Thermal Management Of Electronics Research Articles

Investigation of nanocomposite PNIPAm‐g‐graphene with pre‐lower critical solution temperature rapid thermal response function for chip adaptive cooling: A molecular dynamics and computational fluid dynamics simulations

AbstractTemperature‐sensitive hydrogels have been widely used for rapid adaptive cooling in electronic device thermal management with promising applications. However, existing temperature‐sensitive hydrogels can only regulate the flow in the chip cooling system after the ambient temperature reaches their lower critical solution temperature (LCST). Before reaching LCST, effective rapid heat dissipation for electronic chips is not achievable. This study aims to develop a temperature‐sensitive hydrogel that can provide assisted adaptive cooling for electronic chips before reaching its LCST. This requires the hydrogel to have a thermal conductivity far surpassing existing hydrogel materials. Using the temperature‐sensitive hydrogel PNIPAm and graphene molecules as base materials, this research utilized molecular dynamics simulations to graft graphene molecules onto PNIPAm molecules in different ways, resulting in the temperature‐sensitive hydrogel material PNIPAm‐g‐graphene. Non‐equilibrium molecular dynamics (NEMD) was employed to calculate the thermal conductivity of this material under different temperature conditions. The results indicate that the thermal conductivity of PNIPAm‐g‐graphene can reach up to 1.95474 W/m K (graphene grafted at CH3 functional group, temperature at 280 K). Compared to the thermal conductivity of PNIPAm under the same conditions (0.45 W/m K), the increase in thermal conductivity is significant, demonstrating excellent thermal conductivity compared to PNIPAm. Subsequently, this study analyzed the underlying mechanisms of different thermal conductivities in materials obtained by grafting graphene molecules at different points using the method of overlap in Phonon Density of States Curves (PDOS) from the perspective of interfacial thermal conduction. Finally, through computational fluid dynamics (CFD) simulations, this study investigates the chip's adaptive cooling performance with PNIPAm‐g‐graphene material. The results show that, compared to traditional temperature‐sensitive hydrogels, PNIPAm‐g‐graphene can achieve efficient adaptive cooling of chip hotspots before the cooling fluid temperature reaches its LCST value. This finding is significant for the field of chip cooling. The study proposes a new method for rapid, adaptive cooling of chip hotspots and explores its feasibility from the perspectives of molecular dynamics and CFD simulation. It holds importance in the thermal management of electronic devices and the rapid adaptive cooling of electronic chips.

Boiling-induced thermal degradation of copper inverse opals and its mitigation

Thermal management in power electronics relies on active and passive cooling devices that use porous copper structures. However, these critical components, such as sintered copper and copper inverse opals (CuIOs), degrade rapidly when exposed to working fluids like water and oxygen. This study investigates the thermal reliability of CuIO structures subjected to harsh boiling environments using pool-boiling tests. 10–30 μm-thick porous CuIO structures with a constant 5 μm pore diameter and neck openings of 0.6–1.4 μm are fabricated using electrodeposition on silicon through a polystyrene-sintered template. Pool-boiling heat transfer is mainly performed under a constant heat flux of ∼115 W cm−2 at a saturation temperature of 100 °C. As a result, severe degradation of CuIO structures occurs over 72 h. Therefore, A 50 nm-thick direct gold immersion coating is considered as a mitigation strategy. The gold-coated CuIO surface exhibits structural stability, maintaining a stable temperature and heat transfer coefficient compared to pristine CuIOs. Moreover, a reliability test in HFE-7100 is also conducted for applications with lower heat flux and operating temperature requirements. Extensive reliability tests on CuIOs with and without an Au protective coating reveal no noticeable degradation over 11 days at 50% and 67% of critical heat flux. This study provides essential reliability data for failure modeling and offers valuable insights into mitigation strategies and predictive tools for improving the reliability and life expectancy of CuIOs.

