How do thermal pads work?

There are a lot of different types of thermal interface materials on the market. However, of all the forms available, thermal pads (aka thermal gap pads) are the best choice for mass production. Let’s break down why that is.

What do thermal pads do?

Thermal pads serve the same purpose as every other form of thermal interface material. That is, they sit between two components and transfer heat from one to the other. This usually means dissipating heat from a heat source to a heat sink, to protect a device from overheating.

Thermal pads accomplish this by being effective gap fillers and efficient conductors. The ability of the pad to fill tiny gaps in the assembly is referred to as wet-out, and softer materials tend to wet-out better than firmer materials. A thermal interface material’s inherent conductivity is measured in Watts per meter-Kelvin (W/mK), and the higher the W/mK number, the better that material is at transferring heat.

Silicone thermal pads

Silicone is a highly versatile and effective material for thermal pads. Silicone can be manufactured to a wide range of thicknesses and compression levels to suit an impressive range of design requirements. Additionally, silicone thermal pads provide beneficial electrical isolation properties.

Graphite thermal pads

Graphite is an excellent choice for designs that require a thin, highly conductive thermal interface material. Designed for demanding performance applications, its thinner structure requires relatively smooth and parallel surfaces in order to achieve wet-out and maximum thermal performance.

Other types of thermal pads

Silicone and graphite are two of the most common form-factors used for thermal pads. However, they’re far from the only choices out there. These alternative choices include:

  • Acrylic
  • Polyester
  • Aluminum
  • Fiberglass

These materials each offer unique benefits and drawbacks. They are often chosen for designs that have particularly niche requirements.

Thermal pads vs. thermal paste/grease

Finally, there’s a long-standing debate about which is better — thermal pads or thermal paste? The truth of the matter is, they both get the job done. Selecting one versus the other comes down to design and manufacturing requirements.

Thermal paste can wet-out extremely well, providing an exceptionally thin bond-line and thus great performance at a very low unit cost. However, it also tends to be messy and difficult to control. Precision equipment is required for consistent application, as application by hand makes precision nearly impossible.

This can be an expensive piece of capital equipment, which also requires ongoing maintenance. Additionally, thermal grease can be subject to long-term performance degradation due to factors such as pump-out, thermal cracking and capillary attraction.

Thermal pads, on the other hand, provide an easy-to-use and scalable option for manufacturing. Pads can be fabricated to precise specifications, allowing for fast and easy placement. While a pad is not as compressible as a paste, the range of available materials means thermal pads are extremely effective with any substrate. Additionally, thermal pads maintain their initial performance over the long-term since they are not subject to the same types of degradation as thermal grease.

Sur-Cool thermal pads

Sur-Seal’s Sur-Cool line of silicone thermal pads are designed for maximum affordability and effectiveness. We understand that time is valuable for the engineers we work with. That’s why we guarantee a fast and clear process, starting with selection and design and continuing all the way through fabrication and delivery.

To learn more about how Sur-Seal can help solve your thermal management challenges, get in touch at