Thermal putty and thermal gel are both non-solid TIMs used in electronics, energy, and automotive. They are different in thermal conductivity, application methods, and uses. Incorrect selection may result in unsatisfactory performance and low cost-effectiveness, leading to additional costs and extended production cycles. Continue reading to make wiser choices.
What is Thermal Putty?
Thermal putty is a highly filled, low-flow (clay-like) thixotropic thermal interface material. Its high compressibility and filling capability allow it to be used for larger components and heat sinks (or housings) with gaps and uneven surfaces. Additionally, it provides extra physical protection for vibration applications.
It requires no curing and offers high reliability, but assembly is more complex, making it better for semi-automated production. It performs exceptionally well in applications such as energy storage, IGBTs, and industrial power supplies.
What is Thermal Gel？
Thermal gel is a flowable and wettable thermal interface material. It is better suited for small components and gaps between heat sinks (or housings) with complex surface geometries. With automated dispensing equipment, it is highly suitable for automated production lines. It primarily comes in two types: single-component thermal conductive gel and two-component thermal conductive gel.
Single-component thermal gel maintains a stable semi-fluid state during application, while dual-component thermal gel requires mixing and curing to form a more stable solid state. You can use it in automotive, consumer electronics, LED, power supply, and other applications.
Thermal Putty vs Thermal Gel: Heat Dissipation Capability
Heat Dissipation Capability of Thermal Putty
The thermal conductivity of thermal putty ranges from 1 to 14 W/m·K, offering higher thermal conductivity compared to thermal gel. It performs well in high-heat dissipation load applications and can be used in high-power modules, energy storage systems, and EV battery modules. Additionally, its outstanding compressibility and thixotropy offer superior conformability compared to thermal pads on rough surfaces and components with height differences, minimizing contact thermal resistance.
Heat Dissipation Capability of Thermal Gel
Thermal conductive gel offers thermal conductivity options ranging from 3 to 8 W/m·K. Compared to thermal putty, thermal gel has lower thermal conductivity, making it more advisable for small to medium heat dissipation loads. Additionally, its superior flowability relative to thermal putty allows it to fill gaps smaller than 2mm, achieving minimal bond line thickness and maximizing thermal contact area. However, for larger gaps, the overall thermal resistance may be slightly higher than that of the putty.
Thermal Putty vs Thermal Gel: Usage Complexity
How to Apply Thermal Putty
The installation process for thermal putty is relatively straightforward, requiring no mixing or curing. It involves portioning, controlling the amount applied, and spreading it. However, due to its lower flowability, the application process is cleaner and more controllable. You can also utilize automated dispensing equipment to achieve higher efficiency in automated assembly.
- Clean the Surfaces: Before applying thermal putty, you must first use a dedicated cleaning agent to remove contaminants (including moisture, dust, and unrelated residues) from the surfaces of components, housings, heat sinks, and other surfaces. Contaminants impair the thermal putty’s adhesion capability, leading to reduced reliability. They can also cause air gaps, increasing thermal resistance and diminishing heat dissipation efficiency.
- Apply Thermal Putty: Suppliers typically provide optimal assembly solutions based on your product design, including application areas, spread quantity and thickness, mechanical tolerances, and compression ratios. You can use a spreader or syringe to apply the thermal putty according to drawing specifications, achieving complete surface coverage and filling all rough or uneven areas.
- Install the Heat Sink: After applying the thermal putty, align and press the heat sink or housing onto the surface. Apply sufficient pressure to make the thermal putty fully contact the heat sink surface and compress the thermal compound. Avoid high pressure to prevent component damage or creating a layer too thin to adequately fill uneven gaps.
- Inspection: After installation, remove excess thermal putty and allow it to settle, observing for any sagging. If the assembly is unsatisfactory, remove the putty and reapply it to achieve optimal performance.
How to Apply Thermal Gel
Thermal gel installation methods differ based on whether it is single-component or dual-component. Single-component thermal conductive gel and thermal putty are applied similarly to thermal putty—requiring cleaning, application, and installation—and are more suitable for automated production. Dual-component thermal conductive gel requires mixing and curing in addition to cleaning and application during assembly.
