What is the role of thermal grease in thermal conductive materials?

Most of the cooling system design is actually very simple. The main design principle is to reduce the temperature inside the device through active guidance or the influence of the external environment. Usually, a radiator is installed on the surface of the heat source, and the excess heat of the heat source is guided to the outside through the radiator, so as to reduce the temperature of the device.

 

Thermal grease (thermal paste / thermal compound) is a semi-fluid TIM that fills microscopic air gaps between heat-generating components and heat sinks, reducing interface thermal resistance. In volume electronics manufacturing, thermal grease enables low bond-line thickness and high heat transfer at the component-to-heatsink interface — a critical factor for power electronics, CPU/GPU modules, and automotive inverters.

 

What Is Thermal Grease

Thermal grease is a semi-fluid paste-like thermal conductive material made of silicone oil base material, adding thermal conductivity, temperature resistance, and insulating materials in a certain proportion. It has high thermal conductivity, low interface thermal resistance, and good electrical insulation. It is generally considered to be extremely The best thermal interface thermal material, due to its stable performance, there will be no corrosive substances during operation.

 

Thermal grease itself has excellent interface lubricity. It is evenly spread on the surface of power-consuming electronic components, which can eliminate the air contacting the interface. Because it is a semi-fluid paste, it can effectively fill the rough surface between the interfaces. This increases heat flow and reduces thermal resistance.

There is a gap between the surfaces, and the thermal conductive material represented by thermal grease can effectively reduce the contact thermal resistance between the interfaces and increase the rate of heat transfer between the two, thereby truly improving the heat dissipation effect of the device.

 

Sheen Technology thermal grease performance properties：

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	-

Note: Values are typical ranges; specific grades vary. Sheen Technology provides product-specific datasheets.

 

Thermal Grease vs. Other TIMs

Multi-Parameter Comparison：

Parameter	Thermal Grease	Thermal Pad	Phase-Change	Gap Filler
Thermal Conductivity (W/m·K)	1–5	1–15	3–8	1–12
Thickness (mm)	0.05-0.06	0.3-10.0	0.13-0.5	0.10-0.22
Thermal Resistance (°C·in²/W)	0.016–0.15	0.1–0.9	0.015–0.06	0.045–0.10
Pump-Out Resistance	Poor–Moderate	Excellent	Moderate	Good
Assembly	Dispense + inspect	Pick-and- place	Place + heat activate	Dispense
Rework	Solvent clean	Peel + replace	Heat + clean	Mechanical remove
Cost (relative)	Low	Moderate	Moderate	Low–Mod
Best Application	Thin flat high-heat-flux	Gap filling + isolation	Low resistance + easy handling	Large/variable gaps

Note: Values are typical ranges; specific grades vary. Sheen Technology provides product-specific datasheets.

 

 

Selection Decision Framework：

• STEP 1: Is electrical isolation required? → Yes: pad (or grease + separate film). No: continue.
• STEP 2: What is the gap size? → <100 μm: grease or phase-change. >500 μm: gap filler. 100–500 μm: pad.
• STEP 3: Is reworkability/serviceability critical? → Yes: pad or phase-change (cleaner). No: grease acceptable.
• STEP 4: What is the heat flux? → >50 W/cm²: liquid metal or high-conductivity grease. <20 W/cm²: any standard TIM.
• STEP 5: What is the production volume and process? → High volume + automation: pad (pick-and-place). Low volume + flexibility: grease (dispense).

 

Thermal Grease Application & Reliability

Failure Modes and Quantified Behavior：

Failure Mode	Mechanism	Quantified Impact	Prevention
Pump-Out	Cyclic thermal expansion squeezes grease from interface	Thermal impedance rises 20–50% after 500–1,000 cycles	High-viscosity formulation; controlled BLT; validate per IEC 60068-2-14
Dry-Out	Volatile component evaporation thickens grease over time	Conductivity drops 10–30% after 1,000 h at 150°C	High-temperature stable oil carrier; sealed packaging
Oil Bleed	Low-molecular-weight oil separates and migrates	Contamination of adjacent components; reduced viscosity	Thixotropic formulation; specify low-bleed grade
Void Formation	Air entrapment during dispensing or assembly	Local hot spots; 2–5× higher local resistance	Automated dispensing; controlled compression

 

 

Application-Specific Requirements：

Application	Key TIM Requirement	Typical Grease Grade	Qualification Focus
CPU/GPU modules	Low resistance, thin BLT	3–8 W/m·K	Thermal impedance, pump-out
IGBT power modules	Dielectric + thermal	Insulating grade 1–5 W/m·K	Dielectric (ASTM D149), thermal cycling
Automotive inverters	High-temp stability + cycling	2–6 W/m·K high-temp oil	Thermal shock (IEC 60068-2-14), aging
LED assemblies	Long-term stability, low oil bleed	1–4 W/m·K	Oil bleed, optical contamination
Telecom equipment	Reliability, consistency	2–5 W/m·K	Batch consistency, aging

• Applications: CPU/GPU modules, IGBT power modules, LED assemblies, automotive inverters, telecom equipment.
• Pump‑Out: cyclic thermal expansion squeezes grease from the interface — validate per IEC 60068‑2‑14.
• Dry‑Out: volatile component evaporation thickens grease over time — check aging at operating temperature.
• Dispensing: automated systems achieve ±5% volume tolerance; manual application varies ±20–50%.

 

→ Request Thermal Grease Application & Dispensing Guide

 

FAQ

Q: What is thermal grease made of?

A: Thermal grease is a silicone or hydrocarbon oil carrier loaded with thermally conductive fillers (alumina, zinc oxide, boron nitride). Insulating grades provide electrical isolation; metal-filled grades are electrically conductive. Typical thermal conductivity is 1–12 W/m·K.

 

Q: How does thermal grease reduce interface resistance?

A: It displaces air (0.026 W/m·K) from microscopic surface-roughness valleys, filling gaps and increasing real contact area. This reduces interface resistance by 10–100× compared to dry contact, enabling thin bond lines (20–100 μm).

 

Q: What causes thermal grease pump-out?

A: Cyclic differential thermal expansion between component and heatsink squeezes grease from the interface during thermal cycling. High-viscosity formulations resist pump-out better. Validate per IEC 60068-2-14 for >500 cycle applications.

 

Q: When should I choose thermal grease over a thermal pad?

A: Choose grease when surfaces mate closely (<50 μm BLT) and minimum thermal resistance is the priority. Choose a pad when gap filling, electrical isolation, or repeatable automated placement is required.

 

Thermal grease plays a foundational role in thermal management by minimizing interface resistance at the component-to-heatsink junction. Its thin bond line and conformability make it the preferred TIM for high-heat-flux, tight-tolerance applications. Sheen Technology provides thermal grease products with ASTM-referenced data, dispensing guidance, and application engineering for power electronics and industrial cooling.
 

→ Contact Sheen Technology for Thermal Grease Selection Support