PCB Etching (again!) - chemicals used

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

- chemicals used', on Sun, 24 Apr 2005:

If you could please give the volume of water you use in the tank as well, we could work out the concentration, which would be valid for other tanks.

I think I paid 7 euro for 1 liter. Seems expensive, but you'll only need a little every time.

Tough question. If the exposure time is right, you can cut some corners with the developer and vice versa. I think you can leave it in the developer for a longer time. I recall I tried to strip the resist after etching using the developer used to develop the PCB again. This didn't seem to work, nowadays I expose the etched PCB and develop it again to strip the resist (beats sanding, alcohol or acetone by miles).

If you mix your own developer, you can make a stronger developer solution (with hot water) which will strip the resist without exposing it to UV. I discovered this trick when I was working as a stagiaire at a hospital. Again, this shows the strength and temperature of the developer is quite critical.

I bought a "Top Fin" 150watt heater at PetsMart for about $12.00. The normal full on is about 95F but if you pull up on the knob you can get past the stop and the next full turn will bring it up to 120F. The 150 watt size also goes deeper into the tank than the 100 watt heater that comes with the tank so you can get the whole tank up to working temps before turning on the air.

-- Glenn Ashmore

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

The ratio is 250 grams to the liter. It takes 2 liters to fill the tank so a 1Kg container will make two batches. In my experience AP is a lot better than Feric Chloride. Beside much less mess, at about 120F with the bubbler running it will etch a 2oz board in 14-16 minutes.

I am about to put it to the ultimate test. The current batch of AP has been in the tank for a month and etched about 400 sq. in. of 1 oz and 100 sq.in of 2oz board. Tonight I am etching a two sided 2 oz panel with 24 1x2" boards for my solid state light switches. I will time it and report back.

The

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on the

Ahh, ok -- but that's only about 50 degrees celsius, right? I'm looking at something like 80 degrees, which I assumed most aquarium stuff wouldn't get anywhere near. :-)

Anyway, I've now got 2 of the Kinsten heaters -- putting one each side should do a good job, I think.

tank so

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bubbler

has been

sq.in

back.

Hrm - and you just leave the etchant in the tank, right? doesn't go off at all, or affect the tank (such as blocking the air holes at the bottom)?

Thanks!

Michael

....

as far as google can tell me, it's some sort of cooking thing - heating something in water... do youm mean that fish tanks are heated with, er... ok, I'm lost. :-)

suggestions? :-P

Cheers, Michael

not be

Hrm, that's weird -- the bottle of AP crystals I have recommends a temperature of about 75-80ºC for etching -- it's from dick smith's in Australia.

Damn, and I've already ordered the two heaters, as well... oh well, at least I know for future, now. :-)

Cheers! Michael

caps

microscope it

Ooh, do you have a fancy magnifying setup? :-) My SMD soldering assitance extends to a dodgy pair of magnifying goggles:

and a sharpened soldering iron tip. :-)

Cheers! Michael

No,no,no. AP works best around 35-37C. Even feric chloride should not be heated above about 55C.

-- Glenn Ashmore

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

"Michael" wrote in >

So far so good. I just leave it in the tank. I do remove the heater and put my homemade cover on top. It turns blue with use and there is a very slight precipitate but unless you are making a whole lot of boards I don't think it will be a problem.

I see no sign of it loosing potency. My solutionhas been in the tank for over a month and last night I etched a 60 sq. in. double sided 2 oz board at

Now I need to lay off the coffee today so I can place all these 0805 caps tonight. I thought I had a pretty steady hand but under the microscope it looks like I have Parkinsons. :-(

Has anyone tried citric acid for the stain cleanup?

I read in sci.electronics.design that Michael wrote (in ) about 'PCB Etching (again!) - chemicals used', on Mon, 25 Apr 2005:

No. Think 'bain marie'!

Many years ago, I bought a largish qty, may have been 20Kg, of FeCl from a Dairy supply house, diary farmers used to use it to clean stainless steel vats. I don't know if it's still used for this, but as I had to buy such a large qty as a minimum, and it was very cheap, I just finished the last of that a couple of years ago. So, it may be worth asking around in these circles.

Anyway, they supplied it to me in a metal tin, but the FeCl was in a heavy-duty plastic bag inside.

When mixed ready to use, I stored it in a plastic 1/2 gal jar, I understand it's made from PET.

I read in sci.electronics.design that "Aubrey McIntosh, Ph.D." wrote (in ) about 'PCB Etching (again!) - chemicals used', on Mon, 25 Apr 2005:

It doesn't work very well. Oxalic is better.

I read in sci.electronics.design that Michael wrote (in ) about 'PCB Etching (again!) - chemicals used', on Mon, 25 Apr 2005:

If your aquarium tank reached 80 C or whatever it was, you would have poached fish. A bain marie is like a double saucepan in action, but not in shape, with water in the lower part, for heating things very gently.

I read in sci.electronics.design that Michael wrote (in ) about 'PCB Etching (again!) - chemicals used', on Mon, 25 Apr 2005:

Typical room temperature in Oz!

Citric acid is not a reducing agent, so it won't have much effect on many dyes, but acid-labile ones will fade. Also, bear in mind that the iron will combine chemically with the fabric itself, in some cases, acting as a self-mordanting orange dye. Even chlorine bleaches won't shift that.

But does it leave the colouring of the fabric alone or does it make a white spot instead of a orangish one?