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

Stefan:

My snide remark was meant to imply that most people knows about
the tremendous UV content of sunlight. Sun blocker...anyone?

Dermatology folks are very interested in the UV content of sunlight,
as you can well imagine, so I believe these measurements are accurate:

From the Indian Journal of Dermatology:

"UVA and UVB in sunlight, Optimal Utilization of UV rays in Sunlight for
phototherapy"

...we measured the UVa and UVB irradiance for one year using PMA 2100
meter. UVB irradiance was maximum between 12.00 noon- 1.00 p.m
(19.50µw/cm2 to 40.2µw/cm2) and UVA between 12 noon-1.15 p.m.
(4.70mw/cm2 to 6.59mw/cm2). The ratio of UVA was 1:500 to 1:600 during
early hours and late evening and 1:200 during mid-day. At peak time
(11.30 a.m. to 1.30 p.m.)....

Of course, the amount of UV in sunlight will vary according to
your location. Nevertheless, there is quite a bit of UVA and UVB
in sunlight.........unless you live at the north or south pole.

I used sunlight with Kodak KPR resist in New Jersey,
and California with total success.

If one lives close to the equator, the UV content of sunlight is
quite large, and exposure time is relatively short.

I think the sun exposure technique will work with most of
the resist materials available today.

I always do my PCB fab work during the day.

Nighttime is my time to be with the one I love.

Roland F. Harriston, PD