Thermal Gel vs Thermal Paste: Key Differences Explained

Date：2026-07-25

Thermal interface materials span a spectrum from thin-bondline pastes to gap-filling gels — and choosing between thermal gel and thermal paste is one of the most common decision points faced by electronics design engineers. Both are dispensable TIMs that conform to surface irregularities, but their fundamentally different rheological properties, curing behavior, and gap tolerance define distinct application domains. This guide compares the material science, manufacturing integration, and cost implications of thermal gel versus thermal paste, with a focus on helping engineering and procurement teams make data-driven sourcing decisions.

What Is Thermal Paste?

Thermal paste, also known as thermal grease or heat transfer paste, is a viscous material designed for thin-gap applications. With a thermal conductivity range of 1.0 to 5.0 W/m·K, it is primarily composed of silicone oil and thermally conductive fillers. Thermal paste has low thermal resistance and excellent wetting properties, allowing it to fill microscopic gaps effectively.

Key Features of Thermal Paste:

Non-Curing: Thermal paste remains in its original state and does not harden, making it easy to reapply.
Thin Application: Minimum interface thickness of 0.02mm, making it ideal for thin-gap applications.
Customizable Viscosity: Can be adjusted according to specific customer requirements.
Applications: Best suited for thin-gap applications like CPUs, GPUs, and other high-performance computing devices. It can be applied manually or via screen printing without the need for preheating.

Thermal Paste Specifications at a Glance:

Properties	Color	Thermal Impedance (@30psi)	Thermal Conductivity	Minimum Interface Thickness
Unit	-	℃*in2/W	W/m·K	mm
SG560-10	White	≤0.15	1.0±0.1	0.06
SG560-20	White/Gray	≤0.045	2.0±0.2	0.05
SG560-30	Gray	≤0.03	3.0±0.3	0.05
SG560-40	Gray	≤0.02	4.0±0.4	0.05
SG560-50	Gray	≤0.016	5.0±0.5	0.05
Test Method	Visual	ASTM D5470	ASTM D5470	-

What Is Thermal Gel?

Thermal gel, also referred to as thermal putty or liquid thermal gap filler, is a versatile material available in various formulations, such as single-component silicone gel, dual-component silicone gel, and silicone-free gel. Thermal gels are known for their adaptability to large-gap applications and their excellent thermal conductivity, ranging from 1.0 to 12.0 W/m·K.

Types of Thermal Gel:

Single-Component Thermal Gel (SE Series):
- Thermal Conductivity: 1.0 to 12.0 W/m·K
- Features: Non-curing, low thermal resistance, good wetting and thixotropic properties, and low assembly stress.
- Applications: Ideal for filling thin gaps with large tolerance variations in automotive electronics, smartphones, laptops, and communication devices.
Dua-Component Thermal Gel (SE Series AB):
- Thermal Conductivity: 1.0 to 8.0 W/m·K
- Features: Cures at room temperature, becomes an elastic solid after curing, offers low thermal resistance, and provides cushioning and shock absorption.
- Applications: Suitable for automated dispensing machines and applications requiring durable thermal connections.
Silicone-Free Thermal Gel (AE Series):
- Thermal Conductivity: 1.0 to 3.0 W/m·K
- Features: Non-curing, free of silicone oil migration and siloxane volatility, suitable for silicone-sensitive environments.
- Applications: Designed for filling thin gaps in silicone-sensitive scenarios, using automated dispensing machines.

Thermal Gel comparison table:

Type	SE Series (1-Comp)	SE Series AB (2-Comp)	AE Series (Si-Free)
Conductivity	1.0-12.0 W/m-K	1.0-8.0 W/m-K	1.0-3.0 W/m-K
Cure	Non-curing	Room-temp cure	Non-curing
Post-cure state	Pliable gel	Elastic solid	Pliable gel
Gap range	0.1-5.0 mm	0.2-5.0 mm	0.1-3.0 mm
Reworkability	Easy (non-curing)	Moderate (cured, removable)	Easy (non-curing)
Dispensing	Automated, single-component equipment	Automated, dual-component mixing head required	Automated, single-component
Silicone migration risk	Yes (silicone-based)	Yes (silicone-based)	No (silicone-free)
Key applications	General gap fill, automotive electronics, smartphones, telecom	Vibration-prone assemblies, structural thermal connections	Optical modules, relays, cleanroom, silicone-sensitive

