Homebrew_PCBs

Anyone here etch with CuCl2 but only rely on air for regeneration ? Just
wondering what other peoples experiences are with this etchant.

I'm using HCl + CuCl2 at S.G = 1.36 and etch speed appears to be about
70% of fresh FeCl3 (S.G 1.4) at room temperature. The HCl concentration
I'm running at is approximately 1N (or 40g/l HCl or 1 Moles/liter or
4%). I found S.G of CuCl2 dramatically effects etch speed. e.g CuCl2 at
S.G of 1.15 was about 10 times slower etch speed than at S.G of 1.35.
Commercially, CuCl2 etchant operates between S.G 1.35 ~ 1.45.

Adam

On Sat, 12 Feb 2005 08:31:08 +1100, Adam Seychell
<a_seychell@...> wrote:

>
> Anyone here etch with CuCl2 but only rely on air for regeneration ? Just
> wondering what other peoples experiences are with this etchant.
> I'm using HCl + CuCl2 at S.G = 1.36 and etch speed appears to be about
> 70% of fresh FeCl3 (S.G 1.4) at room temperature. The HCl concentration
> I'm running at is approximately 1N (or 40g/l HCl or 1 Moles/liter or
> 4%). I found S.G of CuCl2 dramatically effects etch speed. e.g CuCl2 at
> S.G of 1.15 was about 10 times slower etch speed than at S.G of 1.35.
> Commercially, CuCl2 etchant operates between S.G 1.35 ~ 1.45.
> Adam

Of course, more CuCl means more etching, i guess it is the same with any
etchant.
I do use H2O2, but i don't regenerate each etch, depending on board size
each second or third time, when the color gets too dark.
When my S.G. was lower i had to use H2O2 more often, but i don't know
exactly what it is right now (i broke the glass thing with the rubber ball
where the hydrometer swims in, stupid me, and since then i haven't
bothered with measuring. The hydrometer is OK but i need to float it in
some other comtainer now, which is more work...

ST

Stefan Trethan wrote:

>
> Of course, more CuCl means more etching, i guess it is the same with any
> etchant.

All references I've seen for hobby etching with CuCl2 is S.G < 1.2,
which in my experience found to be almost useless as an etchant. If
H2O2 is present then etching rate is fast regardless of S.G even with no
CuCl2 present! It seems the etch rate is very sensitive to CuCl2
concentration if and only if the mechanism of regeneration is from
dissolved O2 alone. In other words people seem to be running
HCl+CuCl2+O2 at far lower concentration than what they should. So I'm
wondering who uses HCl+CuCl2+O2 and at what S.G and what are their
experiences ?

Adam

On Sat, 12 Feb 2005 09:50:24 +1100, Adam Seychell
<a_seychell@...> wrote:

>
> All references I've seen for hobby etching with CuCl2 is S.G < 1.2,
> which in my experience found to be almost useless as an etchant. If
> H2O2 is present then etching rate is fast regardless of S.G even with no
> CuCl2 present! It seems the etch rate is very sensitive to CuCl2
> concentration if and only if the mechanism of regeneration is from
> dissolved O2 alone. In other words people seem to be running
> HCl+CuCl2+O2 at far lower concentration than what they should. So I'm
> wondering who uses HCl+CuCl2+O2 and at what S.G and what are their
> experiences ?
> Adam

Yes, i understand that the same way. when i started with my etchant it
took long until the S.G. was high enough to allow etching without H2O2. I
don't know how much different the etch rate now is, between H2O2 added and
not added. It is har to say because i got my bubbler only a while ago, so
i don't have much experience with the much shorter times now. Also, i only
add enough H2O2 to achieve a color change, so it migh not be much "free"
after regenerating the bath.
But remember, if the S.G. gets too high it stops working properly too.


I would only consider going with air oxygen alone if there is really no
way to get your hands on H2O2. A liter lasts years for my use, and it is
"instant". So if i need 5 boards at once i have no problems...


I have suggested that before, but aquarium guys use a reactor to solve
CO2. it is a vertical tube where the water is pumped downwards, and the
CO2 added at the bottom. The stream holds the CO2 in for a long time, and
there are obstacles in the reactor (balls). They say one can set it so
that all CO2 is solved.
Such a setup would surely not solve all air ('cause only 20% oxygen), but
i bet one could increase the effectiveness of a oxygenating system
dramatically with such a reactor.
The aquarium guys pay for pressurized CO2 (or make it chemically) so they
sure want to use every last bubble. If the added complexity of using a
pump is worth the gain for cucl, i dunno.

