In recent years, the risk of overheating, which can lead to reduced performance or even fire and explosion of electronic devices is alarming. Thermal management is essential to maintain such electronic devices operating within their specification. There has been a growing debate about silicone-based and non-silicone TIMs. In this article, we define the characteristics, advantages, and disadvantages of both silicone-based and non-silicone TIMs to make an informed decision when selecting thermal interface materials.
1. Thermal interface materials – TIMs
For the optimum performance and better reliability of a device, it is important to dissipate heat efficiently from the device during its normal operation. That is why thermal interface materials (TIMs) were born. TIM plays a significant role in electronic packages to enhance the heat transfer between contact surfaces. There are a lot of kinds of TIMs on the market. One key factor in choosing a suitable TIM is the composition of the material depending on the application and the desired thermal conductivity. As modern technologies and materials are created, the precise formulation and composition of a thermal interface material may also change over time.
To know more about how to choose the suitable TIMs to enhance the performance of the PCB, you can refer to this article: General Thermal Interface Material TIMs
2. Silicone-based or Non-silicone TIMs
2.1. Silicone-based thermal interface materials
Silicone-based TIMs are broadly used in electronic devices. Silicone is a class of synthetic material based on a polymeric siloxane backbone containing silicon, and oxygen atoms attached to the silicon atoms. It is categorized as elastomers, fluids, or resins depending on the range of crosslinking. Silicone resins are highly crosslinked structures, and at room temperature, they can be either liquid or solid.
Pros
- High thermal conductivity: Heat transfer primarily occurs through vibrations of atoms called phonons. The base polymer in silicone TIMs is a siloxane chain that has strong Si-O bonds, so they efficiently transfer these vibrations along the chain, allowing for efficient heat conduction. That is why Silicone-based TIMs offer higher thermal conductivity compared to some non-silicone alternatives.
- Wide temperature range: Silicone polymers possess strong silicon-oxygen (Si-O) bonds. These bonds are highly resistant to breaking down at both high and low temperatures, allowing the material to maintain its structure and function across a broad spectrum.
- Excellent compressibility: The siloxane backbone has organic groups attached to the silicone atoms that have weaker bonds than the strong Si-O bonds, so they provide some flexibility to the structure. Therefore, the silicone backbone can bend and flex to squeeze into microscopic gaps, even surfaces, and large dimension variations. This ensures optimal thermal contact and improved heat dissipation.
Prostech offers a wide range of silicone-based TIMs which bring high thermal conductivity that enhances heat transfer, helps to extend the product life cycle. Contact us to receive valuable information and consultation from our qualified experts.
Cons
- Outgassing: This phenomenon is the release of volatile gases when silicone-based TIMs are exposed to elevated temperatures and/or low atmospheric pressures. This can be a concern in sensitive electronics applications, optical components, and particularly aerospace applications where outgassing is accelerated due to reduced pressures and may also cause problems within sealed cavity packages.
- Electrical conductivity: While considered insulators at room temperature, some silicone-based TIMs can become slightly conductive at high temperatures because silicon electrons can break loose from the silicon covalent bond. Electrical conduction is enabled by their movement across the lattice. As a result, caution must be exercised to avoid short circuits when employed in applications with exposed electrical connections or sensitive circuitry.
- Pump-out: Most silicone TIMs are not just pure silicone; they contain silicone oil as a base component. Under pressure from the clamping force holding the heatsink in place, the silicone oil within the TIM can get squeezed out of the interface gap. This reduces the amount of TIM material in contact with both the component and the heatsink, hindering effective heat transfer.
All types of materials have their own disadvantages, depending on the environment of use, we will have suitable choices. The drawbacks of non-silicone TIMs are not an issue, as Prostech always proposes solutions that meet all your production requirements.
2.2. Non-silicone thermal interface materials
Silicone-free TIMs are formulations that do not contain silicone compounds. Instead, they are typically based on non-silicone polymers, such as acrylics, polyimides, or ceramics, …
Silicone-free thermal interface materials are emerging as a new choice of thermal interface materials for industries for silicone-sensitive devices in many applications, such as optical, medical, and sensor devices, preventing manufacturers from using silicone-based materials.
Pros
- Low outgassing: Non-silicone TIMs are not built using silicone polymers. As a result, they do not have the same chemical structure with low molecular weight siloxanes attached to the backbone. That is why non-silicone TIMs outgas minimally, minimizing the risk of contamination or degradation of nearby components.
- Electrical Insulation: Certain materials used in non-silicone TIMs inherently possess good electrical insulating properties, even at elevated temperatures. They often have minimal conductive pathways within the material. This reduces the risk of leaking currents at the evaluated temperature. However, it is important to note that not all non-silicone TIMs are created equal regarding high-temperature electrical insulation.
Prostech provides a full range of non-silicone TIMs which are especially eco-friendly and bring excellent electrical insulation for your application. Contact us to discuss and receive consultation from our qualified experts.
Cons
- Lower Compressibility: Many non-silicone TIMs utilize materials that are inherently stiffer or less flexible than the silicone polymers used in silicone-based TIMs so they may be less compressible, which makes it difficult to achieve optimal surface contact and remove air gaps between the heat source and heat sink.
- Become hard after long-term exposure to heat (elastomer): After long-term exposure to heat, the crosslinking reaction will occur at high temperatures. The crosslinking will cause the elastomeric part to become hard. The crosslinking reaction occurs due to free radicals produced by heat. For this reason, after thermal aging, elastomeric non-silicone TIMs showed brittle-like behavior, which will have an impact on the performance and reliability of the device.
3. Conclusion
Characterization of thermal interface materials in electronic applications is necessary to ensure timely product launches such as silicone-based TIMs have better thermal and mechanical properties at higher temperatures than non-silicone TIMs. On the other hand, for applications where electrical insulations are the primary concern, low-k dielectric materials such as non-silicone TIMs are a better choice to enhance the performance and reliability of those devices. Or for silicone-sensitive devices, non-silicone TIMs should be used…
When choosing a thermal interface material, it is important to weigh these potential drawbacks against the advantages of materials. Prostech offers solutions for both silicone-based and non-silicone TIMs that are suitable for your applications.
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