Advanced Packaging and Thermal Management for High Power Density GaN Devices

Abstract

Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) are thermally limited much below the electrical capability of the devices. The unique challenge of a GaN HEMT is its ultra-high heat flux at the micro-scale gate fingers, which cannot be effectively and adequately addressed by conventional packaging and thermal management systems and lead to a large junction-to-ambient thermal resistance. A novel thermal interface material (TIM) that offers unique heat spreading, CTE compliance and ultra-high thermal performance was developed. The new TIM enables attaching GaN die directly onto a copper carrier. The heat spreading feature of the TIM can effectively dissipate heat near junction and greatly reduce the maximum heat flux, which leads to smaller temperature difference across each layer underneath of the TIM. A preliminary demonstration of the technology on a GaN-on-Silicon device shows 50% higher heat dissipation capability, compared to the state-of-the-art pin fin cold plate liquid cooling, while maintaining the device junction temperature at 150°C.