Thermal grease helps transfer heat between hot components such as CPUs and GPUs and cooling devices (usually heat sinks). This article explores the important role of thermal grease, including its composition, characteristics, and how to use it to ensure good heat transfer. We will discuss different types of thermal grease, including silicone, metal, ceramic, carbon based, and liquid metal, and how each grease meets specific needs. This article also explains the correct method of applying thermal grease on CPUs to avoid common errors and misconceptions, demonstrating its extensive role in maintaining the stability and efficiency of electronic devices.
How does thermal grease enhance thermal conductivity?
Thermal grease, commonly known as thermal paste, plays an important role in controlling the heat of electronic devices. Its main function is to facilitate heat transfer from hotter components (such as CPUs or GPUs) to cooler components (such as heat sinks) by filling the air gaps between surfaces. At the molecular level, there are several mechanisms that can explain how thermal oils improve thermal conductivity:
The surfaces of heat sources (such as CPUs) and heat sinks may appear smooth to the naked eye, but in reality, they are rough and uneven on a microscopic scale. These uneven areas will create small air gaps when in contact with the surface, which will hinder heat transfer as air is a poor conductor of heat. Thermal grease will fill these air gaps and replace air with materials with much higher thermal conductivity, thereby improving heat transfer efficiency.
Thermal conductive grease is made by mixing basic materials such as silicone or synthetic oil with thermal conductive particles such as metal, ceramic, or carbon. These particles form a thermal conduction pathway network in the oil, allowing heat to propagate more efficiently than through the base material alone. This network improves the overall thermal conductivity of the interface.
The heat transfer efficiency of an interface is inversely proportional to its thermal resistance. Thermal conductive silicone grease can improve the contact between the heat source and the heat sink, and provide a medium with stronger thermal conductivity, thereby reducing the thermal resistance at the interface. This can dissipate heat more effectively.
Types of thermal grease
Silicon based grease: This is the most widely used universal thermal grease. They contain silicone oil mixed with metal or ceramic conductive particles (such as zinc oxide or aluminum oxide). They are cost-effective and provide moderate thermal conductivity.
Metal based grease: These greases contain metal particles such as silver, aluminum, or copper, making them excellent thermal conductors. Metal based grease has higher thermal conductivity than silicon-based grease, making it an ideal choice for high-performance applications such as gaming PCs or servers.
Ceramic based grease: These greases do not contain metal particles and are composed of ceramic conductors such as aluminum nitride, boron nitride, or silicon carbide. Ceramic based grease is non-conductive, making it highly suitable for applications where conductivity may pose risks.
Carbon based grease: including graphite or diamond powder, these greases utilize the high thermal conductivity of carbon materials. Diamond powder has excellent thermal conductivity and can be used in applications that require excellent heat dissipation.
Liquid metal grease: These greases are composed of alloys such as gallium and have high thermal conductivity, making them suitable for extreme performance applications. However, they have conductivity and may corrode aluminum, so they must be used with caution.
Apply thermal grease correctly on the CPU
Thermal conductive adhesive or thermal conductive silicone grease: which is better? Elaplus Electronic Adhesive Comprehensive Comparison Guide – Elaplus Electronic Adhesive
Common errors and misconceptions in applying thermal conductive silicone grease
Apply too much thermal grease
A common misconception is that the more thermal paste there is, the better the heat dissipation effect. In fact, the function of thermal grease is to fill the small defects on the surface of the CPU and heat sink to improve thermal conductivity. It is not the main conductor of heat. Excessive use can isolate heat sources and reduce heat transfer efficiency. Ideally, apply a thin layer evenly, about the thickness of a piece of paper, or apply a pea sized dot in the center under the pressure of the radiator.
Reuse old thermal grease
Reusing old thermal grease after disassembling the radiator or replacing components is another common mistake. Used thermal grease will dry out and lose its thermal conductivity. When disassembling components, it is best to thoroughly remove the old thermal grease and apply a layer of new grease to ensure optimal thermal contact.
Using the wrong type of thermal grease
Different thermal conductive pastes are designed for different applications and conditions. Some thermal conductive pastes contain metal based compounds that are conductive, and there is a risk if they diffuse onto electrical components and cause a short circuit. Unless you are certain of the conductivity and safe application of the product, please choose non-conductive thermal paste for general use.
Believe that all thermal conductive pastes are the same
There is a misconception that all thermal conductive pastes have equally good performance, so choosing which one is not important. In fact, the composition of thermal paste varies – some include silver or ceramic particles to enhance thermal conductivity. These differences can affect performance, especially in high-performance computing thermal management. It is worthwhile to research and choose a thermal paste that suits your specific needs and budget.
