HDI stands for High Density Interconnector (HDI PCB), which with a high trace distribution density. It uses blind and buried hole technologies, and through processes such as drilling and through-hole metallization, it connects the internal circuits of each layer. HDI PCBs are typically made using a stacked method, and the more layers stacked, the higher the technical level of the board. Advanced PCB technologies are employed, such as stacked vias, electroplated hole filling, and laser direct drilling.