[Tips & Tricks] PCB Etching with(out) chemicals

Frequently asked question on the subject of designing, creating, producing printed boards, veroboards or perfboads and on point-to-point construction techniques.
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Mr. G.
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Post by Mr. G. »

Is it possible to etch a pcb without using chemicals? We get our water from a well, and have a septic tank system. So, I'd rather not have to dump chemicals down the toilet. We also live quite a bit outside of town, so there's no place close to take the spent chemicals to dispose of them.

If not, would any of you be interested in selling me a few etched pcb projects? If the transfer file isn't already available, I can send an Eagle project file, or a transfer file.

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Post by madbean »

You can try a solution of Muriatic Acid and Peroxide. Much less nasty than FeCl and just as effective.

You could try also try electrolysis.
http://www.instructables.com/id/The-Sal ... h-process/

Thing is, even then you are going to left with some kind copper solution, and that still needs to be disposed of. If you are doing a small run, I wouldn't sweat tossing it in the trash as long as it's properly sealed (coke bottle is good for this). Environmentally, though, that is still not too good.

Anyway, I'm starting up a little PCB service, so if you decide you don't want to hassle with it, PM me and we can discuss what you need.

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Post by Mr. G. »

Thanks a lot madbean! I'll probably just send you a pm before too long to discuss what I need.

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Post by lolbou »

Muriatic acid (HCl) is bad too... It will attack the surface of your inox sink, and is harmful to skin, eyes, and breathing organs...

It is quite easier to get rid of it with soda, but it is still harmful...

And peroxide is a strong oxydant that might be dangerous too when misused...

Anyway, etching is quite a strong reaction, and you need "powerful" chemicals... What would be your recipe for the HCl/H2O2 mix (I'm interested as they are easier to find in a lab)...
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Post by RnFR »

just soak up your ferric with some paper towels, put them in a plastic bag and throw them away. i usually don't use more than a few ounces of ferric per board- usually i'll just ball up some paper towel or use a sponge and rub it on the surface to be etched. i get great results that way, and you don't have to use so much etchant. there is really no need to pour so much that you have the pcb totally submersed. just get some rubber gloves and you'll be cool.

i've used muriatic/peroxide but the fumes were really harsh, and there was no way my girl would let me do that indoors. if i want to etch at all in the winter it's with ferric and the method mentioned above.
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Post by Mr. G. »

got another question... What size hole and drill bit should be used for the lead holes?

I really want to give etching my own pcb's a shot. Hopefully I'll be able to talk my wife into doing the printing while she's at work (don't have access to a laser printer myself).

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Post by madbean »

If you are using eagle, then try 27 or 31 setting for drill size. For bits, anything numbered 68 or smaller is okay. I would by a couple of different ones and use the smallest you can get away with. I use different bit sizes for different components.

resistors caps and trannies get the smallest
diodes (like 1n400x) get slightly larger
wires get slightly larger

I use the guassmarkov libraries and set my layouts with a trace size of 32. The drill and pad sizes are preset. Once I'm done with the layout, I use the "restring" function under the 'design rules' button to size up all the pads. If you've laid things out well, you will have plenty of clearance between traces and pads. You can use design rules to automatically check and report problems in your layout for you.

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Post by Mr. G. »

Thanks for the info. I'm trying to use Eagle more and more, as it's starting to get a bit easier. I typically use it to make my layouts, and then use Inkscape to make them "pretty".

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Post by RnFR »

madbean -
check the eagle thread for a question regarding this restring thing.
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Post by potatoolay »

Im a big fan of the muriatic/peroxide solution. 2 parts H202 to 1 part HCl(Muriatic). It works a lot better at room temperature than Ferric Chloride. I usually use the disposable (inexpensive) rubbermade food containers. One to etch in and one to store "spent" solution in until I can dispose of it.

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Post by lolbou »

potatoolay wrote:Im a big fan of the muriatic/peroxide solution. 2 parts H202 to 1 part HCl(Muriatic).
Cheers for the recipe. What about the concentration of H2O2 and HCl (I guess it might change things...)
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Post by juse »

lolbou wrote:
potatoolay wrote:Im a big fan of the muriatic/peroxide solution. 2 parts H202 to 1 part HCl(Muriatic).
Cheers for the recipe. What about the concentration of H2O2 and HCl (I guess it might change things...)

Check out this instructables link - it lays it all out nicely:

http://www.instructables.com/id/Stop-us ... etter-etc/

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Post by soulsonic »

lolbou wrote:
potatoolay wrote:Im a big fan of the muriatic/peroxide solution. 2 parts H202 to 1 part HCl(Muriatic).
Cheers for the recipe. What about the concentration of H2O2 and HCl (I guess it might change things...)
Yes, it certainly does. The peroxide you get at the drugstore is only 3%! So, 2 to 1 works okay, but don't add any water!
With the 3% H2O2, I find 3 to 1 works great.

If you enjoy taking risks... microwave the peroxide before adding the HCl. :shock: The trick is to get it hot, but not quite boiling... but close to that. I tried it once, and my board was done in only about 5 minutes!
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Post by madbean »

I usually do 2 parts acid, 3 parts peroxide. It sometimes works amazingly fast.

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Post by uncleboko »

Ever tried Coca Cola for etching? Go on try it and I guarantee that you'll never drink it again!!!

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Post by soulsonic »

madbean wrote:I usually do 2 parts acid, 3 parts peroxide. It sometimes works amazingly fast.
Do you use 3% Peroxide, or 20% Peroxide?
uncleboko wrote:Ever tried Coca Cola for etching? Go on try it and I guarantee that you'll never drink it again!!!
I haven't tried that, but I have used hot sauce to clean pennies!
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Post by Fuzzer »

I saw Coca Cola clean a Rusty Nail. I don't like to think what it does to my guts.
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Post by jfromel »

I have stopped etching my own boards and use ExpressPCB. They have a Miniboard order that is three boards 3.8"x2.5" with plated through holes, double sided for $51 for 3 boards. I can usually fit 3 or 4 circuits on to one board so the cost per board is pretty cheap.

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Post by soulsonic »

I've used ExpressPCB before. They are very high quality boards; but I do not like their layout program. Since I've started using Eagle, I don't want to use anything else.

I've asked this before, but I'm going to ask again; has anyone tried Futurlec for boards? They say that they accept Eagle .brd files directly without the need to export; that's great for a pcb noob like me, and their prices are dirt cheap.
Anyone?
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Post by lolbou »

Bump for the concentration/percentages of peroxide and chlorhydric acid...

I've found this here: http://wiki.jelectronique.com/realisati ... s_imprimes

Using this:

Acid: 33%
H2O2: 130 volumes (both in DIY stores)

It says this method is the most dangerous (gases?) but the more efficient.

1 water + 0.6 acid + 0.3 perox. (in volume). This is called the slowest method (1um/s is etched, compute with your PCB copper thickness)...

It says it can be done indoor, but is better outdoor... To get rid of the solution, it says to put it in the toilets and to flush... I'll try and use a big bucket of water to check pH and so on...

I'll go and check the chemical reaction to see what gases are produced... If it's O2, well, then, don't smoke, but if it's Chlorine, then don't breathe...
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