With the rapid development of technologies such as 5G communications and high-power chips, thermal management of electronic devices has become a critical bottleneck restricting performance improvement. This study focuses on the heat conduction mechanism of Thermal Interface Materials (TIMs), and significantly enhances the thermal conduction efficiency of the materials through innovative filler compounding strategies and surface treatment processes. The research confirms that zinc oxide (ZnO), with its unique advantages of low thermal resistance, high thermal conductivity (≥40 W/m·K), and low Mohs hardness (approximately 4.5), can effectively balance thermal conductivity, mechanical adaptability, and equipment wear issues, providing a solution for high-power-density electronic devices.
The miniaturization and high-frequency operation of electronic devices lead to a sharp increase in heat generation per unit area, making traditional TIMs increasingly unable to meet heat dissipation requirements. Current research focuses on modifying matrix resins with high thermal conductivity fillers. Materials such as aluminum oxide and boron nitride are widely used due to their excellent insulation properties; however, problems such as interface contact thermal resistance and device wear caused by their high hardness have not been effectively resolved. In contrast, zinc oxide, with its low coefficient of thermal expansion (4.75×10??/K) and flexible characteristics, can form tighter interface contact, but its insulation deficiency limits its development. This study proposes to overcome this limitation through particle size gradient design and surface coating technology.
The core of improving thermal conductivity lies in constructing a continuous thermal conduction network. Fillers with a single particle size tend to form pores (Figure 1), increasing interface thermal resistance. This study adopts a compound system of "large-particle skeleton + small-particle filling":
Large-particle zinc oxide (D50=30 μm) serves as the main skeleton to form the basic thermal conduction path;
Submicron fillers (e.g., heavy spherical nano-zinc oxide developed by Zhaoqing Xinrunfeng High-Tech Materials Co., Ltd., D50=200 nm) fill the gaps between large particles to improve packing density (Figure 2).
Experiments show that when the mass ratio of large to small particles is 7:3, the connectivity of the thermal conduction network is optimal, and the thermal conductivity is 48% higher than that of the single-particle-size system.
Spherical particles have better fluidity than amorphous particles, enabling a higher filling rate (>85 vol%). Due to their smooth surface and uniform particle size, the heavy spherical nano-zinc oxide from Zhaoqing Xinrunfeng significantly reduces viscosity in the silicone grease matrix and prevents filler sedimentation (Figure 3).
A fumed silica coating technology is adopted (Figure 4):
A nano-SiO? insulating layer (thickness ≈100 nm) is constructed on the surface of zinc oxide;
The volume resistivity is increased from 10? Ω·cm to 1012 Ω·cm, meeting the requirements of high-voltage devices.
Organic modification with fatty acids is implemented:
Reduces the interfacial energy between filler and resin, resulting in a 35% decrease in viscosity (tested in accordance with ASTM D4287);
Prevents agglomeration under high filling conditions (Figure 5), ensuring material processability.
*Note: Epoxy resin matrix with 60 vol% filling, including the compound system of heavy spherical nano-zinc oxide.
In the power amplifier module of 5G base stations:
The junction temperature of devices using zinc oxide-based TIMs is reduced by 21 °C (results from infrared thermal imaging);
No interface peeling occurs after 1000 thermal cycles (-40~125 °C), and the hardness change is <5%.
This study addresses the insulation defects and filling process challenges of zinc oxide fillers in TIMs through particle size gradient design, application of spherical particles, and surface coating technology. Experiments demonstrate that the introduction of heavy spherical nano-zinc oxide from Zhaoqing Xinrunfeng High-Tech Materials Co., Ltd. into the compound system can significantly optimize filler packing efficiency and rheological properties, providing a highly reliable heat dissipation solution for high-power electronic devices. Future work will explore the application potential of this material in IGBT modules of new energy vehicles.
