Making of the Jdog (J44 RC Dogfight system) PCB's:
After several attempts and plenty of learning by trial and error the best way I found (I make no claims to be an expert, so do not consider this a definitive guide) for making custom PCB's was:
Using Pre-Sensitised copper-clad board from Maplin (sensitised to UV).
Print off PCB layout (designed on KiCad) on OHP paper.
Double up layers of OHP printed PCB design. This prevents any scratches or marks on the design on one of the layers effecting the finished PCB.
Padded the inside of a CD case and used the CD case to hold the OHP paper and PCB in contact.
Exposed the PCB with a 4W LED array held about 0.4m away to give an even exposure.
An exposure of about 15 min seemed to work well.
Develop with Sodium hydroxide (1teaspoon NaOH in about 250ml of water), use a soft paint brush to brush off the developed mask. Mask developed very quickly (about 1-2 min).
Patch any breaks in the etch resist with an etch resist pen.
Etch the copper (with ferric chloride), use a sponge (dab more etchant on areas etching slowly) to ensure the PCB develops evenly. PCB took about 15min to etch (I suspect the etchant I was using was a bit old, may be a bit quicker with fresher etchant).
Clean PCB.
Note: Take care with the Sodium Hydroxide and the PCB etchant.
