Homebrew PCBs

Absolutely, a single F15T8-BL. One.

OK, I've been using a positive method, pre-sensitized board.  The amount of
time that it takes to cure the resist is a square function of distance
source to object.  Further away, larger the area that can be cured.  But,
the time it takes is increased.  Don't like the time, move closer, but do a
smaller board. In my opinion, however, its like fine adjusting with the
course control.  With a longer exposure time, the lower the probability of
over exposure.  A 10 turn pot instead of a single turn.  Now, if you can
dial in that closely then go for it.  I have found very consistent results
from batch to batch of different coatings.  As the output of the bulb
decreases, as it does with time, I need to do very little, to no
compensating.  By the way, this is not in any enclosure, I set the fixture
on the counter, positon the target on a couple of plastic drink containers,
set the timer, turn on the lamp and go do something else for a couple of
minutes.  There isn't any reflective surface added, black light shining on
all the cookie crumbs on the counter.
The 2 sided fixture that I envision may well end up in a box, but if an
aluminum frame to hold the 2 fixtures and the glass plates between them can
be fashioned sturdy enough, that's where I'll go first.  If I need more
light power then I can put in reflection and if that still isn't good enough
then an additional pair of bulbs, but tonight I'm thinking all of that isn't
needed.
Based on that premise, though I priced 4 fixtures from the source, I only
purchased one.  Came in at $18 with the shipping.  I'll spend the dif on
more cookies.

On Sat, Feb 13, 2010 at 11:08 PM, DJ Delorie <dj@...> wrote:

>
>
>
> Barry Demers <sdad@... <sdad%40chipchristy.com>> writes:
> > I have been using a single bulb 12" from a 6 x 9 board, with a 24
> > min exposure.
>
> A single 15 watt bulb?
>
> I've been pondering upgrading to two-sided UV exposure, but my LED box
> exposes in only 5 minutes.
>
> Can you reduce the exposure time by using mirrors to reflect more of
> the UV light to the board? I.e. something behind the bulbs, or the
> sides of the box. Or is it just going to mess up the quality of the
> exposure?
>  
>



-- 
Thank you,

Barry


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