Double-Sided Boards

Double-panel boards have wiring on both sides, but to use the two-sided wires, you must have proper circuit connections between the two sides. The "bridge" between such circuits is called a via. The via hole is a small hole filled or coated with metal on the PCB, which can be connected to the wires on both sides. Because the area of the double panel is twice as large as that of the single panel, the double panel solves the difficulty of wiring interleaving in a single panel (which can be conducted through the hole to the other side), which is more suitable for circuits that are more complicated than single panels.