Homebrew PCBs

I mixed up a batch of HCl and H2O2 and got good etching (which was
mostly from the HCl).  There were some bubbles but no chlorine gas.  I
etched 6 double sided boards that were on average 20x20 CM in the
first session.  The etchant turned the well described emerald green. 
3 days later, I went to etch another board and got no (or r-e-a-l-l-y
slow) progress.  I bubbled it for about 18 hrs total (with 2 airstones
- lots of bubbles).  Still no etching.  

I got a hydrometer and the density is 1.075.  This is well below the
1.17 recommended by
<http://users.rcn.com/rexa/Projects/CuCl_ech.html>.  From the HCl and
H2O2 I put in, the s.g. should have been 1.029 so I assume that the
difference, 0.046, is from the etched copper in the form of CuCl.  It
appears I have too weak a cucl solution by about 1/4 but I'm not 100%
sure about the chemistry here.  Everything I've read says that it
doesn't take much copper at all so I'm a bit at a loss here.  I need
to get pH measuring capability but the density is clearly wrong.

Any suggestions for fixing?  The page mentioned above recommends CuCl
salts which I have no idea where to get and probably shouldn't have to.

I'm going to put a couple pieces of copper in over night to see if I
can get more copper into solution but its not clear to me that will
actually work.

On Mon, 27 Sep 2004 20:21:36 -0000, Phil <phil1960us@...> wrote:

> I mixed up a batch of HCl and H2O2 and got good etching (which was
> mostly from the HCl).  There were some bubbles but no chlorine gas.  I
> etched 6 double sided boards that were on average 20x20 CM in the
> first session.  The etchant turned the well described emerald green.
> 3 days later, I went to etch another board and got no (or r-e-a-l-l-y
> slow) progress.  I bubbled it for about 18 hrs total (with 2 airstones
> - lots of bubbles).  Still no etching.
>
> I got a hydrometer and the density is 1.075.  This is well below the
> 1.17 recommended by
> <http://users.rcn.com/rexa/Projects/CuCl_ech.html>.  From the HCl and
> H2O2 I put in, the s.g. should have been 1.029 so I assume that the
> difference, 0.046, is from the etched copper in the form of CuCl.  It
> appears I have too weak a cucl solution by about 1/4 but I'm not 100%
> sure about the chemistry here.  Everything I've read says that it
> doesn't take much copper at all so I'm a bit at a loss here.  I need
> to get pH measuring capability but the density is clearly wrong.
>
> Any suggestions for fixing?  The page mentioned above recommends CuCl
> salts which I have no idea where to get and probably shouldn't have to.
>
> I'm going to put a couple pieces of copper in over night to see if I
> can get more copper into solution but its not clear to me that will
> actually work.

Adding copper will not help much.
If you add H2O2, does it go? if not HCl is missing (it usually is bluish  
then).
Get the two-eyedroppers titration gear.
If there is copper, HCl, and H2O2 it must go.
My hydrometer shows about 1.16, and it does go without H2O2, though slow.
It takes a while before there is enough copper to go on it's own. H2O2 is  
so
cheap it isn't required to add any scrap copper.

ST

P.S.: i wonder if really none of you has a ultrasonic cleaner.
I'd like to know if toner is cleaned by it or not.

----- Original Message ----- 

From: "Phil" <phil1960us@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, September 27, 2004 9:21 PM
Subject: [Homebrew_PCBs] advice on CuCl etchant?


