High-performance Thermal Interface Materials Research Articles

General Approach to Hydrolysis Resistive Aluminum Nitride and Its High-Performance Thermal Interface Materials.

Aluminum nitride (AlN), noted for its excellent thermal conductivity and exceptional electrical insulation, presents a promising alternative to traditional ceramic particles in thermal interface materials (TIMs). However, its broader adoption in practical applications is limited by performance degradation due to the vulnerability of its crystal structure to ubiquitous moisture. This study introduces a dual solution, utilizing a mechanochemical method to design a dense outer layer of Galinstan liquid metal (LM) that simultaneously enhances AlN's resistance to hydrolysis and improves its thermal performance in TIM applications. The high surface free energy of the LM layer imparts hydrophobic properties to the AlN surface and, combined with outer metal oxides, forms a dual-layer protective barrier that prevents water penetration, significantly enhancing the TIM's long-term stability in high-humidity conditions. Additionally, the LM layer at the interface improves the thixotropic properties of the TIM and enhances interfacial heat transport through the bridging effect of the LM, resulting in improved rheological mobility and thermal conductivity of the composite material. This win-win surface modification strategy opens opportunities for the practical and durable application of AlN in widespread electronic thermal management.

Low magnetic field alignment of carbon fibers in a polymer matrix for high-performance thermal interface materials

Carbon-based materials like carbon nanotubes, graphene nanoplatelets, graphite, and carbon fibers (CF) are highly promising fillers for enhancing the thermal conductivity of thermal interface materials (TIMs) due to their high thermal conductivity and low thermal expansion. Aligning these fillers can further improve thermal conductivity, but current alignment methods using high magnetic fields are impractical for industrial use. In this study, we investigated the enhancement of the thermal conductivity of CF–polymer composites by aligning CF fillers with a low magnetic field. We observed up to 17 times enhancement of the thermal conductivity (from 3.1 to 52.8 W/mK) in a CF–graphene–polymer composite film by vertically aligning the CF fillers with a magnetic field of 0.75 T. The analysis of the structural properties of the films using X-ray diffraction and field-emission scanning electron microscopy imaging confirmed that the crystalline c-axis of the graphite plates in the CF was oriented perpendicular to the magnetic field direction. The large anisotropy in the diamagnetic susceptibility of the laminated graphene structure of the CF flakes is at the origin of the filler alignment. Furthermore, the thermal conductivity of the composites showed a strong correlation with the degree of filler alignment, which was dependent on the CF–graphene hybridization and the type of polymer matrix. This study provides a scalable and cost-effective method for enhancing the physical properties of carbon composites by controlling their microarchitecture using a low magnetic field.

High-performance thermal interface materials enabled by vertical alignment of lightweight and soft graphene foams

High-performance thermal interface materials enabled by vertical alignment of lightweight and soft graphene foams

Scalable Compliant Graphene Fiber-Based Thermal Interface Material with Metal-Level Thermal Conductivity via Dual-Field Synergistic Alignment Engineering.

High-performance thermal interface materials (TIMs) are highly desired for high-power electronic devices to accelerate heat dissipation. However, the inherent trade-off conflict between achieving high thermal conductivity and excellent compliance of filler-enhanced TIMs results in the unsatisfactory interfacial heat transfer efficiency of existing TIM solutions. Here, we report the graphene fiber (GF)-based elastic TIM with metal-level thermal conductivity via mechanical-electric dual-field synergistic alignment engineering. Compared with state-of-the-art carbon fiber (CF), GF features both superb high thermal conductivity of ∼1200 W m-1 K-1 and outstanding flexibility. Under dual-field synergistic alignment regulation, GFs are vertically aligned with excellent orientation (0.88) and high array density (33.5 mg cm-2), forming continuous thermally conductive pathways. Even at a low filler content of ∼17 wt %, GF-based TIM demonstrates extraordinarily high through-plane thermal conductivity of up to 82.4 W m-1 K-1, exceeding most CF-based TIMs and even comparable to commonly used soft indium foil. Benefiting from the low stiffness of GF, GF-based TIM shows a lower compressive modulus down to 0.57 MPa, an excellent resilience rate of 95% after compressive cycles, and diminished contact thermal resistance as low as 7.4 K mm2 W-1. Our results provide a superb paradigm for the directed assembly of thermally conductive and flexible GFs to achieve scalable and high-performance TIMs, overcoming the long-standing bottleneck of mechanical-thermal mismatch in TIM design.

