Via aspect ratio in PCB

[joniengr081]

The aspect ratio of the via is the ratio of dielectric height to via hole.

Is that true 10:1 has smaller via hole compared to 6:1 ? in 60 mil thick PCB

If yes than manufacturing 10:1 via is more expansive and difficult then 6:1 via, correct ?

[tszaboo]

Smaller drills wear out faster. But you shouldn't really be concerned with this, today drilling a hole is a free step, and they automatically replace the drills after certain number of holes. You only need to make sure you follow the design guides, and that you don't end up unnecessarily with an HDI board.

[joniengr081]

What is an HDI board. I guess this is something related to number of pins in connector or in BGA package per square inch, right ?

[tszaboo]

It's a loosely defined term, meaning High Density Interconnect. Usually it's for boards that have smaller than 0.3mm size vias, less than 0.15mm wide tracks and clearances, blind or buried vias, more than 8 layers. Any of these would place you in the HDI category, which makes the board more expensive.
If you are worried about your vias, just make them larger than 0.3mm hole, and 0.75mm pad, less than a few hundred vias, and most PCB houses will make the board without extra charge.