>I mixed up a batch of HCl and H2O2 and got good etching (which was
> mostly from the HCl).  There were some bubbles but no chlorine gas.  I
> etched 6 double sided boards that were on average 20x20 CM in the
> first session.  The etchant turned the well described emerald green.
> 3 days later, I went to etch another board and got no (or r-e-a-l-l-y
> slow) progress.  I bubbled it for about 18 hrs total (with 2 airstones
> - lots of bubbles).  Still no etching.
>
> I got a hydrometer and the density is 1.075.  This is well below the
> 1.17 recommended by
> <http://users.rcn.com/rexa/Projects/CuCl_ech.html>.  From the HCl and
> H2O2 I put in, the s.g. should have been 1.029 so I assume that the
> difference, 0.046, is from the etched copper in the form of CuCl.  It
> appears I have too weak a cucl solution by about 1/4 but I'm not 100%
> sure about the chemistry here.  Everything I've read says that it
> doesn't take much copper at all so I'm a bit at a loss here.  I need
> to get pH measuring capability but the density is clearly wrong.
>
> Any suggestions for fixing?  The page mentioned above recommends CuCl
> salts which I have no idea where to get and probably shouldn't have to.
>
> I'm going to put a couple pieces of copper in over night to see if I
> can get more copper into solution but its not clear to me that will
> actually work.

Bubbling air takes a long time, adding some H2O2 would be quicker, but will 
dilute the solution, so you might need to evaporate some water from it 
first. Also, you might need to add some more HCl. I do this with FeCl3, to 
regenerate it, so that I gradually end up with a mixture of FeCl3 and CuCl. 
I've used the same solution for some months now by doing this, and it works 
quite well. Only downside is that it's slower than fresh FeCl3.

Leon

Hi Phil,

Is the solution a clear emerald green at the moment? If so I would guess 
that you are short of acid. If it is murky and more an olive-brown 
colour then it needs more oxygen.

Bubbling air through the solution can take a long time. Adding H2O2 is a 
lot faster. My etch tank is quite small (1.5 litre). It does not take 
long for the available oxygen to become exhausted. A teaspoon of 
100volume H2O2 is enough to get it etching well again. If the solution 
starts fizzing when you add the H2O2 and has a chlorine smell you have 
added too much.

Les


Phil wrote:

> I mixed up a batch of HCl and H2O2 and got good etching (which was
> mostly from the HCl).  There were some bubbles but no chlorine gas.  I
> etched 6 double sided boards that were on average 20x20 CM in the
> first session.  The etchant turned the well described emerald green. 
> 3 days later, I went to etch another board and got no (or r-e-a-l-l-y
> slow) progress.  I bubbled it for about 18 hrs total (with 2 airstones
> - lots of bubbles).  Still no etching.  
> 
> I got a hydrometer and the density is 1.075.  This is well below the
> 1.17 recommended by
> <http://users.rcn.com/rexa/Projects/CuCl_ech.html>.  From the HCl and
> H2O2 I put in, the s.g. should have been 1.029 so I assume that the
> difference, 0.046, is from the etched copper in the form of CuCl.  It
> appears I have too weak a cucl solution by about 1/4 but I'm not 100%
> sure about the chemistry here.  Everything I've read says that it
> doesn't take much copper at all so I'm a bit at a loss here.  I need
> to get pH measuring capability but the density is clearly wrong.
> 
> Any suggestions for fixing?  The page mentioned above recommends CuCl
> salts which I have no idea where to get and probably shouldn't have to.
> 
> I'm going to put a couple pieces of copper in over night to see if I
> can get more copper into solution but its not clear to me that will
> actually work.
> 
> 
> 
> 
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs 
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

If the solutions is translucent "emerald green" as opposed to opaque 
dark brown,green then the copper in solution is already completely 
ooxidized. The dark color appears when Cu(I) is present. Its very strong 
color and doesn't need much concentration to turn the solution dark. So 
I think your problem is low concentration of copper(II). If you want to 
etch with copper(II) chloride then I recommend S.G of at least 1.2. I 
run mine at 1.33. Etching at a SG of 1.17 as recommended in 
CuCl_ech.html is far too low I found. You *really* have to load the 
solution with copper. around 150g/L of dissolved Cu. The emerald green 
can get dark at these concentrations. You may need to put a drop on a 
glass sheet to see if its opaque or translucent (i.e does it copper(I) 
or not).

