Homebrew PCBs

I've just done a bit of experimenting with the HCl I bought earlier, and
some 20 Vol (6%) H2O2 from the local Boot's emporium.

A couple of small pieces of PCB material about 1.5 cm in area etched
completely in about 5 minutes at room temperature, with continuous agitation
in a small container. I used about equal quantities of the 32% HCl and 6%
H2O2. The resultant solution is now green, indicating that there are plenty
of cupric ions present. If I re-use the solution, adding some H2O2 from time
to time when it goes blue (excess CuCl2), I should end up with a reasonable
concentration of CuCl3 that I can use. I think that some PCB manufacturers
who use CuCl3 monitor the etchant by measuring the colour continuously and
oxidise it automatically.

Leon
--
Leon Heller, G1HSM
leon_heller@...
http://www.geocities.com/leon_heller

> I've just done a bit of experimenting with the HCl I bought earlier, and
> some 20 Vol (6%) H2O2 from the local Boot's emporium.
> 
> A couple of small pieces of PCB material about 1.5 cm in area etched
> completely in about 5 minutes at room temperature, with continuous
> agitation
> in a small container. I used about equal quantities of the 32% HCl and 6%
> H2O2. The resultant solution is now green, indicating that there are
> plenty
> of cupric ions present. If I re-use the solution, adding some H2O2 from
> time
> to time when it goes blue (excess CuCl2), I should end up with a
> reasonable
> concentration of CuCl3 that I can use. I think that some PCB manufacturers
> who use CuCl3 monitor the etchant by measuring the colour continuously and
> oxidise it automatically.
> 
> Leon
> --
> Leon Heller, G1HSM
> leon_heller@...
> http://www.geocities.com/leon_heller


i find it strange that you didn't find hcl earlier.
it is very easy to get here....
i remember buying it long time ago when i was even too young to buy alcohol
and nobody asked a question.
it is sold here in many shops...

do you want to regenerate always with h2o2?
then i would suggest you stop air agitation.
because it is so volatile i think blowing air through it has only
disadvantages (like stirring coca cola).
the oxygen in the h2o2 is much more effective (i guess some 100 to 1000
times) than air oxygen.

you don't necessarily need to much hcl.
also don't add to much h2o2, it is soon lost after etching.


i use the smallest container which fits the pcb, so minimum etchand (h2o2)
is needed.

i think there is a important difference between cucl etching and hcl + h2o2
etching.
well, you can use h2o2 as a fast substitute for regenerating your cucl but
if you only put it in when etching (to have active h2o2 in the etchant when
the pcb is in) you will get much faster results because also the reaction to
cucl2 is used (not only cucl2 to cu2cl2).
i only guess that, but consider the following:
if you have fresh hcl and fresh h2o2 it also works fast, so it must work off
the solid copper without cucl2 present (yes, this is built instantly but for
t=0+ there is 0).

i think this is the explanation why it is so much faster.
also if you have a perfect regenerated cucl bath it is not so fast as if
there is h2o2 in.


if anyone here with enough knoweledge in chemistry may proof this (or proof
it wrong) i would very appreciate this.


regards
st


(in the moment i have problems with my harddisks. all two in my raid failed
- i know this is not likely due to the disks when both fail but other disks
work on the controller. bad week this.. the mishap with the printer, the
disks, my favourite tv station has changed encryption so i can't see anymore (it
it foreign so i don't get a legal card for it)... bad week, really bad week..
don't wonder if i miss some posts)




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stefan_trethan@... wrote:
>>I've just done a bit of experimenting with the HCl I bought earlier, and
>>some 20 Vol (6%) H2O2 from the local Boot's emporium.
>>
>>A couple of small pieces of PCB material about 1.5 cm in area etched
>>completely in about 5 minutes at room temperature, with continuous
>>agitation
>>in a small container. I used about equal quantities of the 32% HCl and 6%
>>H2O2. The resultant solution is now green, indicating that there are
>>plenty
>>of cupric ions present. If I re-use the solution, adding some H2O2 from
>>time
>>to time when it goes blue (excess CuCl2), I should end up with a
>>reasonable
>>concentration of CuCl3 that I can use. I think that some PCB manufacturers
>>who use CuCl3 monitor the etchant by measuring the colour continuously and
>>oxidise it automatically.
>>
>>Leon
>>--
>>Leon Heller, G1HSM
>>leon_heller@...
>>http://www.geocities.com/leon_heller
> 
> 
> 
> i find it strange that you didn't find hcl earlier.
> it is very easy to get here....

Yes, HCl is the "standard" when you need a strong acid. Its 
volatile, so if you spill a bit it will soon evaporate, 
unlike a sulfuric acid spill which will hang around for a 
millennium. I know here is Australia its very easy to find. 
Sold in 0.5L, 1L & 5L containers at most hardware stores, 
some carry 20L drums for the builders.

> i think there is a important difference between cucl etching and hcl + h2o2
> etching.
> well, you can use h2o2 as a fast substitute for regenerating your cucl but
> if you only put it in when etching (to have active h2o2 in the etchant when
> the pcb is in) you will get much faster results because also the reaction to
> cucl2 is used (not only cucl2 to cu2cl2).
> i only guess that, but consider the following:
> if you have fresh hcl and fresh h2o2 it also works fast, so it must work off
> the solid copper without cucl2 present (yes, this is built instantly but for
> t=0+ there is 0).
> 
> i think this is the explanation why it is so much faster.
> also if you have a perfect regenerated cucl bath it is not so fast as if
> there is h2o2 in.


