Thermal gel and thermal paste are two commonly used thermal interface materials for heat dissipation in electronic devices. Both are used to transfer the heat generated by electronic products to the heat sink. Physically, they may look quite similar at first glance, and both offer effective thermal conductivity. But what are the actual differences between them that matter to you?
If you’re working on a thermal management solution and you are not sure which option to choose, this guide will help. It compares the two products across six aspects, including appearance, thermal conductivity, lifespan, and cost, helping you quickly choose the right product for you.
What is Thermal Gel？
Thermal gel is a liquid type of thermal interface material, designed for efficient filling of large-area gaps and for long-term use. It has excellent cooling performance, high reliability, high stability, and automatic dispensing capabilities. It is perfect for the mass production of electronic products. In the long run, it can help reduce overall costs and is often used in military radar, mobile phones, power supplies, set-top boxes, and other industrial equipment.
What is Thermal Paste(Thermal grease)？
Thermal paste is also known as thermal grease. Compared to thermal gel, thermal paste can achieve very low thermal resistance and superior thermal conductivity due to its excellent wetting, flowability, and ability to fill tiny gaps.
It is more suitable for precise applications in small gaps and has a lower initial cost; However, its performance and lifespan are more susceptible to the effects of temperature and operating environment. Therefore, thermal paste is often used in situations where very high thermal conductivity is initially required.
Key Differences Between Thermal Gel and Thermal Paste
Appearance
Both thermal gel and thermal paste are paste-like materials without a fixed shape. However, thermal paste is thinner, softer, and more fluid, while thermal gel is thicker, more viscous, and less likely to flow—it exhibits thixotropic properties. 
What makes this difference?
From the images below, you can know that their molecular structures are different, and this leads to differences in their fluidity, thermal conductivity, and stability.
Thermal paste
made by directly mixing thermally conductive fillers and small molecules of silicone oil. Therefore, it has excellent wettability, can perfectly fill the tiny gaps between all electronic components and heat sinks, and has very high thermal conductivity.
Thermal gel
produced by first crosslinking those small silicone molecules into long-chain macromolecules, and then mixing them with the conductive fillers. Therefore, it has a certain viscosity and high stability.
In terms of color
Thermal gel products are available in various shades, including blue, green, white, gray, pink, and yellow, whereas thermal paste is typically white or gray.
Thermal Conductivity
The thermal conductivity of thermal paste typically ranges from 1.0 to 8.0 W/m·K.
Because it is thinner and more fluid, it exhibits greater wettability. It can fill surface voids more flexibly and precisely, thereby transferring heat more effectively and displaying extremely high thermal conductivity. However, after long-term use, especially under high temperature and high pressure, it may dry out, oxidize, leak, or solidify.
Additionally, we generally recommend applying thermal paste sparingly, rather than too thickly. （The bond line thickness generally should not exceed 2mm.)
The thermal conductivity of thermal gel typically ranges from 1.0 to 15.0 W/m·K.
The thermal conductivity of thermal gel is not as good as thermal paste. However, it has significant advantages in terms of reliability, such as oiliness and drying out.
Due to its higher viscosity and adhesion, thermal conductive gel is less likely to move or evaporate during long-term use. Depending on the particle size of the filler, it can be used in applications ranging from several hundred micrometers to a few millimeters.
Usage method
You need to apply thermal paste with a scraper. The operation is simple, but excessive or uneven application can affect thermal performance. It requires precise, thin, and uniform spreading of the paste, which makes the labor cost relatively high.
Thermal gel, on the other hand, is applied using a dispensing machine that delivers a fixed amount at specific points. This method saves labor, enables efficient and automated operation, and is better suited for large-area applications.
Application
Due to thermal paste’s excellent and efficient thermal conductivity, as well as ease of application, it is commonly used for cooling high-heat-generating electronic components, such as CPUs, GPUs, transistors, and high-precision DVD decoding boards.
Thermal gel has high reliability, stability, and ease of handling. It is commonly used in heat-generating components such as automotive electronics, communications, 5G chips in mobile phones, security surveillance, and LED lighting. More suitable for filling large gaps or coating broad surfaces, and is commonly used in automotive electronics and communication equipment.
Clean and lifespan
The life of thermal paste depends on the temperature、application conditions. If exposed to extreme temperatures for a prolonged period, it tends to dry out and turn into powder, even crumpling into dust when squeezed by hand. So regular inspection and reapplication are required.
The typical lifespan for thermal gel is about 5–10 years. It shows better performance in stability than thermal paste.
Cost
At the initial stage, thermal paste is affordable and sufficient, and thermal gel requires additional investment in dispensing equipment. Therefore, thermal gel incurs a higher cost. However, for large-area, long-term heat dissipation solutions, considering factors such as heat dissipation area, labor, lifespan, and efficiency, thermal gel can actually be more cost-effective in the long run.
Summary
The main role of thermal gel is to fill mm-level gaps, whereas thermal paste is used for um-level interface wetting.
If you need short-term, high thermal conductivity for small gaps, such as in the cooling of CPUs, GPUs, or SSDs, consider using thermal paste.
Thermal gel will be a better option for your design when you need a long-lasting thermal material for larger areas / multiple spots where extreme thermal conductivity & BLT is not required — such as in automotive electronics or communication equipment.
If you would like to learn more about thermal gel, thermal paste, or other TIM/EMI materials, please do not hesitate to contact us. Gallop Innotek is a one-stop thermal Interface material manufacturer. We can assist you not only with the materials but also with the thermal solutions.
FAQ
1. Is thermal gel better than thermal paste?
Not exactly. They each have their own advantages.
In terms of reliability and lifespan, thermal conductive gel is superior. Its viscosity and adhesion make it less prone to movement and evaporation, less likely to dry out and become oily, and its lifespan can reach 5-10 years. During the production process, you can apply thermal conductive gel with the automated dispensing machines. It can help to save labor and costs, enabling more efficient and large-scale production.
In terms of thermal conductivity, thermal paste has excellent initial thermal conductivity and low thermal resistance. It offers excellent wetting and flowability, filling the tiny gaps between electronic components and heat sinks very well. This helps transfer heat more efficiently. So, thermal paste is suitable for electronic products that require extremely high thermal conductivity initially. However, its stability and lifespan can be affected by ambient temperature. It also typically requires manual application, making it unsuitable for large-scale production of electronic products.