I haven't tried hydrogen peroxide, but from what I gather reading the 
results people have with HCl and H2O2 is that the peroxide is a lot more 
than just a replenisher for converting Cu(I) - > Cu(II). H2O2 must be 
speeding up the reaction a huge amount and also allowing HCl to 
indirectly oxidize copper metal. In the absence of H2O2 then the 
copper(II) chloride is all you have to etch, and its slow, probably 
around 50% to 30% the etch rate of fresh ferric chloride. Regeneration 
completion is determined by color of solution.

If etching in absence of H2O2 (as I assume you are now doing since all 
your H2O2 had been depleted of those few days) then HCl concentration 
does not effect etch rate significantly. The only requirement is the 
solution must be acidic at all times.

Adam

Phil wrote:

> I mixed up a batch of HCl and H2O2 and got good etching (which was
> mostly from the HCl).  There were some bubbles but no chlorine gas.  I
> etched 6 double sided boards that were on average 20x20 CM in the
> first session.  The etchant turned the well described emerald green. 
> 3 days later, I went to etch another board and got no (or r-e-a-l-l-y
> slow) progress.  I bubbled it for about 18 hrs total (with 2 airstones
> - lots of bubbles).  Still no etching.  
> 
> I got a hydrometer and the density is 1.075.  This is well below the
> 1.17 recommended by
> <http://users.rcn.com/rexa/Projects/CuCl_ech.html>.  From the HCl and
> H2O2 I put in, the s.g. should have been 1.029 so I assume that the
> difference, 0.046, is from the etched copper in the form of CuCl.  It
> appears I have too weak a cucl solution by about 1/4 but I'm not 100%
> sure about the chemistry here.  Everything I've read says that it
> doesn't take much copper at all so I'm a bit at a loss here.  I need
> to get pH measuring capability but the density is clearly wrong.
> 
> Any suggestions for fixing?  The page mentioned above recommends CuCl
> salts which I have no idea where to get and probably shouldn't have to.
> 
> I'm going to put a couple pieces of copper in over night to see if I
> can get more copper into solution but its not clear to me that will
> actually work.
> 
> 
> 
> 
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs 
> Yahoo! Groups Links
> 
> 
> 
>  
> 
>

There seems to be some confusion with "CuCl2" etching. There appears to 
be two ways to etch. One is with chemical oxidizer H2O2 and one without. 
If there is only HCl and H2O2 then etching cannot really be called 
"CuCl2" since no copper is present in solution. I found that when 
etching with only CuCl2 then the concentration needs to be very high 
with an SG 1.30 +-0.05 , Regeneration this acidic CuCl2/CuCl solution 
with either air or H2O2 probably makes no difference. *But* when excess 
H2O2 is added in the presents of HCl then CuCl2 may not play a big roll 
in the etch rate. Something else is happening in this reaction since the 
etch rate shoots up dramatically.

So if trying to etch with excess H2O2 + HCl then CuCl2 is less 
important. If you are etching exclusively with CuCl2 then its 
concentration becomes very relevant.

Thanks for all the suggestions - the solution is not olive at all.  It
appears to be a clear, bright green.  I would have called it "lime
green" but its not far from emerald.  So it looks like I need to find
some concentrated H2O2.  Anyone know a source in the Seattle area?

By the way, I think there was some etching going on - the surface of
the copper took on that characteristic flat texture you get when
etching first starts.  Of course, this was after 45 minutes...  sigh...

Phil

--- In Homebrew_PCBs@yahoogroups.com, Les Newell <lesnewell@f...> wrote:
> Hi Phil,
...
>                                                          A teaspoon of 
> 100volume H2O2 is enough to get it etching well again. If the solution 
> starts fizzing when you add the H2O2 and has a chlorine smell you have 
> added too much.
> 
> Les

Thanks, Les.  Where did you get your H2O2?  

