Electronic Packaging Applications Research Articles

Review on Processing, Flame‐Retardant Properties, and Applications of Polyethylene Composites with Graphene‐Based Nanomaterials

AbstractThis paper presents recent developments in graphene‐based nanomaterial (GNM)‐containing flame‐retardant (FR) polyethylene (PE) composites for advanced applications and introduces knowledge gaps and potential solutions. Various nanomaterials have been used to improve the FR properties of PEs. Among these, GNMs score highly because of their superior performance and multifunctional characteristics. By offering a holistic overview of the fundamentals of the FR characteristics of GNMs, the processing and characterization of PE/GNM composites, and the critical aspects related to the development of FR PE/GNM composites for advanced applications, this review provides insights into advances in this area as well as prospects. Furthermore, the kinetics of the FR characteristics of PE and PE/GNM composites are critically discussed in the context of how the FR properties of PE/GNM composites can be tailored by modifying either the surface of the GNM, PE or both, an area seldom discussed in the literature. Moreover, the FR performance of PE/GNM composites is compared with PE/Expandable Graphite (EG) composites because EG has been recognized as a highly efficient and eco‐friendly intumescent FR. In summary, this review offers new insights into the design of advanced PE/GNM composites for automotive, construction, aerospace, and electronic packaging applications.

Enhancing flame retardancy and dielectric performance of epoxy resins through benzoxazine-phosphorus modification

A P/N-containing flame retardant, DOPOBH, was synthesized with salicylaldehyde, p-aminophenol, 9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide (DOPO) and formaldehyde. The performance of DOPOBH in flame retardant modification of 4,4′-diaminodiphenyl sulfone(DDS)/diglycidyl ether of bisphenol A (DGEBA, E−44) system was studied in terms of limiting oxygen index (LOI), vertical burning testing (UL-94) and cone calorimeter test (CCT). When the phosphorus content was 1.5 wt% of the whole system, DOPOBH modified epoxy resin (EP/P1.5) exhibited excellent flame retardancy (achieving a UL-94 V-0 rating and the LOI value of 35.2 %). Compared with pure EP, a 54.3 % decrease of peak heat release rate (PHRR) and ca. 5 times of residue (with an intumescent structure) was obtained with EP/P1.5 in CCT. Based on the results of CCT, scanning electron microscope (SEM), thermal gravimetric analysis (TGA) and thermogravimetry-infrared spectroscopy (TG-IR), DOPOBH was verified to play important roles in both gas phase and solid phase. In addition, the addition of DOPOBH could improve the dielectric properties of epoxy resin and provide new strategies for high-performance applications in electronic packaging.

Microstructure and properties of Cu/Si composites for electronic packaging: Effect of tungsten layer on silicon particles

Cu/Si composite are ideal electronic packaging materials, but the intense formation of Cu-Si intermetallics during preparation leads to a significant decrease in their plasticity and thermal conductivity. In this paper, a W layer was formed on Si particles using the sol-gel method, and Cu/Si composites were prepared by hot pressing. The results show that the maximum thickness of the W layer is 1.64 μm, and the minimum thickness is only 809 nm. The W layer acts as a diffusion barrier, effectively inhibiting the Cu-Si interfacial reaction and intermetallics formation, thus preventing the deterioration of matrix and reinforcement properties. Compared with the Cu/Si composite, the elongation of the Cu/Si@W composite improves from 0.2 % to 1.7 %, and the thermal conductivity increases by 7 times to 233.9 W/(m·K). Additionally, among the four samples, the Cu/Si@W composite has the lowest coefficient of thermal expansion (CTE). The W layer enhances the mechanical properties and thermal conductivity while reducing the CTE of Cu/Si composite for improved electronic packaging application.

