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. This technology enables more components and routing to fit in a smaller area, resulting in thinner, lighter boards with higher I/O counts, shorter signal paths, and better electrical performance. HDI PCBs are ideal for smartphones, tablets, medical implants, IoT modules, and any application demanding miniaturization and high speed.

• 1st-order (1+N+1) - one build-up layer per side; only one laser-drill step is needed.
• 2nd-order (2+N+2) - two build-up layers per side; requires two laser-drill and lamination cycles (can be staggered or stacked micro-vias).
• 3rd-order (3+N+3) - three build-up layers per side; three sequential drilling/lamination cycles.
• Any-layer (ELIC) - every adjacent pair of layers can be interconnected with laser micro-vias, giving the highest density and no fixed "order" limit.