Background:
I am trying to fix a circuit board that has been running in an underwater
environment.  The water was not a planned condition.  The board was in a
waterproof box with waterproof grommets for the cables that came into the
box.  Unfortunately, the CAT-5 cable that went up the antenna tower had
water leaking into the other end of the cable, which was 100 feet higher, so
the water made its way into the enclosure.  Since the enclosure was "water
proof", no water leaked out of the box.  The board ran in this condition for
a while.  I cleaned and dried the board, then added a jumper to replace the
24V power lead terminal on the switching regulator, which had been etched
away.

As I slowly increased the input power to the system, I saw the regulator
start working, but the output voltage didn't rise.  I measured the
resistance from VCC to ground at under 1 Ohm.  I fired up my favorite short
circuit location tool (SS-2) and observed the following:
1.  several short circuits under the BGA chip
2.  several short circuits on areas of board without traces showing on the
top and bottom sides.

Question to the group:
1.  Can running a board under water cause short circuits to form under a BGA
chip?
2.  Can letting a multi-layer circuit board soak in water (with or without
bias) cause shorts to appear on inner layers?
3.  Is there anything that can be done to reverse the action that caused
these shorts?



Thanks,
Carl


Carl Van Wormer
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