Note 1… I have moved to using an UV box built from an insect killer lamp. It works great. The UV light from the LEDs was uneven, and created problems on larger boards. The UV insect killer light is cheap and works really well. I basically ripped apart the standard insect killer box, put a piece of glass on one side and that’s it. Well, I also put a bendable plastic mirror (meant for mending broken side-mirrors for cars) under the two lamps, so that I got even better reflection, but not sure if that makes a difference. I put the PCP on the glass, cover it with a black rubber sheet and turn on the UV lamp for 1 minute 45 seconds. It exposes the boards very consistently. Anyway… read on if you wish.
Note2: I have now started using an applicator as a developer instead of the NaOH based solution. The Applicator is from MegaElectronics. It is a bit difficult to time exactly how long it should be applied, but when using the PCBs from the same website, which have a coloured resist, it’s easy to see the pattern emerge. I’m still testing, but it does seem to give more consistent and better quality boards, in addition to being very easy to use (but remember gloves anyway… it’ll burn through the really thin plastic gloves and burn your finger).
Update 3: I typically order my professional boards now from Seeedstudio. So I use my own equipment to make test-boards, but use SeeedStudio for larger batches.
I really wanted to make my own PCBs. It’s a bit irrational I guess, since prototype cards work pretty well for my kind of requirements, but I want to start soldering surface mount, and that means I have to make my own PCBs.
Some years ago I bought a kit on RadioShack for making PCBs with a pen and an etchant (FeCl). I tried it, using Eagle to draw the schematics first. Not quite satisfactory. I had to do better! A picture before and after etching:
Then I found lots of useful sites on building an own UV box using LEDs. Sites like:http://hackedgadgets.com/2006/10/31/uv-led-pcb-exposure-system/
So I bought 25 LEDs from Ultraleds.co.uk at £0.38 each!
And I built the box below.
I put three LEDs together with a resistor, and I’m running it with my voltage regulator at 12V. It works sooooooooo well. I expose the PCB with resist-film for about 90 seconds, drop it into NaOH (bought specifically for this) and use the FeCl from the RadioShack kit. This is the result. On the left there is a bad board where I forgot to put the printed side next to the PCB. You can see the lines aren’t as ‘in focus’ as the other two. It also hasn’t been etched enough. The middle one is the best. I wrote some text in Eagle and put it on with really small fonts, and you can see it on the bottom. It’s something like .1 mm thick and it appears perfectly!
I’m super happy. Now I can make my own boards! The only problem is that the solder doesn’t flow very well onto it, so I’m buying some flux liquid to see if that helps.