The exposure is fairly critical, especially if your film doesn't have
very high contrast. You can use sunlight but it is very hit-and miss.
You need bright sunlight and a completely cloudless day. Your UV light
may work but exposure time may be quite long.
Either way you need to work out the exposure time. I use pre-sensitised
board but you can use the same technique if you use spray photo-resist.
Take a strip of board and use a knife to cut the plastic light proof
coating into about 5 - 10 strips. Peel off the first strip, place some
blank film over the board and expose for 1 minute. Peel off the next
strip and expose for a minute. Repeat for the rest of the strips. Now
develop the board. You should now be able to work out how much time is
needed to completely expose the resist. You want the minimum time to
completely expose the board.
If you are not used to the process now print one board to check you have
got the exposure right. Like anything it takes practise to get
everything right. By the way, is the £1.20 board paper or fibreglass? I
would recommend using fibreglass even if it is a bit more expensive. It
is a lot more rugged and the tracks are less likely to lift when you
solder it.
Les
Lez wrote:
> Ok I have had enough tonight of TT
>
>
> I need to get 10 little 2 inch ∗ 2 1/2 inch boards done. (only holds a
> pic and some transistors)
>
> I can buy the developer for £1.20, I can get a 8∗4 board for £1.20, so
> for £3.60 I can get everything, except a source of UV..........
>
> I have heard that outside in sunlight can work, any truth in this?
> anyone else do this?
>
> I have never done UV before, so have no idea on where to go with
> exposure times etc.
>
> I happen to have a 9w UV light on the garden pond to kill algae, can
> that be used (badly!)
>
>
>
>
>