- Mixing: Follow the manufacturer’s instructions for the two-component thermal gel, mixing it in the specified ratio. Once mixed, the gel will begin to cure, so apply it promptly to the components according to the supplier’s guidelines for quantity, thickness, and other parameters.
- Degassing Treatment: If small bubbles appear in the mixed thermal gel, this indicates trapped air. Since air has low thermal conductivity and impedes heat transfer, it is best to degas the mixture to remove the air.
- Curing: After application, press the housing or heat sink firmly onto the thermal putty to achieve full contact. Allow it to cure undisturbed. Once cured, the thermal putty remains moist and elastic, enhancing heat dissipation efficiency while delivering superior stability.
Thermal Putty vs Thermal Gel: Bond Strength
Bonding Strength of Thermal Putty
Thermal putty has a certain degree of tackiness, allowing it to adhere better to component and heat sink surfaces for enhanced stability. However, its tackiness is insufficient for permanent bonding, needing mechanical fasteners such as screws or furniture hardware. Its high compressibility and excellent resistance to vibration provide outstanding mechanical stability and are suitable for use in automotive, drone, and similar applications.
Bonding Strength of Thermal Gel
- Single-component Thermal Gel: Single-component thermal gel, similar to thermal putty, provides better adhesion but still requires mechanical fastening. However, its vibration resistance is lower than that of thermal putty.
- Two-component Thermal Gel: Two-component thermal gel, once cured, has high bonding strength, offering extended service life and suitability for vertical mounting applications. Additionally, cured two-component thermal gel retains elasticity, providing extra mechanical protection for components and heat sinks to minimize damage.
Thermal Putty vs Thermal Gel: Reworkability and Reusability
Reworkability and Reusability of Thermal Putty
Thermal putty requires no curing, making installation, removal, and cleanup easy. It also minimizes secondary contamination. Therefore, it can be reworked without damaging components. Although thermal putty has a service life of 2 to 8 years, it undergoes deformation after use. Furthermore, prolonged use accumulates dust and impurities, leading to increased thermal resistance. Once removed, you should apply fresh thermal putty.
Reworkability and Reusability of Thermal Gel
Thermal conductive gel is more difficult to remove and clean compared to thermal putty, often leaving residues that can reduce efficiency during rework. This is particularly true for two-component thermal gels, which become significantly harder and more challenging to remove once fully cured, potentially causing component damage. After use, two-component thermal gels undergo a complete morphological change, making them unsuitable for reuse. They also offer long-term reliability, so they can be used in applications with no maintenance or disassembly.
Thermal Putty vs Thermal Gel: Operating Temperature
Operating Temperature of Thermal Putty
The best operating temperature range for thermal conductive putty is approximately -50 to 150°C, varying by different product models. Select the appropriate grade based on your applications. Under normal usage conditions, it maintains a durable semi-solid putty consistency and retains moisture. It resists flow and pumping 150 °C below, but exceeding this operating temperature may cause hardening, drying out, or oil migration.
Operating Temperature of Thermal Gel
Thermal gel operates within a temperature range of approximately -50 to 150°C. Compared to thermal putty, thermal gel offers a longer life and better stability, with less drying out and pumping out. To minimize the risk of failure, it is best to avoid prolonged use of thermal gel in environments exceeding or falling below its operating temperature range.
Thermal Putty vs Thermal Gel: Service Life and Cost
Service Life and Cost of Thermal Putty
Thermal putty has a service life of approximately 2 to 8 years, which is longer than thermal paste and thermal pads. It has excellent resistance to thermal cycling and is unlikely to migrate or pump out in normal use. Also, it withstands vibration and impact without deformation. However, thermal putty is more expensive than thermal gel. Nevertheless, it has outstanding performance and reliability, and it is highly cost-effective.
