Board density is the level of wiring density or the number of connections per unit area on a printed circuit board. It is a measure of how closely packed the circuitry and components are on the board. HDI (High-Density Interconnect) boards have a higher wiring density per unit area compared to conventional PCBs. HDI boards are known for their finer lines/spaces, smaller via holes, and capture pads that allow for the placement of microvias in select layers and surface pads. This indicates that HDI boards have a higher board density.