Silicone Oil Matrix in Thermal Grease: Filling Medium and Stress Buffer for Thermal Interface Materials

In electronic devices such as CPU/GPU heatsinks, power modules, or LED substrates, thermal grease acts as a Thermal Interface Material (TIM) used to fill the microscopic voids between the chip and the heatsink, thereby reducing contact thermal resistance. Its continuous phase is typically a high-viscosity silicone oil. Although silicone oil itself has a relatively low thermal conductivity (approx. 0.1–0.2 W/m·K), it plays a critical role in dispersing thermally conductive fillers, maintaining interfacial adhesion, and ensuring long-term reliability.

Metal or ceramic heat-dissipating surfaces may appear flat, but they actually possess micrometer-level rough peaks and valleys. If brought into direct contact, air (with a thermal conductivity of only 0.026 W/m·K) would occupy most of the gaps, creating significant thermal resistance. Thermal grease utilizes the silicone oil matrix to carry highly thermally conductive fillers (such as alumina, boron nitride, or metal oxides) into these voids, establishing heat conduction pathways via the solid fillers. In this process, silicone oil acts as a "fluidity carrier," ensuring the fillers are evenly distributed and can adapt to deformation under assembly pressure.

The selection of silicone oil must balance multiple performance criteria: high viscosity ensures the suspension stability of the fillers, preventing sedimentation and stratification; low volatility prevents drying out and failure under prolonged high temperatures; and maintaining elasticity across a wide temperature range (-50°C to over 200°C) helps compensate for periodic displacement stress caused by differences in the thermal expansion coefficients between the chip and the heatsink. Additionally, its electrical insulation prevents short circuits, while its chemical inertness avoids corroding metal interfaces.

It is worth noting that silicone oil itself is not the primary heat conduction path. Instead, it maximizes the thermal connectivity of the solid network by optimizing filler arrangement and interfacial wetting. At the same time, its soft characteristics allow for repeated disassembly and reassembly without damaging the chip surface. From a thermal management engineering perspective, silicone oil-based thermal grease is a "passive thermal bridge builder"—it does not actively dissipate heat, but by eliminating the air insulation layer, it clears the final obstacle for heat transfer from the heat source to the heatsink at the microscopic scale, serving as an indispensable silent support for the thermal reliability of electronic systems.


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