Hi Greg,
I wrote before, but it somehow did not get through:
"The automotive environment is the harshest [short of down-hole drilling] for
electronic assembliies--just look at the millions of SUVs GM has to recall
because of solder joint failures. In a harsh environment, any voids in via
solder fill creates stress risers and thus reduce reliability. What would work for
many years in a telecom environment would fail quickly in an automotive
under-hood environment. The life ratio for unfilled vias is about a factor of 1000.
Thus, in your environment I would not allow any voids in solder-filled vias;
voids in polymeric fills of vias are not very important.
And, as Robert pointed out, solder joint reliability degradation may be even
more important."
However, one really needs to be more specific. Solder fill voids in
through-vias can be a problem in harsh environments [telecomm is not one], depending on
PWB construction, Cu thickness, and Cu quality [ductility]; in benign
environments they are perfectly o.k. with through-vias that are of sufficient quality
to survive assembly processes [who cares if failures occur in 500 instead of
2,000 years].
With through-vias it is even more dangerous to generalize than it is for
solder joints.

Werner Engelmaier

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