Homebrew PCBs

Vlad,
I believe there is two types of glass. One absorbs the UV light the other 
doesn't.
I was told this long ago and not sure if this is true. I don't know what 
the type is I have.

The exposure time was the same when I used the Perspex as when I use the glass.

I used thin glass at one time but it was easily broken.

The light is quite powerful . I think it is about 300 watts. No doubt an 
over kill but it was were free and it has never stopped working.

Your picture of the glass frame is similar to what I use but seeing the 
glass is so thick I only use two clamps one at each end

David


At 12:18 PM 2/21/2006, you wrote:
>David, thanks for the great description of your process. I have one question
>however:
>
>On 2/20/06, David Hopkins <davhop@...> wrote:
>[snip]
>
> >
> >
> > To hold the board and artwork together I use two sheets of 10mm glass 300
> > x
> > 300mm. The sensitized board and the artwork are held between the two
> > sheets
> > of glass and they are held together with large spring paper clips. The
> > reason for two sheets of glass is to do double sided boards.
> >
> > Before the glass I used to use 10mm Perspex (Acrylic) however this
> > scratches easily and one of the trainees spilt developer on them and
> > ruined
> > the Perspex.
>
>
>Doesn't glass (or at least most kinds of glass) tend to absorb UV rays? I
>was under the impression that this was the case. As a result I first tried
>using acrylic, and after finding that it scratches too easily, ended up
>using the thinnest glass I could find -
>http://www.krupin.net/serendipity/uploads/pcb_making_exposure_frame.jpg
>
>It sounds to me that using thick glass would seriously slow down the
>exposure time, especially for people who are using a less powerful light
>than the one you have.
>
>Vlad
>--
>Vlad's shop
>http://www.krupin.net/serendipity/index.php?/categories/2-metalworking
>
>
>[Non-text portions of this message have been removed]
>
>
>
>
>
>
>Be sure to visit the group home and check for new Links, Files, and Photos:
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>
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David Hopkins (VK4ZF)
Queensland
AUSTRALIA
davhop@...
Skype :-   davhop
S 27, 22.294  E153, 11.008