To do this I used KiCad to turn my schematics into board files, then printed these files onto transparencies. Then these printouts are used with special copper clad boards and an ultra-violet light source to transfer the design to the copper. The material on the copper-clad boards gets sensitised by the UV light and then this sensitised material is washed away with caustic-soda and then the exposed copper is etched away with Ferric Chloride. A good step-by-step video is available here: http://www.youtube.com/watch?v=RfelrrZyCYQ
If you watch the video the only real piece of special equipment needed is the Ultra-violet lights. This is what has always put me off in the past. Making a light box and getting the tunes and ballasts and all the stuff needed just seemed like a lot of effort. An off the shelf small light-box costs around £200. However recently whilst looking for LEDs on the Farnell website I spotted some Ultra-violet 5W luxeons (order code 167-8962). These are still expensive £20 but a hell of a lot easier to work with. I decided to get one and give it a try, plus a bottle of etch-resist developer and some Ferric Chloride crystals.
When I got home eager to give it a go I just stuck the Luxeon Star to the inside of an old computer PSU carcass and put a 10R wirewound resistor in series with it. This hold the LED about 3 1/2" (8cm) above the workbench. I then cut out a transparency and fixed it to the PCB and exposed it...I had no idea how long to expose the board for I just put it under for about 6 minutes...
A transparency
The board under the lightsource
The finished board
I couldn't believe how well it all worked! The details all came out even though I'd not bothered to properly ensure the transparency was in close contact with the board. The exposure and develop times were complete guesses but lucky guesses!
For this my first go I rather ambitiously decided to make a double sided board, this didn't work out too well for two reasons. On my first attempt I'd managed to not line up the two sides - in fact one was completely the wrong way round....so this first though promising board was a write off.
I tried another, this time making sure I'd got the sides both the right way round and spending a lot of time lining the sides up very carefully.
Unfortunately this worked....but not very well. The tiny holes, though lined up closely (about 1/2mm out max) were still far enough out that when drilling they got chewed up. Also in Kicad I'd used the default "pad" sizes and these were really quite small...as soon as I stated drilling the through holes they started to tear up and generally be a pain.
So back to KiCad and this time I designed a single-sided board. This was far more difficult and required more thought, the automatic routing tools were not much use and more manual messing was needed but the results are better and allowed me to better lay things out anyway. Also I made all the pads a lot bigger for easier drilling and soldering.
The final board was then etched and gave a very nice result...see below.
The finished board after "tinning"
Board detail
There was only one problem with the board - one trace around the edge didn't come out. This was not so much due to the manufacturing process but I suspect down to the fact that the protective film had lifted at the edge. I had to "botch" this track with a bit of wire and solder for about 1/2"
Anyway I feel it has worked well and on a very small budget! Also there is an added advantage...most light-boxes use a number of tubes - this means that if the transparency is not in perfect contact with the board the lines all become very blurred. However because in this process the light is a point source this is not anything like as big a deal.
On this project the board is just 4"x4" (10x10cm) however for a larger board it should be possible to just lift the lightsource a bit higher above the bench, and increase the exposure time to compensate.
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