Homebrew PCBs

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> The first "problem" I suspect I will run into is getting enough 
> density on the transparency to make sure the "black" areas are dense 
> enough to block out the UV exposure lamp where needed.  Has anyone  
> run into this issue and how do you deal with it?

Chris,

I use the Positive Photo method. In the begining I was using over head 
transparencies and was having trouble obtaining a dark enough photo 
mask, even to the point of using two copies laid on top of one another. 

I switched to Vellum or tracing paper. I use 20# 8.5" * 11" paper and 
run it through the laser printer. Don't use light weight paper, it will 
crinkle in the laser. This paper is extremly translucent to UV light. 
As an example, using a single F15T8BL at 3.5 inches the Over head 
transparency took 10 minutes, the Vellum took 8 minutes to expose. Also 
Vellum is very inexpensive.

I'm able to run a trace between two pads on an IC chip using the vellum.

Ron