# What is the “aspect ratio”?

_Published: 2016-08-12_

The relationship between the diameter of the hole and its length. When a manufacturer states that their production has an “aspect ratio” of 8:1 it means, for example, that the hole’s diameter is 0.20 mm in a 1.60 mm thick PCB.

For HDI structures, a suitable aspect ratio for micro via is normally 0.8:1, with 1:1 preferable for ease of plating.