 Chemical etching divides the copper into separate conducting lines called tracks or "circuit traces", pads for connections, vias to pass connections between layers of copper, and features such as solid conductive areas for electromagnetic shielding or other purposes.The tracks function as wires fixed in place, and are insulated from each other by air and the board substrate material.The surface of a PCB may have a coating that protects the copper from corrosion and reduces the chances of solder shorts between traces or undesired electrical contact with stray bare wires.