--- In
Homebrew_PCBs@yahoogroups.com, Dylan Smith <dyls@...> wrote:
>
> On Mon, 18 Feb 2008, Leslie Newell wrote:
>
> > That one has occurred to me before. I even got as far as
disassembling
> > an old black and white laptop to investigate. The biggest problem
I can
> > see is the thickness of the glass. Unless you have extremely good
> > collimation of the light you will get severe undercutting.
>
> I doubt it would work - the LCD would expose a grid onto your light
> sensitive material (look at your LCD monitor closely - it's a grid
of
> pixels - positive exposure, you'd get tracks composed of very small
> squares).
>
> It would only work with diffuse, very un-collimated light (to avoid
just
> getting a grid pattern), which would mean you'd only be able to use
it for
> very large features.
>
I wondered about that as well, however in their efforts to make every
thing thin and light, the glass screens are getting very thin. If you
had a UV source that gave you reasonably good collimation it might
work.
You might be right about the pixilation problem, however, even the
ink jet and laser printers have that problem. Many times that problem
goes away because when you iron or laminate the paper to the boards
the toner spreads out a little. Perhaps the light spreading out a
little from the thickness of the glass will act the same.
I have a small TV screen I think I will dissasemble and try it on, is
there any one willing to sacrifice a 4" x 4" sensitised board? I have
the UV LED source, but no sensitized boards.