Reliable high-performance cooling always starts with proper thermal interface expertise, and working with Carbice® Pads enables a new industry standard.
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Traditionally, fan-powered air-cooled heat sinks have been used to dissipate heat away from computer processors, but recently liquid cooled devices are gaining popularity as a more efficient solution for extremely high-powered computing applications. Even typical desktop computers rely on high performance cooling devices to keep up with advances in chip technology, which has led to a large variety of consumer-grade coolers on the market.
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With all this variation on the market, consumers may have difficulty deciding which cooler is best for their system. Beyond fan size, power and flashy RGB lighting, the Carbice® Lab team wanted to take a closer look at which interface properties contribute to a heat sink’s ability to effectively cool a high-powered CPU, and how they can be paired with the Carbice® Pad to achieve reliable thermal performance. To understand the relationship between heat sinks, contact surfaces and thermal resistance we need to understand how they work and what role thermal interface materials play in the final solution.
Air-Cooled Heat Sinks
Air-cooled heat sinks have long been the standard for dissipating heat in electronic devices. In desktop PCs, the heat sink typically attaches to the CPU’s integrated heat spreader (IHS) to conduct heat away from the chip package. The heat is transferred from the baseplate of the heat spreader through heat pipes to a fan that pushes the hot air away from the computer.
- Pro: Cost-effective and simple to maintain. No worries over leaking.
- Con: Generally, less effective at cooling high-power processors, which can limit performance under heavy workloads. Bulky and difficult to fit into smaller form factors.
Liquid Cooled Heat Sinks
In desktop computers, all-in-one (AIO) liquid coolers use a closed-loop system where temperature-regulated pumps circulate coolant into a water block and across the surface of a cold plate to maintain cooler chip temperatures. The heated coolant is then transported through tubes into a radiator to be exchanged with air. Built-in fans then force the hot air away from the computer.
- Pro: Highly efficient, especially for high-performance applications.
- Con: More complex and costly to install and maintain than air-cooled systems. Possibility of leaking.
Thermal Barriers
One crucial aspect of cooling performance is often overlooked that can seriously affect the transfer of heat from hot components like CPUs: the quality and application of thermal interface materials (TIMs). TIMs bridge the gap between heat sources and heat sinks, ensuring efficient heat transfer by filling microscopic air gaps that increase thermal resistance.
Due to the imperfect surfaces of both heat sinks and heat sources, tiny air gaps form, increasing thermal resistance and impeding heat transfer. Even the most advanced cooling solutions can be undermined by microscopic air voids, which block the efficient escape of heat.
Even the most advanced cooling solutions can be undermined by microscopic air voids, which block the efficient escape of heat.
Thermal interface materials are essential components that bridge the gap between heat sources and heat sinks, improving thermal transfer by filling microscopic air gaps that impede heat flow. However, the effectiveness of a TIM depends not only on its material properties but also on the mechanical fastening, surface conditions, and applied load during assembly. Proper fastening ensures consistent pressure, maximizing contact between surfaces and enhancing thermal conductance. Without optimal load and flat contact surfaces, even a high-performance TIM cannot function as intended.
For a TIM to be practical in real-world applications, all these factors—material properties, mechanical fastening, and surface conditions—must work together reliably and consistently at scale. This ensures predictable performance and cost efficiency in business and industrial contexts.
To better understand their role, TIMs are categorized into TIM 1, TIM 1.5, and TIM 2 based on their specific applications. TIM 1 is applied directly between the silicon die and the integrated heat spreader (IHS). TIM 1.5 involves a direct-to-die attachment of a heatsink or cold plate without an IHS. TIM 2 is used between the IHS or heat spreader and external heat sinks.
The materials used in thermal interfaces can generally be divided into thermal pastes/greases, pads, phase change materials (PCMs), and low-melting-point alloys (LMPAs). Let’s look at thermal pastes or greases, the most common thermal materials used on CPU heatsinks, and the Carbice® Pad for comparison
Thermal Pastes/Greases
Thermal pastes are designed to efficiently conduct heat and reduce thermal resistance by filling the voids between interfaces. As a liquid, thermal pastes are very good at compensating for uneven contact surfaces and can be applied in various ways to fully bridge the gap between them. They perform well at low fastener loads when surfaces are flat, ensuring effective thermal transfer. However, they can pump out at both low and high fastener loads when the surface has significant curvature or is oriented vertically. Controlling the thickness variation of thermal paste and grease in volume production is challenging, no matter the application approach, leading to quality and yield issues.
