order of copper layers: Copper 1: Front Copper 2: Inner3 Copper 3: Inner2 Copper 4: Back PCB description: 4 layer PCB 0.062 in Copper 1 0.5 oz foil plated to approximately 0.0017 in Dielectric 1-2 0.0119 in Copper 2 1 oz foil (0.0014 in) Dielectric 2-3 0.0280 in Copper 3 1 oz foil (0.0014 in) Dielectric 3-4 0.0119 in Copper 4 0.5 oz foil plated to approximately 0.0017 in FR4 or similar substrate with Er=4.5 (+/- 0.1) double side solder mask black single side silkscreen white 6 mil min trace width and 6 mil min isolation