Thermal Performance of Liquid Metal Pastes Containing low Content of Metal Particles for Thermal Interface Materials in IC Module Electronics

In recent years, considerable attention has been paid to gallium-based liquid metal alloys in their use as thermal interface materials for GPU, APU, and HPC in PC and super computers due to its considerably high thermal conductivity and low contact thermal resistance. Gallium-based Liquid metal paste containing low content of metal particles (LMP-MPs) to enhance thermal performance and controllable BLT of the prepared liquid metal composites for thermal interface materials (TIMs) prepared by in-situ introducing gallium oxide into the liquid metal alloys will be reported in our recent research. In this paper, we will report effect of the composition, particle size/types, and bond line thickness on thermal properties of the LMP-MPs. Thermal properties of the LMP-MPs were measured at 50o C using a thermal tester, TIMA5, based on ASTM-D5470 test methodology. It was found in the present study that the composition and types of metal particles, and BLT have significant influence on thermal conductivity, and the conductivity values increase with an increase of the content of metal particles and BLT. However, thermal resistance varies with the change of composition and BLT of LMP-MPs. Scanning electron microscope (SEM) was used to characterize microstructure of LMP-MPs with different metal particles and sizes. Micrographic morphology of the LMPs-MPs shows continuous frame structure observed with SEM, which could keep liquid metals from spreading out and stabilize the phase. We eventually found the LMP-MPs have the better wetting and adhesion properties on bare Cu, glass and bare Si surface than liquid metal alloys that endows good printability to the LMP-MPs. Continuous monitoring of thermal resistance of LMP-MPs at 45o C and 89o C using a house-made thermal tester shows stable thermal resistance after a few months, which indicates LMP-MPs have excellent thermal reliability in ambient atmosphere.