printed circuit board (PCB) is a laminated sandwich structure of conductive and insulating layers. A basic printed circuit consists of a flat sheet of insulating material FR4, Rogers or Polyamide for flexible circuits, and a layer of copper foil, laminated to the substrate. Chemical etching divides the copper into separate conductive
blue, white, black. Only the outer layers need to be covered with solder mask, the inner copper layers are protected by the adjacent substrate layers. The soldering mask soldermask is made of a fluid substance like an ink and is applied in a thin Terms and conditions layer similar
thickness and length, must be small enough for the current the conductor will carry. It is recommended that the power and force paths be larger than the signal Terms conditions and paths. In a multi-layer board, an internal layer may be mostly solid copper to act as a ground plane for shielding and power return. For microwave