Honeycomb-like porous copper with pleated surface for supporting phase change material with enhanced thermal conductivity and solar thermal storage performance

Paraffin wax (PW) is concerned in the field of thermal storage because of its high thermal storage density, but it generally has problems such as low thermal conductivity, poor shape stability, and low solar absorption, which limit its application in solar thermal storage and thermal management. In this study, a honeycomb-like 3D porous Cu skeleton with a pleated surface was prepared by the salt template method, and the phase change composites (PCCs) were prepared using this 3D thermal conductive skeleton to support PW. The honeycomb-like porous structure with pleated surface has positive effects on the shape stability and solar-thermal conversion of PW. The thermal conductivity, leakage resistance, and solar-thermal conversion efficiency of the PCCs were significantly improved. Among them, the thermal conductivity of PW@PSHCPC2 reached 3.3 Wm−1 K−1, which was 16.5 times higher than that of PW, and the solar-thermal conversion efficiency reached 89.2 %, and a stable current of 61.8 mA was generated in the solar thermal power generation experiment. These results show that these PCCs have great potential for applications in several fields such as solar thermal storage, waste heat recovery, solar power generation, and electronic thermal management.

High-Flexible Phase Change Composites with Enhanced Thermal Conductivity for Electronic Thermal Management

High-Flexible Phase Change Composites with Enhanced Thermal Conductivity for Electronic Thermal Management

Advancing thermal management in electronics: a review of innovative heat sink designs and optimization techniques.

The ongoing trend towards miniaturizing electronic devices and increasing their power densities has created substantial challenges in managing the heat they produce. Traditional heat sink designs often fall short of meeting modern electronics' rigorous thermal management needs. As a result, researchers and engineers are turning to innovative heat sink designs and optimization methods to improve thermal performance. This review article offers an overview of the latest advancements in designing and optimising advanced heat sinks for electronic cooling. It explores various techniques to enhance heat transfer, including advanced surface geometries and microchannels. Additionally, the review covers computational fluid dynamics (CFD) modelling and experimental validation methods used to refine heat sink designs. Further insight into fouling and its prevention has been discussed. The insights provided in this article are intended to serve as a valuable resource for thermal engineers, and researchers focused on managing the heat in high-power electronic systems.

Optimizing heat transfer efficiency in electronic component cooling through fruit waste-derived phase change material

This study focuses on the development and evaluation of heat sinks designed for the thermal management of electronic components operating under low-temperature conditions. Two distinct heat sink configurations were investigated: one featuring a hollow structure without fins and the other incorporating equidistant triangular fins. These heat sinks were subjected to varying heat input levels of 35 W, 40 W, and 45 W. To enhance thermal performance, various thermal enhancement techniques were employed, including the integration of phase change materials, graphene nanoparticles, and nanoparticles coated with dragon fruit extract. The results of this investigation revealed significant improvements in the heating-cooling cycle. It was observed that the heating effectiveness of the heat sink increased by 23 %, 11 %, and 6.8 %, respectively, when employing dragon fruit extract-coated nanoparticles in conjunction with phase change material. After increasing the heat input to 40 W, the heating and cooling cycle of the heat sink containing PCM and without fins was reduced by 18 %. Coating the nanoparticles with dragon fruit extract reduced the heating and cooling cycle time by 37 % compared to the heat sink without fins and PCM included. Further optimisation studies substantiated these findings, affirming the efficacy of the proposed approach. In summary, incorporating dragon fruit extract-coated graphene nanoparticles demonstrated a noteworthy enhancement in the heating-cooling cycle, proportionate to the applied heat input, within the context of finned heat sinks employed for electronic component thermal management.

Thermoconductive Graphene Fluoride Cross-Linked Aramid Nanofiber Composite Films with Enhanced Mechanical Flexibility and Flammable Retardancy for Thermal Management in Wearable Electronics

Thermoconductive Graphene Fluoride Cross-Linked Aramid Nanofiber Composite Films with Enhanced Mechanical Flexibility and Flammable Retardancy for Thermal Management in Wearable Electronics

Thermal analysis of thermoelectric active cooling including external thermal resistances

