PC board making

Hi,

I struggled for a long time trying to make decent PC boards by all sorts of
different techniques but I now have the problems cracked. I can now make
good small boards every time.
What I do is draw the board out in Eagle, Corel draw or some other graphics
package and print out two copies onto clear overhead projector film (I use a
normal inkjet printer). One of the copies I print in reverse (just tell the
graphics prog to flip it) and I then tape these together with the printed
surfaces touching. This doubles the density of the print and seems almost as
good as a litho film for this purpose. I then use commercially coated, light
sensitive PC board from the local surplus electronics shop. I have found
that there are (at least) two distinct types of this board about and you
need to understand the type you have. The one I use is a fibreglass based
board which develops with Sodium Hydroxide. I sandwich the board and the
double 'negative' between a sheet of glass and a piece of wooden board and
expose it to the light from a 35mm projector for about 8 minutes. It then
gets developed in ordinary Caustic Soda drain cleaner, washed in water, and
etched in Ferric Chloride.
The board says you should use ultra-violet light for exposure but I have
found that, if you give it a strong enough blast of ordinary light from the
quartz halogen projector lamp, it works just as well. You could probably get
a similar effect using a car headlight lamp with a bit longer exposure. I
would always try a narrow 'test strip' cut from the edge of any new type of
board to verify timings first. HTH,

Ian
--
Ian W. Wright
Sheffield UK
www.iw63.freeserve.co.uk