Most PCBs have between one and twenty conductive layers laminated (glued) together in a sandwich with insulating plastic. PCBs with more than two layers help construct complex or dense circuits. They are not always used because they are more expensive, and the inner layers are more difficult to inspect and repair.

In more complex PCBs, two or more of the layers are dedicated to providing ground and power. These ground planes and power planes distribute power well. They also prevent radio waves from antennas unintentionally formed by tracks. These planes are rectangular sheets of foil that occupy entire layers (except for small holes to avoid unwanted connection to vias and through-hole components). They distribute electrical power and heat better than narrow traces. Sometimes solid metal PCBs with thin layers of insulation are used. The power electronic substrate carries away waste heat when air cooling is impossible.

Four-layer PCBs with a ground and power plane are often used in high-quality, but cost-conscious audio, avionics and medical electronics. Most consumer products have one or two layers.