Hello Peter,

Well, since no one has responded yet, I'll kick this off:

"Conductive fills" will get you to about 3.5 to 7.0 W/m/deg K - in other
words, not very conductive (copper is 650 W/m/deg K) - from that
perspective there is little advantage, especially when viewed in light of
the disadvantages: fewer suppliers offer conductive fill (as opposed to
non-conductive fills, which can also be plated over); the cost is very,
very expensive; the aspect ratio for holes that can be filled with
conductive fills is lower, which effectively means a longer (bottleneck)
process to fill them; they are much more prone to air voids (which may or
may not be a problem) ..

However,  what is better about them is a much lower coefficient of thermal
expansion than epoxy-based non-conductive fills - and with the higher
temperatures of "lead-free assembly" almost upon us, that may swing the
preference back to conductives. In any event, reliability of via fills
during/after higher peak temperatures or longer dwells is something I as
yet have no data on, but am concerned about. So, that will need watching.

For today, we find that non-conductive fill works fine and if we need
extra heat dissipation, we add copper plating! and thicker planes of
course. The fill doesn't do much and is very very dear.

Valerie







Peter Lee <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
11/30/2005 12:17 PM
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[TN] Conductive Via fill




Hello Technet,

Does anyone have experience with utilizing conductive via fill on PCB for
heat dissipation? How mature is the technology? Is there any
shortcoming/impact on the overall design and manufacturing process?

Comment is greatly appreciated.

Rgds,
Peter



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