of copper foil, laminated to the substrate. Chemical etching divides the copper into separate conductive lines called tracks or circuit paths, pads for stencil connections, metallized holes (vias) for passing connections between layers of copper as solid conductive areas for electromagnetic shielding or other purposes. Each of the conductive layers
mount technology. "Through holes" components are assembled by their legs passing through the board and glued to the pads on the other side. "SMD" components are soldered on the same stencil side of the board. A board can use both methods for soldering components. Today PCBs with components mounted only through holes are
more routing options in the internal layers compared to the two-layer board, and often part of the internal layers are used as a ground plane or power plane, to achieve better signal integrity, higher signaling frequencies, and better power supply decoupling. In multilayer boards, layers of material are stencil laminated together in an