In power electronics, automotive, and other applications, thermal interface materials must offer efficient heat dissipation while achieving electrical safety and mechanical reliability. Thermally silicone rubber serves as a dual solution for heat dissipation and insulation. By understanding its characteristics and applications in this article, you can better determine whether it meets your requirements.
What is the Thermal Silicone Rubber?
Thermal conductive silicone rubber is a thermal interface material that combines thermal conductivity, protection, and insulation. Due to the inherently low thermal conductivity of silicone rubber, it is manufactured by incorporating high-performance metallic fillers into the silicone rubber compound. This process enhances its thermal conductivity while preserving its original high elasticity and insulation properties. It is typically pre-molded into components such as gaskets and end caps. You can use them in electrical equipment, electronic products, communication devices, automobiles, and other applications.
Key Properties of Thermal Silicone Rubber
Thermal Conductivity
Thermal silicone rubber achieves excellent thermal conductivity(typically ranging from 1 to 12 W/m·K) by mixing various thermal conductive fillers such as aluminum oxide, silicon nitride, and aluminum nitride. It can be used for heat dissipation in electronics, industrial equipment, and similar applications, helping to control temperatures and enhance operational stability. Higher-performance thermal conductive silicone rubber is also available for cooling high-power and high-load devices.
High Insulation
Unlike metal-based interface materials, thermal silicone rubber has good electrical insulation properties. Moreover, most thermal conductive fillers are also insulating. They also have high dielectric strength and breakdown voltage. This makes them suitable for high-voltage and sensitive electronic component applications, achieving electrical safety while meeting thermal management needs.
High elasticity
Thermal silicone rubber is soft and compressible while withstanding tension. Thanks to its high elasticity, it resists deformation and damage. When filling gaps between components and heat sinks, it compensates for height differences to minimize thermal resistance. This also allows it to cushion stress on components, reducing costly damage to your precision parts.
Chemical Corrosion Resistance
Thermal conductive silicone rubber resists a wide range of chemicals commonly found in electronic and industrial environments while maintaining stable performance. It also withstands moisture, ozone, and ultraviolet radiation, making it suitable for outdoor applications. Consequently, thermal conductive silicone rubber is very suitable for demanding industrial applications such as automotive electronics, industrial equipment, and energy systems.
High-Temperature Resistant
Thermal silicone rubber offers a broad operating temperature range, withstanding temperatures from approximately -50°C to 200°C without deformation, melting, or performance degradation. You can use it in both low-temperature and high-temperature environments within this range, providing reliable thermal management support.
Long-Term Reliability
Thermal silicone rubber offers outstanding resistance to aging, vibration, and thermal cycling. Compared to thermal grease, it requires less frequent maintenance and replacement while maintaining stable performance. Additionally, it dries out and pumps out less frequently during long-term use. This reliability makes it the first thermal interface solution for automotive, industrial, and communications applications.
Flexible Design and Customization
On one hand, thermal silicone rubber is supplied in solid forms such as gaskets, sheets, and molded parts. It is well-suited for automated manufacturing and mass production. On the other hand, you can also choose thermally conductive silicone rubber with varying thicknesses, hardness grades, and structural reinforcement effects. This makes it meet a wider range of your application.
How does Thermal Silicone Rubber Work？
Fill the Air Gap
Thermal silicone rubber is easy to process and is typically supplied in forms such as pads for simple installation in the gaps between chips, power components, and heat sinks. Its soft, compressible nature allows it to conform exceptionally well to rough surfaces, creating a smooth interface that maximizes thermal contact area between components and heat sinks. Furthermore, it displaces and replaces air within the gap, preventing high thermal resistance air from compromising heat dissipation efficiency. Additionally, it can be processed into various thicknesses and hardness levels to accommodate different surfaces and multi-device height differences.
Transfer Heat
Thermal silicone rubber creates an efficient heat transfer pathway for heating elements. During operation, these elements release amounts of heat. When installed on the surface, thermal silicone rubber rapidly absorbs this heat, preventing thermal buildup that could damage the components. After absorbing heat, the silicone rubber efficiently transfers it to the heat sink for dissipation, maintaining temperatures within normal operating ranges. This prevents performance degradation or damage caused by overheating, extends equipment lifespan, and enhances product reliability.
Mechanical and Insulation Protection
Thermal silicone rubber offers high elasticity and excellent rebound properties. Consequently, it also provides mechanical protection by reducing stress on components from vibration and impact during equipment operation, while offering pressure cushioning. It can also absorb some noise, allowing quieter equipment operation. Furthermore, thermally conductive silicone rubber delivers outstanding insulation properties with high dielectric strength and breakdown voltage, and you can use it near high-voltage and power components. This prevents short circuits and leakage currents, meeting safety regulations to achieve electrical security.
