A via is a small plated hole whose only job is to carry a connection between layers, as opposed to a component hole that receives a lead. A through via spans the whole board, blind and buried vias span only some layers, and microvias are laser-drilled through a single thin dielectric. Every via adds inductance, capacitance and possibly a stub that disturbs fast signals, and its drill size, pad and antipad are design rules agreed with the fabricator.
Drop a via right next to each decoupling cap pad, short and fat, straight down to the ground plane.
Also heard as
- via hole
- plated via
Related terms
PTH
Plated through-hole: a drilled hole whose walls are copper-plated to connect every layer it passes through.
Blind via
Via that starts on an outer layer and ends at an inner layer without passing through the whole board.
Microvia
Very small laser-drilled via, typically 0.15 mm or less across, spanning one thin dielectric layer.
Annular ring
Ring of pad copper left around a drilled hole, which must stay wide enough after the drill wanders.