Are you struggling to decide between thermal grease and thermal putty? Furthermore, when selecting a TIM for your product, you should consider not only thermal conductivity but also assembly tolerances and long-term reliability. This article compares these two TIM solutions to help you determine which material is more suitable for your application.
What is the Thermal Grease？
Thermal grease, also known as thermal paste, is a semi-fluid thermal interface material used to fill gaps between heat-producing components and heat sinks, improving heat dissipation during operation. Owing to its good flowability and high compressibility, it adheres to surfaces with minimal force and effectively fills minute surface irregularities. Benefiting from a low bond line thickness and high thermal conductivity, it minimizes contact thermal resistance and achieves high heat dissipation efficiency, allowing you to use it in high-performance electronic devices.
What is the Thermal Putty？
Thermal putty is a thixotropic thermal interface material, offering greater viscosity than thermal grease. It combines the longevity of thermal pads with the conformability of thermal grease, making it ideal for high thermal load and long-reliability projects. It also achieves low bond line thickness and high thermal contact area, and can be used in thicker component-to-heatsink gaps. It maintains prolonged wetness, minimises pumping out and drying out, offers more consistent performance, and reduces maintenance requirements.
Thermal Grease vs. Thermal Putty: Differences in Application Methods
Thermal putty and thermal grease are not preformed sheet materials like thermal pads. Both require dispensing and application, making their use more complex. However, they do not necessitate mixing or curing steps, rendering their application simpler compared to thermal gel. Nevertheless, with the aid of equipment such as screen printing and automated dispensing systems, they can also achieve high-efficiency mass assembly. Their application process is similar.
Clean the Surface
Before applying thermal grease or thermal putty, you should clean the surfaces to pevent that components, heat sinks, or casings from being free from residual dust, moisture, old thermal interface materials, and similar contaminants. Such impurities increase thermal resistance and may result in an imperfect bond, allowing air ingress and thereby reducing heat dissipation efficiency. You may use specialised cleaning products (isopropyl alcohol and a lint-free cloth) to avoid damaging the components.
Apply Thermal Grease or Thermal Putty
You may control the quantity of thermal grease or thermal putty according to the supplier’s or the manual’s guidance. Excessive application may cause spillage and prove difficult to clean, whilst insufficient application may result in incomplete coverage, influencing its effectiveness. First, apply the thermal grease or putty to the component, then gently press the heat sink or housing onto it. You will need to secure it using screws, clamps, or similar fixtures to prevent displacement during operational vibration and impact, thereby achieving a longer service life.
Thermal Grease vs. Thermal Putty: Differences in Thermal Conductivity
Thermal Conductivity of Thermal Grease
Thermal grease has a thermal conductivity ranging from approximately 1 to 8.5 W/m·K. Whilst lower than thermal putty, it is better than thermal adhesives and thermal tapes. Moreover, it can be compressed to ultra-thin layers, achieving lower thermal resistance than thermal putty. This achieves exceptionally high heat dissipation efficiency, making it commonly used in high-performance and high-power equipment. Moreover, owing to its excellent filling properties, its thermal conductivity remains unaffected by surface roughness.
Thermal Conductivity of Thermal Putty
Thermal putty has a thermal conductivity of approximately 1–14 W/m·K, offering higher thermal conductivity variants compared to thermal grease. Moreover, it effectively fills gaps on both smooth and rough surfaces, thereby reducing thermal resistance in heat transfer pathways. For those seeking superior thermal conductivity, thermal putty is the ideal choice.
Thermal Grease vs. Thermal Putty: Differences in Reusability
Thermal putty and thermal grease, whilst not requiring curing and being very simple to remove, become compressed and deformed after use and may not be suitable for other gaps. Furthermore, used thermal putty and thermal grease will accumulate impurities such as dust, which not only increases thermal resistance but also compromises their filling effectiveness and adhesive properties. This can lead to reduced performance and lifespan, affecting the stability of equipment operation. Furthermore, thermal grease itself has a relatively short lifespan, making repeated use an unreliable long-term solution. Consequently, neither thermal grease nor thermal putty is suitable for reuse; you’d better use a new one.
Thermal Grease vs. Thermal Putty: Differences in Maintenance and Service Life
Maintenance and Service Life of Thermal Grease
Thermal grease has an approximate service life of 12 months. Its lifespan is relatively short. During prolonged use, it may have problems such as pumping out, drying out, or hardening, necessitating frequent maintenance and replacement. When thermal grease deteriorates, its performance diminishes or may even fail. Furthermore, its lifespan is influenced by the operating environment. For example, its optimal temperature range is approximately -50 to 200°C. Exceeding this temperature range may accelerate performance degradation.
Maintenance and Service Life of Thermal Putty
Compared to thermal grease, thermal putty has a longer lifespan, typically lasting between 2 and 8 years. Its longevity is influenced by assembly practices and operating conditions, yet it withstands more thermal cycling. Furthermore, it offers superior stability, maintaining prolonged moisture retention during use and requiring less frequent pumping. Consequently, it demands minimal maintenance, making it suitable for high-reliability products or encapsulation applications.
Thermal Grease vs. Thermal Putty: Differences in Application
Applications of Thermal Grease
Benefiting from its high compliance and low tack line thickness, thermal grease can be applied to both flat and rough surfaces. Being thinner than thermal putty, it is more suitable for use in small gaps. Silicone thermal grease and silicone-free thermal grease are available for your selection. Furthermore, due to its shorter lifespan, you’d be best to use it in products where maintenance is easy to minimise servicing costs. Its high thermal conductivity and low thermal resistance make it suitable for high-performance equipment such as CPUs, GPUs, and IGBTs.
