Homebrew PCBs

Adam Seychell <a_seychell@...> writes:
> I'm interested in your exposure times. I get 60 seconds with negative 
> dry film, grid density 0.28 LEDs/cm^2, BestHongKong 390nm UV LEDs at 
> 20mA, about 100mm PCB to LED gap, measured with inkjet transparency + 
> 5mm window glass in light path.

Just finished some tests.  With the glass and transparency I'm using,
it needs 5.5 minutes of exposure to hit 8 on the step gauge.  That's
with a ~5 inch gap and about 0.2 LEDs/cm^2, as reported before.  The
step gauge helped - I got a perfect exposure on the second try, just
by doing the math!

Note that for two out of two tests I forgot to remove the cover film
before developing :-P

My etch tank seems to be a little pokey these days, though.  I suspect
most of the H2O2 is just H2O by now.  It still etches, but takes
longer.  Not that I'm in a rush ;-) It's still the right color green,
but not as deep as others I've seen.

Still need to practice applying the film, though.  Lots of wrinkles
and bubbles on my first try (good enough for exposure tests, not good
enough for circuitry).