# Alternative PCB etching solutions - Is KMnO4 or NaClO suitable oxidizer?

I need to etch small PCB for my project, since I do this once in a blue moon I would like to try some easy approach, preferably with household items. I'm aiming at the use of acetic acid with hydrogen peroxide to aid the reaction. But this got me wondering what are some other household items usable in the process?

I was able to find potassium permanganate ($\ce{KMnO4}$) which is a strong oxidizer, but I'm not sure if this still holds for water soltuion mixed with acetic acid.

My other idea for strong oxidizer was sodium hypochlorite ($\ce{NaClO}$) found in bleach, but I'm not really sure how safe this is. Even though I will etch only small PCB, 1 by 2 inches, I would rather not endanger myself or anyone else.

Does any of the proposed ideas make sense? Is $\ce{KMnO4}$ or $\ce{NaClO}$ suitable oxidizer for etching PCB using acid solution?

• I only added the everyday-chemistry tag. Otherwise, I think that asking for cheap and safe ways to etch PCBs without killing oneself is a legitimate question. – Klaus-Dieter Warzecha Dec 27 '14 at 10:52
• Yes, it is. But I thought, maybe the answerer has no idea what range of chemicals @jnovacho has available. You had any ideas? Wow! :D – M.A.R. Dec 27 '14 at 11:11
• @MARamezani I've edited the question to narrow it down. I'm interested in use of the two chemicals I've mentioned. – jnovacho Dec 27 '14 at 11:21
• While being extremely strong oxidizer, potassium permanganate tends to produce solids as byproducts. Also, no matter what etching agent you plan to use, you will need acidic solution to avoid producing solids. I highly recommend to search for hydrochloric acid (likely to be available via DIA and pharmaceutic store) or sulfuric acid (available via car service stores, used in lead accumulators). Than add a proper oxidizer, like hydrogen peroxide. – permeakra Dec 27 '14 at 11:41

If you don't want to use the classical solid etchants, such as

• Iron(III)chloride ($\ce{FeCl3}$) or
• Ammonium persulfate ($\ce{(NH4)2S2O8}$) or
• Sodium persulfate ($\ce{Na2S2O8}$)

there's the mixture of hydrogen peroxide ($\ce{H2O2}$) and hydrochloric acid ($\ce{HCl}$) in various ratios.

Typical recipes use

• water
• 30% $\ce{H2O2}$
• 37% $\ce{HCl}$

in a volume ratio of 1:1:1.

Hydrochloric acid can be considered a "household chemical", it was/is available at DIY stores as muriatic acid and typically used to clean brickwork.

I would advise against mixing concentrated (glacial) acetic acid and hydrogen peroxide solutions of higher concentrations. You might end up forming peracetic acid, which is unhealthy and tends to decompose spontaneously (explode) at higher concentrations.

There's another method worth to be mentioned, although the etchant is usually not a household item.

Cupric chloride $\ce{CuCl2}$ in aqueous solution can be used at room temperature to remove metallic copper from the PCB too:

$$\ce{CuCl2 + Cu -> CuCl}$$

Thinking in terms of transition metal waste management, this seems to be pretty nice, since the resulting copper(I) solution can be regenerated (oxidized) to copper(II) (= the etchant) using hydrochlorid acid and hydrogen peroxide. This conference proceeding provides further information.

As far as the permanganate is concerned, it seems that it has been used to desmear PCBs in industry, but it has been superseeded by plasma treatment to avoid damage to the boards.

• In my case, the acetic acid would be vinegar, the one I have at home is 8% water solution. Also the hydrogen peroxide is of medical kind 3% water solution. Thanks for the tip. – jnovacho Dec 27 '14 at 11:11
• @jnovacho I think that you're safe with these concentrations. On the other hand, I can't tell how long the etching will take. – Klaus-Dieter Warzecha Dec 27 '14 at 11:20
• @jnovacho I highly doubt that 3% acetic acid will do much good. – permeakra Dec 27 '14 at 11:30
• @permeakra You're right! I updated my answer and added a more realistic recipe. – Klaus-Dieter Warzecha Dec 27 '14 at 11:44

I’m using $\ce{CuCl2}$ for three years now. I like it a whole lot better than $\ce{FeCl2}$ – it’s cleaner, uses domestically available chemicals, and has less of a disposal problem.

It’s related to “mixture of hydrogen peroxide ($\ce{H2O2}$) and hydrochloric acid ($\ce{HCl}$)” because that produces the same result, ultimately, though there is more than one way to get there. I have in the past tried $\ce{HCl/H2O2}$ and ended up stripping the entire board in a few seconds: but those same chemicals can be used to make $\ce{CuCl2}$ which is far more controlled. I’m not much of a chemist, but my understanding is that $\ce{Cu + H2O2 + HCl -> CuCl2 + H2O}$: the initial reaction eats copper fast but the result is $\ce{CuCl2}$ and the reaction with that is slower.

Here is a practical guide to making and using $\ce{CuCl2}$:

http://techref.massmind.org/techref/pcb/etch/CuCl2.htm