Hi James and other Technetters,

        I've been following this subject on the forum and Just have to put in
my two cents. The comments from both Earl Moon and Kelly Schriver are very
pertinent. I understand the Heat pipe scenario well, but have some concerns
about the open via contracting contaminates. We have built a number of boards
with constrained/thermal cores and usually follow the path mentioned by Kelly.
In the early '80s, we tried to fill with solder, but could never get the solder
to stay in place. Two concerns with solder are: 1) during assembly the solder
may wick away solder from a joint making a poor interconnection, and 2) as in
the case that we tried early on in the SMT effort, is that during assembly it
will errupt out of the hole and create all sorts of problems, among which are
shorts.
        We found that our best approach was to fill the via with a thermally
conductive/electrically insulating epoxy. There are several sources of these
materials available in the industry.

It's not much but there's my two cents worth!
Regards,
Les

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