Thermal management of LED with vapor chamber and thermoelectric cooling

Abstract

A fin heat sink (FHS) is a thermal heat transfer device employed to dissipate heat from a high temperature heat source to a lower temperature surrounding. A typical FHS consists of a flat metal base with an array of cooling fins on top. A problem normally encountered in thermal management of electronic packages is thermal heat spreading resistance which occurs as heat flows by conduction from a high temperature heat source to a low temperature heat sink with different cross-sectional areas. As high powered semiconductor chips are made more compact and requiring greater heat dissipation, more effective cooling systems have to be devised. There are various methods employed to minimize this heat spreading resistance. These include increasing the thickness of the base of the FHS or height of the fins. Another method is to use more expensive highly conductive materials like aluminum, copper and diamond which would increase cost. A more economical alternative would be to combine a flat heat pipe (HP) sometimes termed a vapor chamber (VC) with a conventional FHS to increase effective thermal conductivity at the base. Thermoelectric (TE) is the direct conversion of temperature difference between the junctions of two dissimilar materials (thermocouple) to electricity. The converse is true. A voltage applied between the junctions of the thermocouple creates a temperature difference between them. This effect could be utilized as a heat pump to transfer heat from the cold junction to the hot junction. A dc voltage imposed across a thermoelectric (TE) module causes a temperature difference to be imposed across the surfaces of the resulting in one face to be at a temperature higher than the other face. Heat is absorbed from a heat source in contact with the cold surface and dissipated to a heat sink in contact with the hot surface. This paper presents the results of an investigation conducted to evaluate the performance of VCs and TEs for the thermal management of LEDs.