Homebrew PCBs

Markus Zingg wrote:
> 
> 
> Adam,
> 
> I do have a 20mm grid spacing, and I'm so far satisfied. Even though it
> never formed a problem of any kind, one can SEE the grid on the
> resulting exposed laminate. It's seen like kind of darker and lighter
> circular shaped areas on the exposed resist. Again, developping the
> result always worked excellent with no irritations in the result whatsoever.

That's good to hear it works despite the visible pattern. What is your 
space between the LED and PCB ? I guess the larger the distance the 
greater the light overlap of adjacent LED's and possibly better uniformity.

> At the very surprisingly low prices of these LEDs, I would consider
> using an even more narrow grid. My box (kingbright leds, with what I
> understand only 160mcd typical) result in a one minute exposure time.

The BestHongKong ebay seller Tom pointed out had the better specs 
(tighter spectrum tolerance, polar plot). Interestingly , some LEDs are 
rated in mcd while others rated in mW. BestHongKong 5mm UV LED's are all 
11mW 20 degree. I think I'll get these. But might also get $11 ones from 
Winsome House Store just for fun.

 >.... I would spend the time to build a complete exposure unit to make
> sure they work.

For sure. Some preliminary testing will soon give me estimate of 
exposure times vs grid spacing and test non-uniformity.

I'll be sure to let others know how it goes.

Adam Seychell