Alternative to Solder TIM 1 Using Liquid Metal Reinforced with Z-axis Oriented Carbon Fiber

This paper introduces a new TIM1 technology designed to provide the reliability, thermal performance, and cost reduction necessary to enable the trends of increasing die size and power density. The TIM1 technology presented is as defined as “LMZRT”, comprising a gallium-based liquid metal alloy reinforced with Z-axis oriented carbon fiber. This new material harnesses the superior thermal conductivity and surface wetting of liquid metals while eliminating issues such as spill-out and incomplete die coverage through the integration of a vertically aligned, high-thermal-conductivity carbon fiber framework. LMZRT shows low thermal resistance (less than 3 mm²-K/W at a 150-micron bond line thickness), this is done without need for soldering or backside metallization reducing the cost and complexity of the package. LMZRT has shown stability through multiple solder reflow cycles at 245°C+ and maintains full die coverage, and exhibits no voiding, cracking, or delamination. Furthermore, LMZRT is produced as a durable preform compatible with standard pick and place manufacturing. Cost modeling data is also provided, benchmarking LMZRT against Indium-Silver solder in a TIM1 configuration. Boston Materials envisions LMZRT as a material enabling innovation to overcome thermal management challenges of large body flip chip lidded ball grid array (FCLBGA) packages used across artificial intelligence (AI), machine learning (ML), high-performance computing (HPC), and advanced networking applications.