Electronic Dissipation Research Articles

A spring-mass-damper model based on separated phase flow mode for pulsating heat pipe with adjustive-structured channels

Pulsating heat pipe (PHP) is a kind of efficient passive phase-change cooling device. The pulsating behaviors of the two-phase flow inside PHP significantly affect the heat transfer performance for PHP, the investigation of which will greatly contribute to the optimal design of PHP for electronic heat dissipation in small space. In the present work, the heat transfer performance of PHP is optimized via structure analysis and modeling calculation. A new “spring-mass-damper” model in terms of separated phase flow mode is established, where the frictional pressure loss of the real two-phase flow pattern − slug flow in PHP is considered. Besides, a prototype of PHP with adjustive-structured channel (ASCPHP) is proposed. The heat transfer performance of ASCPHP is evaluated with the newly established model. With theoretical computation method, the frequency of ASCPHP the superiority of ASPHP is also confirmed by comparison with other types of PHPs.

Numerical Study on the Heat Dissipation Performance of Diamond Microchannels under High Heat Flux Density

Heat dissipation significantly limits semiconductor component performance improvement. Thermal management devices are pivotal for electronic chip heat dissipation, with the enhanced thermal conductivity of materials being crucial for their effectiveness. This study focuses on single-crystal diamond, renowned for its exceptional natural thermal conductivity, investigating diamond microchannels using finite element simulations. Initially, a validated mathematical model for microchannel flow heat transfer was established. Subsequently, the heat dissipation performance of typical microchannel materials was analyzed, highlighting the diamond’s impact. This study also explores diamond microchannel topologies under high-power conditions, revealing unmatched advantages in ultra-high heat flux density dissipation. At 800 W/cm2 and inlet flow rates of 0.4–1 m/s, diamond microchannels exhibit lower maximum temperatures compared to pure copper microchannels by 7.0, 7.2, 7.4, and 7.5 °C, respectively. Rectangular cross-section microchannels demonstrate superior heat dissipation, considering diamond processing costs. The exploration of angular structures with varying parameters shows significant temperature reductions with increasing complexity, such as a 2.4 °C drop at i = 4. The analysis of shape parameter ki indicates optimal heat dissipation performance at ki = 1.1. This research offers crucial insights for developing and optimizing diamond microchannel devices under ultra-high-heat-flux-density conditions, guiding future advancements in thermal management technology.

One Stone Two Birds: Anomalously Enhancing the Cross-Plane and In-Plane Heat Transfer in 2D/3D Heterostructures by Defects Engineering.

This study addresses a crucial challenge in two-dimensional (2D) material-based electronic devices-inefficient heat dissipation across the van der Waals (vdW) interface connecting the 2D material to its three-dimensional (3D) substrate. The objective is to enhance the interfacial thermal conductance (ITC) of 2D/3D heterostructures without compromising the intrinsic thermal conductivities (κ) of 2D materials. Using 2D-MoS2/3D-GaN as an example, a novel strategy to enhance both the ITC across 2D/3D interface and κ of 2D material is proposed by introducing a controlled concentration (ρ) of vacancy defects to substrate's bottom surface. Molecular dynamics simulations demonstrate a notable 2.1-fold higher ITC of MoS2/GaN at ρ = 4% compared to the no-defective counterpart, along with an impressive 56% enhancement in κ of MoS2 compared to the conventional upper surface modification approaches. Phonon dynamics analysis attributes the ITC enhancement to increased phonon coupling between MoS2 and GaN, resulting from polarization conversion and hybridization of phonons at the defective surface. Spectral energy density analysis affirms that the improved κ of MoS2 directly results from the proposed strategy, effectively reducing phonon scattering at the interface. This work provides an effective approach for enhancing heat transfer in 2D/3D vdW heterostructures, promisingly advancing electronics' heat dissipation.

Soft and Damping Thermal Interface Materials with Honeycomb-Board-Mimetic Filler Network for Electronic Heat Dissipation.

High-power-density electronic devices under vibrations call for soft and damping thermal interface materials (TIMs) for efficient heat dissipation. However, integrating low hardness, high damping, and superior heat transfer capability into one TIM is highly challenging. Herein, soft, damping, and thermally conductive TIMs are designed and prepared by constructing a honeycomb-board-mimetic boron nitride nanosheet (BNNS) network in a dynamic polyimine via one-step horizontal centrifugal casting. The unique filler network makes the TIMs perform a high through-plane thermal conductivity (> 7.69W m-1 K-1) and a uniform heat transfer process. Meanwhile, the hierarchical dynamic bonding of the polyimine endows the TIMs with low compressive strength (2.16MPa at 20% strain) and excellent damping performance (tan δ > ≈0.3 at 10-2-102Hz). The resulting TIMs also exhibit electrical insulation and remarkable recycling ability. Compared with the commercial ones, the TIMs provide better heat dissipation (4.1°C) for a high-power 5G base station and less temperature fluctuation (1.8°C) for an automotive insulated gate bipolar transistor (IGBT) under vibrations. This rational design offers a viable approach to prepare soft and damping TIMs for effective heat dissipation of high-power-density electronic devices under vibrations.

