>There was a long thread here months ago about a balky A/D
>on a PIC that was 'cured' by using fully opaque (aluminum as I recall)
>tape on the windowed part.
>
>Many years ago I had an 8748 (UV erasable windowed part) that stopped
>working when sunlight through the shop window hit it and just shading
>it with your hand got it to run again! That was pretty old
>technology though...

Any semiconductor PN-junction that is exposed to sunlight will generate
some current flow: the photoelectric effect is used in solar cells. Thus,
if you have a windowed chip exposed to sunlight there will be extra
currents flowing in the chip that you know nothing about and have no
control over, leading to faulty operation. The "newness" of the technology
doesn't matter much, because most chips have PN junctions (as diodes) in
them, even if they're just for input protection.

Stephen.