2D Materials-Based Thermal Interface Materials: Structure, Properties, and Applications.

The challenges associated with heat dissipation in high-power electronic devices used in communication, new energy, and aerospace equipment have spurred an urgent need for high-performance thermal interface materials (TIMs) to establish efficient heat transfer pathways from the heater (chip) to heat sinks. Recently, emerging 2D materials, such as graphene and boron nitride, renowned for their ultrahigh basal-plane thermal conductivity and the capacity to facilitate cross-scale, multi-morphic structural design, have found widespread use as thermal fillers in the production of high-performance TIMs. To deepen the understanding of 2D material-based TIMs, this review focuses primarily on graphene and boron nitride-based TIMs, exploring their structures, properties, and applications. Building on this foundation, the developmental history of these TIMs is emphasized and a detailed analysis of critical challenges and potential solutions is provided. Additionally, the preparation and application of some other novel 2D materials-based TIMs are briefly introduced, aiming to offer constructive guidance for the future development of high-performance TIMs.

High throughput screening of thermal interface materials by machine learning

Till now, it remains a challenge for effective prediction and screening of novel materials with high thermal conductivity, as well as further optimization of the interface thermal resistance. Normally, people have to spend long time on tedious calculations when predicting and screening these materials. In this paper, I combined machine learning with molecular dynamics simulations to investigate the thermal conductive properties of materials with the aim of significantly reducing computational consumption. I first applied molecular dynamics simulations to obtain the relevant properties of materials, then generated models for predicting physical properties by machine learning, and finally made predictions of thermophysical properties of materials. The use of machine learning significantly reduces the prediction time compared to direct molecular dynamics simulations. Especially when the XGBoost and the neural network models are employed, the prediction efficiency is significantly improved. This work guides a new way for the future screening of high-performance thermal interface materials.

Enhancement of thermal conductivity and insulation of silicone thermal interface material through surface modification and synergistic effects of nanofillers for thermal management of electronic devices

Thermal interface materials (TIMs) play an irreplaceable role in highly integrated microelectronic devices. In this work, the addition of acidified carbon nanotubes modified by 3-aminopropyl triethoxysilane (KH550) had an effective enhancement to the thermal conductivity, thermal stability, and electrical insulation performance of silicone grease. On this basis, multi-filled silicone grease composites with better thermal conductivity and electrical insulation were prepared by introducing zinc oxide (ZnO) and Graphene nanoflakes (GNFs). The thermal conductivity of silicone grease achieved 1.438 W m−1 K−1, while the volume resistivity still exceeded 1013 Ω·cm. Additionally, the study explored the impact of varying filler parameters, temperature, and contact pressure on the interface thermal contact resistance of silicone grease. The best performance silicone grease applied to the cooling of the high-power LED exhibited excellent heat dissipation. This work presented a reference for the design and development of low cost, high performance TIMs.

Enhanced tough recyclable hemiaminal dynamic covalent network with boron nitride composites material with high thermal conductivity at low filler content

The demand for thermal interface materials (TIMs) with outstanding heat dissipation capability is increasing due to the advancements of multifunctional, miniaturized and well-integrated electronic devices. Simultaneously, as the accumulation of e-waste continues to grow, the recyclability of TIMs has emerged as a pressing concern. Herein, we introduce a novel approach that combines flow casting and hot pressing to create a tough recyclable hemiaminal dynamic covalent network with boron nitride composites film, which shows exceptional recyclability and high thermal conductivity. This approach was accomplished by combining hemiaminal dynamic covalent networks (HDCNs) with ionic liquid crystal exfoliated boron nitride nanosheets (ILC(Cl)-BNNS) via in situ polymerization. The obtained HDCN/BNNS composites film can enjoy a remarkable in-plane thermal conductivity of 2.72 Wm−1K−1 under a BNNS loading of 9.00 wt%, thus achieving an impressive ≈1195% in thermal conductivity enhancement. Furthermore, the HDCN/BNNS composite film enables the recycling of the composites under mild conditions, resulting in the facile recovery of BNNS with nearly pristine morphology and an impressive yield of 72.50%. This work presents a novel approach for the design of recyclable and high-performance TIMs, offering promising prospects for future applications.

