Optimized TIM1 Solution for Large 2.5D HPC Packages Using Silicone Matrix Containing Liquid Metal Materials

The importance of thermal interface materials (TIMs) has become increasingly critical due to the substantial rise in power and power density within 2.5D/3D high-performance computing (HPC) packages in recent years. There is a pressing need for advanced TIM solutions, particularly TIM1, to be applied onto large 2.5D fanout modules within lidded packages. These solutions are essential for reducing the thermal resistance of junction-to-case and for significantly improving the effect of lateral heat spreading of the lid, which is crucial for addressing local hotspots that can reach up to 3 W/mm². This study introduces an innovative TIM1 approach that incorporates a silicone matrix with liquid metal materials, which has been successfully applied to a lidded 2.5D package with a fanout area almost double the size of a standard reticle. The bond line thickness (BLT) of the TIM1 is consistently maintained within 50~60μm on the periphery and over 95% coverage without delamination across the entire fanout module. This is achieved through a refined dispensing pattern of the adhesive-type TIM1 around the liquid metal material's periphery, coupled with a dam structure near the fanout module's corners to ensure BLT as thin as possible by bonding with both the lid and the substrate. Crucially, the process characterization data not only closely aligns with the design targets established by thermal and mechanical co-simulation analyses but also offers competitive thermal performance with significantly reduced stress compared to solder TIM, as indicated by mechanical simulation results.