Development of a naturally aspired thermosyphon for power amplifier cooling

This paper details the early development steps of a two-phase thermosyphon thermal management solution for power amplifiers (PA) in the telecommunication industry. These components, attached to a vertical PCB within an enclosure between the RF filter and a natural or forced convection heat sink, dissipate a large amount of heat with a high heat flux density. Currently cooled by direct contact to a shared heat sink, they tend to spread heat towards other components of their board, affecting their reliability. A thermosyphon thus appear as an ideal thermal management solution to transport the heat from the power amplifiers in order to dissipate it to a remote and dedicated natural convection heat sink. In the present study, the performance and the heat spreading of a forced convection unit is measured. A thermosyphon solution is then designed with a flat vertical evaporator and a radial natural convection heat sink and condenser. The performance of the thermosyphon thermal management solution is measured and compared to the initial solution. The limits and improvement needs of the thermosyphon solution are then discussed.