--- In
Homebrew_PCBs@yahoogroups.com, stefan_trethan@g... wrote:
> thank you for that information.
> i did know there is a laser but had no idea how it is deflected.
> i thought the fiberoptic cable is for adjusting the intensity of it, but
> possibly it is for both - sync and intensity.
>
> i think it would be possible to convert it, but i would try to move
the pcb
> under (or over, which might be easier but then you can't mount small
pcbs)
> the laser. assembly.
>
> the biggest problem with it i think is th uv laser, its flimsy power
needs
> high sensitivity resist (which requires darkroom?). also it will not
work with
> the lenses in the unit, and not with the fiberoptic sync.
The Nichia UV laser diode has a rated output of 2 mW. Now, that's not
a whole lot of power, but when none of it is lost to the sides or to
other frequencies (like it is with standard UV lamps), it can go a
long ways. Standard photoresist, from what I've seen, requires a
minimum exposure of around 50 millijoules of UV energy per square
centimeter (give or take, depending upon the photoresist), which
translates into 25 seconds of 2 mW-power UV light per square
centimeter. This is certainly manageable for reasonable-sized PCB
boards -- not quick, but not horrendously slow, either. If one uses a
higher-sensitivity photoresist (e.g. 5-10 mJ/cm^2 sensitivity, which
may have been designed specifically for Laser Direct Imaging), the
time can be decreased dramatically.
I'm more and more intrigued by this idea. It may not end up being the
fastest or cheapest way to homebrew a PCB, but it sure would be
interesting :)
Jonathan