Etchant

DJQUIRK · Joined: Aug 07, 2006 Posts: 39 Location: ATLANTA GA

Any thoughts on the best/most efficient etchant solution. Ferric chloride vs. Sodium persolfate (I think that is how its spelled). I'm having issues with the ferric chloride.

blue hell · Posted: Sun Sep 17, 2006 4:31 am Post subject:

It has been a long time since I last did any etching, but I still have some memories, maybe they are still worth someting Very Happy

I never used sodium persulfate but did try ammonium persulfate. That stuff never really lasted very long and it was quite expensive as well. It works much cleaner though.

Ferric chloride is messy, as it stains and corrodes everything around easily (and its a poison) but it works much better. I've tried it two ways. First as pellets that I made my own solution with but later I went to a local etching company which sold it in liquid form. That last one worked best, maybe they added some sort of acid. The pellet stuff didn't last very long either.

However for ferric chloride to work OK the solution should be heated to around 50 degrees celcius which sort of complicates the process. Unheated etching takes a long time and the etching is uneven, when heated I think I got etching times of around 5 minutes and very good results.

I used to place the boards horizontaly (side to be etched up), as vertical placement gave uneven etching. There are however air bubble systems that make etching more evenly for verical placed boards - I've never tried that at home, but it should not be to hard to make your own bubble system (using an aquarium air pump). .

DJQUIRK · Joined: Aug 07, 2006 Posts: 39 Location: ATLANTA GA

I've been buying $4.50 packets of ferric chloride and double sided boards @ about 4" x 6". I heat it up on the stove and I always end up with specks of copper all over the board, when I leave it in the solution long enough to get rid of the copper the etchant starts to undercut the resist and stain the whole board brown. I think part of the problem is that I'm using double sided boards. There is a local Radio Shack that actually still sells components here in Atlanta, but they only sell the double sided boards. There is another electronics store here and they sell sodium persolfate, but I was unsure about it as it comes in a 1/2 gal. bottle with just about 2 tblsp. of powder in the bottom. Is this how it usually is? I'm trying to make Ray's midi to CV convertor.

fonik · Posted: Sun Sep 17, 2006 8:17 am Post subject:

i am using sodium persulfat. you'll have to heat it, too (best results at about 45 degrees celsius). CAUTION: only use plastic container, never use glass/metal or whatever! i have to say that i am using an etching machine, which is a great solution: heating and circulation of the etchant is done by the machine (you'll find construction manuals in the internet). the etching machine is for etching the boards vertically, so it doesn't matter, if they're on- or doublesided...
not only the etchant is of interest, but the resist too. i got great results with press'n'peel blue. it's not good for very small tracks but for design like the ones ray does it should work, i think.

cheers,
matthias
http://www.modular.fonik.de/

ianbargle · Joined: Sep 20, 2006 Posts: 8 Location: california

I bought a liter bottle of liquid ferric chloride at a Fry's Electronics store here in Los Angeles. I've had the bottle for over a year now and it still works fine. I leave the board in my (PLASTIC!!!) container horizontally with the copper side facing up for about 30-40 minutes and I get pretty good results (that's how I etched the board I built my Sound Lab on). I fill a sink full of hot water and float the container in the water...swishing around the ferric chloride by tipping the container slightly. You can order single-sided copper clad boards (at various sizes) from http://allelectronics.com/. They also sell PRESS-N-PEEL film by Techniks that works really well if you're doing the toner transfer method from a laser printer. The only trouble with that stuff is getting all the black off when you're done etching (I ended up having to use a polishing tool with my Dremmel!). The instructions recommend using steel wool. There's a great site about the toner transfer method here:http://www.fullnet.com/u/tomg/gooteepc.htm

fonik · Posted: Sun Sep 24, 2006 11:23 pm Post subject:

or you may take a look at these photoessays:

press'n'peel blue
http://www.tonepad.com/photoessay.asp?photoEssayID=10&sequenceNo=1
using ferric chloride
http://www.tonepad.com/photoessay.asp?photoEssayID=11&sequenceNo=1

i remove the resistant from ready etched pcb using nail lacquer remover, works pretty fine with press'n'peel blue. then i sand the copper with very fine abrasive paper - this the pcb can be soldered like a charm.

cheers,
matthias