have been through this a couple of times in last 20 years,
That was all very interesting - particularly that a 1M-ohm mat was
susceptible to fluorescent light e-m. Two points that are worth making to
clarify:
1. The reason that Al foil is bad is that any static charge on a device
comes out instantly - and the high peak current that flows (even from a few
pF on the gate of a FET) is so high that thermal damage occurs. A resistive
mat is essential to make sure that charge bleeds out slowly enough to
prevent this.
2. It is possible to subtly damage devices without destroying them totally -
leading to change in characteristics, noise and/or lifetime.
The only solution is to follow a good protocol. I put that in place after I
destroyed a rare double FET while repairing a 'scope.
Craig
