Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Leon Heller" <leon_heller@h...>
wrote:
> 
> ----- Original Message ----- 
> From: "dkesterline" <desterline@t...>

> > This idea of CNC photoploting has got my wheels turning.
> >
> > Does anyone know what wavelength the laser emitters in laser printers
> > are?

Red or IR.

> > I'm thinking that it might be passible to photoplot directly onto
> > sensitised boards.
> >
> > There's several rather large issues to address. (wavelength, exposure
> > time, feeding the board- just to name a few)
> 
> It won't work - you need UV, not IR. You also need a *lot* of UV
power at
> the correct wavelength to do it 'on the fly'. It isn't really
feasible with
> the available technology, AFAIK. Think of how much power you need
for, say,
> a 5 minute exposure using ordinary UV exposure techniques.

That power is going all over the place, though. Think of this: you can
look directly at a 100W bulb (ie, about a 20W fluorescent) and at
worst have spots in your vision. But a 2mW laser diode is not eye safe.

The question then becomes how tightly can you focus an IR LED, and how
much power output is available at the focus point?

Steve