Applications of Thermal Putty
The high viscosity and shape retention properties of thermal putty allow it to fill larger gaps and maintain contact without relying on high-pressure compression. Consequently, it can be used in applications requiring greater thickness and lower mechanical pressure. It also offers satisfactory conformability for products with complex surfaces and offers higher thermal conductivity. It is advisable to use it in equipment with stringent reliability requirements. Applications include automotive electronics, battery packs, energy storage systems, and stacked component assemblies.
Thermal Grease vs. Thermal Putty: Differences in Cost
Cost of Thermal Grease
Due to simpler formulations and raw materials, the initial cost of thermal grease is often lower than that of thermal putty. However, thermal grease installation is more complex than thermal grease application, potentially leading to increased rework, higher material consumption, and elevated costs. Furthermore, in high-volume production, additional equipment such as automated dispensing machinery must be procured. Moreover, thermal grease requires frequent maintenance and replacement, which may result in higher long-term costs.
Cost of Thermal Putty
Although thermal putty has a higher initial cost than thermal grease, its high viscosity and gap-filling capability result in superior assembly yield rates, thereby reducing additional expenditure caused by material wastage. Furthermore, its extended service life eliminates the need for frequent replacement maintenance, making it a highly cost-effective choice.
How to Choose Between Thermal Grease and Thermal Putty for Your Project?
Heat Dissipation Requirements
When selecting thermal interface materials for your product, you must first determine its thermal dissipation requirements and choose the right thermal conductivity value. Selection should be based on the maximum load with a sufficient margin to avoid underperformance due to insufficient thermal conductivity. Higher thermal conductivity thermal greases and putty typically command higher prices. Avoid excessively high values to prevent budget overruns. Should suppliers offer thermal simulation services, you may get precise values or select materials guided by their recommendations.
Clearance Dimensions and Contact Pressure
Beyond thermal conductivity, excessive thermal resistance leads to poor heat dissipation efficiency, with assembly fit being a significant factor influencing thermal resistance. Where your product features narrow gaps, thermal grease offers satisfactory coverage and forms an extremely thin bond line. Conversely, thermal putty provides more stable filling in thicker gaps, creating superior thermal transfer pathways. Furthermore, thermal grease requires enough contact pressure between your components and heat sink to maintain performance.
Working Environment
On the one hand, thermal grease and thermal putty have different using temperatures. Thermal grease functions within approximately -50 to 200°C, while thermal putty operates between roughly -50 to 150°C. Specific models have different temperature ranges, allowing selection based on the product’s working environment. Relatively speaking, thermal grease offers better high-temperature resistance. Both materials perform well on rough surfaces and demonstrate excellent stability under low assembly tolerances. Should your product be subject to impact or vibration during operation, thermal putty provides enhanced stability.
Long-Term Reliability
Thermal putty needs less maintenance during use and has fewer problems, such as displacement, drying out, or pumping problems, offering a longer service life. It can be selected for thermal management solutions in high-reliability components such as medical equipment and automotive systems. Particularly for equipment where maintenance is difficult, thermal grease may increase repair and replacement costs.
Thermal Grease vs. Thermal Putty
| Item | Thermal grease | Thermal putty |
| Form | Semi-liquid paste | Thixotropic materials |
| Ease of use | Complex | Complex |
| Repeated workability | N/A | N/A |
| Thermal conductivity | 1 ~ 8.5W/m.K | 1 ~ 14W/m.K |
| Lifespan | 12 months | 2 ~ 8 years |
| Typical operating temperature | -50 ~ 200deg. C | -50 ~ 150deg. C |
| Cost | Lower(High maintenance costs) | Higher |
| Adhesion strength and tackiness | N/A | N/A |
| Maintenance | Frequently | Low |
| Application | Smooth and rough surfaces, small gaps, high-performance applications | Larger gaps, Smooth and rough surfaces, high-performance applications |
FAQs
Is Thermal Putty Better Than Thermal Grease?
This depends on your application. Thermal grease performs best in applications with small gaps and sufficient contact pressure, whereas thermal putty is more suitable for products involving large or variable gaps. When correctly selected and applied, thermal putty can meet long-term reliability requirements.
Can Thermal Grease be Used for Large Gaps?
Thermal grease is better for products where the gap between the heat-generating component and the heat sink is less than 0.2mm. Thermal paste offers poorer reliability; excessive application may lead to pumping out, material migration, or uneven distribution during prolonged thermal cycling. Thermal putty is the better choice for larger gaps.
Does Thermal Putty Dry out over Time?
High-quality thermal grease maintains long-term lubricity during extended operation, has stable performance, and features low oil separation rates with minimal hardening. However, its long-term performance depends on operating temperatures and environmental conditions.
Can Thermal Putty Replace Thermal Pads?
Thermal paste is suitable for applications where gap dimensions vary or where the thermal pad thickness is difficult to control precisely. It also offers better surface conformability compared to thermal pads. However, thermal pads may be more suitable where mechanical support, electrical insulation thickness, or clean assembly is required.
Which is Easier for Mass Production?
In large-scale production with dimensional variations or surface irregularities, thermal paste is generally easier to control. Thermal grease, however, requires strict process control and consistent contact pressure to achieve uniform performance.
Is Higher Thermal Conductivity Always Better for Thermal Grease or Putty?
No. A higher thermal conductivity does not achieve superior practical performance. Thermal resistance must also be considered. The performance of thermal grease and thermal putty is influenced by application thickness, compatibility, joint thickness, and material flow characteristics.
Final Thoughts
Choosing the correct thermal interface material impacts not only heat dissipation efficiency but also product reliability. As an experienced thermal grease and thermal paste supplier with a team of professional engineers, GALLOP INNOTEK offers one-to-one selection guidance. This enhances project efficiency and reduces expenditure.
