Homebrew PCBs

Hi,

I have this question for long time, at the wikipedia entry of ammonium
persulfate of my language is written:

(quick translation)
"(..)
Is possible to make ammonium persulfate at home using

      * 1 liter deionized water
      * 2g sodium hydroxide 
      * 0,5g of any mercury salt ( like mercury nitrate )
(..)"

My question: isn't this wrong??
So its like:
H2O(l) + NaOH(aq) + Hg(NO3)2(aq) -> (NH4)2S2O8
Which seems impossible in my low skills chemistry 

I looked at other language versions and none says anything like this,
googling for it only gives what seems copy cats. Ammonium persulfate is
said to be made by electrolysis of ammonium sulfate and sulfuric acid. 

About 10 years ago I asked someone for ferric chloride alternatives i
remember he says something similar (don't remember the names but was a
salt and caustic soda solution). So whatever gets from that mixture
etches copper??

Since i am writing this is, possible to mix ammonium hydroxide (i get it
here by 2eur liter in 25% as detergent) and sulfuric acid (i get it here
at 1,5eur liter 98%) and do electrolysis with titanium electrodes and
get ammonium persulfate? 
Just asking because once i bought the ammonium hydroxide and once I open
it I wanted to jump in the window to get ride of that horrible smell but
was in a 3rd floor :$ never used and no intentions to.
But is ammonium persulfate reusable? like sodium persulfate or cupric
chloride?

Oh and my language is Portuguese as in
http://pt.wikipedia.org/wiki/Persulfato_de_am%C3%B4nia


Another question, i would like to setup a sodium persulfate etcher, i
tried titanium electrodes and they where dissolved in the bath (the
anode one), is any titanium alloy suitable or i can't escape to buy a
platinum anode for this? 

And is possible to copper electroplate pcb boards with this same sodium
persulfate bath?? (this is only why i wish to have it)

I can get sodium hiposulfite (NaHS04) at 2eur/Kg (pH- for swimming
pools) can i start from this to get the etchant or i should go for
sodium sulfate?
Like this:
NaOH(aq) + H2SO4(aq) \u2192 NaHSO4(aq)
NaHSO4(aq) + NaOH(aq) + e- \u2192 Na2SO4(aq) + H20(l)
Na2SO4(aq) + H2SO4(aq) + e- \u2192 Na2(SO4)2(aq) + H2(g)
(shouldn't work like this but is an idea of what would be great and
simpler)

Thanks,
Simao

Simao Cardoso wrote:
> Hi,
> 
> I have this question for long time, at the wikipedia entry of ammonium
> persulfate of my language is written:


Most people who produce ammonium persulfate would do so by electrolysis 
at cold temperatures with platinum anode at high current density in a 
solution of high concentration of ammonium sulfate. The solubility of 
persulfate is significantly lower than sulfate and allows separation. 
High anode current densities increase persulfate/oxygen ratio since some 
water electrolysis is unavoidable.

I don't think any the chemical reactions you describe would make 
persulfates.

On Tue, 2009-04-07 at 21:22 +1000, Adam Seychell wrote:

> Most people who produce ammonium persulfate would do so by
> electrolysis 
> at cold temperatures with platinum anode at high current density in a 
> solution of high concentration of ammonium sulfate. The solubility of 
> persulfate is significantly lower than sulfate and allows separation. 
> High anode current densities increase persulfate/oxygen ratio since
> some 
> water electrolysis is unavoidable.
> 
> I don't think any the chemical reactions you describe would make 
> persulfates.
> 

Adam, very thanks, you cleared my doubts on this.
Still, there is 2 other questions that I looking for any comment. 

Is ammonium persulfate reusable? like sodium persulfate or cupric
chloride.

Is possible to copper electroplate pcb boards in a sodium persulfate
bath?? Using copper anodes and when the bath is copper saturated. 
This last question is strange, but is why i wish to have it this bath,
if could be possible a 2 in 1.


