Low Thermal Resistance Graphite-Organic Thermal Interface Material for IGBT Power Modules

There is a growing demand for power electronics that can operate under the high temperature and high power conditions that will be encountered in applications such as Hybrid Electric Vehicles. As the coolant temperature used to dissipate heat from the electronics increases, the operation of power semiconductor devices such as Insulated Gate Bipolar Transistors (IGBTs) becomes severly limited, in order to assure that the safe operating-temperature limit of the silicon semiconductor material is not exceeded. A particular problem, related to the packaging of the IGBT modules, is the low thermal conductivity of the thermal interface materials used to bridge the interface between the IGBT module and its heat sink. Thermal interface materials (TIMs) (such as grease, gel, and phase-change materials) have low thermal conductivities, which allow the thermal interface to account for most of the total thermal resistance of an IGBT module package. This project will develop a new TIM, based upon the use of continuous, high-thermal-conductivity graphite fiber encapsulated within a compliant organic matrix. This TIM is estimated to have a thermal conductivity that is 20 to 100 times greater than that of the best available thermal grease. In Phase I, the architecture and composition of the proposed graphite-organic matrix TIM will be evaluated and optimized. The optimal graphite preform design will be determined and the optimal organix matrix material will be selected. Based upon the optimal design, a prototype TIM, suitable for use with a high power IGBT module, will be fabricated and demonstrated. Commercial Applications and other Benefits as described by the awardee: The graphite-based TIM technology should provide lower thermal resistance and thus enable thermal management solutions that improve the operating range for a wide variety of power electronic systems. Commercial applications include electric vehicles, distributed power generation systems, renewable energy systems, and power electronics for harsh environment operation