1+N+1 – PCBs contain 1 “build-up” of high-density interconnection layers.
i+N+i (i≥2) – PCBs contain 2 or more “build-up” of high density interconnection layers. Microvias on different layers can be staggered or stacked. Copper filled stacked microvia structures are commonly seen in challenging designs.
Any Layer HDI – All the layers of a PCB are high density interconnection layers which allows the conductors on any layer of the PCB to be interconnected freely with copper filled stacked microvia structures (“any layer via”). This provides a reliable interconnect solution for highly complex large pin-count device