8L

parameter
Layer: 8 L	
Material: fr-4 Tg170.
Plate thickness: 2.0mm
Copper thickness: 35/18/18/35um.
Line width: 8/5.39 mil.
Most holes: 0.2mm
Surface treatment: ENIG(1U')
Technical difficulties:
Blind buried hole, local thick copper length gold finger 3U, 
impedance control.