Neglecting the application method
The effectiveness of thermal paste largely depends on the application method. Common methods include dot coating, line coating, and application. Each method has its advantages, depending on the processor type and heat sink design. For example, CPUs with multiple cores may benefit from line drawing, ensuring that all cores are fully covered. Understanding the most suitable application method for your hardware can ensure effective coverage without spilling.
Neglecting surface preparation
Before applying thermal grease, proper preparation of the CPU and heat sink surfaces is often overlooked. Dust, oil, or residue can form obstacles that hinder effective heat transfer. Before applying thermal grease, clean both surfaces with a lint free cloth and isopropanol to ensure they are clean and dry.
The function of thermal conductive silicone grease
The following table compares the thermal conductivity performance of processors with and without thermal grease.
Does not contain thermal conductive silicone grease, but contains thermal conductive silicone grease
Due to micro defects and air gaps, the contact effect between the processor and the heat sink is poor, resulting in poor thermal conductivity and high thermal resistance. Fill the small air gap between the processor and the heat sink to increase thermal conductivity and reduce thermal resistance.
Adjust the temperature to a higher working temperature and lower the working temperature
Thermal throttling: More likely to reduce performance to prevent overheating Enhanced performance: Reduce thermal throttling
Shorten component lifespan: Prolonged high temperatures can shorten the service life and extend the service life: Better heat dissipation can extend the service life of components
System stability: Excessive temperature can cause crashes or unexpected shutdowns. Stability: Cooler processors run more reliably, reducing crashes or shutdowns
The ability to maintain high clock speed decreases overall system performance, resulting in a more stable and high-performance system
Overall efficiency decreases for a longer period of time to maintain optimal performance
The significant decrease in user experience during computing tasks and gaming processes is beneficial for high processing tasks such as gaming and video editing
Smoother performance, hardware upgrade interval may be longer
Quantitative analysis idle temperature: 40 ° C idle temperature: 35 ° C
Load temperature: 85 ° C Load temperature: 70 ° C
Thermal resistance: 0.5 ° C/W Thermal resistance: 0.2 ° C/W
Composition and characteristics of thermal conductive silicone grease
chemical composition
Thermal conductive silicone grease is made by mixing base materials (silicone or non silicone) with conductive fillers. These choices will affect its thermal and electrical conductivity, as well as other physical properties.
base material
Silicone grease is widely popular due to its thermal stability and resistance to decomposition over a wide temperature range. They can also provide good electrical insulation, making them an ideal choice for applications that require this characteristic.
When low leakage and low evaporation rates are important, use non silicone based materials such as synthetic oils or esters. In situations where silicone resin contamination may cause problems, such as optical or automotive applications, these are preferred.
Conductive filler
Metal oxides, such as zinc oxide and aluminum oxide, are widely used because they balance thermal conductivity and electrical insulation.
Metal fillers, including silver, aluminum, and copper particles, can improve thermal conductivity but also increase electrical conductivity, which is not applicable to all applications.
Carbon based materials such as graphite and carbon nanotubes, as well as ceramic particles, have high thermal conductivity and no risk of electrical conduction.
Physical property
Thermal conductivity: This measures the ability of a material to transfer heat. The thermal conductivity of thermal grease ranges from 0.5 to 10 W/mK, and special types of thermal grease can achieve even higher values. The higher the thermal conductivity, the better the heat transfer effect.
Viscosity: Viscosity can affect the difficulty of applying oil and the thickness of the oil layer formed between surfaces. Oils with lower viscosity are easy to apply and suitable for thin layer application, while oils with higher viscosity are more suitable for larger gaps or rough surfaces.
Thermal impedance: Thermal impedance measures the resistance to heat flow, taking into account both thermal conductivity and oil layer thickness. The lower the thermal impedance, the higher the heat transfer efficiency.
Working temperature range: The temperature range of the lubricating grease must match the working conditions of the equipment or machinery. Some lubricants are designed specifically for extreme temperatures, including low and high temperatures.
Durability: Over time, thermal grease may dry, harden, or migrate from the application area, thereby reducing its effectiveness. The oil formula can affect its durability and the frequency of reapplication.
Different methods of applying thermal conductive silicone grease
Automatic allocation system
The automatic distribution system ensures consistent and precise application of thermal grease in a professional environment. These systems can be programmed to allocate the exact amount of solder paste required at specific locations on the CPU or GPU, minimizing human errors and variations in coating thickness. This automation can also accelerate the assembly process in the production environment.
