LAYER 4Layer (FLEXIBLE 2L+RIGID 4L) 4-2-4-3-2 Application Blood Sugar Check Thickness 0.38T Structure 2-3L DRILL, 1-2L, 3-4L BLIND VIA Machine Drill Min. 0.1mm Laser Drill BVH Min. 0.1mmSTACK VIA FILL copper plating Cu Plating INNER : VIA FILL / OUT : PTH Min.20+ VIA FILL L/S 50 / 50 (SPECIAL) PSR GREEN Surface treatment ENIG Stiffner PI (3Mil) Impedance 100