new cupric acid etches

[sean k]

I've got the hang of the hydrochloric and hydrogen peroxide etching or think I have. The intial mix of 28% hydrochloric was mixed at about 2/1 with a 12% peroxide mix (27% peroxide + distilled water) and after each etch I add a little more peroxide mix to the point where the mix wasn't going browny orange any more and I added some copper wire cuttings and it now stays kinda bluey green.


Top left is the uglyface with LFO and next to that is auto wah with 13700 by R.A.Penfold.
Bottom row left is the Fuk tave by nelson and next to it is a clari(not) including an etch for the three pots around the LDR/LED... and the LDR/LED.

I still use sharpies over pencil straight onto the copper then use a pen knife to scratch the lines between pads for IC's, Transistors and electrolytic caps. Only problem is that occasionally I kinda change the sharpie drawing from the underlying pencil and the etch takes a little longer where pencil is still visible.

Given that I've still got litres and litres of both the acid and the oxidiser I don't think I'll bother with a fish tank oxygeniser and just add a little oxidiser every so often but this mix really works. No more hot fingers with ammonium persulphate.

[WLS]

Why not just buy acid?

Bill

[biggy boy]

Where do you get hydrochloric acid?
OH wait I think that's the stuff you get from the hardware store for cleaning concrete right?

Orange color? And why do you throw chunks of copper in the acid, to test it or to pre-treat it??

Glen

[sean k]

Hydrochloric Acid and Hydrogen peroxide are both available at pool stores in 27-28% and the distilled water you get at auto stores for batteries. Cut the Hydrogen peroxide down to 1/1 with the distilled water and mix that at 1/2 with the hydrochloric.

After your first etch the liquid will go browny orange which means all the oxygen is attached to the copper so you add some more of the peroxide mix, though you could just aerate it somehow. This will happen for a few etchs until the liquid doesn't go browny orange anymore so you add some pure copper, cut from stranded wire and aerate it with a fishtank blower or somesuch or just add a little more peroxide.

It's supposedly now cupric acid solution and the addition of fresh copper and oxygen keeps it going indefinitely... so I've heard.

Do some searches here for hydrochloric and peroxide and you'll find all you need to know.

[vince76]

I use this solution too...
but different proportion
3 parts acid
2 parts Hydrogen peroxide
no distilled water
I use to keep the solution at warm temperature (say 30-40 °C)
It works good and fast

I can't understand about adding copper to solution... for what I understood from experience, at a certain point is a good thing to add Hydrogen peroxide as the copper is added by the etching process directly from the board...

How many times you re-utilize your solution?

Hope I was clear...
V.

[biggy boy]

OK thanks
This sounds interesting, may give it a try.
It sounds like it would be cheaper then buying the etching chemical at the electronics supplier.



Edit:
One more thing. Is this solution Sharpie marker friendly?
Some times I need to touch up a laser printed board with a marker.

Glen

[RedHouse]

I use this solution too...
but different proportion
3 parts acid
2 parts Hydrogen peroxide
no distilled water

I been using just the opposite 3 parts Hydrogen Peroxide to 1 part Acid.

Heads-up, when buying acid read the label look for it's %, it seems to come in different strengths. I bought a 2-pack of Acid (often called Muratic) at a large hardware store (cough, cough, Home Depot) which was less expensive and also etched much slower than the jug I bought at another hardware store, reading the label I noticed the 2-pack was 16% and the other jug was 30%. So even factoring-in the discount for buying the two pack, it still didn't work out to be a good deal, it etched much slower and I used twice as much etc.
(for some reason I hate a slow etch, maybe I'm just getting old)

[MikeH]

I did an experiment a while back with different concentrations of Muriatic (30%ish) and Hydrogen Peroxide (regular drug store variety)  I used 5:1, 4:1, 3:1, 2:1 and 1:1 mixtures of acid to HP, on the same size piece of copper, and found that 1:1 mix was the fastest.  Although the 2:1 and 3:1 mixtures finished literally one minute later.  So the actual mix isn't that crucial, IMO.  I just eyeball about 1:1 and go with it.


Although- I didn't try any mixtures of more HP to less acid.  General intuition tells me it shouldn't be faster, but you never know.

[vince76]

Oh I forgot
acid is 33%
Hydrogen peroxidE is 3%

when I transfer the toner sometimes there's a tace needing correction because not all toner is transfered. (oh my english)
I correct with a correction pen, something used in office to blank some part of documents (don't know how explain better) and is resistant to acid solution.

V.

[SonicVI]

I use 1 part 28% HCl and 2 parts 3% H2O2 and it works pretty fast, much faster than ferric chloride anyway.   My solution never turns anything but green.

[John Lyons]

It's been said before but you can get 40% Peroxide at beauty supply shops.
Why pay for water with the 3% solution?
I use 2:1 H2o2/muratic

john

[vince76]

agree, but
it's what i had 
V

[biggy boy]

OK I got a jug brewing right now . Threw in some copper chunks as per Sean.
Oh smelly stuff it is!!!

[Barcode80]

It's been said before but you can get 40% Peroxide at beauty supply shops.
Why pay for water with the 3% solution?
I use 2:1 H2o2/muratic

john

yep, that's my recipe too, except i've recently lowered to 30 volume from 40 because the etch was a little too fast for me.

[sean k]

Hey Folks, I ain't a chemist... and got a good telling off when I rang one, an industrial chemist, to find out where to get the hydrogen peroxide at 30 odd percent! He eventually told me, right at the end after giving me a lecture about safety... pool shop. Anything over 30%, here in NZ, requires a special licence.

I mix the 28% hydrogen peroxide with distilled water to bring it down to about 14%.

So the initial etchs give off chloride but after mixing in more hydrogen peroxide this doesn't happen so much so I'm guessing that the change is to cupric acid which possibbly needs extra copper to graft with the hydrogen left over so the free oxygen can do it's work... I really have no idea but it doesn't need more hydrochloric but benefits from added oxygen and copper.

So I looked up cupric acid and its actually cupric chloride acid
http://members.optusnet.com.au/eseychell/PCB/etching_CuCl/index.html

It's all right here... more than you'll ever need to know. It even mentions adding stranded copper wire... Amazing what you don't need to learn on the internet   

[RedHouse]

It's been said before but you can get 40% Peroxide at beauty supply shops.
Why pay for water with the 3% solution?
I use 2:1 H2o2/muratic

john

John,

Is your 2:1 ratio using beauty-shop 40% Peroxide? 

[Barcode80]

It's been said before but you can get 40% Peroxide at beauty supply shops.
Why pay for water with the 3% solution?
I use 2:1 H2o2/muratic

john

John,

Is your 2:1 ratio using beauty-shop 40% Peroxide? 

i don't know if his is, but mine is. although as mentioned before i use 30% now.

[biggy boy]

I have etched my second board, using the HCL mix.
and have to say I love it!
It faster and cheaper.

Thanks Sean for creating this post!
It was very timely, as I was out of the Ferric etchant and about to go drop some more money on more of it.

[sean k]

Tidied up at photobucket so heres the image again... just so theres one picture in the thread.