Homebrew PCBs

>   I don't know what to say about ionic contamination either, I have no
> idea what it is ;)   How does it effect a board?  Does it rot the
> FR-4?

Ionic contamination creates low impedance shorts all over the board.
Sometimes they will not exist when you first power the board up, but can
show up in a matter of hours. Low levels can cause clock drift, or
intermittent oscillator startup.

Very frustrating.....
Ron