Carbice Pads
Carbice thermal pads offer exceptional reliability and durability, and consistency of application in volume production. Thanks to the patented aligned carbon nanotube-metal core structure, Carbice pads maintain their thermal conductance over long periods, ensuring consistent performance throughout the product's lifespan. Many thermal pads, including Carbice, must account for factors like fastening load, surface structure, curvature, and device surface area to ensure optimal thermal performance. Carbice leverages aligned carbon nanotubes and advanced polymer science to combine the properties of solids and liquids, enabling easy adaptation to uneven surfaces.
Testing Coolers
To examine the relationship between the heat sink fastening, surface and thermal resistance, we tested several of the leading desktop coolers on the market. We selected a mix of air-cooled and liquid-cooled devices across various price points to capture a wide range of quality and performance levels in our test.
Using the AMD Ryzen 9 9950X Granite Ridge AM5 4.30GHz 16-Core as the CPU, we measured the effective cooling of the Carbice® Pad combined with the various cooling devices. To establish a baseline, we included results for three high-performance greases, demonstrating that the Carbice® Pad performs like a grease at its best—which is unique for a scalable pad solution. We also mapped the surfaces of the various coolers and the CPU using our proprietary Carbice® SIM modeling software to analyze the surface differences between the coolers and the CPU. We measured the cooler surface curvature to analyze its effect on thermal resistance. We captured the peak, or highest area of surface curvature, and compared that with CPU temperature readings.
For our test setup, we selected OCCT, a highly regarded stability testing software with advanced features like per-core CPU testing and adjustable GPU load testing. We collected the CPU temperature readings with each cooler after 15 minutes of cycling to reach a steady-state temperature at 100% CPU utilization.
This allowed our team to push the CPUs to their absolute limits, subjecting them to extreme workloads and intense operating conditions.
*Kraken temperature significantly reduced by adjusting the torque to create optimal contact pressure with the device.
This chart shows the relationship between surface curvature and temperature (°C) for different coolers. It highlights the temperatures measured using the Carbice® Pad, along with the surface readings for each cooler device.
Our testing indicates that heat sinks engineered to make excellent contact with CPU heat spreaders can significantly improve heat transfer, resulting in cooler, more reliable CPUs. The flatter heat sinks are also more repeatable test to test and indicate that results will be more consistent in high-volume production. Flatter surface contact with the heatsink was more important for good thermal performance than price points, with even the most affordable air-cooled devices being good options for maintaining low temperatures during testing.
Highlighting the Noctua NH-D15 G2 LBC
The Noctua NH-D15 G2 LBC is a great example of a heatsink that’s both engineered to minimize surface curvature and designed to conform to the lidded surface of the AMD processor. The minimal curvature in the Noctua heatsink combined with the Carbice® Pad resulted in the lowest device temperatures (74℃), even under the stress of 100% CPU utilization.
The CPU temperature at 100% utilization was approximately 20℃ to 30℃ below the critical thermal throttling threshold using Carbice and the Noctua heatsink together. Thermal throttling occurs when a CPU's internal sensors detect temperatures high enough to potentially cause damage to the chip. To protect the component, the system automatically reduces performance and power consumption. This safeguard ensures the CPU's longevity but can result in reduced performance during demanding tasks like intense gaming or high-performance computing.
The Carbice® Pad, paired with the Noctua heatsink, delivered exceptional cooling performance—keeping CPU temperatures a remarkable 33% below the throttling limit under extreme workloads.
High Curvature Devices
The two AIO liquid coolers (The LIAN LI ALC360 and the NZXT Kraken) exhibited the most curvature among any of the cooling devices. This curvature caused extremely uneven surface contact between the cold plates and the CPU lid. The blue areas on the pressure mapping images below represent areas with the best contact, while the yellow to red areas represent poor contact due to curvature in the baseplate.
