I think that the best way to get really good
negative or positive artwork is to use
lithographic film. Using litho film entails
more process steps i.e. camera and photo darkroom
work, but the quality of the boards that
can be produced via this method are
superior to all others.
Roland F. Harriston
∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗
pcb.easy wrote:
>
> Snip
> > 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
>
>