Via array (power via stack)
Beginner
A cluster of tiny upright links that joins power wires on different layers.
Novice
A cluster of vias, the tiny vertical connectors between wiring layers, placed where two power wires on different layers cross. Stacks of them carry current down from the thick upper wires to the thin rails.
Expert
Sized for resistance and electromigration, since vias are a common failure point. Large arrays on the layers in between can grow into metal patches that block signal routes, so tools limit their rows and columns or keep the pass-through layers at minimum width.