Thermoelectric active cooling uses nontraditional thermoelectric materials with high thermal conductivity, high thermoelectric power factor, and relatively low figure of merit (ZT) to transfer large heat flows from a hot object to a cold heat sink. However, prior studies have not considered the influence of external thermal resistances associated with the heat sinks or contacts, making it difficult to design active cooling thermal systems or compare the use of low-ZT and high-ZT materials. Here, we perform a non-dimensionalized analysis of thermoelectric active cooling under forced heat flow boundary conditions, including arbitrary external thermal resistances. We identify the optimal electrical currents to minimize the heat source temperature and find the crossover heat flows at which low-ZT active cooling leads to lower source temperatures than high-ZT and even ZT→+∞ thermoelectric refrigeration. These optimal parameters are insensitive to the thermal resistance between the heat source and thermoelectric materials, but depend strongly on the heat sink thermal resistance. Finally, we map the boundaries where active cooling yields lower source temperatures than thermoelectric refrigeration. For currently considered active cooling materials, active cooling with ZT < 0.1 is advantageous compared to ZT→+∞ refrigeration for dimensionless heat sink thermal conductances larger than 15 and dimensionless source powers between 1 and 100. Thus, our results motivate further investigation of system-level thermoelectric active cooling for applications in electronics thermal management.

Optimizing spray cooling systems: A comprehensive study on influential parameters and their effects on heat transfer under varied heat flux conditions

This research explores the heat transfer characteristics of spray cooling under heat flux conditions ranging from 10 to 200 W/cm2 through numerical simulations. We examined the effects of spray height, spray pressure, surface tension, contact angle, system pressure, and gravity on spray cooling efficiency, to optimize spray cooling systems. Furthermore, we validated the simulation results through experiments and found a good agreement between the two. Key findings include a consistent increase in the heat transfer coefficient with rising heat flux. Under specific heat flux density, increased spray pressure leads to a gradual decline in wall temperature and improved wall temperature uniformity, but the reduction rate slows as pressure continues to increase. Lower spray heights can improve cooling efficiency, but may reduce temperature uniformity. Additionally, heat transfer performance in the two-phase zone improves with higher surfactant (Tween 20) concentration, with a 75ppm solution reducing cooling wall temperatures by 7.4 K compared to pure water. Spray processes at 10 kPa and 50 kPa result in lower wall temperatures before entering the two-phase zone compared to atmospheric pressure, improving cooling efficiency and temperature uniformity. Finally, differences in spray cooling effects under varying gravities manifest primarily during the two-phase heat exchange stage, with the temperature difference widening with increasing heat flux density. These insights offer valuable guidance for spray cooling applications in electronic thermal management.

Automotive Silicon Carbide Power Module Cooling With a Novel Modular Manifold and Embedded Heat Sink

Abstract The next generation of integrated power electronics packages will implement wide-bandgap devices with ultrahigh device heat fluxes. Although jet impingement has received attention for power electronics thermal management, it is not used in commercial electric vehicles (EVs) because of the associated pressure drop and reliability concerns. In this paper, we present a modular thermal management system designed for automotive power electronics. The system achieves superior thermal performance to benchmarked EVs while adhering to reliability standards and with low pumping power. The system utilizes a low-cost and lightweight plastic manifold to generate jets over an optimized heat sink, which is embedded in the direct-bonded-copper (DBC) substrate. The embedded heat sink concept leverages additive manufacturing to add elliptical pin fins to the DBC substrate. The heat sink geometry is optimized for submerged jet impingement using a unit-cell model and an exhaustive search algorithm. The model predictions are validated using unit-cell experiments. A full-scale power module model is then used to compare the DBC-embedded heat sink against direct DBC cooling and baseplate-integrated heat sinks for single-sided (SS) and double-sided (DS) cooling concepts. Using the SS and DS DBC-embedded cooling concepts, the models predict a thermal resistance that represents a reduction of 75% and 85% compared to the 2015 BMW i3, respectively, for the same water-ethylene glycol inverter flowrate. We have shown that an inverter with a 100-kilo-Watt-per-liter power density is achievable with the proposed design.