Both AIO coolers had almost 10 times the curvature or over 200 microns more height at the peak surface level than all the air-cooled devices in the study, except for the Vetroo U6PRO cooler, which still had 50% less curvature than the liquid coolers. We believe this high curvature in liquid coolers can be caused by internal fins inside the cold plate designed to generate a larger surface area to spread and dissipate heat. This is an important tradeoff to consider when deciding on the value of moving to a liquid cooler vs air cooler. Even though liquid cooling offers the best potential for cooling, establishing good thermal contact to the chip — with a flat surface and good TIM — is vital to realize this potential.
Even though liquid cooling offers the best potential for cooling, establishing good thermal contact to the chip — with a flat surface and good TIM — is vital to realize this potential.
Optimizing Thermal Performance with the Kraken Device and Carbice
Looking at the Kraken device, we can see that it exhibits both the highest curvature of any of the devices tested, at 250 µm, and the highest temperature reading during our testing. Since thermal performance is a combination of fastener load, surface structure and material properties, we hypothesized that a small adjustment needed to be made to create better contact between the CPU lid, the Carbice pad and the heatsink. To address this, we applied additional pressure to the heatsink by adjusting the torque on its attachment. Rather than compensating for high curvature with a higher-resistance, thicker thermal pad, the Carbice team focused on enhancing compression to improve contact, which leverages the unique "low-stress-transfer mechanics" of Carbice pads.
As illustrated in the following chart, thermal readings dropped substantially. This indicates that the stock assembly load of the Kraken may be too low and modest adjustments to the design can have a substantial impact on system performance.
Leveraging the Unique Properties of Carbice® Pad
The Carbice® Pad features highly compressible carbon nanotubes with unique elastic mechanical properties. These properties allow it to safely accommodate higher pressures by evenly absorbing and distributing force across the interface. Carbice Pads have a zero Poisson's ratio and and effectively zero CTE (coefficient of thermal expansion) in an interface, which is breakthrough valuable new physics in a TIM that ensures low device stress and elimination of the typical shear and compressive failure modes in a thermal interface. Attempting similar pressure adjustments with liquid thermal paste could lead to increased risks of pump-out and degradation over time, and could transfer high stress concentrations to the chip and crack it.
In Conclusion
The effectiveness of heat transfer using a heat sink depends on several factors, including the quality of the heat sink itself and the quality of its contact with the heat source. Often, the surface structure of the heat sink baseplate plays a significant role in its ability to dissipate heat, whether it is air-cooled or liquid-cooled.
Our findings suggest that the surface flatness and compatibility of heat sinks may be more indicative of cooling performance than the cooling method or price point itself.
Additionally, fastening loads plays a critical role in ensuring effective heat transfer. Proper load distribution maximizes contact between the heat sink and the heat source, enabling thermal interface materials to perform optimally by filling micro-gaps and maintaining consistent heat transfer.
The extreme variation in surface structure and manufacturing processes across heat sink devices is a key reason why unreliable thermal greases and PCM materials remain widely used. The ability of liquid-based materials to conform to uneven surfaces continues to drive the widespread adoption of thermal pastes and PCMs, despite their known tendency to cause failures at the component interface over time. The costs associated with these failure modes—which do not occur with Carbice—are typically absorbed by manufacturers and component suppliers, ultimately being passed on to the end consumer in the form of additional costs and failures. Carbice believes it’s time to change that narrative with a more reliable and cost-effective solution – a solid elastic pad that performs like a liquid. In fact, pads have long been the preferred method for heat sink attachment in volume production due to advantages in assembly and repair, as long as they can meet the thermal performance requirement, which is now possible with Carbice Pad.
Carbice empowers system designers to achieve consistent, high-performance cooling by optimizing key factors such as contact pressure, surface flatness, and the advanced material properties of the thermal interface material. By addressing these critical elements holistically, Carbice ensures optimal heat transfer across a variety of system designs, from compact setups to high-powered industrial applications, delivering unmatched reliability and efficiency. Our Carbice Lab team is available to support your team with design, analysis, testing, and materials.
Interested in partnering with Carbice to unlock the most reliable cooling for your devices?
Contact our team today.
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