In normal  CuCl2 etching (without chemical oxidizer) then 
the CuCl is a product of the etching, which films on the 
copper surface and slows down etching. As you know the H2O2 
instantly regenerates the etchant, by converting all the 
CuCl back to green CuCl2. So I would agree with your 
comments that H2O2 speeds up etching because CuCl is quickly 
chewed up. In a pure solution of HCl and H2O2, then the 
exact reaction with copper metal must be something more 
complicated. I wonder if the etching speeds up as the CuCl2 
concentration rises, from zero initially.
The air regenerated CuCl2 etching solutions need a very high 
concentrations of copper for it to be effective. The color 
looks a very dark green inside a container, and you can only 
see it as clear transparent green liquid when looking 
through no more than a few mm thick, such as a drop on to a 
surface.  The solubility of CuCl2 is amazingly high. At 0\ufffd 
you can dissolve 700g in of cupric chloride dihydrate in 1 
liter, thats eqivilent to holding 300g of elemental copper.

Adam

> 
> 
> stefan_trethan@... wrote:
> >>I've just done a bit of experimenting with the HCl I bought earlier, and
> >>some 20 Vol (6%) H2O2 from the local Boot's emporium.
> >>
> >>A couple of small pieces of PCB material about 1.5 cm in area etched
> >>completely in about 5 minutes at room temperature, with continuous
> >>agitation
> >>in a small container. I used about equal quantities of the 32% HCl and
> 6%
> >>H2O2. The resultant solution is now green, indicating that there are
> >>plenty
> >>of cupric ions present. If I re-use the solution, adding some H2O2 from
> >>time
> >>to time when it goes blue (excess CuCl2), I should end up with a
> >>reasonable
> >>concentration of CuCl3 that I can use. I think that some PCB
> manufacturers
> >>who use CuCl3 monitor the etchant by measuring the colour continuously
> and
> >>oxidise it automatically.
> >>
> >>Leon
> >>--
> >>Leon Heller, G1HSM
> >>leon_heller@...
> >>http://www.geocities.com/leon_heller
> > 
> > 
> > 
> > i find it strange that you didn't find hcl earlier.
> > it is very easy to get here....
> 
> Yes, HCl is the "standard" when you need a strong acid. Its 
> volatile, so if you spill a bit it will soon evaporate, 
> unlike a sulfuric acid spill which will hang around for a 
> millennium. I know here is Australia its very easy to find. 
> Sold in 0.5L, 1L & 5L containers at most hardware stores, 
> some carry 20L drums for the builders.
> 
> > i think there is a important difference between cucl etching and hcl +
> h2o2
> > etching.
> > well, you can use h2o2 as a fast substitute for regenerating your cucl
> but
> > if you only put it in when etching (to have active h2o2 in the etchant
> when
> > the pcb is in) you will get much faster results because also the
> reaction to
> > cucl2 is used (not only cucl2 to cu2cl2).
> > i only guess that, but consider the following:
> > if you have fresh hcl and fresh h2o2 it also works fast, so it must work
> off
> > the solid copper without cucl2 present (yes, this is built instantly but
> for
> > t=0+ there is 0).
> > 
> > i think this is the explanation why it is so much faster.
> > also if you have a perfect regenerated cucl bath it is not so fast as if
> > there is h2o2 in.
> 
> 
> In normal  CuCl2 etching (without chemical oxidizer) then 
> the CuCl is a product of the etching, which films on the 
> copper surface and slows down etching. As you know the H2O2 
> instantly regenerates the etchant, by converting all the 
> CuCl back to green CuCl2. So I would agree with your 
> comments that H2O2 speeds up etching because CuCl is quickly 
> chewed up. In a pure solution of HCl and H2O2, then the 
> exact reaction with copper metal must be something more 
> complicated. I wonder if the etching speeds up as the CuCl2 
> concentration rises, from zero initially.
> The air regenerated CuCl2 etching solutions need a very high 
> concentrations of copper for it to be effective. The color 
> looks a very dark green inside a container, and you can only 
> see it as clear transparent green liquid when looking 
> through no more than a few mm thick, such as a drop on to a 
> surface.  The solubility of CuCl2 is amazingly high. At 0\ufffd 
> you can dissolve 700g in of cupric chloride dihydrate in 1 
> liter, thats eqivilent to holding 300g of elemental copper.
> 
> Adam
> 
> 

i'm not sure if it speeds up from zero with no cucl in.
i think i remember it was almost as fast when made up fresh.
maybe half the speed, but i'm very sure it was not slower.

i think for only occassional etching the regenerating with h2o2 is a good
option.
it is quite good available (as pool supply also in 5l cans) and not too
expensive.

what i would be interested in is how the hcl percentage would be best and
what happens with the copper, is it also growing steady like cucl? (i think it
is so, sometimes it seems to need additional hcl).

i maket this more or less by guessing what the etchant may need if it
doesn't work and then add what i think would be the right amount. it would be nice
to know what is going on, and to keep the pocess closer to optimum (i'm sure
sometimes i put too much h2o2 in and also the hcl may be too high (fumes)).


i read one should not store this etchant in a airtight bottle.
what do you think about it?
i have it in a glass bottle (don't use plastic) and in the lid i have a tiny
hole with a "safety valve" glued on top. this is a small plastic cone, open
on top, which has plastic foam in it. it lets through the air if necessary
but if i ever accidently knock over the bottle it provides good protection
against spilling etchant through the tiny hole.

if i use a airthight bottle, do you think the pressure of the h2o2 may burst
it?
i think not but i don't want to risk anything.


regards
stefan



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