Experimental study about the impact of open cell aluminium foam (OCAF) insertion in salt-based phase change material (PCM) for electronics thermal management

Thermal management of electronic components is a critical task in a harsh thermal environment. Spacecraft and satellites' electronics are susceptible to highly intermittent heating and cooling thermal conditions, which imposes challenges for robust thermal management system design. Phase change materials (PCM) are a promising solution for overcoming these challenges and enhancing thermal control performance. The lower PCM thermal conductivity and PCM supercooling limit PCM utilisation in electronic thermal control systems. The present study aims to provide solutions for enhancing the heat transfer within the PCM, boosting the PCM thermal conductivity, and diminishing the PCM supercooling. The open-cell aluminium foam (OCAF) was adopted for boosting the heat transfer within the PCM. A thermal management module (TMM) integrated with a salt-based PCM/OCAF composite was developed for electronics thermal management. The TMM was tested under intermittent thermal conditions of heating and cooling. An electric heater and Peltier cooler were affixed to the TMM for the heating and cooling process, respectively. Three levels of heat fluxes were adopted: 700, 1000, and 1400 W/m2. The heating process lasted one hour; then, the TMM was cooled by the Peltier element to the initial temperature. The research novelty covers the gap in understanding how OCAF affects salt-based PCM supercooling when subjected to varying heating loads during intermittent cycles. The outcomes reported a remarkable improvement in thermal management efficiency. The PCM-based TMM reduced the highest temperature by about 20.4 %, 21.6 %, and 23 % at the three heating levels. The OCAF diminished the PCM supercooling curiously. The reduction in PCM supercooling was 43.5 % compared to the 100 % PCM case obtained at the heat flux of 1400 W/m2.

Interface regulation of diamond-doped GaInSn composites

Diamond-doped GaInSn thermal interface materials have broad application prospects in the field of electronic thermal management. However, the poor wettability of diamond and liquid metal makes the fabrication of composites through simple mechanical agitation difficult. In this study, the wettability between GaInSn and diamond was improved by reducing the surface tension of liquid metal and improving the anisotropy of the diamond surface. The diamond/liquid metal (Dia/LM) interface structure was regulated by controlling the gallium oxide content. Ga2O3 was enriched in the GaInSn and diamond contact surface, which can reduce the surface tension of the liquid metal, improve the wettability of GaInSn to diamond, produce a mechanical locking force with the diamond surface, strengthen the bonding between the liquid metal and the diamond, and reduce the thermal resistance of the liquid metal/diamond interface. The Dia/LM interface structure was controlled by using crushed diamond. Result shows that the wettability of the surface (111) of the diamond was the best. The (100) and (110) planes with poor wettability were cut by the crushed diamond cleavage step, and the area of the crystal plane with poor wettability was reduced, thus improving the wettability of the liquid metal. The improvement of the crushed diamonds' wettability was verified by molecular dynamics calculation. The composite preparation technology of diamond and the GaInSn liquid metal was optimized, and the high-performance Dia/LM thermal interface material was prepared by ultrasonic-assisted and micro-oxidation methods.

An LBM study of multichannel flow boiling for electronic thermal management coupling flow instability mitigation

The rising heat dissipation requirement on electronic devices urges a more efficient and energy-saving cooling strategy to keep the equipment operating within a safe temperature range. Multichannel flow boiling provides a straightforward solution to this challenge due to enormous latent energy of vapor preventing heat accumulation. However, pressure drop minimization and flow instability mitigation should also be considered for optimizing multichannel design. Hence, a Lattice Boltzmann Method (LBM) study on multichannel flow boiling process is conducted to provide design-based suggestions. The effects of surface wettability, channel number, input heat flux, and inlet velocity on the two-phase flow characteristics, heat transfer coefficient enhancement, dimensionless pressure drop, and flow instability are compared to examine the overall performance. Non-dimensional pressure drop is proposed for comparison through dividing the pressure drop under two-phase flow stage by the pressure drop under single-phase flow stage. Results show that hydrophilic coating prevents the film boiling transition at high input heat flux and reduces the maximum temperature for safer electronic operation. Designing a dense channel array can enhance the overall HTC but also significantly increase flow instability on the inlet, leading to shorter pumping operation life. A hybrid design of multichannel with downstream microgap region is proposed, and results indicate great mitigation ability with the increase of gap length and inlet velocity. These findings offer an invaluable blueprint for multichannel heat sink design and reveal the mechanisms of flow boiling enhancement.

