After years of building high powered printed circuits I found a few isuess
with the mot and T/g

First is if you are any where near the maximum operating temp of any
material your way to hot. The Temp the lamiantors give is a max temp for a
very short time. not for long periods. The material will degrade both in
phisical strenght as well as voltage dialectric properties. one fr4 160 t/g
I tested lowered the dialectric from 1100 volts per mil to 250 volts per mil
in as little as 100 hours at the MOT. remember the T/g is the temp at which
the material is going plastic, not  a good thing when you are using it to
carry components and sensitive copper vias and traces.
I see in forums all the time designers stating with fact that FR4 can take
120-180 degrees C  this is not so, take a pieace of Ffr4 AND PUT IT IN A
OVEN ( NOT IN YOUR HOUSE OVEN)  AND SEE WHAT IT LOOKS LIKE AFTER 30 HOURS AT
MOTIt will be brown and starting to show fibers on top. Add some heat sinks
or more air flow and get the temp down to a more resonable level.

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