High damping, soft and reprocessable thermal interface materials inspired by the microstructure of skin tissue

Thermal interface materials (TIMs) play a critical role in heat dissipation of modern electronics with their development towards integration and miniaturization. Shock-induced vibration damage is another extremely harmful to electronics, which requires TIMs remarkable damping properties, reprocessability, softness, and high thermal conductivity. However, current TIMs still lack the ability to dampen vibrations and reprocessability, because integrating these properties into one TIM still remains a dilemma. Inspired by the synergistic effects of fiber networks and adipocytes in skin tissue, here, we report on a high damping, soft and reprocessable TIM, by infusing viscous polymer into polybutadiene bottlebrush polymer network meanwhile combing with aluminum nitride filler. The obtained TIMs show damping factor as high as 0.95–1.0 in the frequency range of daily life (1–300 Hz), excellent reprocessability efficiency (92 %), low Young's modulus (55.8 kPa) and thermal conductivity of 2.25 W m−1 K−1. Analyzing the polymer structure and chain dynamics by rheology, broadband dielectric spectroscopy, solid state nuclear magnetic resonance, and FTIR spectroscopy, we confirm that these excellent properties is attributed to the enhanced migration ability of polymer chains, thermally conductive aluminum nitride fillers, and hierarchical hydrogen bonds in the bottlebrush polymer network. We further demonstrate the potential application of the TIMs in heat dissipation of an electronic device under vibrations. The current work provides a unique structure design approach towards high-performance TIMs in shock-resistant electronics.

Enhancing thermal transport of epoxy composites with vertically aligned graphene in situ grown on the thermal interface.

The escalating demands for miniaturization, integration, and portability in electronic devices have underscored the criticality of efficient heat dissipation. The utilization of high-performance thermal interface materials (TIMs) to fill the gaps between contacting surfaces holds significant potential for enhancing heat transfer efficiency. Herein, we successfully enhance the thermal properties of the epoxy composite TIM by integrating in situ grown vertically aligned graphene on the metal surface using radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD). To investigate the effect of vertical graphene on epoxy, the sandwich structure of copper/vertical graphene-epoxy/copper (Cu/VG-EP/Cu) is fabricated by incorporating epoxy resin. The experimental results demonstrate that the thermal conductivity of VG-EP reaches 2.06 W m-1 K-1 and achieves an impressive 1215% maximum enhancement. Furthermore, the numerical simulation findings show that vertical graphene consistent with the temperature gradient exhibits the highest heat transfer efficiency. This work presents an in-depth study of vertically aligned graphene within the epoxy resin, highlighting the advantages of vertically aligned fillers and offering novel perspectives for the advancement of TIMs.

Alveoli-Mimetic Synergistic Liquid and Solid Thermal Conductive Interface as a Novel Strategy for Designing High-Performance Thermal Interface Materials.

Thermal interface materials (TIMs) are in desperate desire with the development of the modern electronic industry. An excellent TIM needs desired comprehensive properties including but not limited to high thermal conductivity, low Yong's modulus, lightweight, as well as low price. However, as is typically the case, those properties are naturally contradictory. To tackle such dilemmas, a strategy of construction high-performance TIM inspired by alveoli is proposed. The material design includes the self-alignment of graphite into 3D interconnected thermally conductive networks by polydimethylsiloxane beads (PBs) -the alveoli; and a small amount of liquid metal (LM) - capillary networks bridging the PBs and graphite network. Through the delicate structural regulation and the synergistic effect of the LM and solid graphite filler, superb thermal conductivity (9.98 ± 0.34W m-1 K-1) can be achieved. The light emitting diode (LED) application and their performance in the central processing unit (CPU) heat dispersion manifest the TIM developed in the work has stable thermal conductivity for long-term applications. The thermally conductive, soft, and lightweight composites are believed to be high-performance silicone bases TIMs for advanced electronics.