ST

Stefan Trethan wrote:

> On Sat, 12 Feb 2005 09:50:24 +1100, Adam Seychell
> <a_seychell@...> wrote:
>
>
>>All references I've seen for hobby etching with CuCl2 is S.G < 1.2,
>>which in my experience found to be almost useless as an etchant. If
>>H2O2 is present then etching rate is fast regardless of S.G even with no
>>CuCl2 present! It seems the etch rate is very sensitive to CuCl2
>>concentration if and only if the mechanism of regeneration is from
>>dissolved O2 alone. In other words people seem to be running
>>HCl+CuCl2+O2 at far lower concentration than what they should. So I'm
>>wondering who uses HCl+CuCl2+O2 and at what S.G and what are their
>>experiences ?
>>Adam
>
>
>
> Yes, i understand that the same way. when i started with my etchant it
> took long until the S.G. was high enough to allow etching without H2O2. I
> don't know how much different the etch rate now is, between H2O2 added and
> not added. It is har to say because i got my bubbler only a while ago, so
> i don't have much experience with the much shorter times now. Also, i only
> add enough H2O2 to achieve a color change, so it migh not be much "free"
> after regenerating the bath.
> But remember, if the S.G. gets too high it stops working properly too.

That could be true, although I have not tested for upper limit for CuCl.
It is possible that the etchant rate may be maximum when operating at
saturation, i.e CuCl2 crystals settling on the bottom of the solution.
In this case there is no "too high" S.G because it is limited by
solubility.

I know saturation for NH3 + CuCSO4 + (NH4)2SO4 etchant I once
experimented with did not show signs of etching slow down. This was a
complete surprised to me since it seemed intuitive that saturation would
not allow any additional dissolved copper and so cause the etching to
stop. It was impressive to watch simultaneously action of ammonia copper
sulfate crystals growing on the surface and etching of the plate. A
continuous cycle of new crystals were being form and then breaking away
falling to the bottom of the solution.

There are other etchants that can be run at saturation. The big problem
here is sludge or solids build up, while having no real advantage in
etch rate compared to operation of a solution near saturation. One
example of an etchant is pH neutral saturated ammonia copper chloride.
The overall reaction is

2Cu + O2 + 2H20 -> 2Cu(OH)2

The dissolved portion of copper is in the form of copper chloride
complexed with ammonia. The solution consists of copper chloride and
ammonia. All free ammonia is driven off by evaporation, so the solution
doesn't stink. The Cu(OH)2 formed is a pale blue sludge that is very
annoying and messy, and I suspect the reason why no one uses it. About
the only good thing with this etchant is the regeneration chemicals are
nothing but air and water, a truly cheap etchant.

Just an example of etching at saturation.

> I would only consider going with air oxygen alone if there is really no
> way to get your hands on H2O2. A liter lasts years for my use, and it is
> "instant". So if i need 5 boards at once i have no problems...

Yes, the rate of regeneration can be slow for a typical air bubbler in a
vertical tank. Regeneration time after etching a single PCB should be
less than one hour for a basic setup. The bulk of solution will tolerate
the small increase in CuCl ( copper(I) chloride ) that results after
etching. Thereafter the air bubbler continues to run until all CuCl is
oxidized to CuCl2 as indicated by change in solution color. A more
accurate way is to get a test tube and put a few drops in, then add some
water until it goes pale blue color, and look for signs of white
precipitate. The while solid formed is CuCl or copper (I) chloride. It
falls out of solution because you've reduced the net Cl- ion
concentration which is necessary for solubility of copper(I) chloride.

But as you say if H2O2 is readily available then that might be less
hassle than leaving your air bubbler going for an extra hour after etching.

Adam

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:

> Anyone here etch with CuCl2 but only rely on air for regeneration ?

Just

> wondering what other peoples experiences are with this etchant.
>
> I'm using HCl + CuCl2 at S.G = 1.36 and etch speed appears to be about
> 70% of fresh FeCl3 (S.G 1.4) at room temperature. The HCl concentration
> I'm running at is approximately 1N (or 40g/l HCl or 1 Moles/liter or
> 4%). I found S.G of CuCl2 dramatically effects etch speed. e.g CuCl2 at
> S.G of 1.15 was about 10 times slower etch speed than at S.G of 1.35.
> Commercially, CuCl2 etchant operates between S.G 1.35 ~ 1.45.
>

My CuCl is about 1.2 SG and is still pretty slow. no amount of
bubbling regens it. H2O2 make all the difference but its still
taking abourd 40 minutes to etch a board. The literature I've seen
seems to say 1.17 is the target SG. I guess I should dump some more
copper in.

