The definition of HDI (High Density Intrerconnection) circuit board refers to the microvia (Microvia) with the hole diameter below 6mil, the hole ring diameter (Hole Pad) below 0.25mm, the contact density above 130 points/square inch, the wiring Printed circuit boards with a density of more than 117 inches/square inch and a line width/spacing of less than 3mil/3mil. HDI circuit boards are mainly used in mobile phones, cameras, video cameras, notebook computers, network cards, IC substrates, military, medical and other fields.

Generally speaking, HDI circuit boards have the following advantages:
1. Reduce costs
2. Increase wiring density
3. Conducive to the use of advanced packaging technology
4. Better electrical performance and signal accuracy
5. Better reliability
6. Can improve thermal properties
7. Can improve radio frequency interference, electromagnetic wave interference, electrostatic discharge
8. Increase design efficiency