Hello bjeff65,
18. May 2003, 21:01:39, you wrote:
(my comments mixed)
b> So I've decided to put it in the form of a question:
b> If you needed to put together a positive photoresist exposure setup
b> for small PCBs (no bigger than 4" x 6") and your only option are from
b> the typical home improvement store/department (think Home Depot,
b> Lowe's, Walmart, etc.)
b> what would you choose and why?
b> To assist in your answer I'll list some of the options that I've seen:
b> ∗ Standard incandecents
I do not recommend.
b> ∗ Standard/Daylight flourescents.
I do not recommend.
b> ∗ Black light incandecents
b> ∗ Black light flourescents
These may work.
b> ∗ Plant grow light incandecents/flourescents
Never tried.
b> ∗ Halogen
b> ∗ Floods of all types.
b> ∗ Compact flourescents
b> ∗ Germicidal flourescents (not really an option, but interested in
b> comments)
Never use them if you are not wearing protective googles that absorb UV-C
spectrum
I can not remember at the moment for the good link discusing the spectral
sensitivity of the photo resists, but all the informations that I've read
are stating that the max. sensitivity is around 340 nm, or UV-A part of
spectrum (under which you can get some tan without the burns caused by
UV-B). UV-C, from germicidal lamps, can cause the irrecoverable damage to
your eyes, so stay as far as possible from them (unless you need to erase
some UV-EPROMS).
My typical setup is as follows:
∗ Two fluorescent UV lamps (Philips) that are declared to have the peak
radiation value around 340 nm, placed in the wooden box, cca 11 cm
apart, with homebrew reflectors.
∗ Exposure time (determined with the 21 step Stoufer wedge) from 20 cm
distance: 5 min.
∗ I'm always using presensitized (spelling?) boards that I'm obtaining
in the local electronic shop.
∗ Developer: 7-10 gm/l Lye in pelets.
∗ Developing time cca. 2 min.
∗ Etchant: Fe3Cl solution
∗ Developing tank: homebrew one (similar to the Techno-Isel) vertical
with heater and air bubbler (porous teflon tube, often used for fish
tanks - made in Taiwan)
∗ Etching time cca. 10-15 minutes
For typical design for exposing unit, best is to visit:
www.thinktink.com , but my exposing unit is without colimating grid, and
I'm able to produce the 8/8 boards if needed be. The Fluorescents can be
easily obtained from local Philips or Osram rep. All ypu have to ask are
the fluo's for the solarium's.
And for the transparencies, I'm using services from one graphic design
buro, where the owner is a friend of mine, and all my artworks are made
on thye graphical film, directly from the PostScript files.
--
Best Regards,
Zoran
mailto:
zasto@... www.zas-elmed.co.yu