Homebrew PCBs

ghidera2000 wrote:
> My third board was a flop. My plexi weight had a slight curve in it 
> and I didn't notice - lost the traces in the center during 
> development. For the fourth I used the curve to my advantage and 
> propped up the sides with my first two (discarded) boards.
> 
> I also changed from the MG boards to a different brand. No choice, 
> store didn't have MG. This one claimed 60 second exposure with a UV 
> source and 6-8 minutes with a florescent. I thought my UV florescent 
> would qualify as a UV source - it doesn't (silly me :D) Exposed for 
> 60 seconds and tossed it into the developer. Sat there for two 
> minutes with zero effect. I rinsed it off and re-exposed for 6 
> minutes (board is gone, may as well experiment). Developed in like 1 
> minute and it was PERFECT. Couldn't believe it. I expected to see a 
> ghost of the first exposure but there was none at all.
> 

The fluros good for photoresists (i.e. lots of 365nm energy) are known 
as "BL" or blacklight. They are white color when off and emit 
violet/blue when on. They are used in insect zappers and available 
from most electrical stores or wholesalers.

Did you do the sliding black plastic trick to determine optimum 
exposure times ?  You move the black plastic across a blank PCB every 
30 seconds and a distance of say 1 cm. Then you have a board divided 
into exposed strips covering from 0 to 300 seconds and in 30 seconds 
increments.