Laser assisted applications
An advanced method is to use laser technology. Before applying thermal grease, the laser will slightly heat the thermal grease to reduce its viscosity and make it more evenly distributed on the chip surface. This technique is particularly useful for thicker pastes or situations that require precision.
Screen Printing Techniques
Screen printing originated from the electronics manufacturing industry and can efficiently apply thermal paste. Use a mask to define the application area, and use a tool similar to a scraper to evenly apply the thermal paste onto the mask, ensuring that the coating is uniform and the edges are precise. This method is most suitable for assembling multiple processors simultaneously.
Screen Printing Techniques
Precision template method
Template method is to place the template above the CPU or GPU and leave gaps where thermal paste needs to be applied. Apply thermal paste onto the template, then remove excess thermal paste to ensure that the thickness and shape of the applied thermal paste are consistent.
Precision template method
Application of phase change materials
Phase change materials (PCMs) melt and solidify at specific temperatures, absorbing or releasing heat during the process. PCM can be used as a gasket or sheet, which melts and adheres to the surface of the chip when heated. Although PCM is not a traditional paste, it provides an innovative alternative that offers consistent thermal conductivity without the need for liquid compounds.
Ultrasonic application
Ultrasonic applications use vibration to evenly distribute thermal paste on the surface of chips. This technology is very suitable for achieving extremely thin thermal paste layers in high-precision environments. It also helps to eliminate bubbles that may hinder thermal conductivity.
3D printing of thermal paste
Emerging technologies allow for 3D printing of thermal paste, enabling precise deposition of thermal paste in patterns optimized for heat transfer. By adjusting the geometry of the paste application based on the heat output of different chip regions, this method may completely change the application of thermal interface materials in the future.
Conclusion
Thermal grease is beneficial for controlling the heat in electronic devices, greatly affecting their performance, reliability, and service life. This article emphasizes the importance of selecting suitable thermal grease by studying different types of thermal grease and their application methods. Understanding the working principle of thermal grease, which improves thermal pathways, reduces thermal resistance, or enhances heat transfer, can help us understand its role in designing and maintaining electronic devices. New application methods such as automation systems, laser assisted technology, and 3D printing of thermal conductive compounds indicate that precise and efficient thermal management can be achieved in the future. With the advancement of technology, continuous research on thermal grease ensures that electronic devices perform beyond expectations in the rapidly developing technological world.
Frequently Asked Questions [FAQ]
How to store thermal conductive silicone grease?
To ensure the thermal grease maintains its effectiveness, please store it in a cool and dry place, away from direct sunlight. The grease pipe cover should be tightened to prevent air from entering and grease from drying out. Keep upright to avoid leakage and ensure consistent composition for optimal results in the next use. Avoid extreme temperatures as they can alter the chemical structure of oils and affect their performance.
Tags: Thermal grease, Thermal grease, Silicone grease
What is the difference between thermal conductive gel and thermal conductive silicone grease?
Thermal conductive gel and thermal conductive grease are materials used to enhance heat transfer between computer CPU, radiator and other components. Their main differences lie in their physical characteristics and usage methods. Thermal grease is a viscous paste that needs to be manually applied to ensure even distribution and fill the small gaps between surfaces. On the other hand, thermal conductive gel is usually provided in the form of precoating pad or semi-solid, which is easier to handle and apply. However, because of its predefined thickness and poor flexibility in filling uneven surfaces, it may not always provide an effective heat transfer layer.
Where should thermal grease be applied?
Before installing cooling devices such as heat sinks or liquid cooling blocks, it is necessary to apply thermal grease to the surface of the processor (CPU or GPU). Apply a thin and uniform layer of silicone grease directly onto the surface of the chip that generates heat. This layer of silicone grease can act as a medium, effectively transferring heat from the chip to the cooler, and optimizing the performance of the equipment by reducing its operating temperature.
What are the drawbacks of thermal conductive silicone grease?
Applying thermal grease may be troublesome. It requires precision, any excessive application may result in overflow onto other components.
Over time, thermal grease will dry out, lose its thermal conductivity, and even leak out between surfaces, requiring reapplication.
Some thermal grease contains conductive materials, which may cause short circuits or damage to electronic components if used improperly.
What is the effective period of thermal conductive silicone grease?
The effective period of thermal grease is 3 to 5 years, depending on the quality of the grease and the working conditions of the equipment. Over time, oils and fats will dry or degrade due to thermal cycling, thereby reducing their heat transfer efficiency. If the temperature of the device starts to rise abnormally or the device has been used for many years, it is recommended to check and replace the thermal grease.
Tags: Thermal grease, Thermal grease, Silicone grease
