More electronics


Making PCBs: Seven Easy Steps.

1: Draw! I use CorelDraw with a grid set to 0.1" and some predefined shapes. This gives me enough flexibility to design small PCBs. There are plenty specialised design packages around though. Draw the layout as seen from the component side if you are using leaded components.
2: Print! I use a HP Laserjet 4 at 600 dpi (more than enough for most designs) to print on talc, the semi-transparent paper used for technical drawings. It does reduce the contrast a bit compared to overhead sheets, but the toner sticks better (giving blacker lines) and it is a lot cheaper.
3: Expose! I use a makeshift apparatus built of wood and containing 4 UV TLs at about 10" away from a thick glass plate. Always use glass (it's flat and stays that way) and keep it clean. Put the talc with your design toner-up on the glass plate. The off-the-shelf PCB material with its photo sensitive layer goes on top of that. Use a weight (I use a disk from a dumb-bell) to make sure everything is steady and flat. Fry for about 5 minutes. The time that yields best results differs from set-up to set-up; use trial-and-error. Don't look into the light!
4: Develop! I use straight NaOH. The more environmentally-friendly developers don't seem to work as well. Be careful with NaOH, it's quite nasty. Don't leave the PCB in too long, a few dips is usually enough. Rinse between dips to remove the rests of the photo sensitive layer in the places you don't want it, it tends to stick a bit.
5: Etch! I use iron-III-chloride with a dash of chloric acid in a bowl I wouldn't prepare food in anyway. The stuff gives nice brown stains on almost everything that are almost impossible to remove; don't spill it. There are many recipes around for etching liquid, so many I wouldn't be surprised onion soup would do. By all means, try your own! Move the PCB around from time to time and be patient. Special etching machines are a lot faster!
6: Drill! I use a small model-makers drill you could probably buy at Radio S. Go for the drill bits with the thick shaft, they are steadier.
7: Cut! I use a strong, sharp knife to give a first cut and then break the PCB on the edge of a table. Very thin PCBs (0.5 - 1mm) can be cut with a good pair of scissors.


This page was created by Oscar den Uijl, oscar@den-uijl.nl