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Views: 0 Author: Site Editor Publish Time: 2025-12-16 Origin: Site
The demand for computing power is huge. AI chips, like advanced GPUs and CPUs, now push the limits. Their thermal design power (TDP) is very high. It often exceeds 700 watts per chip. Sometimes it even nears 1000 watts. Traditional air cooling systems cannot handle this heat load. Air cooling has completely failed at these power densities.
Direct Liquid Cooling (DTC) is now the necessary solution. DTC involves placing a cold plate directly onto the chip. This is the main trend in modern data centers. But the liquid cold plate needs an extremely efficient thermal interface. This interface must connect the small, hot chip to the large cold plate.
This is where the heat pipe module comes in. This module includes standard heat pipes and Vapor Chambers (VC). It acts as a core thermal spreading component. It sits between the chip and the final liquid cold plate.
This article explains the critical role of these heat pipe modules. It shows how they use phase change heat transfer. This transfer solves two main problems. It solves the problem of high local heat flux density. It also solves the problem of non-uniform heat generation on AI chips.
Heat pipe modules are superior heat transfer devices. They use phase change to move heat. This makes them much more efficient than solid metal conductors.
Heat pipes work through a simple, continuous cycle. A working fluid is sealed inside a vacuum tube.
Evaporation (Heating Zone): Heat from the AI chip causes the fluid to vaporize. This absorbs a large amount of heat energy (latent heat).
Transport: The vapor travels rapidly down the tube to the cooler zone.
Condensation (Cooling Zone): The vapor cools down and turns back into a liquid. This releases the latent heat to the cold plate.
Return: The liquid returns to the heating zone through a wick structure (capillary action).
The entire process is extremely fast. This phase change cycle gives the heat pipe its special advantage. The heat pipe's effective thermal conductivity (keff) is much higher than Copper. It can be 5 to 100 times greater.
The Vapor Chamber (VC) is a special form of heat pipe. It is designed to be flat and two-dimensional.
The VC works on the same principle as a heat pipe. However, it spreads heat across a plane instead of a line. This function is essential for AI chips. These chips have concentrated heat points. The VC quickly captures the heat from these points. It then disperses the heat uniformly across its entire top surface. This action prepares the heat for the next cooling stage.
The VC ensures heat does not linger at the source. This ability makes it indispensable for modern GPU cooling assemblies.
AI chip thermal design faces two main physical challenges. Heat pipe modules are specifically designed to address both challenges effectively.
GPU and CPU dies do not heat up evenly. Certain functional blocks, like the main computing cores, generate intense, localized heat.
The heat flux density (W/cm^2) at these core areas is extreme. It can be hundreds of watts per square centimeter. If a standard cold plate is placed directly on top, the heat cannot spread fast enough. This causes the local junction temperature (Tj) to rise rapidly. High Tj leads to performance throttling. It also causes material degradation.
The Vapor Chamber solves this problem immediately. The VC base plate contacts the chip. It instantly captures the intense heat from the hot spots. It converts this heat into vapor inside its chamber. This vapor rapidly condenses across the cooler areas of the VC surface. This process effectively homogenizes the heat flux. The entire top surface of the VC becomes almost isothermal. This prevents dangerous localized overheating.
The heat must eventually reach the liquid coolant. Heat pipe modules act as the vital bridge in this transfer.
Liquid cold plates are typically large components. They need large contact areas for efficient heat exchange. The AI chip itself is small. The heat pipe module is the best interface between these two sizes. It receives the high-flux heat from the small chip. It then spreads that heat efficiently across the larger surface of the liquid cold plate.
When the heat is transferred through an isothermal VC, two things happen. First, the heat input to the liquid cold plate becomes uniform. Second, the liquid cold plate can then maximize its own efficiency. It can utilize all its internal channels and fins fully. This ensures the best possible convective heat transfer to the fluid. Without the VC or heat pipes, the liquid cold plate would only work efficiently directly above the chip's core.
Engineers must choose the right type of phase change device. This choice depends on the chip layout and the system geometry.
Both heat pipes and VCs use the same principle. But their geometry dictates their best use.
| Parameter | Vapor Chamber (VC) | Heat Pipe (HP) | Best Application Scenario |
|---|---|---|---|
| Spreading/Isothermal Ability | Excellent (Fast planar dispersion) | Moderate (Better for directional transport) | Direct contact with the high-flux chip core. |
| Structural Flexibility | Low (Must remain mostly flat) | High (Can be bent, shaped to bypass obstacles) | Moving heat long distances to a remote heat sink. |
| Cost | Higher (Complex internal structure) | Lower (Standardized tube manufacturing) | |
| Applicable Heat Flux | Extreme ($>500\text{W}/\text{cm}^2$) | Moderate to High |
The VC is the superior choice for the direct chip interface. It handles the extreme non-uniform flux best. Heat pipes are then often used as conduits. They move the spread-out heat to a remote liquid cold plate or heat exchanger.
A typical AI cooling solution is a hybrid module. It links the chip to the DTC system.
The heat must pass through a specific stack of materials. The stack includes:
The design must focus on minimizing the thermal resistance at the two TIM interfaces. The VC must have excellent flatness. This flatness is required to mate perfectly with both the chip and the cold plate. The VC acts as a perfect isothermalizer. It turns a complex heat source into a simple, uniform one for the liquid cold plate.
Heat pipe modules are more than just heat movers. They are key components for boosting system performance and ensuring long-term reliability.
The high efficiency of the heat pipe module has direct benefits for the chip.
The module's low thermal resistance means the chip runs cooler. This translates directly to a lower chip junction temperature (T_j). A lower $Tj is critical. It allows the AI chip to operate at higher clock speeds. It allows for longer Boost periods. This maximizes the computational throughput.
Heat pipe modules provide excellent thermal uniformity. They remove hot spots effectively. This removal reduces the maximum temperature difference (DeltaT_max) across the chip surface. Reduced temperature cycling and thermal gradients significantly lower the risk of thermal stress. This action substantially increases the overall lifespan and reliability of the AI hardware.
Designing and manufacturing phase change devices is complex.
Gravity Effect: Standard heat pipes can be affected by gravity. Their performance drops if they are oriented poorly against gravity. Server design must account for the heat pipe's optimal working angle to ensure reliability.
Sealing and Cleanliness: Heat pipes and VCs require perfect internal sealing. The working fluid and wick structure must be extremely clean. Any non-condensable gas drastically reduces efficiency. This requires high-precision stamping and expert brazing or welding (processes mastered by Winshare Thermal).
High-Pressure Integrity: The VC must handle high internal pressure at elevated temperatures. The structure must be robust.
TDPs will keep climbing. The industry is moving toward hybrid solutions. These solutions include very thick VCs or even micro-channel liquid cold plates placed directly above the VC. The role of the thermal spreading component remains central to future AI cooling solutions.
The heat pipe module is a core thermal management component. It is indispensable in the modern AI server cooling chain. It efficiently solves the fundamental problems of localized hot spots and difficult heat transport.
The module provides an isothermal surface. This surface is necessary for the final liquid cold plate to work at peak efficiency. As TDP continues to climb, the thermal spreading capability of VCs and heat pipes becomes the essential foundation. It is the key to unlocking the full performance potential of direct liquid cooling.
Winshare Thermal offers end-to-end capabilities. We design and manufacture VCs, custom heat pipe modules, and high-performance liquid cold plates. We offer integrated thermal solutions for the most demanding AI applications. Contact us to optimize your AI server thermal architecture.
