Thermally Conductive but Electrically Insulating Polybenzazole Nanofiber/Boron Nitride Nanosheets Nanocomposite Paper for Heat Dissipation of 5G Base Stations and Transformers

Abstract

The rapid development of 5G equipment and high-power density electronic devices calls for high thermal conductivity materials for heat dissipation. Dielectric polymer composites are highly promising as the electrical insulation, mechanical property, thermal stability, and even fire retardance are also of great importance for electrical and electronic applications. However, the current thermal conductivity enhancement of dielectric polymer composites is usually at the cost of lowering the mechanical and electrical insulating properties. In this work, we report the facile preparation of highly thermally conductive and electrically insulating poly­(p-phenylene benzobisoxazole) nanofiber (PBONF) composites by incorporating a low weight fraction of functionalized boron nitride nanosheets (BNNSs). With strong electrostatic interaction, the BNNSs are encapsulated by PBONFs, and the constructed robust interconnected network makes the nanocomposites exhibit a nacre-like structure. Accordingly, the nanocomposite paper has a high in-plane thermal conductivity of 21.34 W m–1 K–1 at a low loading of 10 wt % BNNSs and exhibits an ultrahigh strength of 206 MPa. Additionally, the nanocomposite paper exhibits superior electrical insulation properties up to higher than 350 °C and excellent fire retardance. The strong heat dissipation capability of the nanocomposite paper was demonstrated in 5G base stations and control transformers, showing wide potential applications in high power density electrical equipment and electronic devices.

Flexible, Highly Thermally Conductive and Electrically Insulating Phase Change Materials for Advanced Thermal Management of 5G Base Stations and Thermoelectric Generators

“…However, with the significant growth in energy consumption of 5G base stations, existing heat dissipation technologies can hardly fulfill the operation requirements of 5G hardware systems. In fact, a high operation temperature may cause automatic under-clocking of the chips to ensure the safety of the base station, which can inevitably reduce the transmission rate and exacerbate the transmission delays [ 37 ]. Therefore, it is of great importance to reduce the operation temperature of the chips to attain higher operation efficiency of 5G base stations.…”

“…In this case, nano-carbon and metallic filler cannot be used because of their high electrical conductivity enhancement effect on the composite materials. Hexagonal boron nitride nanosheet ( h -BNNS) is an ideal filler because of its ultrahigh thermal conductivity, high radius-to-thickness ratio, wide band gap and low density [ 36 , 37 ]. Herein, highly thermally conductive phase change nanocomposite (PCN) films with an aligned and overlapping interconnected BNNS network were prepared combining coaxial electrospinning, electrostatic spraying (designated as ‘es’) and hot-pressing in sequence.…”

A Malleable Composite Dough with Well-Dispersed and High-Content Boron Nitride Nanosheets

“…PTFE-based composites with a high TC are important thermal management materials for communication devices because their low dielectric constant and loss tangent has limited interference on signal transmission, while conventional heat dissipation films, such as conductive graphene or copper films, can seriously interfere with signals. Other reported high-TC polymer-based composites inevitably have to sacrifice dielectric constant and loss tangent. , Therefore, the areas near the antennas of 5G mobile devices are prohibited from using existing thermal management materials due to the interference of the signals. The BNNS/PTFE composite with 20 wt % BNNS exhibits a high TC while maintaining a low dielectric constant (2.44 at 15 GHz) and dielectric loss tangent (0.001 at 15 GHz) (Figure S15a,b), outperforming previously reported low dielectric PTFE-based composites (Table S5).…”

“…Other reported high-TC polymer-based composites inevitably have to sacrifice dielectric constant and loss tangent. 53,54 Therefore, the areas near the antennas of 5G mobile devices are prohibited from using existing thermal management materials due to the interference of the signals. The BNNS/PTFE composite with 20 wt % BNNS exhibits a high TC while maintaining a low dielectric constant (2.44 at 15 GHz) and dielectric loss tangent (0.001 at 15 GHz) (Figure S15a,b), outperforming previously reported low dielectric PTFE-based composites (Table S5).…”

Liquid Metal-Assisted High-Efficiency Exfoliation of Boron Nitride for Electrically Insulating Heat-Spreader Film

“…Hexagonal boron nitride (h-BN), an analogy to graphite, has a typical layered structure with alternating boron (B) and nitride (N) atoms linked with each other via covalent bonds, which attracts increasing attention in widespread applications, such as biomedical, dielectrics, thermal management, − and lubricating . It could be theoretically exfoliated into few- or single-layer boron nitride nanosheets (BNNSs) that behave with superior electrical, optical, and thermal characteristics compared to bulk h-BN. , However, unlike the case of graphite, N atoms in every layer are located exactly above or below the B atoms in the adjacent layer with the distinctive structure of h-BN, which contributes to the inherently high polarity of B–N bonds and the much stronger interlayer “lip–lip” interactions, making top-down exfoliation more challenging …”