Two-state model of energy dissipation at metal surfaces.

The rates and pathways of chemical reactions at metal surfaces can be strongly influenced by energy dissipation due to the nonadiabatic excitation of metallic conduction electrons. The introduction of frictional forces to account for this dissipation has been quite successful in situations for which the nonadiabatic coupling is weak. However, in cases where nonadiabatic coupling is strong, such as when electron transfer occurs, the friction model is likely to break down. Ryabinkin and Izmaylov have proposed 2-state and 3-state alternatives to the friction model for introducing electronic dissipation in molecular dynamics simulations. Here, we examine their 2-state model using some simple examples of atom-surface scattering. We find that, with the addition of decoherence, the 2-state model can produce quite promising results.

Preparation, Microstructure and Thermal Properties of Aligned Mesophase Pitch-Based Carbon Fiber Interface Materials by an Electrostatic Flocking Method.

The mesophase pitch-based carbon fiber interface material (TIM) with a vertical array was prepared by using mesophase pitch-based short-cut fibers (MPCFs) and 3016 epoxy resin as raw materials and carbon nanotubes (CNTs) as additives through electrostatic flocking and resin pouring molding process. The microstructure and thermal properties of the interface were analyzed by using a scanning electron microscope (SEM), laser thermal conductivity and thermal infrared imaging methods. The results indicate that the plate spacing and fusing voltage have a significant impact on the orientation of the arrays formed by mesophase pitch-based carbon fibers. While the orientation of the carbon fiber array has a minimal impact on the shore hardness of TIM, it does have a direct influence on its thermal conductivity. At a flocking voltage of 20 kV and plate spacing of 12 cm, the interface material exhibited an optimal thermal conductivity of 24.47 W/(m·K), shore hardness of 42 A and carbon fiber filling rate of 6.30 wt%. By incorporating 2% carbon nanotubes (CNTs) into the epoxy matrix, the interface material achieves a thermal conductivity of 28.97 W/(m·K) at a flocking voltage of 30 kV and plate spacing of 10 cm. This represents a 52.1% increase in thermal conductivity compared to the material without TIM. The material achieves temperature uniformity within 10 s at the same heat source temperatures, which indicates a good application prospect in IC packaging and electronic heat dissipation.

Multifunctional phase-change composites for green electromagnetic interference shielding and thermal response prepared under the guidance of an impedance matching strategy.

With the advent of the information age, electromagnetic hazards are becoming more serious. In view of environmental protection, green electromagnetic interference (EMI) shielding materials with little or no secondary reflection have become the ideal choice. In this paper, by freeze-drying, high-temperature carbonization, coating and impregnation backfilling, we prepared carbonized Ni-MOF/reduced graphene oxide/silver nanowire-polyimide@polyethylene glycol composites (Ni@C/r-GO/AgNW-PI@PEG) with gradient conductivity based on impedance matching. The impedance matching layer Ni@C/r-GO-300 reduces the reflection of electromagnetic waves from the surface of the material, the dissipation layer Ni@C/r-GO-600 provides excellent electromagnetic wave dissipation capability, and the reflection layer AgNW-PI ensures that the electromagnetic waves are reflected back into the material. Meanwhile, the EMI shielding performance value of Ni@C/r-GO/AgNW-PI@PEG reaches 62.3 dB with an ultra-low reflectivity (R) of 0.04. In CST simulations, the intrinsic mechanism of electromagnetic energy loss within the material is revealed by energy loss density cloud maps. In addition, heat from high-temperature objects is transferred through the highly thermally conductive AgNW-PI membrane to the long-channel Ni@C/r-GO backbone. Therefore, the composites prepared on the basis of impedance matching will accelerate the use of EMI shielding materials for the thermal management of portable electronic devices and battery heat dissipation packaging.