Thermal Gel Service Life and Cost
Thermal gel also has a long life, commonly lasting 5 to 10 years. Two-component thermal gel, after curing, offers an even longer service life. You can use it for products with high reliability requirements. If your product is sensitive to silicone, opting for silicone-free thermal gel is advisable to avoid risks of silicone migration. Additionally, thermal gel is cheaper, and it has lower assembly costs in mass production. It is a highly economical choice.
Thermal Putty vs Thermal Gel: Applications
Thermal Putty Applications
- New Energy Vehicles: Components in vehicles often have significant height differences and larger gaps, while also demanding higher vibration resistance. Thermal putty is the ideal thermal interface material for battery modules, on-board chargers (OBCs), inverter control boards, and ECUs. It not only achieves satisfactory large-area filling but also has high reliability.
- Energy Storage Systems: You can use thermal putty in the PCS modules, battery management systems, MOS/IGBTs, and control units of energy storage systems.
- Industrial Power Supplies and Power Modules: They withstand high-frequency thermal cycling and improve reliability during continuous operation.
- Communication Equipment: Thermal putty resists UV radiation, high temperatures, and aging, and can be used in outdoor communication equipment. You can apply it in AAU RF modules, power supply modules, power amplifier chips, and similar components. Temperature control enhances the stability and accuracy of signal reception and transmission.
- Servers & Data Centers: If you are seeking a suitable thermal interface material solution for VRM, GPU power supply, or power indicator modules in servers or data centers, thermal putty is a good choice. Its high thermal conductivity meets stringent reliability requirements. Moreover, it can replace multiple-size shims and simplify the BOM.
Applications of Thermal Gel
- Consumer Electronics: Compared to thermal putty, thermal gel performs better in small gaps, and it is very suitable for precision electronics and highly integrated products. It also offers higher mass production efficiency and can be used in various devices such as smartphones, cameras, VR/AR equipments and tablets.
- High-end Servers: Thermal conductive gel offers low bonding line thickness at reduced pressure. You can use it for heat dissipation in CPU chips, HBM memory, ASICs, and other components while minimizing damage to precision elements.
- Medical Electronics: Thermal gel offers silicone-free models with low-volatility silicones, preventing contamination of silicone-sensitive components. It can be used for temperature control in imaging equipment control modules, sensors, and testing instruments, improving measurement accuracy and avoiding errors.
- Industrial Automation Control: Two-component thermal gel achieves exceptional vibration resistance after curing, allowing you to choose it for industrial automation products like PLC modules and sensors. It offers stable, continuous operation for equipment, minisize downtime, and boosts production efficiency.
How to Choose Between Thermal Putty and Thermal Gel
Select Based on Heat Dissipation Requirements
You should first determine the thermal load of your product and select a thermal interface material capable of meeting this thermal dissipation requirement. Suppliers can provide thermal simulation testing to help you obtain more accurate values. Thermal putty offers higher thermal conductivity options and is better for products with higher thermal loads. Thermal gel, on the other hand, is better for products with medium to low thermal loads.
Select Based on Gap Sizes
Thermal putty has low flowability and resistance to collapse, adapting well to highly uneven surfaces. It can be better used for larger components, heat sinks, or enclosures, effectively filling dimensional tolerances. In contrast, thermal gel offers higher flowability, making it ideal for forming low bond line thickness in small gaps. If your product’s gap is less than 1mm, thermal gel is a good choice. For gaps over 1mm, thermal putty has better performance.
Select Based on the Working Environment
- Vibration Environment: You can choose based on whether the product is susceptible to vibration and impact. Thermal putty offers stronger cushioning and is more advisable for high-vibration applications, such as in automobiles. Additionally, a two-component thermal gel is also suitable for high-vibration environments.
- Stress Sensitivity: You can select based on the pressure the component can withstand. Thermal putty requires greater pressure during assembly, providing better structural support for power modules, IGBTs, MOSFETs, and similar components. Thermal gel causes less damage to stress-sensitive components and is easier to use for precision chips, high-density PCBs, and similar applications.