Ternary Metals in Phase Change Polymers for Efficient Thermal Management of Electronics

AbstractPhase change materials (PCMs) are paramount for the thermal management of electronics. However, the present PCMs encounter a dilemma in balancing the thermal conductivity and effective latent heat, compromising the heat dissipation function of PCMs for electronics. This work successfully integrates ternary metals and polymer science to design novel PCMs composed of a ternary metal (TM, Ga0.20In0.46Sn0.34) with precise composition and polyethylene glycol (PEG) by physical blending. Due to the introduction of PEG with high melting enthalpy, the ternary metal in PEG (TM@PEG) simultaneously has high thermal conductivity (7.086 W m−1 K−1), desirable effective latent heat (143.6 J cm−3), suitable phase change range, and durability. During thermal management, the thermal conductivity and effective latent heat of TM@PEG contribute to suppressing the working temperature and delaying the temperature rise rate of electronics, respectively. Hence, the TM@PEG effectively behaves as the thermally conductive grease for LEDs and CPU to control the working temperature of electronics in a reasonable range. This work offers a new perspective for TM applied in thermal management.

Heat transfer and pressure drops during high heat flux flow boiling of low-GWP refrigerants in 200 μm-wide multi-microchannels

Thermal management of electronics is continuously challenged by increasing heat fluxes to be dissipated at minimum power consumption. This study investigated the pressure drops and the heat transfer coefficient of two low-GWP refrigerants, R1234yf and R1234ze(E), during flow boiling at high heat fluxes. The test geometry comprised 25 parallel microchannels, 200 μm wide, 1200 μm deep and 1 cm long, nominally. Inlet orifices were used to stabilize the flow. A parametric analysis involving the mass flux and heat flux was conducted for nominal saturation temperatures of 30.5C∘ and 40.5C∘, resulting in a maximum confinement number NConf of 2.16 for R1234yf and 2.52 for R1234ze(E). As the applied heat flux was increased from low to near-critical values, the two-phase heat transfer transitioned from a heat-flux-dominated mode to a convection-dominated one. The flow finally approached dryout, which led to the critical heat flux upon further heating. The experimental results were analysed through a regression with relevant non-dimensional groups, in particular the confinement number, NConf, the equivalent wall Biot number, Bi, the boiling number, Bo, the convection number, Co, and the Weber number, We. It was shown that Bo and Bi had a major influence in the heat-flux-dominated region, while Co and NConf determined the performance in the convective region, mainly due to the establishment of an intermittent annular flow. The total channel pressure drops were evaluated through the experimental measurement of the pressure drops in the inlet-outlet manifold, and the orifices. Due to the short channel length and the high heat fluxes, the pressure drops were dominated by the momentum change contribution, which accounted for at least 60% of the total pressure drops in the lowest case. The flow-wise heat transfer coefficients and the channel pressure drops were compared with the predictions of existing correlations, showing generally a fair agreement.

Electrically gated molecular thermal switch.

Controlling heat flow is a key challenge for applications ranging from thermal management in electronics to energy systems, industrial processing, and thermal therapy. However, progress has generally been limited by slow response times and low tunability in thermal conductance. In this work, we demonstrate an electronically gated solid-state thermal switch using self-assembled molecular junctions to achieve excellent performance at room temperature. In this three-terminal device, heat flow is continuously and reversibly modulated by an electric field through carefully controlled chemical bonding and charge distributions within the molecular interface. The devices have ultrahigh switching speeds above 1 megahertz, have on/off ratios in thermal conductance greater than 1300%, and can be switched more than 1 million times. We anticipate that these advances will generate opportunities in molecular engineering for thermal management systems and thermal circuit design.

Analyzing long-term reliability and potential of organic eutectic Phase Change Material as thermal batteries

