Thermal Interface Materials Difference

Thermal interface materials are used for the thermal management of heating elements across various industries. They primarily have types such as thermal pads, thermal pastes, thermal tapes, and thermal putties. Different types of thermal interface materials possess different application methods, thermal conductivity properties, and uses. This article provides comprehensive information on common thermal interface materials, enabling you to make more solution-targeted choices after exploring the knowledge.

What are Thermal Interface Materials？

Thermal interface materials encompass a wide range of products, including thermal pads, thermal tapes, thermal pastes, thermal compounds, and various other categories.  They are all used to fill the gap between the heating elements and heat dissipation devices within your various equipment, helping to transfer and dissipate heat from the ICs. They typically have excellent thermal conductivity and low thermal resistance, effectively filling voids to enhance heat transfer efficiency. Different types of thermal interface materials offer different characteristics, making them suitable for virtually all your thermal management requirements.

Thermal Pad

What is the Thermal Pad？

Thermal pads are preformed, flexible solid sheets. They are typically manufactured using a base material (such as silicone) with added thermal conductive materials and curing agents to produce pads of varying thicknesses and thermal conductivity properties. You can select a thermal pad of suitable thickness based on the gap size between components and heat sinks, and mount it easily onto surfaces without requiring precise metering or manual application. For enhanced stability, adhesive layers can be incorporated into specific thermal pad variants.

Types of Thermal Pads

• Silicone Thermal Pads: Utilizing silicone as the base material, silicone thermal pads get excellent elasticity, enabling them to conform seamlessly to surfaces. Their thermal conductivity typically ranges from 1 to 15 W/m·K, and reliable operation between -50°C and 200°C. They also possess electrical insulation properties, permitting safe use in your electronic products to enhance the reliability of devices such as mobile phones and computers.
• Silicone-Free Thermal Pads: For components sensitive to silicone, silicone-free thermal padsare an ideal thermal interface material. Typically utilizing resins instead of silicone, they offer higher thermal conductivity than air (1–6 W/m·K) while eliminating potential hazards from silicone oil and vapour found in silicone pads.
• Graphite/Graphene Thermal Pads: Crafted from high-performance graphene materials, Graphite thermal padsand graphene thermal pads offer extended service life, superior temperature resistance (-40°C to 400°C), and exceptional thermal conductivity (graphene pads: approx. 70-130 W/m·K; graphite pads: up to 1950 W/m·K). They are ideal for your projects with high thermal dissipation demands. Moreover, they are exceptionally compatible with silicon-sensitive components.
• Carbon Fibre Thermal Pads: Benefiting from carbon fibre materials, carbon fibre thermal padscombine durability with lightweight construction. They offer higher thermal conductivity (16–50 W/m·K) than standard silicone pads and are also suitable for silicon-sensitive applications. Furthermore, they possess specialized electromagnetic interference (EMI) resistance, enabling their use in electronic devices requiring EMI shielding.
• Ultra Soft Thermal Pads: For those seeking lower contact thermal resistance, ultra-soft thermal padsare an ideal solution. More pliable than standard thermal pads, they have exceptional conformability to fill surface irregularities, thereby minimizing thermal resistance caused by trapped air. Consequently, they typically offer higher thermal conductivity (up to 12 W/m·K). Furthermore, they provide cushioning against device vibration and impact, enhancing stability.

Advantages of Thermal Pads

• Convenient Installation: Thanks to its pre-cut, pre-formed design, thermal pads offer simpler installation compared to thermal putty. They eliminate the need for precise quantity control or manual application. You should only select the appropriate thermal padsand cut them to the correct size for the component. This streamlined process reduces operational steps, providing significant advantages in your high-volume production.
• Long Service Life: Thermal pads can maintain continuous operation for 2 to 10 years without failure.  Compared to thermal grease, which dries out and requires frequent replacement, they not only reduce maintenance requirements but also offer superior durability for you.
• Supportive Adhesive Layer: Certain models of thermal pads can incorporate an adhesive layer upon request, enabling more secure installation in applications subject to vibration and impact(such as automotive systems).
• Reusability: Should the shape and dimensions of your thermal pad remain unchanged and its thermal performance remain satisfactory, it may be reused. However, if you have selected a thermal pad with an adhesive layer, this layer will become ineffective after use and may increase thermal resistance, so it is unsuitable for reuse.