>

Simao Cardoso wrote:
> On Tue, 2009-04-07 at 21:22 +1000, Adam Seychell wrote:
> 
>> Most people who produce ammonium persulfate would do so by
>> electrolysis 
>> at cold temperatures with platinum anode at high current density in a 
>> solution of high concentration of ammonium sulfate. The solubility of 
>> persulfate is significantly lower than sulfate and allows separation. 
>> High anode current densities increase persulfate/oxygen ratio since
>> some 
>> water electrolysis is unavoidable.
>>
>> I don't think any the chemical reactions you describe would make 
>> persulfates.
>>
> 
> Adam, very thanks, you cleared my doubts on this.
> Still, there is 2 other questions that I looking for any comment. 
> 
> Is ammonium persulfate reusable? like sodium persulfate or cupric
> chloride.

Sodium and ammonium persulfates behave very similar, and you cannot 
reuse either of them. Oxygen (from H2O2 or O2) regenerated cupric 
chloride is the only practical reusable etchant for homebrew PCBs.

> 
> Is possible to copper electroplate pcb boards in a sodium persulfate
> bath?? Using copper anodes and when the bath is copper saturated. 
> This last question is strange, but is why i wish to have it this bath,
> if could be possible a 2 in 1.

You can copper electroplate from just about any solution containing 
copper ions, but the question is can you electroplate with thick smooth 
ductile uniform deposits. With all the effort that goes into formulating 
a copper plating solution, I highly suspect you won't find anything 
useful from spent etchants.

On Thu, 2009-04-16 at 14:25 +1000, Adam Seychell wrote: 
> 
> Sodium and ammonium persulfates behave very similar, and you cannot 
> reuse either of them. Oxygen (from H2O2 or O2) regenerated cupric 
> chloride is the only practical reusable etchant for homebrew PCBs.
> 
> You can copper electroplate from just about any solution containing 
> copper ions, but the question is can you electroplate with thick
> smooth 
> ductile uniform deposits. With all the effort that goes into
> formulating 
> a copper plating solution, I highly suspect you won't find anything 
> useful from spent etchants.
> 

What a mess! My hope to find a usable and clean way to do PTH boards is
a proven waste of time for me. Much wanted the same and am sure not the
one with skills for it. 
I completely fooled myself with sodium persulfate. I really thought it
was reusable, fooled by very convincing speculation on the web. I just
wanted a reusable source os cooper anodes and a metallic resist
compatible etchant. I spent some time searching for a way to use
peroxy-sulfuric etchant for this. And then found sodium persulfate, and
it seem better for the purpose than peroxy-sulfuric.

Searching for patents on sodium persulfate only gives microetch uses.
'Printed Circuits Handbook' says persulfate based continuous
regenerative etchants are no longer used. Looking for all the posts in
this list for the matter only refers to a 'one use only' etchant.

What i had in mind was a copper electro winning system based on platinum
anode and copper/steel/titanium plates for cathode, it will deposit
copper and regenerate the persulfate 'from the sulfate' again. Will be
really great to be, and is written like that all over the web, but to
end with all the doubts the etchant reaction is: 
Na2(SO4)2 + Cu+ --> Na2SO4 + CuSO4 
Or like this?
Na2(SO4)2 + H20--> Na2SO4 + H2SO4 + H2O2
H2O2 + H2SO4 + Cu --> CuSO4 + 2H2O
basically both are right but the second ends with the speculation that
fooled me right?

Potassium persulfate is sold has a 'swimming pool oxy choke' (12eur/kg
here). And persulfates seems to be used as a solid source of oxygen on
chemistry (and explosives too).

>From the sodium persulfate microetch patents is said that is a slow
etchant and the presence of sodium sulphate lower the etch rate a lot
more. My use idea will end up having sodium persulfate, sodium sulphate,
sodium bisulphate and sulfuric acid all present. So very slow.

The other things was sodium persulfate is more compatible with metallic
resists than cupric chloride, it can be used with nickel (tin or
tin/lead with additives). And disregarding the quality of the plated
copper it also seemed a possible plating setup. 
But my questions was more about time and energy efficiency. After etch,
leting the copper cathodes there will saturate the bath in copper,
inverting the polarity with the board on circuit, it will plate copper
in the board (disregarding the plating quality). But to etch again will
be needed much recover time and energy (and platinum anode losses). I
really thought everyone that uses sodium persulfate use it like this and
the question was to know if this time and energy cost worth it.