Study on the microstructure and properties of HfCxNy-Cu composites prepared by spark pulse sintering

In this work, novel HfCxNy-Cu composites with varying HfCxNy contents were fabricated via subsequent spark pulse sintering (SPS). The influence of HfCxNy addition on the mechanical properties, wear properties, and electrical conductivity of the HfCxNy-Cu composites was systematically studied. The 5HCu composites exhibit a hardness of 136.8 HV and an electrical conductivity of 50.2 % ICAS. Whereas, the hardness of the 10HCu composites increased to 148.3 HV. Moreover, 5HCu composites rather than 10HCu exhibited better lubrication performance and wear resistance, the average friction coefficient and wear rate were measured to be 0.41 and 0.026 mg/min, respectively. The potential applications of HfCxNy-Cu composites include high-temperature structures and electronic device heat dissipation.

The Effect of Channel Arrangement on the Performance of Dual Piezoelectric Fans

Piezoelectric fan is widely used in electronic products heat dissipation. Channel arrangements affect the cooling performance. Flow and temperature distributions in five schemes: (1) large space, (2–4) top opening channels with different restricted extents, and (5) channel with four enclosed sides) were investigated. Time average velocity distributions reveal the flow characteristics of two high-speed cooling fluids forming from blade roots. The cooling fluids gradually converge in the middle of blade tips and disperse downstream. Scheme (5) has the highest velocity of 8 m/s due to the strongest sucking and driving effects of negative and positive pressure zones. Air ventilation rates of schemes (1–5) cover the range from 1.21 × 10−3 to 2.07 × 10−3 m3/s. For schemes (1–4), the maximum ventilation always comes from top boundary, with the percentage above 80%. Among all schemes, the maximum temperature of scheme (1) is lowest, which is 467.401 K. However, the highest space-time average heat transfer coefficient is obtained in scheme (1), up to 54.02 W/(m2·K). The value decreases sequentially in schemes (5, 2, 4 and 3). Mismatch between main flow velocity and heat transfer coefficient highlights the three-dimensional sucking effect of piezoelectric fan.

Performance analysis of a novel flat lay-type synthetic jet pump with Y-shaped jet chamber.

Recently, synthetic jet pumps have been expected to be used in electronic heat dissipation devices due to the vortex suction phenomenon for transporting fluids. Aiming to improve the delivery ability of the jet pump to output fluid continuously, a novel flat lay-type synthetic jet pump (FLTSJP) with a Y-shaped jet chamber is proposed in this paper. Based on the synthetic jet effect, the pump chamber continuously outputs fluid in one cycle. The output performance of FLTSJP is theoretically analyzed to be affected by the outlet cone angle. The one-cycle flow mechanism of the fluid in the Y-shaped jet chamber is simulated. FLTSJP is manufactured, and a test system is built. Experiments show that the Y-shaped jet chamber effectively improves the output performance. The optimum flow rate and outlet pressure were both reached at 160V and 40Hz, which were 20.63 ml/min and 333.43Pa, respectively. This FLTSJP effectively improves the output performance of synthetic jet pumps and provides a new research concept of water-cooled devices for electronic heat dissipation.

Design and Thermal Performance of Ultra-Thin Flat Plate Heat Pipes with Composite Wick for Electronic Cooling

The rapidly increasing heat load and high-density packaging of electronic devices demand heat dissipation devices that possess miniaturization and high thermal performance. A series of ultra-thin flat plate heat pipes (UPHPs) with thicknesses of 1.2 mm was prepared to satisfy this demand. Strengthening rib optimization and capillary optimization were processed to restrict the entrainment limit and capillary limit of the UPHPs. Furthermore, surface modification technology with composite nanostructure coated was introduced to improve the surface wettability of capillary wick. Finally, the heat transfer capacity of the UPHPs was experimentally tested. The influence of capillary structure and liquid filling ratio on the heat transfer characteristic was investigated in detail. This work provides insight into the design and application of UPHPs for the new generation of electronic devices.

Enhancement of flow boiling in the microchannel with a bionic gradient wetting surface

Flow boiling in microchannels is promising to enhance electronic heat dissipation (urgently required). However, vigorous boiling in a narrow space can trigger serious flow reversal and heat transfer deterioration, restraining further performance enhancement. In this work, a bionic gradient wetting surface was developed to overcome the challenge. The upstream hydrophobicity and surface variation induced flowing bubble expansion and frequent interface fluctuation, benefiting the backflow suppression and churn flow appearance. While the downstream hydrophilicity improved liquid supply and vapor venting, preventing partial dry-out and pressure drop increase. The flow regimes on the bionic surface were demonstrated by the quantitative analysis of two-phase flow, exhibiting the shortest backflow duration time and the second-high frequency of churn flow appearance. Moreover, the gradient wettability showed negligible oscillations in average wall temperature and pressure drop and achieved the maximum enhancement rate of 50.1% and 63.2% for the heat transfer coefficient and performance evaluation criterion, respectively. The surface combination scheme incorporated the merits of different wetting surfaces and significantly enhanced the integrated performance, showing immense potential in high-efficient thermal management applications.

