PCB Etching (again!) - chemicals used

Save money and hassle. Buy pre-made developer in a bottle. If you ruin one PCB by mixing the developer wrong you undo your savings. BTW, you'll only need a little bit of developer every time.

I use ferric chloride which can be re-activated by adding hydrochloric acid (can be bought at any grocery store of pharmacist). I'm using the same etchant for over 15 years now.

I read in sci.electronics.design that Nico Coesel wrote (in ) about 'PCB Etching (again!) - chemicals used', on Sat, 23 Apr 2005:

Where do you think all the copper went? Or do you make five boards a year? (;-)

You can't get back ferric chloride by adding HCl. What MAY be happening is that you are actually now using cupric chloride CuCl2 as the etchant. That gets converted to cuprous chloride Cu2Cl2 and you CAN convert that back with HCl.

Probably less... But I etched quite a large amount of boards over the years.

This is an ongoing discussion. However, the fact is that it works (the boards get etched).

Here is a snippet from an FeCl FAQ I put together almost a decade ago:

" Regenerating FeCl 'Regenerating' Ferric Chloride is quite simple, just add HCl (Hydrochloric acid).

Theory: According to my sources the following happens:

When the etching starts the copper is converted by this reaction:

(The HCl is actualy supplied as 4H3O+ and 4Cl- because it's dissolved in water)

When Oxygen is added to the etching bath the following happens:

the last reaction shows that the 4Fe2+ ions are regenerated to 4Fe3+ (The ion which makes the etching process work.) As you can see the HCl is used and the Ferric Chloride is regenerated. "

snipped-for-privacy@puntnl.niks (Nico Coesel) wrote in news: snipped-for-privacy@news.planet.nl:

How do you get the REMOVED COPPER(that came off your etched PCBs) out of your FeCl when "reactivating" it?

Where does it go?

ruin

Ahh, fair enough -- any idea where to get stuff like that? I've just never seen it, although I do restrict all my google searches for PCB product purchases to "site:.au".

Also, you mention mixing the developer 'wrong' -- what ill effects does that have? I understand that if it's too strong it'll strip the stuff off too quickly, and potentially damages copper (is that right?), but most hobbyist sites say that the exact mix isn't really that important

-- as long as it's about 1:20 or so. (50g for 1L of water)

hydrochloric

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ahh, excellent. Yeah, I've read that some people use FC, but a lot of other places recommend AP as it seems 'easier' to use. But if FC can be stored properly, I might make the switch... Is there anything important to know about storage? ie. a tightly sealed plastic bottle would do?

Cheers!

Michael

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Hrm, that's good to know... do you know if it will work fine with the kinsten etching tank that I have (referenced in the link in my first post)? I don't see why it wouldn't, as it's all plastic (and glass, for the heater), I'm just led to believe that it's pretty nasty stuff (worse than ammonium persulphate) and I don't want to end up with nasty results. :-)

Cheers!

Michael

It forms cupric chloride, eventually, which is an etchant in its own right.

Leon

Hey Michael, I used to use Ammonium Persulphate but Ferric Chloride is much better. I got 4L from a PCB maker but you can get it here

Cheers.

I read in sci.electronics.design that Nico Coesel wrote (in ) about 'PCB Etching (again!)

- chemicals used', on Sat, 23 Apr 2005:

You didn't mention the oxygen before. I'm still not convinced, because FeCl2 is not likely to reduce molecular oxygen, but that is more plausible.

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Yeap, I've actually made a nice UV light box from scrap bits of wood, with 4 x 15W UV tubes. Combined with my 1200 DPI laser printer, I can get 20mil spacings (8mil tracks with 12mil between) out pretty easily

-- it's just etching it that's the problem.

Cheers!

Michael

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Ha -- I actually broke my heater for the Kinsten tank on Friday. (Left the water level slightly lower than 1000ml, and the top of the heater got too hot and cracken when [much] colder water splashed up on it.) I've ordered 2 more heaters for it -- I'll probably put one either side of the tank, to heat it twice as fast. ;-)

I was surprised you got an aquarium heater to get it to the temperatures required, though -- all the ones I've seen have thermostats which would limit the temperature to a much lower range. Did you get one and modify it? Or do you just etch at a cooler temperature? How much did it set you back?

Cheers, Michael

Ahhh, fair enough. I don't actually check RS and farnell, much - their prices depress my poor uni student budget too much. ;-)

Hrm, that's interesting -- mine's definately not too strong, but I'm thinking it could be too weak. Some areas didn't develop properly, and I just presumed it wasn't exposed enough in my light box. Shouldn't it be the sort of thing that I can just leave it in the developer for longer if it isn't concentrated enough?

Ta, Michael

I use Amonium Persulphate in a Kinsten etching tank and it works great. Made a couple of modifications though. Bought a higher wattage aquarium heater at the pet store so I can get the tank up to working temperature a lot faster and made a cover from 1/2" acrylic to reduce evaporation between sessions. I use the same solution for about a month etching 8 to 10 boards.

Takes about half a 1kg bottle of MG Chemicals amonium perulphate crystals to mix enough to fill the tank and it is FAR cleaner than feric chloride.

-- Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at:

I read in sci.electronics.design that Michael wrote (in ) about 'PCB Etching (again!) - chemicals used', on Sun, 24 Apr 2005:

Both are medium-soft oxidizing agents. I suspect that the only thing 'worse' about FeCl3 is that it stains everything orange-brown, and it's difficult to get rid of the stains, especially on some materials where the iron attaches chemically to the molecules of the material.

Well, in order to make ferric chloride etch fast, you need to add oxygen. That's one of the reasons ferric chloride is used in foam or spray etching machines. Lots of oxygen in the air.

I bought the stuff I use from Farnell.

If it is too strong or too warm, it will strip all the resist of the board (happened to me once). If it is not strong enough, it won't strip all the exposed areas. Temperature is also important. I always use the developer at room temperature. I usually use around 25cc of developer for a small board.

Any glass or plastic bottle will do as long as it is not made from nylon.

^^^^^^^^^ Wrong word, it should read 'impossible'. I drove my mother mad with FeCl stains :-)

Anyway, I've been etching boards since I was a teenager. My father (who has a degree in chemistry) decided ferric chloride the safest stuff for me to use.

Most likely, I use a plastic ice-cream container to do my etching in as my boards are usually small. Fingers I find don't fall off when inserted in the FC, I may go out on a limb here but I'm sure it would take a while to feel any effect from leaving any FC on your skin for a while. Water cleans up OK.

BTW, if you go down this road with the Press-n-Peel, I think a laser printer is the go.

Cheers.

I read in sci.electronics.design that Nico Coesel wrote (in ) about 'PCB Etching (again!) - chemicals used', on Sun, 24 Apr 2005:

I suspect it's more an effect of the turbulence clearing away the CuCl2 from the etch site. It would be interesting to see if N2 or CO2 bubbles would increase the etch rate or not.