Homebrew PCBs

Hi guys,

Does anyone know off-hand what the required ratio of Hydrochloric Acid 
to Peroxide is when starting off a cupric chloride etch bath?

I've tracked down these 'starter' chemicals on ebay:
   HCl: 
http://cgi.ebay.co.uk/BRICK-CLEANER-CEMENT-REMOVER-CONCRETE-REMOVER-ACID-/250631108343?pt=LH_DefaultDomain_3&hash=item3a5ac736f7
    or 
http://cgi.ebay.co.uk/Disclean-Brick-Cleaner-2-x-5lts-/390122417591?pt=LH_DefaultDomain_3&hash=item5ad51badb7

   H2O2: 
http://cgi.ebay.co.uk/2x200ML-Bell-Hydrogen-Peroxide-9-Anti-Septic-Bacterial-/130392225994?pt=UK_Health_HealthCare_RL&hash=item1e5bfb78ca

This is 17.5% strength HCl, and 9% H2O2. Assuming this is strong enough 
to start a cupric chloride bath (with a sufficient amount of air and 
scrap copper provided), what sort of mix ratio would I need to make a 
viable etchant?

Do I need to target a specific pH? That is, do I need to buy litmus 
paper and so on too?

What about titration and specific gravity control -- is that necessary? 
I have some sodium hydroxide granules in the cupboard (CIF Photoresist 
Developer; I've been using MEGA CPD5 instead because it's less harmful 
and harder to screw up), but would need to hunt down a suitable 
indicator chemical and glassware...

Thanks,
-- 
Phil.
ygroups@...
http://www.philpem.me.uk/

On 11/11/2010, at 5:41 AM, Philip Pemberton <ygroups@...> wrote:

> Hi guys,
> 
> Does anyone know off-hand what the required ratio of Hydrochloric Acid 
> to Peroxide is when starting off a cupric chloride etch bath?
> 
> 
I personally don't think it's very critical. I started a bath quite a few years ago with simply a small amount (1cm in bottom of tank) of spent ammonium persulphate etchant ( ie it was loaded with copper ) and added about half a tank of hcl. This is one of those fairly common vertical plastic tanks that's about the size of an a4 page of paper. Added copper, heater, bubbler, and it turned green. Don't think it even took that long. So yeah I didn't use peroxide at all. That same tank is still going. 


> Do I need to target a specific pH? That is, do I need to buy litmus 
> paper and so on too?
> 
> What about titration and specific gravity control -- is that necessary? 
> I have some sodium hydroxide granules in the cupboard (CIF Photoresist 
> Developer; I've been using MEGA CPD5 instead because it's less harmful 
> and harder to screw up), but would need to hunt down a suitable 
> indicator chemical and glassware...
> 
I've never measured gravity or ph of mine. When it's bright clear green it's good to go. Dark brown means it needs bubbling. Eventually you'll get precipitates in bottom (solution's saturated) I just pour off the liquid, clean out the precipitates, and top up with fresh hcl. 

Andrew

[Non-text portions of this message have been removed]

The usual recipies are designed for one part 37% acid and two parts 2% 
peroxide.  Since you're using a weaker acid and a stronger peroxide, 
you'll have to figure out the new ratios, but it will probably end up
being two parts acid to one part peroxide.  Never add peroxide to acid! 
  Always add acid to peroxide.

You don't need to worry about the chemistry until it stops etching :-)
But note: the peroxide breaks down over time, so make enough solution to 
use in a week or two.  You can always grow more solution later.

http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/
http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/

If you want to skip right to CuCl, I found that about half a pound of 
copper converts 3 liters of CuCl etchant.

Im using a 25% hcl and 30% peroxide diluted to 3% for large boards and semi professional manufacturing. The process is not very critical but you shoul BE AWARE THAT CHLORINE GAS IS RELEASED when cupric chloride is forming. Do this in a VERY well ventilated area and if possible get a chemical mask, use protective googles, gloves,etc. Best clothes to wear in this case is pure polyester because its not afected by the acid, a large plastic apron, meat industry kind, is also a good idea.

When initially mixing hcl and h2o2 remember the triple A, Allways Add Acid to water, in other words, first put the water and the slowly add the acid or you will have a wild exotermic reaction.

Do not store this solution in metal or allow it to get in contact with metal. Do not use more than 3% h2o2 or the reaction with copper can go wild, i read somewhere that some rocket use peroxide and cooper as propeller.

Maintainig the solution s very simple, a green esmerald color is a good color, when it start to turn brown because of too much cooper retained, add more h2o2 until it goes ligth green again. From time to time you would see that besides having a ligth green color the etchant takes to much time to work, this is because the acid gets diluted (regeneration with h2o2 generates h2o as subproduct) and you simple have to had more hcl.