Filler of Thermal Silicone Rubber
Aluminum Oxide(Al₂O₃)
As cost-effective thermal fillers, alumina and thermal silicone rubber can be processed into the most commonly used universal thermal silicone pads. It is easy to fill, making them ideal for high-volume manufacturing, and they offer excellent electrical insulation properties. While their thermal conductivity is moderate, and excessive filling reduces the silicone rubber’s flexibility, they remain a low-cost solution. Alumina-filled silicone rubber can be utilized in consumer electronics, power supplies, industrial equipment, and similar applications.
Boron Nitride(BN)
Boron nitride offers higher thermal conductivity than aluminum oxide, making for more efficient heat dissipation with lower fill levels while maintaining electrical insulation. For selecting thermal silicone rubber in high-power-density applications, boron nitride-filled formulations are an excellent solution. However, due to more complex processing and superior performance, it requires a higher cost than aluminum oxide. You can choose from projects such as automotive electronics, servers, and high-power modules.
Aluminum Nitride(AlN)
Aluminum nitride is a material with high thermal conductivity and high insulation properties, suitable for projects demanding superior performance. However, its processing is more complex and incurs higher costs. Additionally, it readily reacts with water, leading to performance degradation and compromising its long-term stability. It should not be used in humid environments.
Magnesium Oxide(MgO)
Magnesium oxide also has high thermal conductivity, but its performance is not good when used alone. Furthermore, it is less machinable than aluminum oxide. Due to its lower cost (compared to AlN), it is often blended as a composite filler and mixed with high-performance fillers to reduce overall expenses.
Silicon Dioxide(SiO₂)
Silicon dioxide has low thermal conductivity and does not enhance the thermal conductivity of thermal conductive silicone rubber. As a functional filler, it improves the rheological properties, mechanical strength, and dimensional stability of thermal conductive silicone rubber. This allows thermal conductive silicone rubber to achieve better processability and performance stability.
Graphite and Graphene
Graphite and graphene are more advanced thermal interface materials, commonly used in applications demanding the highest thermal performance. They have extremely high thermal conductivity and possess in-plane thermal diffusion capabilities, allowing not only heat transfer but also rapid dispersion of localized heat across a surface. This enhances heat dissipation efficiency while preventing localized overheating. However, they also have excellent electrical conductivity and are not insulating. Therefore, you may not use it for insulation applications.
Common Forms of Thermal Silicone Rubber
Thermal Silicone Rubber Pad
Thermal silicone rubber is often pre-molded into thermal pads with various thicknesses and thermal conductivity properties. This form brings extremely convenient installation, eliminating the need for precise dispensing and application required by thermal pastes. They offer excellent processability, allowing customization of dimensions, thickness, hardness, and more to suit your product specifications. Precise cutting is also achievable. Furthermore, they provide high stability, require minimal maintenance, and deliver significant cost-effectiveness.
Adhesive-Backed Thermal Silicone Rubber
Thermal conductive silicone rubber can be laminated with materials such as fiberglass, PET, and PI to enhance dimensional stability and improve tensile resistance. Additionally, to achieve stronger adhesion, you can opt for thermal conductive silicone rubber with adhesive backing, available in either single-sided or double-sided configurations. This facilitates better surface filling and delivers longer-lasting stability. However, it does not provide high bonding performance, so mechanical fastening is required.
Thermal Silicone Rubber End Cap
Thanks to silicone rubber’s high elasticity, high-temperature resistance, excellent insulation properties, and sealing capabilities, it can be made into thermally conductive silicone rubber end caps. Thermally conductive silicone rubber end caps have lower thermal conductivity, but their first function is to offer physical and high-temperature protection alongside electrical insulation. On one hand, they shield tubing and rod assemblies from damage caused by friction, impact, contaminants, and other hazards. On the other hand, they protect components that are not heat-resistant. They also serve as high-voltage insulating materials, improving electrical safety
Applications of Thermal Silicone Rubber
Consumer Electronics
Thermal silicone rubber delivers satisfactory heat dissipation performance for both low-heat-load electronics and high-performance devices. Components such as SoCs, power ICs, and shielding covers in smartphones, tablets, computers, cameras, routers, and similar devices can utilize thermal silicone rubber. Furthermore, it is very lightweight and can be processed into thin sheets, enabling its use in compact, portable wearable devices and other applications.
Automotive Electronics
Thermal management using thermally conductive silicone rubber is highly suitable for components such as BMS, power modules, OBC, motor controllers, and MOSFETs in automobiles. On one hand, it is corrosion-resistant and durable, capable of withstanding the harsh environments of automotive electronics while meeting high reliability requirements and providing stable heat dissipation. On the other hand, it can withstand shocks and vibrations during vehicle operation, thereby extending the service life of components.
Industrial Power and Energy
Thermal silicone rubber resists UV radiation and moisture, making it suitable for outdoor industrial power applications such as inverters and IGBT modules. Thermal conductive silicone rubber can also be used in energy storage battery systems, photovoltaic inverters, charging stations, and similar applications. It efficiently cools high-performance electrical equipment, enhancing the stability of power systems. This reduces maintenance requirements and prevents severe consequences from equipment downtime.