Phil wrote:

>
>
> My CuCl is about 1.2 SG and is still pretty slow. no amount of
> bubbling regens it. H2O2 make all the difference but its still
> taking abourd 40 minutes to etch a board. The literature I've seen
> seems to say 1.17 is the target SG. I guess I should dump some more
> copper in.
>

If bubbles don't regenerate then your out of acid because ;

2CuCl + O + 2HCl -> 2CuCl2 + H20

note HCl is needed for regeneration.

If you see signs of bright blue copper hydroxide then your defiantly out
of acid. Put a drop on a piece of glass and it should turn from the dark
opaque green to bright green in under an hour due to air exposure. If
not change color then no acid.

Hi Adam-

I have been using the CuCl you helped me to get going over a year ago.
I have not modified the original solution at all, other than by
etching boards. Air is all I use to regenerate.

I use a large vacuum pump as an air source and run it through a
"sparger" (as described at the Think and Tinker website) in the tank.
The solution has continued to etch well, with only the air this method
introduces during board etching.

The amount of etchant in my tank is roughly 20 litres IIR. Agitation
with this method is quite substantial; the surface is bubbling and
roiling quite energetically. I usually etch small boards, perhaps 3"
by 6" max, and etch times of under 20 minutes at room temperature are
typical.

The SG, just measured, is 1.262

Grant

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:

> Anyone here etch with CuCl2 but only rely on air for regeneration ?

Just

> wondering what other peoples experiences are with this etchant.
>
> I'm using HCl + CuCl2 at S.G = 1.36 and etch speed appears to be about
> 70% of fresh FeCl3 (S.G 1.4) at room temperature. The HCl concentration
> I'm running at is approximately 1N (or 40g/l HCl or 1 Moles/liter or
> 4%). I found S.G of CuCl2 dramatically effects etch speed. e.g CuCl2 at
> S.G of 1.15 was about 10 times slower etch speed than at S.G of 1.35.
> Commercially, CuCl2 etchant operates between S.G 1.35 ~ 1.45.
>
> Adam

A short PS to my last poat. When I started using this etchant in May
2003 the SG was 1.245; as noted last post it is now 1.262.

Gramt

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:

> Anyone here etch with CuCl2 but only rely on air for regeneration ?

Just

> wondering what other peoples experiences are with this etchant.
>
> I'm using HCl + CuCl2 at S.G = 1.36 and etch speed appears to be about
> 70% of fresh FeCl3 (S.G 1.4) at room temperature. The HCl concentration
> I'm running at is approximately 1N (or 40g/l HCl or 1 Moles/liter or
> 4%). I found S.G of CuCl2 dramatically effects etch speed. e.g CuCl2 at
> S.G of 1.15 was about 10 times slower etch speed than at S.G of 1.35.
> Commercially, CuCl2 etchant operates between S.G 1.35 ~ 1.45.
>
> Adam

grantfair2001 wrote:

>
> A short PS to my last poat. When I started using this etchant in May
> 2003 the SG was 1.245; as noted last post it is now 1.262.
>
> Gramt

Thanks for the info. Its just that I've seen wide variations in etch
performance with this etchant, so I'm just trying to nut out what makes
it work. It seems S.G > 1.30 and acid > 1M. Might one day do a series of
controlled tests. 20 minutes sounds reasonable, for your setup.

Hi Adam -

An automated process would take the tedium and time out of it. But do
you know of sensors up to the job? A SG sensor might not be too hard
to improvise. But molarity?

Grant


--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:

> grantfair2001 wrote:
> >
> > A short PS to my last poat. When I started using this etchant in May
> > 2003 the SG was 1.245; as noted last post it is now 1.262.
> >
> > Gramt
>
> Thanks for the info. Its just that I've seen wide variations in etch
> performance with this etchant, so I'm just trying to nut out what makes
> it work. It seems S.G > 1.30 and acid > 1M. Might one day do a

series of

> controlled tests. 20 minutes sounds reasonable, for your setup.

grantfair2001 wrote:

>
> Hi Adam -
>
> An automated process would take the tedium and time out of it. But do
> you know of sensors up to the job? A SG sensor might not be too hard
> to improvise. But molarity?