Key Differences Between Thermal Gel and Thermal Paste

Thermal Conductivity:
- Thermal paste typically has a conductivity of 1.0 to 5.0 W/m·K, suitable for thin-gap applications.
- Thermal gel offers a wider range of 1.0 to 10.0 W/m·K, making it more versatile for varying gap sizes.
Application and Reworkability:
- Thermal paste is non-curing and ideal for thin, precise applications.
- Thermal gel, particularly non-curing types, adapts to larger gaps and remains flexible, making it easier to rework.
Durability:
- Dual-component thermal gels cure into an elastic solid, providing better structural stability and shock absorption compared to thermal paste.
Use Cases:
- Thermal paste excels in high-performance computing environments like CPUs and GPUs.
- Thermal gel is more suited for applications with larger gaps or variable tolerances, such as automotive electronics and telecommunication devices.

Which One Should You Choose?

Ask these questions to determine the right material:

What is your gap range?
· Under 0.2 mm with flat, machined surfaces → Thermal paste is optimal.
· 0.2-5.0 mm or variable tolerance stack → Thermal gel required.
What is your dispensing setup?
· Single-component pneumatic or auger valve equipment available → Either paste or single-component gel works.
· Willing to invest in dual-component mixing and metering equipment → Dual-component gel unlocks cured-state durability.
· Manual dispensing / low volume → Both are viable; paste is typically lower cost per gram.
Is silicone migration a concern?
· No → Standard silicone-based paste or gel.
· Yes (optical assemblies, relays, cleanroom, downstream conformal coating) → Silicone-free paste or silicone-free gel (AE Series) required.
What reliability profile is needed?
· 5+ year field life with minimal thermal degradation under thermal cycling → Dual-component cured gel preferred.
· Frequent rework expected, or short product lifecycle → Non-curing paste or single-component gel acceptable.
· Vibration environment (automotive, railway, industrial) → Cured gel provides structural integrity and shock absorption.

Industry-Specific Application Guidance

Automotive Electronics

EV battery management systems (BMS), onboard chargers, and DC-DC converters combine high thermal loads with significant vibration and temperature cycling.

Dual-component thermal gel (SE Series AB) is the dominant choice for gap filling between power semiconductors and liquid-cooled cold plates, providing both thermal conductivity and vibration resistance.
For silicone-sensitive automotive applications (e.g., camera modules, LiDAR sensors), silicone-free AE Series gel prevents optical surface contamination over the vehicle's 10-15 year service life.

5G Telecommunications

Remote radio units and active antenna units contain GaN power amplifiers generating concentrated heat loads while sharing sealed enclosures with sensitive optical transceivers.

Single-component thermal gel bridges the variable gap between amplifier packages and the die-cast housing, accommodating manufacturing tolerances without paste's risk of pump-out over years of solar-loaded outdoor operation.
Silicone-free formulations prevent long-term siloxane deposition on optical interfaces.

Server & HPC

High-performance CPU and GPU cooling in data center servers demands thermal paste's ultra-thin bondline capability.

LED Lighting & Power Supplies

thermal paste and thermal gel for led light

LED driver ICs and power supply transformers benefit from thermal gel's ability to fill irregular cavities and bridge multiple component heights within a single assembly.

Non-curing single-component gel allows rework during production while providing consistent thermal performance across the unit's operational life.

Thermal Gel & Paste Solutions from Sheen Technology

Sheen Technology offers a complete range of dispensable thermal interface materials:

Product	Conductivity	Type	Best For
Thermal Grease (Paste)	1.0-5.0 W/m-K	Non-curing, silicone-based	CPU/GPU, RF modules, thin-gap precision interfaces
SE Series Single-Comp Gel	1.0-12.0 W/m-K	Non-curing, silicone-based	Automotive, telecom, gap fill 0.1-5.0 mm
SE Series AB Dual-Comp Gel	1.0-8.0 W/m-K	Curing, silicone-based	Vibration environments, structural thermal connections
AE Series Silicone-Free Gel	1.0-3.0 W/m-K	Non-curing, silicone-free	Optical, relays, cleanroom, silicone-sensitive