Heat sinks based on liquid metal for power electronics cooling applications

Abstract

Power semiconductor devices are key components for efficient power conversion in a wide range of industrial applications. The continuous trend toward increasing the power capability and decreasing the chip area of the semiconductors results in the generation of high heat fluxes, due to the power losses. Also, power electronics are one of the most common components of the power converter to fail, as a result of the thermomechanical stress within the structure of power module caused by large junction temperature swings (∆Tj). Effective and efficient thermal management systems should therefore be employed to dissipate the excess heat to the ambient environment and reduce the thermomechanical stress. Liquid metals received little attention as heat transport agents thus far, in spite of their excellent thermophysical properties. Also, their high electrical conductivity allows for driving them with a magnetohydrodynamics (MHD) pump, which is a reliable and low–power device. Hence, a thermal management system based on Ga68In22Sn10 liquid metal coolant is able to remove high heat fluxes, requires low operating power and provides high reliability; all desirable attributes for modern power electronic applications. This thesis focuses on the design and development of a cooling system based on liquid metal for conventional insulated–gate bipolar transistors (IGBTs), which are the most widely used power electronic switches for medium–to–high power conversion applications. The proposed heat sink is attached to the IGBT power module and liquid metal is impinged directly against the baseplate with the use of an integrated MHD pump, thus eliminating the need for thermal interface material (TIM). Moreover, an adaptive thermal management method based on liquid metal flow control is presented that is able to significantly reduce ∆Tj . Also in this thesis, the design and development of a liquid metal heat sink for press–pack IGBTs (PPIs) is proposed. Traditionally, water is used for cooling PPIs in high–power applications. However, ionised particles are developed in the cooling system that contribute to the corrosion of the piping system. Therefore, the use of a thermal management system based on liquid metal increases the heat dissipation capability without corroding the cooling structure. Analytical work is performed on the design of both heat sinks and the implementation of the temperature control method. The thermal performance of both heat sinks, as well as the adaptive heat sink control, are experimentally validated.