Dry-Contact Thermal Interface Material with the Desired Bond Line Thickness and Ultralow Applied Thermal Resistance.

Efforts to directly utilize thixotropic polymer composites for out-of-plane thermal transport applications, known as thermal interface materials (TIMs), have been impeded by their mediocre applied thermal resistance (Reff) in a sandwiched structure. Different from traditional attempts at enhancing thermal conductivity, this study proposes a low-bond line thickness (BLT) path for mitigating the sandwiched thermal impedance. Taking the most common TIM, polydimethylsiloxane/aluminum oxide/zinc oxide (PDMS/Al2O3/ZnO), as an example, liquid metal is designed to on-demand localize at the Al2O3-polymer and Al2O3-filler interface regions, breaking rheological challenges for lowering the BLT. Specifically, during the sandwiched compression process, interfacial LM is just like the lubricant, dexterously promoting the relaxation of immobilized PDMS chains and helping fillers to flow through mitigating the internal friction between Al2O3 and adjacent filler. As a result, this TIM first time exhibits a boundary BLT (4.28 μm) that almost approaches the diameter of the maximum filler and performs an ultralow dry-contact Reff of 4.05 mm2 K/W at 40 psi, outperforming most reported and commercial dry-contact TIMs. This study of the low-BLT direction is believed to point to a new path for future research on high-performance TIMs.

Improving thermal conductivity of graphene films with assistance of melamine

Due to the high degree of integration and high-power-density, excessive heat accumulation significantly endangers the performance of electronics. Therefore, developing high-performance thermal interface materials has become particularly vital for ensuring the regular operation of the electronics. Graphene-based materials attract great attention due to graphene’s intrinsic excellent thermal conductivity. However, the internal defects in graphene and the lack of interlayer heat conduction pathways between graphene microsheets dramatically reduce the thermal conductivity of graphene-based materials. Herein, melamine is used to improve the thermal properties of graphene films prepared by thermal reduction of graphene oxide (GO) microsheets. With an addition of 3 wt% of melamine, the in-plane and through-plane thermal conductivities of the graphene films with a thickness of 35 μm reach 1.32 × 103 and 5.09 W m−1 K−1, respectively. This is likely due to the covalent connection of graphene microsheets through amide structure formed by the chemical reaction between melamine and GOs, and the remedy of defects in graphene by nitrogen doping with the assistance of high-temperature annealing. The operation temperature of LED is greatly reduced, when the prepared graphene films is used as thermal interface material, compared to other commercial products. The results provide a promising way to improve the thermal properties of graphene films, which is of great significance for various applications, such as thermal management for high-power-density electronics.

Synergistic effects of oriented AlN skeletons and 1D SiC nanowires for enhancing the thermal conductivity of epoxy composites

As electronic devices are moving towards miniaturization and integration, the demand for ceramic/polymer composites with high thermal conductivity (TC) are increasing significantly. Herein, we reported a novel idea for rational design and delicate construction of anisotropic three-dimensional thermally conductive networks via the ice template method, using stearic acid-modified AlN particles (AlNm) as the primary filler and SiC nanowires (SiCNWs) as the secondary. As predicted, the as-prepared epoxy (EP)-based composites achieved a maximum TC of 2.56 W·m−1·K−1 in vertical direction at a filling fraction of 55 vol %, which was 12.8 times higher than that of pure EP. More importantly, the enhancement mechanism of composite TC was further demonstrated by realistic heat transfer process and finite element simulations. Furthermore, the prepared composites also displayed excellent thermal stability, high mechanical strength and good dielectric property, indicating that this strategy provides a promising insight for the design of high-performance thermal interface materials (TIMs).

