Graeme Smith wrote:
>
> On this same topic....
>
> I have been wondering, if it would be possible to get a UV exposure
> system going on my Logical Devices Eprom Eraser....
>
> The idea I came up with was to do something to increase the
> coverage of the light by putting some sort of reflecter behind the bulb.
> I noticed that placement of the chips was important to recover from
> that pesky "configuration bit not blank" message, which suggests that
> the buff box, does not have even coverage for reflective rays.
>
> I have been assured that the UV eraser bulbs tend to be the wrong
> frequency for Photo-etching, but it seems likely that I could change
> the bulb, or have both bulbs in the same case, and simply switch back and
> forth on a toggle switch.
>
> This would mean that I could expose card sized circuit boards for the cost
> of the bulb, and circuitry to connect it. I thought of using Aluminum Foil
> as the difuser/reflecter, but I am unsure about its reflective
> frequencies.
>
> A freind suggested that it would be much better at UV, than silver, which
> for some reason, he figures is transparent at those frequencies.
>
> Anyways, does anyone see any reason why I COULDN't rebuild my current box
> into a combinatoin exposure system?
>
>                                 GREY
>
> GRAEME SMITH                         email: grysmith@freenet.edmonton.ab.ca
> YMCA Edmonton
>
> Address has changed with little warning!
> (I moved across the hall! :) )
>
> Email will remain constant... at least for now.

Hi,
For the exposure of my PCBs I do use a self made exposure unit consist
of the following:
2 fluorescent tubes (non UV but the standard one) 1,5 feet long encolsed
in a white (painted) wooden box which is size so it can accommodate the
lambs and their control gear (starter,chock etc.). The box has about
15cm hight and on top there is a 4mm thick glass.
The exposure time depends on the thickness of the photosensitive spray
but my standart time (by experience) is between 8 and 10 minutes.
There is no need for pure UV light since the photoresist is sensitive to
visible light (around blue light).
The advantage of the long exposure time, the system takes, is that 1 or
2 minutes of overexposure it is not critical.

Regards
Kypros