Disadvantages of Thermal Pads

• Not Suitable for Highly Uneven Surfaces: Thermal pads have a uniform thickness, which can create air pockets in applications with significant height variations. This leads to increased thermal resistance and reduced heat transfer efficiency. Therefore, it is more suitable for you to use it in a flat component.
• Limited Thickness: Thermal pads are manufactured in various thicknesses (up to 20mm) and can be customized to your requirements. However, if the gap between your components and heat sink is minimal, thermal paste would be more appropriate.

Thermal Tape

What is the Thermal Tape？

Thermal tape is another preformed thermal interface material, composed of fibreglass and thermally conductive material. However, unlike thermal pads, it features double-sided adhesive layers protected by release liners. Consequently, it provides robust fixation between your components and heat sinks. In certain low-temperature and portable applications, you may even dispense with screws for additional reinforcement. However, owing to its combined adhesive and thermal properties, its thermal conductivity is lower (1–5 W/m·K), making it suitable for projects with modest heat dissipation requirements.

Advantages of Thermal Tape

• Combining Bonding and Thermal Conductivity: Thermal tape offers an ideal solution, providing an excellent means of bonding heat sinks to portable devices while enhancing thermal dissipation. In certain stable, low-load applications, it reduces the need for mechanical fasteners.
• Easy Installation: Like thermal pads, thermal tape eliminates the need for precise metering and complex application procedures. Furthermore, in certain applications, it requires no mechanical fastening, further simplifying the installation process.
• High Cost-Effectiveness: Thermal tape is typically more economical than thermal pads and thermal pastes, and it can maintain performance for 6 to 12 months without requiring frequent replacement. Consequently, it is a highly cost-effective solution for you.

Disadvantages of Thermal Tape

• Low Thermal Conductivity: Whilst its adhesive properties confer dual functionality to thermal conductive tape, this high adhesion comes at the expense of reduced thermal conductivity. Compared to thermal pads and thermal pastes, it performs poorly in projects demanding high heat dissipation.
• Application Limitations: Given that thermal pads are stiffer than thermal paste and that two tape thicknesses cannot be used within a single component, it is advisable for you to avoid them on uneven surfaces. Furthermore, if the gap between your component and heat sink is very small, thermal tape may be difficult to install, making thermal paste a more suitable option.

Thermal Paste

What is the Thermal Paste？

Thermal paste(thermal grease) primarily consists of silicone oil blended with highly thermally conductive materials such as aluminium nitride or aluminium oxide. It exists not as a solid but as a fluid paste. This enables it to achieve better void-filling properties on complex component surfaces, minimising thermal resistance between the heat-generating element, the paste itself, and the heat dissipation equipment, thereby delivering superior thermal management. However, the application process for thermal paste is more intricate and requires more maintenance.

Types of Thermal Paste

• Silicone-Based Thermal Grease: Silicone-based thermal pastes are more commonly used, manufactured from silicone compounds and thermal conductive materials. They have greater resistance to high temperatures (- 55 to 200°C) and maintain their performance over extended periods than non-silicone thermal grease.
• Non-Silicone Thermal Grease: Non-silicone thermal paste uses silicone-free polymers as an alternative to silicone-based materials. It does not release silicone oil or emit silicone vapour during use, allowing you to use it in silicone-sensitive products. Consequently, it facilitates the cooling of heat-generating components while enhancing safety.

