Thermal characteristics of vertically-integrated GaN/SiC-on-Si assemblies: A comparative study

Paper in proceeding, 2019

This work investigates the thermal characteristics of a vertically-stacked, heterogeneously-integrated assembly intended for millimetre-wave communications systems. The assembly combines materials that enable the generation of high output power as well as high degree of integration for improved performance, and vertical integration of the different materials enables a compact footprint. Suitability of thermal solutions based on metal pillars, solder balls, and ball grid arrays (BGA) is investigated. Both ideal, fully-populated arrays of interconnects and partially-filled ones more suitable for practical implementations are considered using theoretical calculations and numerical thermal simulations. With the assumptions used, simulation results show that arrays of Cu pillars and large solder bumps with a pitch of 150 μm provide good thermal performance also with a simplified grid and reduced number of interconnects. In the current geometry, the most important locations for the pillars and bumps are near the heat sources, and the use of a rim of interconnects around the assembly perimeter can reduce the temperature by several degrees - even when the majority of the other interconnects is focused beneath the heat sources.