High Density Interconnect
High Density Interconnect (HDI) is one of the fastest growing technologies in the PCB industry. The HDI board has a higher wiring density, finer spaces and lines, minor vias and capture pads, and higher connection pad density compared to a conventional PCB. Drilling the smallest of micro-vias is usually done by Laser Drill Technology, and the HDI boards often contain blind and/or buried vias (as opposed to through vias from surface to surface).
By using HDI technology, designers have the option to place more components on both sides of the board. Decreased component size and pitch allow for more I/O in smaller geometries. This means faster transmission of signals and a significant reduction in signal loss and crossing delays. The placement of the parts on a HDI board needs extra precision compared to a conservative board design due to miniature pads and fine pitch of the circuitry on the HDI board.
For instance, HDI technology makes reducing an 8 layer through-hole PCB to a 4 layer HDI micro-via PCB possible. The wiring capabilities of a well-designed 4 layer HDI PCB can achieve the same or better functions than that of a standard 8 layer PCB.
Although the micro-via process increases the cost of the board, the proper design with reduction in layer count and material use reduces cost, and many times would bring savings.