Hello John,

Via plug is one of the fastest growing requests of board buyers/users today.
Mainly in the arena of electrical interconnection in the CSP or sub .8mm BGA
substrates.  Thermagon is a very good thermal dielectric (www.thermagon.com)
and their "in-situ" hole fill may be what your looking for, although it is
best used to bond PCBs to alum or copper heat plates.  It can also be readily
used as the dielectric system for single, double or multilayer boards. It is
conventional E-glass with a modified epoxy that has 10x betterment of thermal
transfer properties.  We use a high silver content epoxy hole fill supplied
by three different suppliers.  These are all great materials but will not do
a thermal transfer job very well.  If it is a through PCB thermal transfer
you can't beat the performance of an additional plated through hole combined
with copper planes (large and or small).  The challenge is where does the
heat go from there and how. That is an assembly issue and volume has
everything to do with appropriate configuration.  I've done quite a bit of
that send a reply to continue the thread.

Boston Brad