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Global data centers face previously unheard-of demands for processing power and energy consumption due to the quick development of artificial intelligence, large-scale data processing, and high-performance computing. High-performance server chips, which are the foundation of computing power, show steadily rising transistor integration and operating frequencies, which cause power density to grow exponentially. Modern AI accelerator chips, such as the NVIDIA H200, for example, have thermal design power (TDP) of up to 700 watts. In light of this, effective thermal management techniques are crucial for both chip stability and unlocking their full computational potential.Thermal interface materials (TIMs), serving as the foundational components in cooling systems that connect chips to heat sinks, fill microscopic voids, and establish efficient thermal pathways, directly determine the upper limit of an entire cooling solution's efficiency. Facing the severe challenge of kilowatt-level thermal flux densities, TIM technology is undergoing profound transformations—from material formulations to application processes.
From Air Cooling to Liquid Cooling: Evolutionary Demands on TIM in Cooling Architectures
Traditional server air cooling solutions can no longer meet the thermal demands of single chips generating hundreds to thousands of watts. Currently, cold plate liquid cooling has become the standard thermal configuration for high-performance servers. This solution directly dissipates chip heat through coolant flowing through precision cold plates. The theoretical upper limit of heat dissipation for single-phase cold plates can reach 1400 watts, sufficient to cover the demands of current and next-generation high-power chips. Within liquid cooling systems, microscopic and macroscopic gaps between the cold plate and the chip package lid must be filled. The core function of TIM here is to fill irregular voids between interfaces, displace low-thermal-conductivity air, and establish a continuous, efficient thermal conduction pathway. This ensures the massive heat flux generated by the chip is transferred to the cold plate with minimal thermal resistance.
The evolution of thermal architecture demands orders of magnitude higher performance from TIMs. Traditional low-performance TIM products are wholly inadequate for cooling high-computing-power chips. Industry consensus indicates that TIMs serving these kilowatt-level heat flux chips require thermal conductivities of at least 6 to 8 W/m·K to be viable solutions. Products with thermal conductivities of 8 W/mK and above occupy the pinnacle of the thermal interface material performance pyramid, representing the current zenith of material synthesis, filler technology, and manufacturing processes.
Current Status Review: Material Reliability Challenges in High-Computing Environments
Under actual operating conditions involving high power and extended runtime cycles, even high-performance TIMs face severe long-term reliability challenges. Public industry data reveals that on certain early-deployed high-computing-power server motherboards, the gray paste-like TIM (typically high-performance thermal grease) applied between chips and heat sinks has exhibited noticeable physical deformation and pumping phenomena. Concurrently, the use of white block-shaped thermal pads covering power supply modules and surrounding chips on motherboards indicates a significant increase in TIM usage within system-level thermal design. These phenomena reveal two core issues: First, extreme thermal loads and temperature cycling exert immense pressure on TIM stability, accelerating material aging.Second, coordinated cooling throughout the motherboard has replaced isolated hotspot management in high-performance server thermal design, necessitating a variety of highly dependable TIM types with extensive performance characteristics.
Technical Frontiers: TIM Types and Selection for High-Performance Chips
The industry currently uses and creates the following types of high-performance TIM solutions to meet the high thermal demands of high-performance server chips:
1. High-Performance Phase-Change Thermal Interface Materials: These materials make handling and transportation easier because they stay solid at room temperature. In order to achieve ultra-low thermal resistance at the interface, the material softens or liquefies when it reaches the phase-change temperature, which is usually between 45 and 60°C. This effectively fills interfacial microvoids. The material maintains cohesive qualities to prevent pumping out after phase transition. It is one of the best materials for liquid cooling high-power CPUs and GPUs, especially for large-scale chips that are sensitive to interface pressure, with thermal conductivities that typically range from 6 to 10 W/mK.
2. Greases and Gels with High Thermal Conductivity: Thermal conductivities greater than 8 W/mK can be attained with specially designed greases and gels that contain large amounts of sophisticated, highly thermally conductive fillers like boron nitride, aluminum oxide, or diamond. Thermal gels that are applied using precision dispensing or liquid injection molding provide excellent resistance to thermal shock, high coverage, and low thermal resistance. They are appropriate for complex geometries or heat transfer interfaces with height differences. Low volatility, resistance to drying out, and anti-pumping capabilities under extended high temperatures are important challenges.
3. Metal-Based Interface Materials: These comprise alloy foils based on indium with low melting points and liquid metals. Near-theoretical-limit interfacial heat transfer is made possible by liquid metals' exceptionally high intrinsic thermal conductivities, which are usually greater than 15 W/mK. However, extremely accurate application methods and encapsulation designs are required due to their electrical conductivity, fluidity, and potential to corrode substrate materials. Indium foil is frequently utilized in specialized applications requiring exceptional reliability because it provides a solid-state metal solution with plastic deformation capability and no pumping risk.
4. Advanced Carbon Materials and Composite Gaskets: Composite gaskets or films with carbon nanotube arrays, graphene, or highly oriented graphite films as thermal fillers show remarkable in-plane thermal conductivity, which facilitates surface heat diffusion in chips. When filled with high aspect ratio boron nitride flakes, novel polymer-based composite gaskets achieve vertical thermal conductivities greater than 12 W/mK while retaining electrical insulation. For next-generation high-power chips, this offers a promising solution.
Conclusion
Thermal management for high-performance server chips represents an engineering challenge in the race against heat flux density. While thermal interface materials (TIMs) are not active cooling components, they serve as the critical bottleneck determining the fundamental efficiency of cooling systems. The paradigm shift from air cooling to liquid cooling has not diminished the demands on TIMs; rather, their importance has multiplied as they directly determine whether liquid cooling systems can fully unlock kilowatt-level heat dissipation potential. Currently, thermal conductivities of 6-8 W/mK serve as the entry threshold for high-performance chip applications, while products exceeding 8 W/mK represent the pinnacle of technological competition. Looking ahead, as chip power consumption advances toward the kilowatt range, demands for TIM will transcend the singular metric of “high thermal conductivity.” Instead, the focus will evolve toward comprehensive capabilities encompassing “ultra-high thermal conductivity, long-term stability, aging resistance, and process compatibility.” Continuous breakthroughs and mature applications of cutting-edge technologies—such as phase-change materials, liquid metals, and advanced carbon composites—will form the critical material foundation underpinning the ongoing evolution of next-generation data centers and artificial intelligence computing infrastructure.
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