Communication Equipment and Data Centers
If you are seeking suitable thermal management solutions for servers, 5G base station chips, CPUs, and similar components, thermally conductive silicone rubber offers not only high heat dissipation efficiency but also stable performance. Its use enhances the long-term operational safety of equipment, reduces system failures and malfunctions, and extends service life.
LED Lighting
LED lighting and display devices generate heat during working, triggering thermal shutdown protection. This can result in uneven brightness or even damage. Thermally conductive silicone rubber can be used in LED lamp heat sinks, PCBs, and other components to optimize operating temperatures and extend LED lifespan. Additionally, it provides electrical insulation to ensure safety. In linear and architectural LED installations, aluminum profiles for LED lighting can also provide a rigid housing for LED strips while helping transfer heat away from the light source.
Medical Industry
Thermal silicone rubber is non-toxic and easy to install. You can select medical-grade thermal silicone rubber to meet the high hygiene standards of the medical industry. Thanks to its compliance with long-term continuous operation requirements and reliable performance, it can be used in medical power supplies, diagnostic equipment, imaging systems, and more. However, it should not be used in components of silicone-sensitive projects.
How to Choose the Right Thermal Silicone Rubber
Thermal Conductivity Requirements
You need to select a thermally conductive silicone rubber with enough performance based on the component’s heat dissipation requirements. Materials with higher thermal conductivity (W/m·K) always have better heat dissipation efficiency. A thermally conductive silicone rubber with appropriate thermal conductivity should maintain normal temperatures for components operating at peak performance. You may contact suppliers for professional thermal imaging and thermal simulation testing to make a more informed choice.
Clearance Dimension and Thickness
The thermal dissipation performance of thermal conductive silicone rubber is not only influenced by thermal conductivity. It is significantly influenced by thickness. While thinner thermal conductive silicone rubber exhibits lower thermal resistance, it may increase contact thermal resistance if it fails to fill air gaps. Thicker thermal conductive silicone rubber can address surface-level differences, but excessive thickness not only increases thermal resistance but also leads to higher costs.
Operating Temperature Range and Hardness
Different grades of thermal silicone rubber have different temperature tolerances. You should select the appropriate grade based on the operating temperature to achieve stable performance during continuous operation. Most thermal silicone rubbers also resist chemical corrosion, UV exposure, and moisture, enabling their use in harsher environments. Additionally, thermal silicone rubber can be customized to different hardness levels to achieve different conformability and mechanical strength. You may choose based on your product’s stability and compression requirements.
FAQs
Does Thermal Silicone Rubber Age or Degrade Over Time?
Thermal silicone rubber has a long service life. It has high chemical and thermal stability, resisting aging caused by high temperatures, ultraviolet radiation, ozone exposure, and thermal cycling. Unlike thermal grease, it does not dry out or pump out over time.
What Thickness of Thermal Silicone Rubber Should I Use?
Thermal silicone rubber offers options ranging from extremely thin to thick thermal conductive silicone rubber, catering to most applications. You should select the most suitable thickness based on gap dimensions, surface flatness, and required compression. Avoid excessive thickness that increases thermal resistance, or excessive thinness that reduces heat transfer efficiency.
Is Thermal Silicone Rubber Suitable for Automated Assembly?
Yes. Thermosensitive silicone rubber is typically processed into gaskets, die-cut parts, and similar components. It offers easy installation and is suitable for mass and automation production. It provides excellent quality control for large-scale manufacturing.
Thermal Silicone Rubber vs Thermal Pad
Thermal silicone rubber can be made into thermal pads of varying thicknesses and thermal conductivities for heat dissipation, offering improved installation and cutting properties. Beyond thermal silicone rubber, thermal pads also include silicone-free thermal pads, carbon fiber thermal pads, and phase-change thermal pads.
Thermal Silicone Rubber vs Thermal Grease
Thermal silicone rubber is a solid elastomer material, while thermal grease is a semi-fluid material. Thermal grease can achieve extremely low thermal resistance, but is prone to drying out and pumping out. Thermal silicone rubber provides stable thickness, electrical insulation, and longer life, making it suitable for high-volume assembly.
Can Thermal Silicone Rubber be Used in High-Voltage Applications?
Yes. Thermal silicone rubber has electrical insulation properties and is commonly used in high-voltage and power electronics applications. It provides effective thermal conductivity while maintaining electrical isolation between components and heat sinks.
Final Thoughts
Thermal silicone rubber combines heat dissipation, electrical insulation, flexibility, and long lifespan. It achieves consistent thickness and performance over extended periods, making it good for products demanding reliability and clean assembly. With over 10 years of experience, GALLOP INNOTEK delivers high-quality customized thermal silicone rubber solutions.