Interface microstructures in the wetting of Cu by equiatomic GaInSnBiZn high-entropy alloy

This study investigates the wetting characteristics, interface microstructure evolution of equiatomic GaInSnBiZn HEA on Cu under high vacuum with sessile drop method to extend its electronic packaging applications. Optimal conditions involve a 350 °C temperature maintained for ∼20 min to prevent Bi loss, resulting in a contact angle inversely proportional to temperature and reaching a minimum of ∼15.6°. A dual-layer of Cu9Ga4 and CuGa2 forms at the HEA/Cu interface, consistent with thermodynamic predictions, featuring lower activation energy and growth driven by bulk alloy diffusion. Base on the interface microstructures, Cu9Ga4 and CuGa2 act as diffusion barriers, restricting the movement of other elements while promoting the accumulation of Zn at the interface. The wetting mechanism may be determined by the oxide (Cu2O) removal reaction (i.e., reaction between Ga and Cu2O).

Effect of polymer infiltration and pyrolysis (PIP) on microstructure and properties of high volume fraction SiC/Al composites prepared by a novel hybrid additive manufacturing

High-volume-fraction SiC/Al (HVF-SiC/Al) composites have a wide range of applications in aerospace, optics, automotive and electronic packaging. However, because the hardness, brittleness and wear resistance increase with the increase in the volume fraction, it is difficult for traditional methods such as machining, to process HVF-SiC/Al composites to complex components. Therefore, in this paper, a novel method of the hybrid additive manufacturing is proposed to fabricate complex-structures SiC/Al composite parts. The effect of polymer infiltration and pyrolysis (PIP) on microstructure and properties of HVF-SiC/Al composites is investigated. The results show that the mechanical properties of the SiC preforms can be effctively enhanced by the PIP process, and this enhancement makes the SiC preforms meet the conditions for subsequent vacuum-pressure infiltration. The mechanical property of HVF-SiC/Al composites show a huge increase when in creasing the volume fraction of SiC. In particular, the flexural strength of HVF-SiC/Al composites increased from 202.28 MPa to 380.87 MPa, and the coefficient of thermal expansion (CTE) has also been reduced from 11.80 to 6.28 × 10−6/K, when the volume fraction of SiC increases from 42 to 80 vol%. For optimise the PIP process in the future, three theoretical models are used to predict the relationship between the CTE and the volume fraction of SiC. The results show that the experimental data are more consistent with the predicted values based on the Kerner's model, but deviate from the Rule-of-mixture (ROM) and Turner's models. Importantly, the complex-structures SiC/Al composite parts was successfully fabricated by this hybrid additive manufacturing.

Prediction of mechanical properties and fatigue life of nanosilver slurry in chip interconnection

This article investigates the failure mode and mechanism of copper pillar solder joints in temperature cycling experiments, focusing on a Cu/nano Ag/Cu solder joint structure. The hot pressing bonding condition at 300 °C with insulation for 10 s is chosen for the experiments. Based on the life test results, the thermal cycling fatigue life of the nanosilver solder joint is determined to be 2050 cycles. To gain further insights, finite element software ANSYS is employed to simulate nanosilver solder joints in flip chips, revealing the stress–strain distribution within the solder joints. The simulation utilizes the Anand viscoplastic constitutive model for the solder joint, providing a reasonable representation of the stress–strain behavior under thermal cycling load. Notably, the simulation highlights that the maximum stress and strain occur in the contact area between the solder joint and the copper column. To enhance accuracy, the calculation equation is refined using relevant experience, resulting in a prediction of the thermal fatigue life of nanosilver solder joints. This prediction aligns closely with the experimental results. The research outcomes not only contribute valuable insights into the behavior of nanosilver solder but also serve as a reference for its application in electronic packaging.

