Improvement of Thermal Conductivities for Epoxy Composites via Incorporating Poly(vinyl benzal)-Coated h-BN Fillers and Solvent-Assisted Dispersion

Enhanced thermal conductivity of epoxy resin by incorporating three-dimensional boron nitride thermally conductive network

Packaging insulation materials with high thermal conductivity and excellent dielectric properties are favorable to meet the high demand and rapid development of third generation power semiconductors. In this study, we propose to improve the thermal conductivity of epoxy resin (EP) by incorporating a three-dimensional boron nitride thermally conductive network. Detailedly, polyurethane foam (PU) was used as a supporter, and boron nitride nanosheets (BNNSs) were loaded onto the PU supporter through chemical bonding (BNNS@PU). After immersing BNNS@PU into the EP resin, EP-based thermally conductive composites were prepared by vacuum-assisted impregnation. Fourier transform infrared spectrometer and scanning electron microscope were used to characterize the chemical bonding and morphological structure of BNNS@PU, respectively. The content of BNNS in BNNS@PU/EP composites was quantitatively analyzed by TGA. The results show that the thermal conductivity of the BNNS@PU/EP composites reaches 0.521 W/m K with an enhancement rate η of 30.89 at an ultra-low BNNS filler content (5.93 wt. %). Additionally, the BNNS@PU/EP composites have excellent dielectric properties with the frequency range from 101 to 106 Hz. This paper provides an interesting idea for developing high thermal conductivity insulating materials used for power semiconductor packaging.

Design of Interconnected Carbon Fiber Thermal Management Composites with Effective EMI Shielding Activity

Heat dissipation efficiency and electromagnetic interference (EMI) shielding performance are vital to integration, miniaturization, and application of electronic devices. Flexible and designable polymer-based composites are promising candidates but suffer from unavoidable interfacial thermal resistances, anisotropic thermal conductivity, and low shielding of EMI limiting application. Herein, multifunctional epoxy resin (EP)-based composites with an interconnected carbon fibers (CFs) network structure containing a low thermal resistance interfacial were prepared by high-temperature calcination and infiltration. The coherent heat and electron transfer pathways constructed with self-oriented CFs cloth connected by carbon nanotubes (CNTs) converted from leaf-shaped zeolitic imidazolate frameworks (ZIF-L) and stable magnetic property provided by cobalt nanoparticles contained in the CNTs made composites to an integrated in-plane thermal conductivity of up to 7.50 W m^-1 K^-1, a through-plane thermal conductivity of 1.96 W m^-1 K^-1, and an EMI shielding effectiveness of 38.4 dB. Furthermore, the mechanical properties of CFs and the junction effect of CNTs endowed the composites with stability of mechanical property, thermal conductivity, and EMI shielding effectiveness after multiple bendings. The finite element simulation further verified the advantage of CFs network linked by CNTs on heat transfer. This work provides the desired design for the construction of a multifunctional polymer-based composite used in advanced electronic equipment.

Quasi-isotropically thermoconductive, antiwear and insulating hierarchically assembled hexagonal boron nitride nanosheet/epoxy composites for efficient microelectronic cooling

Herein, Pebax functionalized h-BNNSs (P-BNNSs) fabricated by a mechanical exfoliation and in-situ modification process are employed to improve the thermal conductivity and antiwear performance of epoxy resin (EP). Pebax can effectively improve the dispersibility of P-BNNSs, achieving hierarchical assembly of P-BNNSs in EP matrix during EP curing process to form a multinetwork structure only at a low P-BNNS filling contents (≤6 wt%). This multinetwork structure can act as excellent heat conductive pathways to realize simultaneously vertical and horizontal heat diffusion, obtaining quasi-isotropical thermal conductive P-BNNS/EP composites. Fascinatingly, a through-plane thermal conductivity of 3.9 W/(m·K) and an in-plane thermal conductivity of 2.9 W/(m·K) are obtained. More importantly, this special structure can simultaneously improve the antiwear, mechanical and electrically insulating performances of pure EP. The friction coefficients and wear rates of P-BNNS/EP composites (P-BNNS contents ≤ 6 wt%) are dramatically decreased to less than 0.2 and 1 × 10^-5 mm³/(N·m), comparing with those of pure EP which are over 0.6 and 2 × 10^-5 mm³/(N·m), respectively. The enhanced tensile stress of over 110 MPa and electric volume resistivity of over 1.50 × 10¹³ Ω·cm are also observed for P-BNNS/EP composite films. These improved properties make the P-BNNS/EP composites very promising as packaging or heat dissipation materials in the high density integration systems and high frequency printed circuit boards.

Advances in Studies of Boron Nitride Nanosheets and Nanocomposites for Thermal Transport and Related Applications

Hexagonal boron nitride (h-BN) and exfoliated nanosheets (BNNs) not only resemble their carbon counterparts graphite and graphene nanosheets in structural configurations and many excellent materials characteristics, especially the ultra-high thermal conductivity, but also offer other unique properties such as being electrically insulating and extreme chemical stability and oxidation resistance even at elevated temperatures. In fact, BNNs as a special class of 2-D nanomaterials have been widely pursued for technological applications that are beyond the reach of their carbon counterparts. Highlighted in this article are significant recent advances in the development of more effective and efficient exfoliation techniques for high-quality BNNs, the understanding of their characteristic properties, and the use of BNNs in polymeric nanocomposites for thermally conductive yet electrically insulating materials and systems. Major challenges and opportunities for further advances in the relevant research field are also discussed.

Preparation and mechanism research of bio-inspired dopamine decorated expanded graphite/silicone rubber composite with high thermal conductivity and excellent insulation

This study looked at the process of designing and synthesized expanded graphite (EG) and modifying it with bio-inspired dopamine (DOPA). This is a process used to improve the thermal conductivity and dielectric properties of methyl vinyl silicone rubber (VMQ). The results demonstrated that the EG-DOPA-VMQ composites acquired an exceptional thermal conductivity of 1.015 W mK^-1at the loading of 10 wt%, approximately 480% higher than that of pure silicone rubber (0.175 W mK^-1). This enhancement is mainly attributed to the improved dispersion capability of EG-DOPA and the robust interfacial interaction between EG-DOPA-VMQ interfaces; specifically, this is the result when compared with pristine EG. Moreover, throughout this process, the composites maintained an excellent insulating property with a resistance of ≈10¹²Ω · cm; this particular result was due to the DOPA deposited on EG surfaces because they acted as an insulating layer, inhibiting the electron transfer in composites. Overall, this work demonstrated that it could present a promising strategy for synchronized manufacturing of polymer composites with high thermal conductivity and insulating capability.