Select Based on Production Method
Thermal putty and thermal gel both need dispensing and application, necessitating additional robotic or manual dispensing equipment. And they can semi-automate and automate production. Due to thermal putty’s lower flowability and use in thicker applications, its application is easier to control, making it good for high-volume automated production. Thermal gel demands higher precision dispensing, better for semi-automated production.
Service Life and Budget
Thermal gel and thermal putty both offer long service life, and both can be used for your products requiring high reliability and low maintenance. Thermal gel is more cost-effective for mass production due to its lower price point. While thermal putty is more expensive, it provides superior heat dissipation capabilities, making it the better choice when enhanced thermal performance is needed.
Thermal Putty vs Thermal Gel
| Item | Thermal gel | Thermal putty |
| Form | Flowable(Cures to a solid state) | Thixotropic materials |
| Ease of use | Complex( 2-Part requires mixing and curing) | Complex (Requires dispensing robot or manual dispenser) |
| Repeated workability | N/A | N/A |
| Thermal conductivity | 3 ~ 8W/m.K | 1 ~ 14W/m.K |
| Service life | 5-10 years | 2-8 years |
| Typical operating temperature | -50 ~ 150deg. C | -50 ~ 150deg. C |
| cost | Low | Low |
| Adhesion strength and tackiness | Higher | Lower |
| Application | Automated production, smooth and rough surfaces, and small gaps, permanent fixation | Larger gaps, smooth and rough surfaces, and high-performance applications |
FAQs
Does Thermal Gel Dry Out Over Time?
Thermal gel has a longer life than thermal putty and maintains long-term moisture retention and stable performance. Under normal operating conditions and within its service life, it will not dry out. However, prolonged use at temperatures exceeding its optimal operating range may cause drying and oil separation.
Which TIM is Better for EV battery systems?
Thermal putty may be more suitable for EV battery modules. This is because battery modules typically have larger structural tolerances, and thermal putty can better compensate for height differences and fill large gaps, thereby maximizing thermal contact area. Thermal putty can also provide vibration damping for EV battery modules.
Is Higher Thermal Conductivity Always Better?
No, heat dissipation performance depends not only on thermal conductivity but also on factors like interfacial thermal resistance and operating temperature. Excessively high thermal conductivity may result in a costly price tag. You should select thermal putty or thermal silicone with appropriate thermal conductivity and properly install and use it.
Can Thermal Putty be Dispensed Automatically?
Yes. Thermal conductive putty can be precisely dispensed using robots for automated assembly. However, it requires a higher initial investment and is better suited for high-volume and long-term production. Nevertheless, it offers better quality control and reduces material waste.
What Thickness Should I Use?
The application thickness of thermal putty and thermal gel should be determined by factors such as surface roughness, gap size, and contact pressure. It must adequately cover surface irregularities and fill gaps. We provide end-to-end guidance from design to prototyping, saving the cost and time of rework and replacements.
Can Thermal Putty Replace Thermal Pads?
This is different based on your application. Thermal putty offers thermal conductivity ranging from 1 to 14 W/m·K, while thermal pads provide higher options. On complex surfaces and in larger gaps, thermal putty achieves better filling capability than thermal pads. However, if you require simpler assembly and automated production, thermal pads are more suitable.
Silicone vs Non-Silicone Thermal Gel
Silicone thermal gel is composed of silicone oil and thermal conductive fillers, while silicone-free thermal gel contains no silicone components. Silicone-free thermal gel does not produce silicone oil or silicone gas during thermal cycling. It is right for silicone-sensitive applications such as optical modules, communication equipment, and precision electronic systems. Silicone thermal gel, on the other hand, offers a wider operating temperature range, superior elasticity, and lower cost.
Final Thoughts
Thermal putty is for products with high thermal conductivity and large gaps, while thermal gel is better for medium to low thermal conductivity and small gaps. As a 10+ years supplier of TIMs, GALLOP INNOTEK provides high-quality thermal putty, thermal gel, and other alternative solutions. Contact us for selection support.