Recent Advances in Nanoclay‐ and Graphene‐Based Thermoplastic Nanocomposites for Packaging Applications

ABSTRACTOver the past few years, thermoplastic nanocomposites reinforced with different types of nanofillers have seen widespread use in the automotive, pharmaceutical, food packaging and electronic sectors. Among the different nanofillers used to fabricate thermoplastic composite–based packaging materials, nanoclay and graphene are very beneficial for producing high‐barrier packaging materials. The high aspect ratio and large surface area of both nanoclay and graphene facilitate uniform filler dispersion and tortuous path in the thermoplastic matrix, which ultimately improves the physico‐mechanical, thermal and barrier to oxygen, water vapour and light as well as antimicrobial properties, which are key requirements for packaging materials. Because graphene nanomaterials are electrically and thermally conductive, these thermoplastic nanocomposites may display excellent electrical‐, thermal‐ and microwave‐shielding capabilities, allowing them to be used in electronic packaging. This review aims to summarize the preparation and characterization of thermoplastic nanocomposites based on different types of nanoclay, graphene and graphene derivatives, as well as their prospective applications in food and electronic packaging. This review paper also discusses the factors that can affect the performance and attributes of these packaging materials, such as processing conditions, types of nanofillers, functionalization or modification of nanofillers for better filler dispersion and so forth. This paper presents a comprehensive and state‐of‐the‐art article on nanoclay‐ and graphene‐loaded thermoplastic nanocomposite–based packaging materials.

Bioinspired Thermal Conductive Cellulose Nanofibers/Boron Nitride Coating Enabled by Co-Exfoliation and Interfacial Engineering.

Thermal conductive coating materials with combination of mechanical robustness, good adhesion and electrical insulation are in high demand in the electronics industry. However, very few progresses have been achieved in constructing a highly thermal conductive composites coating that can conformably coat on desired subjects for efficient thermal dissipation, due to their lack of materials design and structure control. Herein, we report a bioinspired thermal conductive coating material from cellulose nanofibers (CNFs), boron nitride (BN), and polydopamine (PDA) by mimicking the layered structure of nacre. Owing to the strong interfacial strength, mechanical robustness, and high thermal conductivity of CNFs, they do not only enhance the exfoliation and dispersion of BN nanoplates, but also bridge BN nanoplates to achieve superior thermal and mechanical performance. The resulting composites coating exhibits a high thermal conductivity of 13.8 W/(m·K) that surpasses most of the reported thermal conductive composites coating owing to the formation of an efficient thermal conductive pathway in the layered structure. Additionally, the coating material has good interface adhesion to conformably wrap around various substrates by scalable spray coating, combined with good mechanical robustness, sustainability, electrical insulation, low-cost, and easy processability, which makes our materials attractive for electronic packaging applications.

Fused Deposition Modeling of Isotactic Polypropylene/Graphene Nanoplatelets Composites: Achieving Enhanced Thermal Conductivity through Filler Orientation.

High-performance thermally conductive composites are increasingly vital due to the accelerated advancements in communication and electronics, driving the demand for efficient thermal management in electronic packaging, light-emitting diodes (LEDs), and energy storage applications. Controlling the orderly arrangement of fillers within a polymer matrix is acknowledged as an essential strategy for developing thermal conductive composites. In this study, isotactic polypropylene/GNP (iPP/GNP) composite filament tailored for fused deposition modeling (FDM) was achieved by combining ball milling with melt extrusion processing. The rheological properties of the composites were thoroughly studied. The shear field and pressure field distributions during the FDM extrusion process were simulated and examined using Polyflow, focusing on the influence of the 3D printing processing flow field on the orientation of GNP within the iPP matrix. Exploiting the unique capabilities of FDM and through strategic printing path design, thermally conductive composites with GNPs oriented in the through-plane direction were 3D printed. At a GNP content of 5 wt%, the as-printed sample demonstrated a thermal conductivity of 0.64 W/m · K, which was 1.5 times the in-plane thermal conductivity for 0.42 W/m · K and triple pure iPP for 0.22 W/m · K. Effective medium theory (EMT) model fitting results indicated a significantly reduced interface thermal resistance in the through-plane direction compared to the in-plane direction. This work shed brilliant light on developing PP-based thermal conductive composites with arbitrarily-customized structures.

