Best Price 16 Layers Prototype Board HDI Multilayer PCB What is HDI PCBs? HDI PCB (High-Density Interconnect Printed Circuit Board) is a circuit board built with very fine lines/spaces (≤ 100 µm), micro-vias (≤ 150 µm), blind/buried vias, and often sequential lamination or laser-drilled stacked vias, so that more components and routing can fit in a smaller area. The result is thinner, lighter boards with higher I/O counts, shorter signal paths and better electrical performanc