A Full-component recyclable Epoxy/BN thermal interface material with anisotropy high thermal conductivity and interface adaptability

Thermal interface materials (TIMs) with excellent heat dissipation capacity are highly desired for the development of miniaturized, integrated, and dense electronic devices. In addition, with the increasing accumulation of e-waste, the recyclability of TIMs has also become an urgent concern. Herein, a fully recyclable TIM with high thermal conductivity and conformability to the rough surface was prepared based on the synthesized epoxy vitrimer and boron nitride (BN) nanosheet. Results revealed that only by simple hot-pressing, the filled BN could be easily oriented in the plane and led to a thermal conductivity of 3.85 W m−1 K−1 with the BN content of 40 wt%, which was 30 times higher than that of the pristine epoxy resin and 4.3 times higher than the composite before hot-pressing treatment. The electronic device made of the prepared composite exhibited a 20 °C lower core temperature than the commercial silicone material, due to the superior thermal conduction and mechanical compliance. Moreover, benefiting from the multistage degradation mechanism of the synthesized epoxy vitrimer, the fabricated composite could be efficiently chemically recovered under mild conditions, demonstrating the BN recovery rate of 96.2% and other organic raw materials recovery rate of 73.6% to 82.4%. This work provides us with a new strategy for the design of recyclable and high-performance TIMs.

Facile and Scalable Strategy for Fabricating Highly Thermally Conductive Epoxy Composites Utilizing 3D Graphitic Carbon Nitride Nanosheet Skeleton.

The application of high-performance thermal interface materials (TIMs) for thermal management is commonly used to tackle the problem of heat accumulation, which influences the performance and reliability of microelectronic devices. Herein, a novel three-dimensional (3D) carbon nitride nanosheet (CNNS)/epoxy composite with high thermal conductivity was developed by introducing 3D CNNS skeleton fillers prepared by a facile and scalable strategy assisted by a salt template. Benefiting from the continuous heat transfer pathways formed in the CNNS skeleton, 17.0 wt % 3D CNNS/epoxy composites achieve a superior thermal conductivity of 1.27 W/m·K, which is 6.35 and 1.57 times higher than those of epoxy resin and convention CNNS/epoxy, respectively. With the aid of theoretical model analysis and finite element simulation, the pronounced enhancement effect of the 3D CNNS skeleton on the thermal conductivity of epoxy composites is found to be attributed to the continuous 3D CNNS thermally conductive network, the diminished CNNS-CNNS interfacial thermal resistance, and the effective interfacial interactions between epoxy and CNNS. In addition, the 3D CNNS/epoxy composites possess high electrical insulation and desirable mechanical strength. Therefore, 3D CNNS/epoxy composites are promising TIMs for advanced electronic thermal management.

A binder-free ice template method for vertically aligned 3D boron nitride polymer composites towards thermal management

Hexagonal boron nitride (BN) is an attractive filler candidate for thermal interface materials, but the thermal conductivity enhancement is limited by the anisotropic thermal conductivity of BN and disordered thermal pathways in the polymer matrix. Herein, a facile and economic ice template method is proposed, wherein BN modified by tannic acid (BN-TA) directly self-assemble to form vertically aligned nacre-mimetic scaffold without additional binders and post-treatment. The effects of the BN slurry concentration and the ratio of BN/TA on three-dimensional (3D) skeleton morphology are fully investigated. The corresponding polydimethylsiloxane (PDMS) composite via vacuum-impregnation achieves a high through-plane thermal conductivity of 3.8 W/mK at a low filler loading of 18.7 vol%, which is 2433% and 100% higher than that of pristine PDMS and the PDMS composite with randomly distributed BN-TA, respectively. The finite element analysis results theoretically demonstrate the superiority of the highly longitudinally ordered 3D BN-TA skeleton in axial heat transfer. Additionally, 3D BN-TA/PDMS exhibits excellent practical heat dissipation capability, lower thermal expansion coefficient, and enhanced mechanical properties. This strategy offers an anticipated perspective for developing high-performance thermal interface materials to address the thermal challenges of modern electronics.