Preparation and performance of alumina/epoxy-siloxane composites: A comparative study on thermal- and photo-curing process

Although epoxy-based composites that consist of inorganic fillers and matrixes are widely used in “conventional” electronic packaging applications due to their excellent insulation and robust properties, they limit their uses in “advanced electronic packaging” which requires enhanced thermal conductivity. However, conventional thermal curing methods for fabrication of epoxy-based composites do not fulfill sufficient thermal conductivity. Herein, we apply photo-induced curing strategy for fabricating alumina-incorporated epoxy-siloxane composites that consist of sol-gel derived siloxane matrix and bimodal sized alumina particles as a thermally conductive filler. We investigate how curing mechanism (thermal- or UV-curing) and varying the ratios of the alumina particles of two different sizes affect the various physical properties. It is found that photo-curing process makes greatly enhanced thermal conductivity, low thermal expansion, and high mechanical robustness compared to thermally-cured composites. As the results, we can achieve significantly enhanced thermal conductivity (>11 W/m K) with high thermal stability and mechanical robustness.

Laser Processing of Polyimide and Molybdenum Substrates for Extreme Environment Electronics

A desire in today’s electronic packaging technologies is to create more dense electronic packaging schemes. One method to achieve more dense electronic package integration is to use three-dimensional interconnects to minimize interconnect physical dimensions. Three-dimensional interconnect technologies, such as interposers, require a method of connecting electronics to electronic packages vertically. Thru silicon vias are a widely studied and explored vertical interconnect technology used in a variety of electronic packaging applications. Though silicon has high material hardness, the brittle nature of silicon substrates is a concern for robustness and reliability. These concerns only increase when the desired interconnect application is in extreme environments, such as cryogenic temperatures. A potential alternative to silicon in thru-via applications in extreme environments is molybdenum. Molybdenum is a commonly used material in many applications, such as automotive and aerospace, and has high material strength. Molybdenum is also a low coefficient of thermal expansion material, comparable to silicon, which in combination with high material strength lends to high reliability at extreme temperatures. A challenge of working with refractory metals such as molybdenum is that conventional CNC machining techniques require the use of machining coolants that may not be compatible with fabricated electronics and/or processes can become costly due to tool wear and the need for specialized equipment. Additionally, using molybdenum as a thru-via substrate requires the need for an electrically insulated layer, such as polyimide, within drilled molybdenum thru-holes to prevent the molybdenum substrate from shorting via connections. One potential solution to the above challenges is developing laser processing techniques to cut and drill molybdenum and polyimide. Laser processing is becoming a preferred method for inexpensive prototyping with high resolution and design versatility. This work seeks to meet the challenges described by developing laser cutting and drilling techniques for both molybdenum and polyimide for the use in cryogenic applications. This work will describe two laser processing configurations utilizing two different lasers to laser machine molybdenum and polyimide. This work will first describe the process strategies of laser cutting and drilling molybdenum as a stand-alone substrate. Aspects of laser processing on molybdenum, such as pattern repetitions and scanning speeds, will be described. Process parameter variations will be compared directly and evaluated. Additionally, post-laser processing steps, such as abrasive blasting, will be described and discussed. Next, the fabrication steps to achieve an insulating layer of polyimide in laser drilled holes as well as on each surface of the molybdenum will be detailed. Once polyimide has been cured, laser processing parameters to realize thru-holes in the polyimide-filled molybdenum drills will be presented. Adhesion of polyimide on the molybdenum substrate will be verified and demonstrated through the use of confocal scanning acoustic microscopy before and after polyimide laser processing. Cryogenic performance will be verified by completing confocal scanning acoustic microscopy after submersion in liquid nitrogen (~77 K) and compared with the pre-submersion microscopy images. Processes detailed in this work will open opportunities for future development of molybdenum-based interconnect structures for use in cryogenic applications. Acknowledgement We thank the Alabama Micro/Nano Science and Technology Center (AMNSTC) for providing access to fabrication and characterization facilities used in this work.

