There is disclosed an apparatus of planar heat pipe for cooling, which may be embedded in a printed circuit board for cooling of heat-dissipating components.The apparatus includes two panels that are both metal clad on one side, at least one of the panels being grooved on its metal clad side, the panels being assembled by their metal clad sides to form a sealed cavity, the cavity being filled with a fluid, the fluid circulating by capillary action along the grooves towards zones exposed to heat where it vaporizes.Application: electronics, cooling, printed circuit boards