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Sketched and etched
Posted by Chris
on
Sunday, April 12, 2009
It took four attempts and lots of cleaning and scrubbing of the copper board (after each one failed) and I managed to ruin a wooden cutting board, using it as a heat proof mat (d'oh!) but finally here it is: one complete (almost) etched PCB board.
It's a bit ropey on some of the traces, and some of the pads do look very close together, but all in all, a success! Mostly.
A couple of tracks broke before I got to the etching stage but I figured that they could be patched up with some silver paint. On the very left-hand edge and right-hand edges of the board you can see a couple of tracks that are incomplete: this is probably due to not putting enough pressure on the board at the edges while transferring the image onto the copper board.
By far the most difficult part was transferring the PCB image onto the copper.
It took a few attempts trying to work out which way around (mirrored or not) the image needed to be - in the end I printed the PCB layout without flipping it. The process of transferring it onto the copper resulted in a mirrored layout. But considering that the components will be mounted onto the top (i.e. non-track) side of the board, this worked out just right. So if you're trying this at home, there's no need to mirror your PCB layout (if you're mounting your components onto the same side as the tracks, then you do need to mirror the PCB image before printing it).
The PCB layout was printed onto single-sided Kodak Photo paper on a Xerox Phaser Laser printer. After printing, I split the photo paper, removing the thick "backing" from the shiny part of the paper. For the first few tries, I ironed the image onto the board, pressing and moving for about ten minutes. After allowing to cool, I peeled the image off and the tracks around each edge of the board came away too. I also tried baking the board in a hot oven for ten minutes (with a stone quiche dish to add pressure during "cooking") after ironing, but had the same problem when it came to peeling the paper away.
On the fourth (and already I'd decided last) attempt I spent a good fifteen minutes applying pressure with the iron. I then moved the iron around, and then smoothed over the entire surface using just the very tip of the iron. The paper looked scorched and the tracks started showing through. I soaked the whole lot in cold water and left for half an hour, before rubbing and peeling the paper away from the copper.
Even so, at this point, a couple of tracks broke away (they obivously hadn't fused properly onto the copper) and I had to use a craft knife to remove some of the more stubborn bits of paper.
The etching solution from Maplin was a white powder which dissolved in warm water. Unlike other corrosives, which appear brown and stain everything yellow, this was clear and after the copper board was put into it, started to turn blue.
It took about 15-20 minutes for all the copper to be completely removed from the board, then I left it a little longer, as I had some quite fiddly bits and I wanted to be sure that all the unwanted copper was removed.
The moment of truth came when the board was rinsed then rubbed with a light sanding block, to remove the black toner (and leftover bits of paper). The end result - as you can see above - was not exactly perfect, but with a bit of work, should prove a suitable board for my next project.
It's a bit ropey on some of the traces, and some of the pads do look very close together, but all in all, a success! Mostly.
A couple of tracks broke before I got to the etching stage but I figured that they could be patched up with some silver paint. On the very left-hand edge and right-hand edges of the board you can see a couple of tracks that are incomplete: this is probably due to not putting enough pressure on the board at the edges while transferring the image onto the copper board.
By far the most difficult part was transferring the PCB image onto the copper.
It took a few attempts trying to work out which way around (mirrored or not) the image needed to be - in the end I printed the PCB layout without flipping it. The process of transferring it onto the copper resulted in a mirrored layout. But considering that the components will be mounted onto the top (i.e. non-track) side of the board, this worked out just right. So if you're trying this at home, there's no need to mirror your PCB layout (if you're mounting your components onto the same side as the tracks, then you do need to mirror the PCB image before printing it).
The PCB layout was printed onto single-sided Kodak Photo paper on a Xerox Phaser Laser printer. After printing, I split the photo paper, removing the thick "backing" from the shiny part of the paper. For the first few tries, I ironed the image onto the board, pressing and moving for about ten minutes. After allowing to cool, I peeled the image off and the tracks around each edge of the board came away too. I also tried baking the board in a hot oven for ten minutes (with a stone quiche dish to add pressure during "cooking") after ironing, but had the same problem when it came to peeling the paper away.
On the fourth (and already I'd decided last) attempt I spent a good fifteen minutes applying pressure with the iron. I then moved the iron around, and then smoothed over the entire surface using just the very tip of the iron. The paper looked scorched and the tracks started showing through. I soaked the whole lot in cold water and left for half an hour, before rubbing and peeling the paper away from the copper.
Even so, at this point, a couple of tracks broke away (they obivously hadn't fused properly onto the copper) and I had to use a craft knife to remove some of the more stubborn bits of paper.
The etching solution from Maplin was a white powder which dissolved in warm water. Unlike other corrosives, which appear brown and stain everything yellow, this was clear and after the copper board was put into it, started to turn blue.
It took about 15-20 minutes for all the copper to be completely removed from the board, then I left it a little longer, as I had some quite fiddly bits and I wanted to be sure that all the unwanted copper was removed.
The moment of truth came when the board was rinsed then rubbed with a light sanding block, to remove the black toner (and leftover bits of paper). The end result - as you can see above - was not exactly perfect, but with a bit of work, should prove a suitable board for my next project.
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