Contents 1 Materials 2 Preparing the circuit 2.1 Creating the artwork 2.2 Trace Width 2.3 Pads 2.4 Orientation 2.5 Ground 3 Printing the circuit 4 Clean the Copper 5 Transfering the toner 5.1 Paper Residue 5.2 Pro Tip 6 Etching 6.1 The Paper Resudue Solution 6.2 Finishing the etch 7 Drilling

Materials

Equipment

• Goggles
• Mask
• Gloves
• Cloths Iron
• Scotch-brite pads
• Laser Printer
• Some plastic dishes

Consumables

• Copper clad PCB
• Staples 'photo basic gloss' paper, SKU 471861
• Muriatic Acid (Available in gallon+ jugs at home center)
• Hydrogen Peroxide, first aid concentration (Available at CVS, Sol's)
• Acetone (Available at home center)
• Baking soda
• Water

Preparing the circuit

Creating the artwork

You can use any graphics layout or PCB layout software you want, provided you can print the circuit out. I use Inkscape, but there must be something better. You will want the copper areas to be black, as you will be etching away any copper not covered by the toner.

Trace Width

Over-etching is more common than under-etching, so I make densely packed traces as wide as I can, with only a little space in between. It is a lot easier to clear away extra copper than to magic in missing copper.

Pads

Make them as big as you can. Etch out holes in the middle to guide the drill bit later on. The holes in the pads are VERY important if you are drilling by hand (even with a drill press).

Orientation

Viewed from the copper side the traces will mirror image your print out. If you are using through-hole components it is easiest to design the circuit from the component side, as if you were looking at the chips and using x-ray vision to see the copper. The artwork you prepare will be right-way-round if you think like this. If you are doind surface mount stuff you will again be working from the component side and making your artwork right-way-round. You will then mirror it before you print it out.

If you are mixing surface mount and through hole... Be smart.

Ground

When I started I would have ground traces snaking everywhere. Now I just leave all the free space on the board un-etched and ground it. It is a lot easier to forget the ground traces. Just make sure the ground is contiguous when you are done. This also means there is less copper to etch away which makes that step faster. Soldering to it can be a little messier.

Printing the circuit

First print it out on regular paper, and lay your components on it, to make sure everything fits. Once you are happy print on the shiny side of the photo paper. It may take a few tries to get the paper right side up from the manual feed tray of your printer.

Print as many copies as you can fit on a single sheet; it might take a few to get the transfer right. Leave yourself at least half an inch, if not a couple inches, of free space around each copy.

Clean the Copper

Clean the copper with acetone and the scotch-brite pad. You don't want any oxide or finger prints or oils or grime at all. I use Brasso on very dirty coper.

Transfering the toner

Heat the iron up to 11.

Iron on a nice flat heat resistant surface. Place the printout toner side down against the copper. If the board fits under the iron I just leave it there for 5 min heating. Work over the board with the iron pressing good and hard, paying attention to get the edges well too. By the end of the transfer the paper should be stuck to the board, and the board will be too hot to pick up. Don't burn yourself.

Place the board and paper in a dish of water. Let it sit for maybe 10 minutes and then peel off starting at one corner. You'll want to fold the corner entirely over flat and then peel at a very acute angle, so you are not pulling UP. Chances are the paper will eventually give out and you'll want to repeat this from the opposite corner. While you want to get all of the tough backing off you are OK leaving on some thin paper residue.

Paper Residue

Most similar instructions will tell you to use a toothbrush and scotch-brite to scrub all of the paper away. I find that this will damage your finer traces and it will take 2 or 3 tries to get a good, undamaged transfer. Leave it on and learn the trick in the next section!

Pro Tip

Get your own iron, you will ruin it sooner or later. Do not use your Roommate's, girlfriend's or wife's.

Etching

Put on your mask and gloves.

The etchant I use is 2 parts hydrogen peroxide, just the first-aid concentration from CVS or wherever, to one part muriatic acid. If you don't know which to pour first you probably shouldn't do this. The answer is to pour the acid into the peroxide so you don't get hurt bad. This etchant is not good on metal things, you can use a glass or plastic dish. I use the disposable plastic Tupperware type things. The dish should be deep so you don't splash.

The Paper Resudue Solution

Add the peroxide to the etch dish and put your PCB, paper residue and all, in there. Leave it for half an hour. Go watch TV or something. I don't think you can leave it like this too long, I have never gone over 30 minutes.

After the peroxide soak pour the acid into the dish and agitate. The paper will float right off and the copper will begin to disappear. I rub the PCB with a cotton swab (gloved hand!) to make sure to brush away any remaining paper.

Finishing the etch

Gently agitate. The etchant will turn from clear to clear green as it eats copper. Maybe it should take 5 minutes. If it is taking forever and very green you may need new etchant. I haven't worked up how much copper it can eat yet.

When it is done take the board out and pop it into a dish of water with some baking soda in it to neutralize the acid. Dry it and clean the toner off with acetone.

Drilling

I use little bits from the hobby store (Dan's Crafts & Things in ROC) in my dremel. Chuck them so there is a quarter inch of bit poking out or you will break them. Put the board on a few sheets of cardboard to drill through into. Have at it.

After drilling a few holes your hand will be tired from holding the thing. You could get a mini drill press, or a dremel drill press attachment. If you are cheap like me get a bungee cord and hang the dremel from it with the tip of the bit just a couple mm above the pcb. Now you can hold it lightly with two fingers and drill a few holes at a time between repositioning the board.