There is disclosed a planar heat pipe for cooling, which is embedded in a printed circuit board for cooling of heat-dissipating components (13). The planar heat pipe includes two panels (1, 2) that are both metal clad on one side (4, 5), at least one of the panels (1, 2) being grooved (9) on its metal clad side, the panels (1, 2) being assembled by their metal clad sides to form a sealed cavity (8), the cavity (8) being filled with a fluid (10), the fluid (10) circulating by capillary action along the grooves (9) towards zones exposed to heat where it vaporizes.