Homebrew PCBs

>Perhaps you all can comment on whether you think this flash from the past
> will work.
>
>Back in the day I used to plot PCB's using an old flat bed plotter with
water
> proof ink in the pen. Getting the pens to work reliably and cleaning them
was
> always a headache.
>
>All this talk about UV resist got me thinking - what if I were to mount a
UV
> LED (laser diode?)with a lens or whatver it takes to focus a small dot on
a board
> on the table and put it in the plotters pen hoder. I then coat the board
with UV
> resist and let the plotter expose it. I might even be able to use the pre-
> sensitized boards.


Provided you can get the right laser & the right resist, it'll work fine.
I've seen UV lasers around 400nm, some resists would work with that.

Similar has been done before, the last one I remember was someone wrapping
film around a drum and exposing that with a laser.  I think he used the guts
of a laser printer, hence the drum.

Even that isn't new, many many years ago I work for a company making film
masters for bar codes, you'd put the film on a XY table, the computer (a BBC
micro of all things) would move the laser around plotter-style.  Develop the
film and off you went.

Of course you're trying to skip that step, but there's plenty of prior work.

You might be able to take a UV tube and use something like a magnifying
glass lens to focus it, exiting though a small hole to cut down on scattered
light ruining things.  A bit like a pinhole camera in reverse.  Might be
worthwhile looking at plano-convex lens (used in lasers, flat one side,
curved on the other), they're rather good at focussing to a small dot.  Use
both.

Tony