Hi,
Unfortunately, a correction is needed.
>1. In fact if the via hole is plugged the
>mask will cushion the effect of z-axis expansion.
This is not correct--where the plug helps is in the x,y-expansion trying to
compress the barrel. This is important for inner-layer [post] separation. The
solder mask plug actually has a worsening effect as far as z-axis differential
expansion is concerned because its CTE is larger than that of copper; however,
because it is soft (it is likelt to be incompressible, however), this effect
is not significant.

Regards,
Werner Engelmaier

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