I really want metallic resist because dry film covering the holes gives
much work and don't has the enough successful rate. Toner transfer or
direct printing, even if another plating step is required, is much more
pleasant. But i need a matching etch. 
'Printed Circuits Handbook' refers tin/nickel for cupric chloride, maybe
nickel works? Tin/lead is the cheapest but the matching peroxy-sulfuric
etch is not so cheap... 35% hydrogen peroxide is not easy to find (my
veterinarian sister says it is used to wash big animals foots but i had
no luck to find it anyway). But still using 35% hydrogen peroxide gives
much waste etchant, and a expensive etchant. 

But I really have to stop embracing what seems easy, if i ever want to
get a PTH system. But in a last breath of crazy ideas, there is any
other way to add oxygen to a sulphuric acid etchant? There is who says
hot concentrated sulphuric acid is usable as etchant but with really
toxic gases. But about bubbling oxygen gas? Nobody uses this, is just
expensive or not efficient? And water hydrolysis? The power and anode
(platinum) costs are acceptable?

Very thanks,
Simao

At 8:06 pm ((PDT)) Mon Apr 27, 2009, in Digest 2765 Simao Cardoso wrote:

>On Thu, 2009-04-16 at 14:25 +1000, Adam Seychell wrote:
> > Sodium and ammonium persulfates behave very similar,
> > and you cannot reuse either of them. [snip]
>
>[snip most of Simao's reply] but to
>end with all the doubts the etchant reaction is:
>Na2(SO4)2 + Cu+ --> Na2SO4 + CuSO4
>Or like this?
>Na2(SO4)2 + H20--> Na2SO4 + H2SO4 + H2O2
>H2O2 + H2SO4 + Cu --> CuSO4 + 2H2O
>basically both are right but the second ends with
>the speculation that fooled me right?

Please explain: what speculation? Also note that the
second of the three reactions is not balanced :-(


Regards, LenW

On Tue, 2009-04-28 at 20:55 +0100, Len Warner wrote:

> >[snip most of Simao's reply] but to
> >end with all the doubts the etchant reaction is:
> >Na2(SO4)2 + Cu+ --> Na2SO4 + CuSO4
> >Or like this?
> >Na2(SO4)2 + H20--> Na2SO4 + H2SO4 + H2O2
> >H2O2 + H2SO4 + Cu --> CuSO4 + 2H2O
> >basically both are right but the second ends with
> >the speculation that fooled me right?
> 
> Please explain: what speculation? 
The best words your find in this really good written post.
http://www.electro-tech-online.com/electronic-projects-design-ideas-reviews/8272-pcb-etchant.html#post668389
He calls it 'Eternally-replenishable Novel Etching Solution (based on
persulfate-type etchant)'. And a something that work like that is what i
was looking but isn't that simple.

> Also note that the
> second of the three reactions is not balanced :-(
I didn't care about it at the moment, none was balanced. The point was
to say that peroxide is formed and is the key in the reaction (i now
think). And not the sulfate ion alone.
> 

>

Simao Cardoso wrote:
> What i had in mind was a copper electro winning system based on platinum
> anode and copper/steel/titanium plates for cathode, it will deposit
> copper and regenerate the persulfate 'from the sulfate' again. 

I think you better first know if you can achieve high enough ratio of 
S2O8/SO4 using such an etch tank configuration. Remember, you are 
competing with electrolysis of water. Expect electrolysis efficiency to 
go through the floor without any S2O8 salt isolation.

> I really want metallic resist because dry film covering the holes gives
> much work and don't has the enough successful rate. 

You may find as I eventually did after several years of home PTH 
plating, that the additional complexity of operating and maintaining a 
metal plating resist tank (acid tin sulphate or tin/lead fluroborates ) 
far out ways the minor problems with hole tenting. You just have shape 
up on your drilling skills a little more.
There is also other problems that come with hobby pattern plating PCBs, 
such as copper surface residues after photoresist developing, use of 
complex controlled alkaline etchants and tin metal attack in NaOH 
photoresist strippers.

Best of luck.

Adam.