A simple float might be done with a block of polyethylene plastic with a
small stone tied to it somehow. But the S.G is fairly slow changing and
doesn't require frequent measurement so using hydrometer will not be a
problem, and you know its accurate. The hydrometer will be essential
when mixing/making your first batch of etchant.

Acid molarity is best done by titration. You don't need indicator since
your end point is the first signs of the copper precipitate. In fact
one of the technical staff at http://www.oxfordvue.com told me in a
email that titration of copper chloride etchant should only be done
using the copper hydroxide precipitate for end point detection. He said
the high copper levels interfere with pH and causes most indicators not
to work. I tried eye dropper method but the drop size of etchant is
about 1.5 times volume that of sodium hydroxide. Counting drops is very
inaccurate. Instead I use a 1.0 cm^3 measuring pipette and a pipette
sucker. Take 1.0 mil of etchant into about 20 cm^3 tap water, then
titrate with 1M NaOH solution, until I see first signs of precipitate.
Note that towards the end point the solution must be mixed and the NaOH
added slowly so make sure all the acid has reacted. I sometimes heat in
a microwave oven for a few seconds before doing the titration to speed
up the reaction of last traces of acid towards the end point.

Glass measuring pipettes and the suckers are about $2 to $3. The problem
is only lab supplies have this kind of stuff.

I built an autotitrator with a chemistry student some years back. It
used a syringe pump driven by a stepper. We were dropping NaCl
solution into silver nitrate IIRC (I supplied mechanical/electronic
assistance, he did the chemistry). The probe was expensive but he
borrowed it from the school. Would there be a probe which would
detect the endpoint in this case? Or would visual inspection be just
as good - in terms of time required?

Grant

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:

> grantfair2001 wrote:
> >
> > Hi Adam -
> >
> > An automated process would take the tedium and time out of it. But do
> > you know of sensors up to the job? A SG sensor might not be too hard
> > to improvise. But molarity?
>
> A simple float might be done with a block of polyethylene plastic

with a

> small stone tied to it somehow. But the S.G is fairly slow changing and
> doesn't require frequent measurement so using hydrometer will not be a
> problem, and you know its accurate. The hydrometer will be essential
> when mixing/making your first batch of etchant.
>
> Acid molarity is best done by titration. You don't need indicator since
> your end point is the first signs of the copper precipitate. In fact
> one of the technical staff at http://www.oxfordvue.com told me in a
> email that titration of copper chloride etchant should only be done
> using the copper hydroxide precipitate for end point detection. He said
> the high copper levels interfere with pH and causes most indicators not
> to work. I tried eye dropper method but the drop size of etchant is
> about 1.5 times volume that of sodium hydroxide. Counting drops is very
> inaccurate. Instead I use a 1.0 cm^3 measuring pipette and a pipette
> sucker. Take 1.0 mil of etchant into about 20 cm^3 tap water, then
> titrate with 1M NaOH solution, until I see first signs of precipitate.
> Note that towards the end point the solution must be mixed and the NaOH
> added slowly so make sure all the acid has reacted. I sometimes heat in
> a microwave oven for a few seconds before doing the titration to speed
> up the reaction of last traces of acid towards the end point.
>
> Glass measuring pipettes and the suckers are about $2 to $3. The

problem

> is only lab supplies have this kind of stuff.

On Mon, 21 Feb 2005 16:51:33 -0000, grantfair2001
<grant.fair@...> wrote:

>
> I built an autotitrator with a chemistry student some years back. It
> used a syringe pump driven by a stepper. We were dropping NaCl
> solution into silver nitrate IIRC (I supplied mechanical/electronic
> assistance, he did the chemistry). The probe was expensive but he
> borrowed it from the school. Would there be a probe which would
> detect the endpoint in this case? Or would visual inspection be just
> as good - in terms of time required?
> Grant

A PH sensor might work, but i find the whole automatic control would be a
major effort,
and would far outweigh the effort of manual care in about all situations i
can imagine.

CuCl is really easy to care for, there are broad tolerances and it is
recoverable if you mess it up.

