Novel 3-D super-thermal conducting heat management design and delayed cooling using phase change materials are adopted to lower the temperature inside LEDs and other devices. The cooling mechanism uses a fin structure with hollow fins to dissipate heat to the environment. The hollow space inside the fins is connected to an interior chamber, where a liquid to vapor phase change material (L-V PCM) is provided to transfer heat from the LED chips to the surface of the hollow fins. The LED chips are mounted on an evaporator located at the bottom of the chamber. A liquid reservoir is provided, and the evaporator surface is hydrophilic with an additional wick structure to transport the L-V PCM liquid to the evaporator surface. The fins are parallel to each other and are either parallel or perpendicular to the evaporator surface. This structure has superior performance and is inexpensive to manufacture.