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Whats a good etch resist pen for making pcbs?

post #1 of 17
Thread Starter 
I've tried sharpie and various other brands but none gives me the results that I want (especially thin traces). I've tried layering lines with the sharpie but hazing/spotting still occurs after etching. Small letters are non-existant and ends up to be little specks. I use a small glass dish with a lightbulb to heat the solution before dropping in the board. Do those pre-sensitized boards with/or the laser toner transfer method give a much cleaner result?
post #2 of 17
I've used various paints and a good artist's brush
with perfect results. Have you tried
the laser printer/transfer method?
This is best, I think.

I've always mixed 1 part boiling water and
three parts warm (room temp) etching solution (FeCl). Works nicely; etching time of
five to ten minutes.
post #3 of 17
Thread Starter 
You mix boiling water to the chloride? I was told that water will neutralize the effects of the solution.

edit: what kind of paint did you use?
post #4 of 17
Of course, the fecl becomes weaker, but the ratio I
mentioned still works well.
At the time, it just seemed to be the simplest thing
to do...

I used latex based paints. Hard to
clean off if you let it completely dry.
It sticks to copper well, and you get
nice, thick (heightwise) traces
post #5 of 17
Thread Starter 
Thanks Arzela.
post #6 of 17
ive used a double ended sharpie before, but the results were only OK... nothing great... better for touching up.

if you have access to it, i like using letraset rub ons for it as well.. you can get some nice fine traces, and perfectly strait lines...
post #7 of 17
If you go to a place that sell's art and drafting supplies, the special pens they sell are said to be better than Sharpies. Sharpies are only useful when you need the ability to use alcohol to erase something. You might use the Sharpie to do the basic layout, and then trace over it with something better.

I don't recommend diluting the etching solution, because you can reuse it. The only reason to dilute it is if you dump it down the drain after each use, and there's no good reason to do that.

The toner transfer method is very tricky to get right if you use a regular iron. You either end up smudging the toner, or it doesn't stick properly so it peels up off the board. They'll sell you a $300 lamination machine that gives you the proper temperature, heating time and pressure, but for that much money you can get a high-end photo etching setup complete with a heated etching tank with aggitator and a UV exposure lamp. I just started doing photo etching and I love it. It's the only way to fly, IMHO.

I recommend getting your supplies at Circuit Specialists. Their prices are lower than anyone's, and I especially like the fact that they have multiple brands of supplies, so you can choose what you like. Most other places stick with just one brand (usually MG Chemicals). I bought the $40 thin etching tank. It uses less etchant than other setups, and it's a lot chaeper than the MG etching tank. I did get the MG exposure lamp kit, though...that's worthwhile if you want fast (10 min.) exposures.
post #8 of 17
I'd think that Michron pens (fine artist's pens) would do the job well (you can get them in sizes down to at least .5mm, if not smaller)
post #9 of 17
nail polish.
post #10 of 17
If I need to dash off a quick prototype board, I use the tried-n-true Sharpie brand permanent marker pens by Sanford (black, of course). I have found that two steps are necessary to ensure excellent results with the Sharpie pen:

1. Clean the bare copper board with brass wool and wipe with alcohol before writing the layout.

2. After laying out the board, bake it in a toaster oven for just long enough to get it... well, toasty. Seriously, I run the toaster long enough for the top elements to turn a dull red then let the board cook for a minute. This hardens the ink more thoroughly and faster than waiting for it to air dry.

Sodium persulfate solution is my favorite etchant, btw, because it is clear, doesn't produce any noxious fumes when hot and working, and the byproducts (sodium sulfate and copper sulfate) are less environmentally hazardous than ferric chloride.
post #11 of 17
Thread Starter 
Very nice to know all of of this. The only things I found on the net were basic instructions for ferric chloride. I think I'll tinker with the cheaper solutions and move on if the results doesn't satisfy me. Thanks everyone.
post #12 of 17
Another alternative if your just doing one or two boards, is to get a starter kit. The local elctronics place in Toronto sells a photo etch kit, with everything you need but etching solution. comes with two boards, developer, pen, rub on pads.... costs about 20 bucks canadian
post #13 of 17
The main problem with the persulphates is that they degrade over time. If you make only a few boards a year, it'll get pretty expensive to keep replacing your supply. You're supposed to use it all up in a matter of months according to what I've read.
post #14 of 17
Quote:
Originally posted by tangent
The main problem with the persulphates is that they degrade over time. If you make only a few boards a year, it'll get pretty expensive to keep replacing your supply. You're supposed to use it all up in a matter of months according to what I've read.
This is quite true for the solution, but in powder form the persulfates have an indefinite shelf-life.
post #15 of 17
I have gotten into PCB etching and my opinion is:

The marker method and the toner transfer method do not yield perfect results.

The photo etching method with pre sensitized boards is the best I know and yields great results.

You will need 7-10 gramms of NaOH dilluted 1 liter of water. This is the developer.

You will need a FeCl3 solution (about 0,5Kg of solid FeCl3 for a liter of water though you dont need 1 liter of it, much less) or buy it ready made from your local shop. This is the etchant.

The exposure :
You print out on the best quality of your inkjet on a transparency the design of the pcb. You take the pre sensitized board out of the bag and take off the protective sticker of the surface. You quickly put the transparency (theres no need to hurry too much its not that sensitive. But dont take too long.) on the board surface and turn the lamp on and wait for 10 minutes. The same can be done using the sun. But you have to be quicker.
You can use almost any strong lamp to expose it around 10 minutes (I did 12 miunutes with a 125W light bulb) or use the sun for ten minutes.

The developing:
Just place the board in some of the developer solution and agitate until you will be able to see a crisp and clear image of your circuit. Then take it out wash and wash it well.

The etching:
Place the board in the etchant solution and have the container you will use to etch the board in , in a larger container that you will be refilling with hot almost boiling water everytime it cools. Then you will be seing the copper be removed sooner or later . Just keep agitating and keep the water on the larger container warm so that the FeCl3 is warm too and works. Then you will see that all you have left is copper only where you want. (Where the transparency was black and the light couldnt pass through)

Then wash the board and expose it again to light for like ten minutes. Put it back in the developer for a few minutes (so that the protective layer is off your copper traces for good)) and wash it again . You are ready and you have a perfect pcb.

Its not very difficult and the results are as good as it gets at home. Try it.

Use other people's experience to save time and be able to go beyond them.
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