Hi Eddie,
In a sense you are of course correct that the reliability of the PTV is not a
function of how the hole is spec'ed. However, knowing the drilled hole
diameter (and other parameters) allows calculation of the reliability of the Cu
barrel; as well as proper FEA to determine the loading at the innerlayer
attachments.
And even a good Fab house cannot afford the resources needed to understand
and measure PTV reliability. How often do they measure tensile strength and
elongation? Do they ever measure ductility, since elongation is a rather poor
indicator of foil ductility? Do they [can they afford to] run IST or HATS tests on
any of their coupons?
Granted, most Fab houses to a good quality job, but in the high-end PCB cases
good quality is not adequate--good design and material choice has to be part
of the picture and the Fab house knows too little about the product to
influence that--it is the customers that need to get themselves more educated.

Werner

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