By the way, german texts about HCl H2O2 etching usually have bad things to
say about stability, going through walls and blasting roofs off in
industrial applications and similar stuff. Only exaggeration with a small
core of truth, or..? I could only imagine violent reactions with MAD
amounts of H2O2. (Which is easy to do in tiny containers but much harder
in a bigger tank). Anyone having first hand facts about those scare
stories?

ST

grantfair2001 wrote:

>
> I built an autotitrator with a chemistry student some years back. It
> used a syringe pump driven by a stepper. We were dropping NaCl
> solution into silver nitrate IIRC (I supplied mechanical/electronic
> assistance, he did the chemistry). The probe was expensive but he
> borrowed it from the school. Would there be a probe which would
> detect the endpoint in this case? Or would visual inspection be just
> as good - in terms of time required?
>

I can't think of anything quicker simpler than titrating with a pipette
or a long length eye dropper. The good news is we only need a ball park
figure of acid and it seems anything > 1M is good while < 0.1M is not so
good.
See if you can get a long eye dropper that has a measuring mark about
half way up. Just take one sample of etchant into a glass jar, with some
water, then using same eye dropper take one sample of 1M NaOH. Drip into
glass gar until copper precipitate forms. Note relative how much NaOH
was used and thats your approximate acid molarity.

Adam

Stefan Trethan wrote:

>
> A PH sensor might work, but i find the whole automatic control would be a
> major effort,
> and would far outweigh the effort of manual care in about all situations i
> can imagine.

pH will not give reliable acid molarity simply because HCl is a strong
acid and pH will be very low for a very wide range of acid
concentrations. Even if pH would give you measurement, pH electrodes are
a LOT more expensive and cumbersome to use than simple eye dropper and
NaOH.

On Tue, 22 Feb 2005 09:22:11 +1100, Adam Seychell
<a_seychell@...> wrote:

>
> pH will not give reliable acid molarity simply because HCl is a strong
> acid and pH will be very low for a very wide range of acid
> concentrations. Even if pH would give you measurement, pH electrodes are
> a LOT more expensive and cumbersome to use than simple eye dropper and
> NaOH.

someone asked for a probe to automatically measure titration endpoint.
Of course without titration ph won't work.

I use eyedroppers and it is really quite simple.

ST

Stefan Trethan wrote:

> On Tue, 22 Feb 2005 09:22:11 +1100, Adam Seychell
> <a_seychell@...> wrote:
>
>
>>pH will not give reliable acid molarity simply because HCl is a strong
>>acid and pH will be very low for a very wide range of acid
>>concentrations. Even if pH would give you measurement, pH electrodes are
>>a LOT more expensive and cumbersome to use than simple eye dropper and
>>NaOH.
>
>
>
> someone asked for a probe to automatically measure titration endpoint.
> Of course without titration ph won't work.

Oh, in that case, I think a pH probe would be a very accurate way to
determine the end point. Its just complete overkill for our purposes.

>
> I use eyedroppers and it is really quite simple.

Agreed.

Dang, I've still got that autotitrator...thought maybe I had found a
use for it.

I do have a student grade burette which I used once right after I got
the CuCl solution working. But since it continues to work I haven't
bothered with it.

If etch time is the dependent variable, what independent variables
might be involved? Temperature, molarity, and SG?

We know that temperature increases shorten etch times, but they also
introduce problems such as fuming. So what is your guess about how the
others interact and how would you check the hypothesis out? (Assuming
temperature and agitation and amount of air are held constant.)

Grant

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:

> grantfair2001 wrote:
> >
> > I built an autotitrator with a chemistry student some years back. It
> > used a syringe pump driven by a stepper. We were dropping NaCl
> > solution into silver nitrate IIRC (I supplied mechanical/electronic
> > assistance, he did the chemistry). The probe was expensive but he
> > borrowed it from the school. Would there be a probe which would
> > detect the endpoint in this case? Or would visual inspection be just
> > as good - in terms of time required?
> >
>
> I can't think of anything quicker simpler than titrating with a pipette
> or a long length eye dropper. The good news is we only need a ball park
> figure of acid and it seems anything > 1M is good while < 0.1M is

not so

> good.
> See if you can get a long eye dropper that has a measuring mark about
> half way up. Just take one sample of etchant into a glass jar, with

some

> water, then using same eye dropper take one sample of 1M NaOH. Drip

into

> glass gar until copper precipitate forms. Note relative how much NaOH
> was used and thats your approximate acid molarity.
>
> Adam