Advantages of Thermal Paste

• Low Bond Line Thickness(BLT): Once thermal paste is secured between components and heat sinks, it can be compressed to an extremely thin layer whilst filling surface gaps. This minimises contact thermal resistance, thereby optimising the thermal conductivity performance of the paste.
• High Thermal Conductivity: On the one hand, thermal paste offers superior thermal conductivity, providing an ideal solution for your projects with high heat dissipation demands. On the other hand, thermal paste exhibits greater conformability than thermal pads or thermal tapes, enabling excellent spreading and adhesion across component and heat sink surfaces to minimise porosity.
• High Cost-Effectiveness: High-performance thermal pads incur higher costs, while low-cost thermal tapes fail to meet demanding thermal management requirements. Thermal paste offers satisfactory performance at a lower budget than thermal pads. Although you will need to service it more frequently during prolonged use, it is also a highly cost-effective solution overall.

Disadvantages of Thermal Paste

• Application Complexity: The steps involved in applying thermal pasteinclude cleaning, controlling quantity, spreading, installation, and securing, and are more complex. Moreover, controlling the quantity and the spreading process is not easy. You should pay particular attention to preventing insufficient coverage of rough surfaces due to under-application or increased thermal resistance caused by over-application. As thermal paste is not suitable for reuse, this may result in additional installation time and material wastage.
• Prone to Spillage: Thermal paste possesses a degree of fluidity and may spill during installation and use. Compared to the neater thermal pads and thermal tape, you will require more cleaning and maintenance when using thermal paste.
• Frequent Replacement: Thermal paste will harden and dry out during prolonged operation, leading to diminished performance and reduced heat dissipation efficiency. Its lifespan is relatively short, approximately 12 months. Therefore, you should periodically inspect and replace the thermal paste to maintain efficient heat dissipation performance.

Thermal Putty

What is the Thermal Putty？

As a semi-solid thixotropic material, thermal putty is very soft and gets a degree of fluidity. It combines the advantages of thermal pads and thermal grease. During application, you may press it onto the heating element and heat sink surfaces with minimal force, compensating for surface irregularities more effectively than thermal pads, while exerting exceptional lower stress on the PCBs. Furthermore, thermal putty maintains stability for longer periods than thermal grease, rarely spilling or drying out, and does not require frequent replacement.

Advantages of Thermal Putty

• Low Bond Line Thickness(BLT): Like thermal paste, thermal putty can also achieve an extremely thin contact thickness under minimal pressure once installation and fixing are complete. This minimises obstruction to heat transfer, maximising the thermal putty’s performance.
• High Thermal Conductivity: On the one hand, thermal putty achieves superior thermal conductivity (1–15 W/m·K) compared to conventional thermal pads. On the other hand, its low bond line thickness further helps the thermal putty in minimising contact thermal resistance, thereby maximising heat dissipation. Consequently, if you require a thermal interface material for demanding thermal management applications or large-scale cooling projects, thermal putty is the preferred choice.
• Long Service Life: Compared to thermal pastes that dry out during use and require frequent replacement, thermal putty effectively resolves this problem. It achieves a service life of approximately 2 to 8 years, maintaining its moisture and stable performance even under frequent and continuous use. This not only reduces the costs associated with frequent replacements but also eliminates the need for additional maintenance.
• Wide Applicability:Firstly, thermal paste can be employed in high-efficiency mass production. It requires neither mixing nor curing time. Secondly, it accommodates components and heat sink gaps of various thicknesses (0.1–4mm). Furthermore, it facilitates improved inventory management.

Disadvantages of Thermal Putty

• Complex to Use: Although thermal putty’s installation and maintenance are simpler than thermal paste, it boasts a longer service life. However, compared to pre-formed and pre-cut thermal tapes and pads, thermal putty is mandatory to consider its high entry-cost for investing in the dispensing robots or manual dispenser, and even some high training/maintenance cost, even though it’s a cost-efficient solution for high-volume projects with stable & low-labor involved consideration. This introduces additional steps, increasing operational complexity.

