Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

I've started fiddeling around with photoresist spray and developing it
using caustic soda, and have a few questions as the board is still not
coming out 100%


1) How thick should the photo resist be sprayed on. After I've sprayed
it on and its dried you can clearly see the purple film - there's no
gaps.

2) After you put the board in CS - how do you know when to take it
out? I can see the tracks clearly but the pcb is still have a layer of
the purple stuff on it. Should the purple film vanish completly
(except for on the tracks)

3) Which is a better etchent to use - Ferric Chloride (mine works
really slowly even when heated up - like 30-40mins) or Hydrochloric
Acid+Hydrogen Peroxide

I've done another board (etched) and the top half of it is perfect -
nice clear tracks. But on the bottom half none of it is etched. If I
leave it in too long it starts to eat away the tracks, but still
doesnt touch the bottom section? Does this sound like too thick spray?