The current century is experiencing a notable and expeditious transition toward environmentally sustainable and renewable energy sources to mitigate the effects of climate change. Solar energy is a widely utilized renewable energy source due to its abundance and cleanliness despite its disparate distribution. Integrating Latent Heat Energy Storage (LHES) components into solar energy storage systems can potentially mitigate anomalies in solar radiation. Phase Change Materials (PCMs) are widely regarded as the most commonly utilized substance for Thermal Energy Storage (TES). The thermal management potential of a TES system is substantially hindered due to the limited thermal conductivity of PCMs. The present study attempts to create a binary eutectic PCM for employment in desalination systems, electronic thermal management, and other medium-temperature applications. The melt blending approach was used to synthesize a Binary Eutectic PCM (BEPCM), mixing paraffin and palmitic acid, and the composite's thermophysical properties were evaluated. The stability of BEPCM was confirmed by using the techniques of Thermogravimetric Analysis and Fourier Transform Infrared Spectroscopy. The synthesized BEPCM's thermal conductivity was 0.256 W⸱m−1⸱K−1 (an increase of 11.3 % above palmitic acid). The melting point and latent heat values were found to be 55 °C and 160 J/g. An in-depth morphological and thermophysical analysis following 4000 thermal cycles validated the EPCM's long-term reliability. Thus, a cost-effective, robust, and reliable PW-PA-based BEPCM was manufactured. The composite benefits TES systems operating at moderate temperatures due to their improved thermophysical capabilities.

Membrane-encapsulated, moisture-desorptive passive cooling for high-performance, ultra-low-cost, and long-duration electronics thermal management

Membrane-encapsulated, moisture-desorptive passive cooling for high-performance, ultra-low-cost, and long-duration electronics thermal management

Influence of processing conditions on the titanium/nickel contact metallization on a silicon wafer for thermal management

Thermal management of both digital and power electronics is becoming challenging with device miniaturization and a need for delivering higher power. Diamond thin films and substrates are attractive for thermal management applications in power electronics because of their high thermal conductivity. However, deposition of diamond by microwave plasma enhanced chemical vapor deposition requires high temperatures, which can degrade metallization used in power electronic devices. In this research, Titanium (Ti)- Nickel (Ni) thin films are deposited by direct current magnetron sputtering on p-type Silicon (Si) (100) substrates using a physical mask for creating dot-patterns for measuring properties of the contact metallization. The influence of processing conditions and post-deposition annealing in Argon and hydrogen at 380 °C for 1 h on the properties of the contact metallization are studied by measuring the current - voltage characteristics and Hall effect. The results indicated ohmic contact resistance for both, the as-deposited films and after post annealing treatments. In addition, the results on contact resistance, resistivity, carrier concentration and hall mobility of wafers extracted from Ti/Ni metal contact to p-type Si (100) are presented and discussed.

Parametric analysis of a PCM-based heat sink for electronic device thermal management

Integrating conventional Heat Sinks with Phase Change Materials (HS-PCM) is a novel strategy for the thermal management of electronic devices. Although various studies attempted to investigate the impact of PCM on the operating temperature of electronic devices, the influence of PCM properties on the performance of the HS-PCM system remained unknown. Therefore, in the present study, an accurate three-dimensional HS-PCM system is designed and simulated to evaluate the effect of PCM properties, including thermal conductivity, enthalpy, specific heat capacity, and liquidus temperature, on the operating temperature of this system. In this order, the HS-PCM system is simulated at multiple operating conditions during both the working and cooling phases. Notably, an experimental setup is fabricated to compare the numerical outputs against the experimental data. Additionally, the Support Vector Regression with Hybrid (HSVR) kernels is used to predict the performance of the HS-PCM system. The hyperparameters of this machine learning model are optimized by implementing Grey Wolf Optimizer (GWO). It is found that raising the liquidus temperature of the PCM can have a minor impact on the working duration of the chipset while it dramatically impacts the cooling process of the system. Also, increasing the enthalpy and heat capacity of the PCM has a favorable effect on the working time of the chipset but extends the cooling process. Thermal conductivity is the only parameter which its enhancement has a positive impact on both the working and cooling duration of the chipset. Raising the thermal conductivity of the PCM from 0.05 W/(m·K) to 0.8 W/(m·K) improves the working duration of the chipset from 22 min to 24 min. Based on the outcomes, the most effective factor on the working time of the chipset is the enthalpy, followed by heat capacity, thermal conductivity, and the liquidus point of the PCM. According to the findings, the GWO-HSVR model can accurately forecast the outcomes of the HS-PCM system at the both working and cooling phases. In the testing process of the model, the values of R2 for the working and cooling phases are calculated to be 0.99174 and 0.99775, respectively.