Phase Change Material

The form of phase change materials is not fixed, as they undergo a solid-liquid transition in response to temperature changes. During heat absorption, they transform into a liquid state and lower the ambient temperature. During heat dissipation, they revert to a solid state and release thermal energy. This enables phase change materials to self-regulate temperature and maintain stability. Therefore, it is highly suitable for you to use them as thermal interface materials. They consistently maintain the optimal operating temperature for your components, preventing thermal fluctuations.

Advantages of Phase Change Material

• Easy Installation: In normal conditions, phase change materials exist in a solid state, allowing them to be placed directly like thermal pads without complex procedures. As temperatures rise, they absorb heat and transition to a liquid state. This high-fill capability on rough surfaces enables ultra-thin bonding layer thicknesses. Furthermore, removal is easy.
• Low Contact Thermal Resistance: When components generate heat, the phase-change material can transform into a state characterised by high flexibility and compliance. Consequently, it better fills surface irregularities, minimising contact thermal resistance and enhancing heat dissipation efficiency.
• Fatigue Resistance: Phase change materials maintain stable performance during frequent and prolonged solid-liquid transitions. They can withstand approximately 27,000 solid-liquid cycles without failure. Unlike thermal pastes, they do not dry out or pump out readily, thereby eliminating your need for frequent maintenance and replacement.

Disadvantages of Phase Change Material

• Lower Thermal Conductivity: Due to manufacturing composition limitations, phase change materials have lower thermal conductivity (2–8.5 W/m·K), particularly organic phase change materials made from paraffin or polyethylene glycol. Benefiting from low interfacial thermal resistance and high latent heat capacity, they achieve considerable heat dissipation efficiency. However, for your higher-load thermal management requirements, they may not deliver satisfactory performance.
• High Cost: Compared to thermal interface materials such as thermal tape, thermal grease, and thermal pads, thermal interface materials may need a higher initial investment.
• Application Limitations: Phase change materials typically require specific temperatures (45–60°C) to initiate transition and operate effectively within the range of -55 to 125°C. Furthermore, they undergo shape deformation during operation. You must assess whether these conditions align with your application requirements before selection.

Thermal Interface Materials Difference

FAQs

Which Thermal Interface Material offers the Most Effective Heat Dissipation?

This depends on the type of thermal interface material and your application. Thermal putty generally achieves satisfactory heat dissipation due to its extremely low contact thermal resistance and high thermal conductivity. Certain types of thermal pads, such as graphite thermal sheets, possess exceptionally high thermal conductivity.

Why Use Thermal Interface Materials?

Because air cannot assist heating components in achieving efficient heat dissipation, and heat accumulation can lead to diminished product performance or even damage. Thermal interface materials enhance heat dissipation efficiency, thereby improving your product performance while extending the operational lifespan of your equipment.

How Thermal Interface Materials Work?

Thermal interface materials reduce thermal resistance by displacing air, thereby enhancing heat transfer. They increase the thermal contact area through filling. Furthermore, they introduce higher thermal conductivity to facilitate efficient heat dissipation.

Can Thermal Paste Replace Thermal Pads?

Thermal paste can fulfil almost all the application requirements of thermal pads and achieve more satisfactory heat dissipation results on highly rough component surfaces.

How Should Thermal Interface Materials be Stored?

You should keep new and unused thermal interface materials in their original packaging, stored in a dry environment free from ultraviolet light. Furthermore, you must pay attention to their shelf life and ensure they are used before expiry.

Are Thermal Pads Conductive?

For enhanced safety in electronic applications, most thermal pads are designed to be insulating. However, conductive thermal pads are also available upon request, offering electrical conductivity up to 20,000 S/cm.

Final Thoughts

This article provides information on five phase-change materials, which we hope will assist you in your selection. Should you be seeking a reliable thermal interface material (TIM) supplier, GALLOP INNOTEK offers over 10 years of experience alongside comprehensive customised solutions. Please do not hesitate to contact us at any time.