Multi-physical and anti-corrosion properties of graphene-reinforced epoxy nanocomposite coatings for industrial applications

Polymer-based coatings are widely used as a protective barrier to corrosion, but their performance is not sufficiently sustainable for industrial applications due to the formation of micropores and microcracks during solidification. Graphene is a promising reinforcing element acting as a filler for polymeric coatings. This study used 1–5 wt% graphene synthesized by the electrochemical exfoliation process as a reinforcing nanofiller to manufacture graphene-reinforced epoxy nanocomposite (GREN) coatings. Copper was used as a substrate material for coating with GREN by a bar coating method. GREN coatings were characterized by X-ray diffraction, Raman spectroscopy, FTIR spectroscopy, FESEM, and EDX. A comprehensive investigation was conducted on the various multi-physical properties of GREN coatings, including coating thickness, surface roughness, adhesiveness, surface wettability, water absorptivity, thermal stability, electrical conductivity, and anti-corrosion capabilities. The results exhibited that graphene fills micro-pores produced in epoxy during solidification. The surface roughness significantly decreased to 0.25 µm with the addition of 5 wt% graphene in pure epoxy. In addition, the adhesiveness, thermal stability, and electrical conductivity of GREN coatings increased with the increase in graphene content. The GREN coatings containing 3 wt% and 5 wt% graphene revealed hydrophobic surface showing 94° and 102° water contact angle, respectively. In the electrochemical analysis and immersion test in 3.5 % NaCl solution for 600 h, the GREN coatings showed higher corrosion resistance without compromising their electrical conductivity compared to the pure epoxy. Based on the results, GREN can be a promising coating material for aerospace, mining, and electronic packaging applications. Apart from this, the results of this work will explore the new significance in industry, where multi-physical properties from a single nanocomposite coating are crucial.

Pressureless sinter-joining of micron-Ag flake pastes at 160 °C enabled by solvent and interface engineering

Pressureless sinter-joining of cost-effective micron-Ag flake pastes at temperatures below 200 °C poses significant challenges due to their poor surface activity and low tapped density. Herein, we propose a novel solvent and interface engineering approach to enhance the contact among adjacent micron-Ag flakes and between the flakes and substrates. The solvent-enhanced sintering process is proposed, and its effect on the resistivity and shear strength of sintered Ag patterns and joints is studied in detail. Results show that the solvents with high wetting abilities on the Ag flakes and substrates are instrumental in achieving low resistivity and high shear strength in the sintered Ag patterns and joints. In particular, when the solvents possess high surface tension, they generate strong capillary adhesion among Ag flakes and substrates. This reduces the gap between Ag flakes and substrates, thereby promoting bonding among the Ag flakes by minimizing the distance of atom diffusion. Finally, mixed solvents of 50 % α-Terpineol and 50 % dipropyleneglycol methyl ether acetate show a synergistic effect due to the balance between wettability and surface tension, which enables the sintered joints to achieve an exceptional shear strength of 27 MPa even at an ultralow temperature of 160 °C. This achievement represents the state-of-the-art pressureless sinter-joining of Ag pastes and holds promising potential for practical use in power electronic packaging applications.

Spark plasma sintering of Al–SiC composites with high SiC content: study of microstructure and tribological properties

The article presents the results of the microstructure and tribological properties of Al–xSiC composites (x = 70 and 90 wt% SiC) produced in spark plasma sintering (SPS). Due to their attractive thermal, physical, and mechanical properties, aluminum matrix composites with high-volume fractions of silicon carbide (> 50%) have become a major area of interest as a potential material for multifunctional electronic packaging and cryogenic applications. The SPS process was carried out in a vacuum atmosphere under various conditions. Composites with a density close to theoretical (96–98%) were obtained. X-ray diffraction and scanning electron microscopy with EDS analysis were used to characterize the microstructure. Mechanical properties were determined by hardness measurements and a three-point bending test. The tribological properties of the composites were determined utilizing a block-on-ring tribotester. As a criterion for wear resistance, weight loss measured under specific friction conditions, that is, depending on the type of material and the applied load, was adopted. The researched materials were characterized by an even distribution of the carbide phase in the matrix. Composites with the highest SiC phase content (90 wt%) had higher hardness (2537 HV1) and flexural strength (242 ± 15 MPa) with worse wear resistance at the same time. The weight loss of this composite was 0.43 and 0.76% for friction under loads of 100 and 200 N, respectively, and was 360 and 270% higher than that determined for the composites with the lower content of the SiC phase (70 wt%). The wear rate was three times higher for the Al-90wt%SiC composites.

