High-Density Interconnect (HDI) Circuit Boards, also known as HDI PCBs, have a higher wiring density per unit area compared to traditional printed circuit boards. HDI PCBs are characterized by one or more of the following features: microvias (blind vias and buried vias), laminate structures, and considerations for high signal performance. https://www.pcbhamal.com/pcb-fabrication-capabilities/hdi-pcb/