High-enthalpy aramid nanofiber aerogel-based composite phase change materials with enhanced thermal conductivity

Solid-liquid phase change materials (PCMs) have the advantages of easy adjustment of the phase transition temperature, high heat enthalpy, and small volume change, which endow them with great application potential in thermal management. However, problems such as low thermal conductivity, inherent stiffness, and liquid flow of solid-liquid PCMs limit their functional applications. Herein, high-enthalpy composite PCMs supported by polymer aerogel are reported, which can prevent long-range crystallization and provide shape stability before and after phase transition. In this work, aramid nanofiber (ANF) aerogel was used as the carrier, polyethylene glycol (PEG) was used as the PCMs, and the encapsulation of PEG in aerogel was realized by vacuum impregnation. The resulting polymer aerogel-based composite PCMs exhibit a large phase change enthalpy (175.1 J/g) at a PEG content of 95.4 wt%, accompanied by a good thermal conductivity of 1.03 W/m⋅k. Benefiting from the excellent phase change thermal management performance and temperature adjustability, the composite has promising applications in high-end electronic equipment, heat dissipation and pipeline insulation.

A bio‐based multifunctional composite material: Boron nitride and wood fiber to construct thermally conductive cross network

AbstractThe high demand for thermally conductive materials in the housing and packaging industry of electronic device highlights the necessity for the development of novel thermal conductivity materials. In this study, waste poplar wood was delignified and combined with boron nitride (hBN) to establish a blend system with a cross thermally conductive network. Using the vacuum‐assisted resin transfer molding process, a biobased composite material was prepared with high thermal conductivity (1.41 W m−1 K−1), mechanical strength (flexural strength of 100.7 MPa and tensile strength of 40.0 MPa), flame retardancy, and water resistance. Compared with raw wood, the incorporation of hBN increased the thermal conductivity of the prepared material by 1324.2%. The high thermal conductivity performance surpassed that of most polymers and elastomers commonly used in electronic component heat dissipation materials, indicating the enormous potential of the prepared composite material in the field of heat dissipation materials.

MWCNTs-GNPs Reinforced TPU Composites with Thermal and Electrical Conductivity: Low-Temperature Controlled DIW Forming.

As an effective technique for fabricating conductive and thermally conductive polymer composites, a multi-filler system incorporates different types and sizes of multiple fillers to form interconnected networks with improved electrical, thermal, and processing properties. In this study, DIW forming of bifunctional composites was achieved by controlling the temperature of the printing platform. The study was based on enhancing the thermal and electrical transport properties of hybrid ternary polymer nanocomposites with multi-walled carbon nanotubes (MWCNTs) and graphene nanoplates (GNPs). With thermoplastic polyurethane (TPU) used as the matrix, the addition of MWCNTs, GNPs and both mixtures further improved the thermal conductivity of the elastomers. By adjusting the weight fraction of the functional fillers (MWCNTs and GNPs), the thermal and electrical properties were gradually explored. Here, the thermal conductivity of the polymer composites increased nearly sevenfold (from 0.36 W·m-1·k-1 to 2.87 W·m-1·k-1) and the electrical conductivity increased up to 5.49 × 10-2 S·m-1. It is expected to be used in the field of electronic packaging and environmental thermal dissipation, especially for modern electronic industrial equipment.

Enhanced thermal properties of epoxy composites by constructing thermal conduction networks with low content of three-dimensional graphene

Micro/nano electronic devices heat dissipation depends heavily on the thermal interface materials (TIMs). Despite notable progress, it is hard to efficaciously enhance the thermal properties of the hybrid TIMs with high-load additives due to an absence of effective heat transfer routes. Herein, the low content of three-dimensional (3D) graphene with interconnected networks is adopted as the additive to improve the thermal properties of epoxy composite TIMs. The thermal diffusivity and thermal conductivity of the as-prepared hybrids were dramatically improved by constructing thermal conduction networks after adding 3D graphene as fillers. The 3D graphene/epoxy hybrid’s optimal thermal characteristics were observed at 1.5 wt% of 3D graphene content, corresponding to a maximum enhancement of 683%. Besides, heat transfer experiments were further performed to determine the superb heat dissipation potential of the 3D graphene/epoxy hybrids. Moreover, the 3D graphene/epoxy composite TIM was also applied to high-power LED to improve heat dissipation. It effectively reduced the maximum temperature from 79.8 °C to 74.3 °C. These results are beneficial for the better cooling performance of electronic devices and provide useful guidelines for advancing the next-generation TIMs.