Preparation and properties of branch‐leaf‐like polyimide composite films with high thermal conductivity and low dielectric loss

AbstractPolyimide (PI) is widely used in the communication field benefited from its low dielectric properties and good electrical insulating properties, however, its low thermal conductivity simultaneously limits its application in electronic packaging. Delayed heat dissipation can exacerbate the thermal stress generated by device operation to damage electronic structures, thereby affecting work efficiency. As a result, it is necessary to improve the thermal conductivity of polyimide and maintain excellent dielectric performance. Here, we demonstrate the polyimide (BPDA‐ODA) composites with ordered structure are prepared by filling commercial polyimides with aramid nanofibers connection nitrides greatly improve thermal conductivity and maintain the low dielectric loss. When the filling amount of SBN@CN is 30 wt%, the thermal conductivity increases to 1.162 W/mK, which is 8 times higher than that of pure PI (0.0147 W/mK). Moreover, thermal stability and mechanical properties are maintained, realizing that the dielectric constant is about 3.81 and the dielectric loss is as low as 0.0034 at 100 MHz, which endows a new insight for the application of polyimide in electronic packaging.

Designing insulative SiC coating layer on the artificial graphite particle to achieve synergy of wave absorption and thermal conduction

Artificial graphite powders possess attractive intrinsic thermal conductivity (TC) and sphericity for a high loading, but their poor electrical insulation hinders the electromagnetic wave (EMW) absorption for applying in the field of electronic packaging. Herein, the spherical artificial graphite coated by insulating silicon carbide (SG@SiC) layer with integrated functionalities of outstanding EMW absorption and excellent TC are synthesized via a facile gas-solid chemical reaction. The surface of the prepared SG@SiC particles features abundant nanometer-sized pores that facilitates to regulate impedance matching, which favors to realize superior EMW absorbing performance. Interfacial polarization introduced by the core-shell structure and inherent conduction loss are more conducive to elevating the EWM-absorbing of SG@SiC. The SG@SiC composites achieve a TC of 3.28 W m−1 K−1 at a loading of 73.7%, which increases 16.2 times higher than initial silicone rubber (SR). In addition, the SG@SiC composite demonstrated exceptional wave-absorbing properties with a minimum reflection loss (RLmin) of −31.9 dB at a frequency of 7.9 GHz and an effective absorption bandwidth (EAB) of 2.9 GHz under the thickness of 2.0 mm. Given these superior properties, the versatile SG@SiC composites open up an avenue to integrate EMW absorption and thermal evacuation in a single component for electronic packaging applications.

Near-zero thermal expansion in a wide temperature range of lightweight mMnZnSnN/AlSi with high thermal conductivity

Lightweight materials with near-zero thermal expansion (NZTE) and high thermal conductivity have potential applications in precision instruments, aerospace industry and electronic packaging due to their high thermal stability. In this study, multiphase Mn3Zn1-xSnxN (MnZnSnN) with abnormal negative thermal expansion (NTE) were used to inhibit the positive thermal expansion of AlSi. The resulting composites multiphase-MnZnSnN/AlSi (mMnZnSnN/AlSi) achieved NZTE (0.40 × 10-6 °C-1) in a wide temperature range (-5–60 °C, ΔT = 65 °C). Compared with other NZTE materials, mMnZnSnN/AlSi exhibits high thermal conductivity of 60 W·m-1·K-1 and high bending strength of 211 MPa. The density of the composite is only 4.46 g/cm3, 45% lower than invar alloy. This work provides guidance for designing and fabrication of aluminum matrix materials with combined advantages of wide temperature range zero thermal expansion behavior, high thermal conductivity and high mechanical properties.