Phil

On Tue, 28 Sep 2004 14:22:59 +0100, Les Newell <lesnewell@...>  
wrote:

> Hi Phil,
>
> I got it from an internet chemical supplier, along with the acid and
> copper oxide. Their minimum order is something like 50UKP so it is not
> practical to just get the H2O2 from them.
>
> Les

That must be huge amount of acid and H2O2 for ~~100eur.

I got it from a local chemicals shop for i think 6eur/l for H2O2, with the  
bottle.
Refill is cheaper but i haven't used it up yet.

ST

Hi Phil,

I got it from an internet chemical supplier, along with the acid and 
copper oxide. Their minimum order is something like 50UKP so it is not 
practical to just get the H2O2 from them.

Les

Phil wrote:

> --- In Homebrew_PCBs@yahoogroups.com, Les Newell <lesnewell@f...> wrote:
> 
>>Hi Phil,
> 
> ...
> 
>>                                                         A teaspoon of 
>>100volume H2O2 is enough to get it etching well again. If the solution 
>>starts fizzing when you add the H2O2 and has a chlorine smell you have 
>>added too much.
>>
>>Les
> 
> 
> Thanks, Les.  Where did you get your H2O2?  
> 
> Phil
> 
> 
> 
> 
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs 
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

thanks,  I'm finding 30% H2O2 but at like $70/500 mL.  That's not
worth it to me, I'd rather buy Ammonium Perchlorate powder at $25/kg.    

Its quite a "new" experience using a local phone book...  lol

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
> On Tue, 28 Sep 2004 14:22:59 +0100, Les Newell <lesnewell@f...>  
> wrote:
> 
> > Hi Phil,
> >
> > I got it from an internet chemical supplier, along with the acid and
> > copper oxide. Their minimum order is something like 50UKP so it is not
> > practical to just get the H2O2 from them.
> >
> > Les
> 
> That must be huge amount of acid and H2O2 for ~~100eur.
> 
> I got it from a local chemicals shop for i think 6eur/l for H2O2,
with the 

> bottle.
> Refill is cheaper but i haven't used it up yet.
> 
> ST

On Tue, 28 Sep 2004 16:01:27 -0000, Phil <phil1960us@...> wrote:

> thanks,  I'm finding 30% H2O2 but at like $70/500 mL.  That's not
> worth it to me, I'd rather buy Ammonium Perchlorate powder at $25/kg.
>
> Its quite a "new" experience using a local phone book...  lol
>

That's a mean price. i think i could get it mail order for roughly double
of what i pay locally. (means ~12eur/l). keep looking.

ST

Hi Stefan,

I bought a lot of acid because I use it for removing rust as well. I 
also bought sulphuric acid for anodising and a number of other chemicals.

Les

> 
> 
> That must be huge amount of acid and H2O2 for ~~100eur.
> 
> I got it from a local chemicals shop for i think 6eur/l for H2O2, with the  
> bottle.
> Refill is cheaper but i haven't used it up yet.
> 
> ST

yeah, found cheaper - $15/4 oz (approx 25 cL).  I had to add a fair
amount of acid and about 1.5 oz of the H2O2 to get etching.  Still too
expensive but the store has one gallon (3.8L) of 35% for $40.  I may
just go for that but will try some more bubbling to see if I can
oxidize it that way.  AP is starting to look cheaper all the time.

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
> On Tue, 28 Sep 2004 16:01:27 -0000, Phil <phil1960us@y...> wrote:
> 
> > thanks,  I'm finding 30% H2O2 but at like $70/500 mL.  That's not
> > worth it to me, I'd rather buy Ammonium Perchlorate powder at $25/kg.
> >
> > Its quite a "new" experience using a local phone book...  lol
> >
> 
> That's a mean price. i think i could get it mail order for roughly
double

> of what i pay locally. (means ~12eur/l). keep looking.
> 
> ST