Step 7: Create The PCB
I designed the PCB in Eagle CAD, but it's already done so you can just download the PDF and print it out. I've included 4 of them in the PCB if you want extras.
The method I used is the "toner transfer method". What you do is print the PCB design out on a laser printer. It MUST be a laser printer, inkjet printers use liquid ink that will not transfer like toner does. Then, cut the design out of the paper, leaving just a little white around it (just make it square, don't try to follow the lines). Clean the copper surface of a blank copper clad board, then lay the paper (printed side down) against the PCB. Notice that the printout is mirror imaged, this is on purpose as it will flip when transferred to the board.
Put the PCB blank side down against a heat resistant surface, with the paper face down on top of the copper. Then get a hot clothes iron and press it down against the paper. This will melt the toner, adhering it to the PCB. Put a fair amount of pressure down on it to make sure every bit of it melts. Lif the iron up, rotate it, and put it back down (don't drag it across the paper, you might smear the toner if it's hot). Keep changing the orientation to cover every bit of the paper with full heat. This may take a few tries to master the technique but it's an easy way to make nice boards on the cheap.
After heating, take the PCB and let it cool down (it will probably be too hot to pick up at first). After it's cool enough to carry, take it and submerge it in soapy warm water. VERY GENTLY start rubbing the back of the paper with your finger (not your fingernail, that will scratch the paper and could damage the transfer. After the water has soaked in a bit, you can start to gently pick apart the paper starting at the outside. You should be able to get at least the top layers of the paper to start to peel off without pulling up any of the toner. After most of the paper is gone, gently rub the paper with a bit of pressure to break up the paper fibers that still may have toner attached to them. Get as much of the paper as you can off without damaging the toner, you can etch around a bit of paper threads but once the toner is gone it is hard to fix.
If you mess up, you can use acetone (nail polish remover) to remove the toner and start over, you can also use a scouring pad to gently scrape it away, though a scouring pad may damage the copper layer if you use it too much. Keep trying until you get one that is perfect or very close. I had one pad fall off and a few minor breaks in mine. I touched them up with a Sharpie marker but the etchant still ate through it.
After you've got your board ready, cut the part of the board you want out of any board you want to keep unused with a dremel. Then take the board that you want to etch and stick it in some etchant solution (I used ferric chloride, but there are many things that will dissolve copper).
Wear rubber gloves when doing this, it will keep your hands from turning weird colors and staining things, also do this over some newspaper and I would recommend doing it in the garage or unfinished basement so you don't stain carpet or nice floors.
After etching, there should be no copper visible but under the black toner. This means it's ready, take the board out and then use acetone (nail polish remover) to get rid of the black toner and expose the copper. Now you're ready to solder, assuming there are no major missing parts (a little break isn't a big problem, you can bridge it with solder, a missing pad is harder to fix, but mine was close enough to the trace that it bridged easily.
After you get the toner off, use a tiny drill bit and a drill press to drill the holes. I used a cheap $15 drill with a "drill stand", a holder that makes a cheap drill into a cheap drill press. I used some tiny drill bits that were for model railroading to drill the tiny holes. There are a lot of holes to drill, don't miss any, and drill starting at the copper side because it's easy to line up the hole right where it's marked on the board. Take your time and it shouldn't be a problem.
After drilling the holes, go over the board and look for any spots where the copper didn't dissolve between two traces. There were a few spots that I had to cut out with a knife, one was the SCK line shorted with the AVCC and wouldn't program but works great after I scraped out the tiny flake of copper bridging the traces.
The method I used is the "toner transfer method". What you do is print the PCB design out on a laser printer. It MUST be a laser printer, inkjet printers use liquid ink that will not transfer like toner does. Then, cut the design out of the paper, leaving just a little white around it (just make it square, don't try to follow the lines). Clean the copper surface of a blank copper clad board, then lay the paper (printed side down) against the PCB. Notice that the printout is mirror imaged, this is on purpose as it will flip when transferred to the board.
Put the PCB blank side down against a heat resistant surface, with the paper face down on top of the copper. Then get a hot clothes iron and press it down against the paper. This will melt the toner, adhering it to the PCB. Put a fair amount of pressure down on it to make sure every bit of it melts. Lif the iron up, rotate it, and put it back down (don't drag it across the paper, you might smear the toner if it's hot). Keep changing the orientation to cover every bit of the paper with full heat. This may take a few tries to master the technique but it's an easy way to make nice boards on the cheap.
After heating, take the PCB and let it cool down (it will probably be too hot to pick up at first). After it's cool enough to carry, take it and submerge it in soapy warm water. VERY GENTLY start rubbing the back of the paper with your finger (not your fingernail, that will scratch the paper and could damage the transfer. After the water has soaked in a bit, you can start to gently pick apart the paper starting at the outside. You should be able to get at least the top layers of the paper to start to peel off without pulling up any of the toner. After most of the paper is gone, gently rub the paper with a bit of pressure to break up the paper fibers that still may have toner attached to them. Get as much of the paper as you can off without damaging the toner, you can etch around a bit of paper threads but once the toner is gone it is hard to fix.
If you mess up, you can use acetone (nail polish remover) to remove the toner and start over, you can also use a scouring pad to gently scrape it away, though a scouring pad may damage the copper layer if you use it too much. Keep trying until you get one that is perfect or very close. I had one pad fall off and a few minor breaks in mine. I touched them up with a Sharpie marker but the etchant still ate through it.
After you've got your board ready, cut the part of the board you want out of any board you want to keep unused with a dremel. Then take the board that you want to etch and stick it in some etchant solution (I used ferric chloride, but there are many things that will dissolve copper).
Wear rubber gloves when doing this, it will keep your hands from turning weird colors and staining things, also do this over some newspaper and I would recommend doing it in the garage or unfinished basement so you don't stain carpet or nice floors.
After etching, there should be no copper visible but under the black toner. This means it's ready, take the board out and then use acetone (nail polish remover) to get rid of the black toner and expose the copper. Now you're ready to solder, assuming there are no major missing parts (a little break isn't a big problem, you can bridge it with solder, a missing pad is harder to fix, but mine was close enough to the trace that it bridged easily.
After you get the toner off, use a tiny drill bit and a drill press to drill the holes. I used a cheap $15 drill with a "drill stand", a holder that makes a cheap drill into a cheap drill press. I used some tiny drill bits that were for model railroading to drill the tiny holes. There are a lot of holes to drill, don't miss any, and drill starting at the copper side because it's easy to line up the hole right where it's marked on the board. Take your time and it shouldn't be a problem.
After drilling the holes, go over the board and look for any spots where the copper didn't dissolve between two traces. There were a few spots that I had to cut out with a knife, one was the SCK line shorted with the AVCC and wouldn't program but works great after I scraped out the tiny flake of copper bridging the traces.
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Shadyman says:
Mar 3, 2010. 10:14 AMReply
You can fix breaks in the toner transfer by using a sharpie. The sharpie marks won't dissolve in the acid, and can be removed later with isopropyl alcohol. :)
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