any harm by the time it has been diluted millions of times. It's only a
litre ot so every six months - it's negligible.

By the time you dump it in this way, you aren't dumping pure ferric
chloride by any means! You're dumping a residual amount of ferric
chloride, plus a bunch of copper chloride.

Small quantities are acceptable, here in the UK.

Leon

On 29 May 2006 01:54:56 -0700, "Leon"
wrote:


Dave Platt wrote:
In article .com,
Leon wrote:

I just flush it down the toilet. I think that ferric chloride is used
for water treatment and I can't see the small amount of copper doing
any harm by the time it has been diluted millions of times. It's only a
litre ot so every six months - it's negligible.

By the time you dump it in this way, you aren't dumping pure ferric
chloride by any means! You're dumping a residual amount of ferric
chloride, plus a bunch of copper chloride.

Small quantities are acceptable, here in the UK.

Leon

A book I read a long time back recommended mixing spent solution with
concrete powder and sending the resulting brick to the dump. Seems like
one of the best ideas I have heard of if you really care about possible
impacts.