Tritation is a good form of control but I never done it yet.

I hope this helps and if anybody knows something better please share with the rest.


--- In Homebrew_PCBs@yahoogroups.com, Philip Pemberton <ygroups@...> wrote:

>
> Hi guys,
> 
> Does anyone know off-hand what the required ratio of Hydrochloric Acid 
> to Peroxide is when starting off a cupric chloride etch bath?
> 
> I've tracked down these 'starter' chemicals on ebay:
>    HCl: 
> http://cgi.ebay.co.uk/BRICK-CLEANER-CEMENT-REMOVER-CONCRETE-REMOVER-ACID-/250631108343?pt=LH_DefaultDomain_3&hash=item3a5ac736f7
>     or 
> http://cgi.ebay.co.uk/Disclean-Brick-Cleaner-2-x-5lts-/390122417591?pt=LH_DefaultDomain_3&hash=item5ad51badb7
> 
>    H2O2: 
> http://cgi.ebay.co.uk/2x200ML-Bell-Hydrogen-Peroxide-9-Anti-Septic-Bacterial-/130392225994?pt=UK_Health_HealthCare_RL&hash=item1e5bfb78ca
> 
> This is 17.5% strength HCl, and 9% H2O2. Assuming this is strong enough 
> to start a cupric chloride bath (with a sufficient amount of air and 
> scrap copper provided), what sort of mix ratio would I need to make a 
> viable etchant?
> 
> Do I need to target a specific pH? That is, do I need to buy litmus 
> paper and so on too?
> 
> What about titration and specific gravity control -- is that necessary? 
> I have some sodium hydroxide granules in the cupboard (CIF Photoresist 
> Developer; I've been using MEGA CPD5 instead because it's less harmful 
> and harder to screw up), but would need to hunt down a suitable 
> indicator chemical and glassware...
> 
> Thanks,
> -- 
> Phil.
> ygroups@...
> http://www.philpem.me.uk/
>

On 11/11/10 01:31, DJ Delorie wrote:
> The usual recipies are designed for one part 37% acid and two parts 2%
> peroxide.  Since you're using a weaker acid and a stronger peroxide,
> you'll have to figure out the new ratios, but it will probably end up
> being two parts acid to one part peroxide.

That suits me fine -- it's easier to get the acid in large quantities 
than the peroxide.

 > Never add peroxide to acid!
>    Always add acid to peroxide.

Yep, I've heard the old saying:
"Add acid to water, just like you ought to!"

Acid + water is an exothermic reaction, just like mixing FeCl3 granules. 
Throw water into acid and you get localised boiling, fizzing and hot 
steam... not really a good thing when dealing with corrosive substances.

> If you want to skip right to CuCl, I found that about half a pound of
> copper converts 3 liters of CuCl etchant.

So just chuck 1lb of copper pipe into the tank, and leave it with the 
air pump running?

You mention that the peroxide degrades in about a week, am I right in 
thinking this only applies to the HCl+H2O2 etchant, i.e. by the time 
it's CuCl, this is of little effect?

Do sealed bottles of peroxide degrade in the same way, or just open bottles?

I suspect I'll probably buy enough peroxide for two attempts, i.e. 
2-litre tank, 3 parts chem = 660ml a time, or 1.2l peroxide, and a 
5-litre bottle of brick cleaner (about the cheapest way to buy it). Just 
in case I screw something up...!

Thanks,
-- 
Phil.
ygroups@...
http://www.philpem.me.uk/

On 11/11/2010 01:39 PM, Philip Pemberton wrote:
>> If you want to skip right to CuCl, I found that about half a pound of
>> copper converts 3 liters of CuCl etchant.
>
> So just chuck 1lb of copper pipe into the tank, and leave it with the
> air pump running?

Well, you want enough copper to get the density to the low end of the 
useful range, but not so much that you get to the high end.  You want to 
build the rest of the density with circuit boards :-)

but do that *after* you etch your first batch of boards.  The hcl+h2o2 
etchant is pretty fast at first, might as well take advantage of it.

> You mention that the peroxide degrades in about a week, am I right in
> thinking this only applies to the HCl+H2O2 etchant, i.e. by the time
> it's CuCl, this is of little effect?

I don't add more peroxide to my CuCl tank any more, but I do add more 
acid occasionally (the Cl in CuCl has to come from somewhere)

> Do sealed bottles of peroxide degrade in the same way, or just open bottles?

If they're in *dark* sealed bottles, should be fine for longer.  They're 
cheap and easy to get though, use the 2% you can buy in supermarkets and 
drug stores.