PCB is composed by coper foils seperated with isolating materials. To build a PCB with more than two layers, PCB manufacturer assemble following items un PCB comportant plus de deux couches, le fabricant de PCB doit assembler plusieurs composants :

  • Core : This is an epoxy plate with two coper foils.

  • Copper foils or layers
  • Prepreg : One or more glass fiber sheets mixed with epoxy to isolate two copper layers


Copper layer thickness is often rated in ounces (oz). Higher number means that copper layer is thicker and also means that more current can flow through it. 1 oz coper foil is equal to 1 oz weight for a 1 inch² area (43.94 kg/m²). Standard copper layer thickness are 0.5 oz, 1 oz et 2 oz.

Weight Thickness (mils) Thickness (mm)
1/2 oz 7 mils 0.18 mm
1 oz 14 mils 0.36 mm
2 oz 28 mils 0.72 mm


Soldermask protects PCB traces, it also gives color to PCB (green, red, black).

PCB Manufacturer adjusts soldermask clearance over chips pads.

In CAD software, clearance shall be set to pad size.

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