Homebrew PCBs

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.

Les

Dave Miller wrote:
> Does any one know if LCDs are transparent to UV? Would it be possible 
> to replace the backlight on a LCD display (like a LCD computer monitor) 
> and do a contact exposure to a sensitized PCB with the PCB image 
> displayed on the LCD? A number of monitors have sufficient resolution 
> to do fine traces if when the LCD is clear UV is transmitted and the UV 
> is blocked when the LCD is dark (or visa versa if you have positive or 
> negative resist).
> Having disassembled a LCD monitor it does not look like it would be too 
> difficult to replace the cold cathode lamp with UV LEDs. (Unfortunately 
> the LCD was cracked or I would have tried the experiment). This would 
> eliminate the need for photo-plotting, printing on Velum, or overhead 
> material. With a white light behind the LCD, you would get what you saw.
>