Bob Blick <bobblick <at> ftml.net> writes:

> > 2) Bind sheet face down (and flat) to presensitized board. Cover with
> > real
> > glass as it is transparent to UV. Do this in a low light environment.
>=20
> I've used glass and plexiglass and not noticed a difference. I thought
> glass blocked more UV than plastic?

Both glass and some plastics absorb UV, but at the thickness tipically used=
 (~1
mm for glass) the absorbance is not too high.  More important is that the g=
lass
is "optical quality", without swirls. =20


>=20
> I have had problems peeling it off afterward. The toner sticks a little
> bit.
>=20
> > 3) Expose assembly to UV light. Sunlight will work but a UV light box i=
s
> > better. Mine is a black light installed in a toolbox. Never got a clear
> > number on exposure time. Seems to be trail and error but consistent onc=
e
> > you get it to work.

I used a fluorescent lamp at 15-20 cm from the board/mask/glass stack.  It =
was
while ago, but IIRC 75W lamp is OK.  Some even reported the use of 100W
incandescent lamp.  It might not work with all sensitized boards, I got min=
e
from Jameco, the brand is DATAK I believe.


> > 6) Remove the rest of the photoresist. A bit unclear here. Is this a
> > light
> > and develop a second time step? Or a physical process

I scrubbed with a scrubber/foam pad sold for kitchen cleaning. As last step=
,
200-400 grit sandpaper and water rinse.  I used purified water for final ri=
nse
since tap water often has too many minerals in it (actually I have never te=
sted
if just tap water is OK, seems easier to just rinse in distilled water any =
way).=20

Sergey Dryga
http://beaglerobotics.com




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