A printed circuit board (PCB) is disclosed. The PCB includes a main body. A first surface of the main body is a connecting surface for electrical components. A second surface of the main body is a conductive cooper foil layer operating as ground wires. A plurality of grooves is arranged on the conductive cooper foil layer. The grooves pass through the conductive cooper foil layer to connect to the main body of the PCB. The thermal stress generated in the PCB welding process can be effectively released via the grooves. The inflation of the conductive cooper coil is relieved such that the PCB is prevented from being wrapped or cooper bubbling. In this way, the operation efficiency is enhanced and the manufacturing cost is reduced.