This is currently a rough guide to the equipment we have for DIY PCB etching and how to use it.
Print your design mirrored on to tracing paper. The printer in the main room works well, select 600dpi, disable any toner saving options and use the manual feed.
Place the printed design toner side up in the UV exposure box, peel off the protective cover from the PCB laminate and place it copper side down over your design.
Close the box and expose for ~2.5 minutes. After exposure the design may be visible on the PCB but can be very hard to see.
This step removes any photoresist that has been exposed to UV light in the previous step.
Immerse the PCB in a solution of the developer crystals (mixed according to the instructions). The design should show up clearly within a few seconds. Agitate for about a minute then remove the PCB and rinse with plenty of water.
Plug in and turn on the etch tank, give it some time to warm up.
Put your PCB in it, it takes somewhere around 12 minutes to etch. It's finished when all the unwanted copper is gone. If left too long then you'll start getting rough edges and/or breaks in small tracks.
After a short dip in the etchant, all copper to be removed should turn a dull pink. If not, the PCB is either under-exposed or under-developed. You can try rinsing the PCB with plenty of water and returning to the develop step for 10-20 seconds, before continuing with etching.
Once etched, remove the board and rinse with lots of water before touching the board.
This step removes the rest of the photoresist from the board. Apply a few drops of methylated spirit to the board and allow it to coat it, wait a few seconds, rinse (or rub gently).