1、HDI structure：2+N+2 with stacked vias
2、Laser micro vias(0.1mm big)：L1-L2、L3-L4、L16-L15、L15-L14
3、Buried hole between L2 and L15.Buried holes are filled with resin and plated over by copper.
4、Specific impedance control with 50+/-5 Ohms and differential impedance control with 85+/-8.5 Ohms