Water-Assisted Transformation of Aluminum Alloys to Ceramic Nanowires and Aerogels

Ceramic nanowires (NWs) and their-based aerogels hold great promise for manufacturing and applications of polymer nanocomposites with otherwise unattainable mechanical and thermal properties. Unfortunately, conventional routes for the synthesis of ceramic NWs commonly suffer from the use of costly or toxic chemicals, low production rate, and complex and expensive procedures. Here, we report on a water-assisted route for the cost-effective, scalable transformation of bulk aluminum–lithium alloys into ceramic alumina NWs and aerogels. In this study, we employ water as the intermediary solvent for dealloying to form monolithic porous Li-doped aluminum metal, which can then be converted to ultralong metal–organic NWs, then to hydroxide NWs after hydrolysis and finally to NW aerogels after freeze-drying. As a high-performance thermal interface material for electronic devices, the oxidized alumina NW aerogels infiltrated with epoxy show significantly improved thermal properties. Our study shows great potential for the scalable production of ceramic NWs using a low-cost and environmental-friendly route for various applications.

Pie-rolling-inspired construction of vertical carbon fiber high thermal conductivity hybrid networks

Carbon fiber (CF) with a high thermal conductivity (Tc) of 1100 W m−1 K−1 along its one-dimensional (1D) direction is considered a promising filler for fabricating high-performance thermal interface material (TIM). However, Tc in the radial direction of CF is far less than 10 W m−1 K−1 determines that Tc highly depends on the orientation of CF. In this study, polydimethylsiloxane (PDMS)/short carbon fibers (SCFs)/Al spherical particle (PDMS/SCFs/Al) composite is firstly prepared. SCFs are then arranged into horizontal (0°), inclined (45°), and vertical (90°) orientations, respectively, utilizing a convenient “pie-rolling” method that does not rely on any specific instrument. As a result, the vertically oriented SCFs together with Al spherical particles establish an effective thermal conductivity-three-dimensonal (3D) network, and the Tc of the through-plane is as high as 10.46 W m−1 K−1, while the in-plane Tc is 6.23 W m−1 K−1 measured from a steady-state method. The anisotropic thermal conductivity is also verified by a hot-disk method. The working mechanism and thermal conductivity of oriented SCFs and Al spherical particles composites are being studied using finite element simulation. In addition, the change in surface temperature of the composites during heating and cooling stage is observed using an infrared thermal imaging camera. A 16 ℃’s temperature decline demonstrates that the high-efficiency heat transfer along the vertical orientated carbon fiber-based 3D network was successfully realized in SCF-90 when it was used as a TIM between a bare die and heat pipe of a laptop. This work illustrates the prospect of using SCFs to prepare a high thermally conductive 3D network could be used in the future thermal management of electronic devices.

Compliance-tunable thermal interface materials based on vertically oriented carbon fiber arrays for high-performance thermal management

With the ever-shrinking characteristic dimension of chips and the increasing of packaging density, heat dissipation has become the most critical technology challenge for electronic devices. The development of high-performance thermal interface materials (TIMs) for enhancing thermal coupling and minimizing thermal resistance between heterogeneous components is the key to achieving efficient thermal management of electronic devices. Herein, we report a high-performance carbon fiber/polydimethylsiloxane (CF/PDMS) TIM based on the construction of vertically oriented carbon fiber arrays and the modulation of PDMS's crosslinking density. The resulting CF/PDMS TIM exhibits highly desirable characteristics of through-plane thermal conductivity up to 43.47 W/m∙K (only 20 vol% loading), outstanding elastic compliance similar to soft biological tissues (stress ∼ 35 kPa at 35% compressive strain), and excellent resilience performance (resilience rate of 85% after compression cycles). In addition, the heat dissipation capability of CF/PDMS TIM is improved further by forming interconnected heat-conducting structures on the CF/PDMS TIM's surface. The optimal CF/PDMS TIM in microprocessor cooling application exhibits superior heat dissipation capability and stability during 1000 power cycles, resulting in a 68 °C reduction in the chip temperature compared with the state-of-the-art commercial TIM. This work opens up a new avenue for fabricating high-performance TIMs that meet the heat dissipation requirements of high-performance computing.