Significant enhancement of comprehensive properties of SnBi solder through the addition of Cu@Ag core-shell particles

As a critical low-temperature lead-free solder, SnBi eutectic solder was known for its abundant lamellar structures of Bi-rich phase, which often resulted in problems such as brittleness, low electrical conductivity, and low thermal conductivity. In this study, a method was introduced to enhance the comprehensive properties of SnBi solder by adding Cu@Ag core-shell particles. Our results revealed that the modified SnBi solder exhibited significant refinement in both grain size and intragranular eutectic structures, resulting in a shift from the original brittle fracture mode to a mixed brittle and tough mode and a consequent increase in tensile strength by 21%. Moreover, the modified solder demonstrated a significant 59% increase in electrical conductivity by forming interconnected highspeed channels for electron migration. In addition, the addition of Cu@Ag core-shell particles to SnBi solder resulted in remarkable contributions of both electrons and phonons to thermal conductivity, with its value of 41.33 W m−1 K−1. Our research addressed partial property deficiencies of SnBi solder, which could be valuable in expanding its application in low temperature electronic packaging.

Magnetic-induced dynamically enhanced in-plane or out-of-plane thermal conductivity of BN/Ag NWs@Ni/epoxy composites

The thermal conductivity of polymer composites could be improved through the orientation of fillers in specific directions. Here, a novel strategy to fabricate BN/Ag nanowires@Ni/epoxy composites (BN/Ag NWs@Ni/EP) to dynamically improve the in-plane or out-of-plane thermal conductivity of the composites in real-time by changing the direction of the magnetic field was investigated. The thermal conduction path was constructed by Ag NWs bridging between BN flakes. Ag NWs@Ni would be oriented in the in-plane or out-of-plane direction by changing the direction of the magnetic field. The out-of-plane or in-plane thermal conductivities of the composites were 0.824 and 0.723 W m−1K−1 at 40 wt% BN/Ag NWs@Ni content, and the corresponding TCEs were 429% and 359% respectively when Ag NWs@Ni was oriented in the out-of-plane or in-plane direction. Meanwhile, BN/Ag NWs@Ni/EP exhibited good mechanical and dielectric properties, which were beneficial for its industrial application in electronic packaging. This strategy provides the possibility for the applications that required the adjustment of the heat conduction direction in real-time.

Strategy for Constructing Epoxy Composites with High Effective Thermal Conductive Capability Based on Three-Dimensional Cellulose and Multiwalled Carbon Nanotube Network

High effective thermal management materials have become a crucial factor for the reliability and lifetime of devices. Herein, epoxy resin (EP) composites with superior thermal conductive efficiency were fabricated via the homogeneous dispersion of carboxylated multiwalled carbon nanotubes (CMWCNTs) in cellulose nanofiber (CNF) aerogels, and then the EP precursors were impregnated and cured. The thermal conductivity of EP/CNF/CMWCNT thermosets containing only 0.65 wt % CMWCNTs increased from 0.19 W·m–1·k–1 for pristine EP to 0.93 W·m–1·k–1 and increased by 389.5%. As a result, the composites presented excellent heat absorption and dissipation performance, which are demonstrated by the infrared thermal camera tests. Besides, the composites showed highly electric insulating performance, and its volume electrical resistivity was as high as 6.48 × 1015 Ω·cm–1 due to the low content of CMWCNTs in thermosets. The glass-transition temperature of EP/CNF/CMWCNT composites increased from 132.6 °C for neat EP thermosets to 153.3 °C, as indicated by the dynamic mechanical analysis. Moreover, thermal mechanical analysis demonstrated that the resultant EP composites possessed excellent dimensional stability. The obtained EP/CNF/CMWCNT composites were allowed to work at a higher temperature environment. This presented research work provided an alternative approach for preparing EP composites with highly efficient thermal management and electrical insulation performance, which allowed their application in electronic packaging, devices, and other electronic applications.