Exploration of the dynamics of non-Newtonian Casson fluid subject to viscous dissipation and Joule heating between parallel walls due to buoyancy forces and pressure

Vertical channels between two flat plates have a wide range of engineering applications, such as heat exchangers, chemical processing equipment, electronic component heat dissipation, and so on. Therefore, this analysis examines the significance of variable properties on the dynamics of Casson fluid in a vertical channel due to mixed convection when thermal radiation and Joule heating are significant. The combined effects of temperature-dependent plastic dynamics viscosity and temperature-dependent thermal conductivity are analyzed. Moreover, the evaluation of heat transfer is further supported by viscous dissipation. The nondimensional governing equations are elucidated analytically by employing the perturbation technique and numerically by Runge–Kutta method with the shooting technique. The effects of numerous dimensionless parameters on fluid flow are featured through graphs. In addition, the heat transfer rate and the skin friction coefficient are computed and scrutinized. It is reported that velocity depicts enhancing behavior for higher values of the Casson fluid and slip parameters. It has also been observed that the fluid temperature decreases with an increase in the thermal conductivity parameter.

Numerical simulation of UAVs electronic equipment heat dissipation under a low-altitude environment

Unmanned aerial vehicles are widely applied in military and daily life with the usage of leeding air to dissipate heat from electronic equipment through cold-plate cooling, which takes advantage of its simple structure and low weight. However, this cooling method is greatly affected by the flight height of the vehicle, especially in hot regions and at low altitude. To evaluate the cooling effect of the cold plate heat sink under different environmental conditions, a numerical model was established and the following parametric studies were carried out. Firstly, a numerical model of bleeding air cold-plate cooling was established via the COMSOL platform and the mesh was automatically generated for simulation based on the physical field control. The solar radiation intensity in the selected cities was also taken into consideration. Subsequent simulations based on partial adjustment of the model were conducted to evaluate the heat dissipation performance of Unmanned aerial vehicles under low attitude conditions. The results indicated that the heat-generating components should be arranged closer to the cold plate, the working modules should be encapsulated with materials with larger thermal conductivity and the advanced electric modules with less heat generation benefit for Unmanned aerial vehicle thermal management.

Flexible phase change composite films with improved thermal conductivity and superb thermal reliability for electronic chip thermal management

High-performance flexible composites with excellent thermal management ability are essential to dissipate the heat generated in electronic systems. Herein, micro-encapsulated phase change material (MPCM) with n-Docosane core and MF resin shell is prepared. The obtained MPCM exhibits large phase change enthalpy (192.9 J/g). Subsequently, flexible composites are prepared by incorporating the MPCM, multi-walled carbon nanotubes (MWCNT) and hexagonal boron nitride (h-BN) in styrene-ethylene-propylene-styrene (SEPS) polymer matrix. At 30 wt% MPCM, the phase change enthalpy of 60.6 J/g is achieved. 3 wt%MWCNT/10 wt%h-BN/30 wt%MPCM composites show improved thermal conductivity of 0.44 W m−1 K−1, which is 95.5 % higher than pure SEPS. The composites are applied in chip for thermal energy dissipation, the temperature of chip’s lower surface is only 62.6 °C, which is 22.84 % lower than pure SEPS. Overall, the MWCNT/h-BN/MPCM composites with superior thermal properties and mechanical characteristics are promising in the field of electronic equipment thermal dissipation.

Ultrafast electronic heat dissipation through surface-to-bulk Coulomb coupling in quantum materials

The timescale of electronic cooling is an important parameter controlling the performance of devices based on quantum materials for optoelectronic, thermoelectric and thermal management applications. In most conventional materials, cooling proceeds via the emission of phonons, a relatively slow process that can bottleneck the carrier relaxation dynamics, thus degrading the device performance. Here we present the theory of near-field radiative heat transfer, that occurs when a two-dimensional electron system is coupled via the non-retarded Coulomb interaction to a three-dimensional bulk that can behave as a very efficient electronic heat sink. We apply our theory to study the cooling dynamics of surface states of three dimensional topological insulators, and of graphene in proximity to small-gap bulk materials. The ``Coulomb cooling'' we introduce is alternative to the conventional phonon-mediated cooling, can be very efficient and dominate the cooling dynamics under certain circumstances. We show that this cooling mechanism can lead to a sub-picosecond time scale, significantly faster than the cooling dynamics normally observed in Dirac materials.