Thermal Management Of Microelectronic Devices Research Articles

Visualization investigation on heat and mass transfer of Al2O3 nanofluid in vapor chamber

As the vapor chamber (VC) moves towards ultra-thinness to meet the thermal management of microelectronic devices, achieving efficient heat transfer within a limited space poses severe challenges. In this study, a visualization VC with a thickness of only 0.9 mm was designed to investigate the heat transfer effect and boiling behavior of nanofluid applied on VC. The influences of Al2O3-deionized water (Al2O3-DW) with different mass concentrations and filling ratios on the heat transfer characteristics and flowing behavior were explored. The results indicated that the addition of nanoparticles improved the temperature uniformity and startup performance of VC. At 0.3 wt%, nanofluid promoted bubbles generation and growth, enhancing the phase-change process. The minimum thermal resistance was 1.46 K/W, representing a 13.6 % reduction compared to that of DW. However, at 0.6 wt% and under high filling ratios or heat load, excessive nanoparticles tended to accumulate on the surface of bubbles by surface tension during the boiling process and were pushed to the gas–liquid interface under the pressure gradient, resulting in deteriorated heat transfer. The results also found that deposition of nanoparticles further enhanced heat transfer. Nonetheless, the nanoparticles were detached from the substrate as the bubbles boiled, and the enhancement effect gradually diminished. The relevant research findings provide guidance for the application of nanofluids in ultra-thin VC.

A computational search for the optimal microelectronic heat sink using ANSYS Icepak

The efficient thermal management of microelectronic devices is crucial for their reliability and performance. Heat sinks, particularly those with inline and staggered fin arrangements, are vital in achieving this goal. This study leverages the advancements in computational fluid dynamics (CFD) software to explore the optimal heat sink design for microelectronic devices. While prior research has extensively investigated heat sink design, this work offers novelty by employing ANSYS Icepak software for simulations. This approach enables a comprehensive thermal performance and pressure drop analysis for two distinct fin cross-sections. The study investigates heat sink assemblies housed within a confined space, simulating a realistic operating environment for microelectronic devices. The heat sink is designed to cool a single heat source (chip) mounted on a substrate board. In this paper, two types of fin sections, circular and conical, are studied for two types of fin configurations, inline (IA) and staggered (SA), which are analysed with 36 fins in each case. Each fin is constructed from aluminium and has specified dimensions. Air serves as the cooling fluid within the cabinet, dissipating heat generated by the chip. When comparing the performance of circular pin and cone fins at the same power and mass flow rate, the results indicated that the maximum temperature for circular pin fins is 0.46% of the maximum temperature for cone fins, and they have a higher pressure drop, especially for staggered arrangements. Moreover, the maximum temperature for staggered arrangements is lower than that for inline configurations by a factor of up to 1.17% and 2.035% for circular fins and cone pin fins, respectively. This article focuses on a deep understanding of the design of microelectronic cooling systems. It aims to continuously improve pressure and thermal efficiency by maintaining the minimum limits of pressure drop within the confined space and obtaining the optimal configuration for efficient heat dissipation.

Thermal Management of Microelectronic Devices Using Nanofluid with Metal foam Heat Sink.

Microelectronic components are used in a variety of applications that range from processing units to smart devices. These components are prone to malfunctions at high temperatures exceeding 373 K in the form of heat dissipation. To resolve this issue, in microelectronic components, a cooling system is required. This issue can be better dealt with by using a combination of metal foam, heat sinks, and nanofluids. This study investigates the effect of using a rectangular-finned heat sink integrated with metal foam between the fins, and different water-based nanofluids as the working fluid for cooling purposes. A 3D numerical model of the metal foam with a BCC-unit cell structure is used. Various parameters are analyzed: temperature, pressure drop, overall heat transfer coefficient, Nusselt number, and flow rate. Fluid flows through the metal foam in a turbulent flow with a Reynold's number ranging from 2100 to 6500. The optimum fin height, thickness, spacing, and base thickness for the heat sink are analyzed, and for the metal foam, the material, porosity, and pore density are investigated. In addition, the volume fraction, nanoparticle material, and flow rate for the nanofluid is obtained. The results showed that the use of metal foam enhanced the thermal performance of the heat sink, and nanofluids provided better thermal management than pure water. For both cases, a higher Nusselt number, overall heat transfer coefficient, and better temperature reduction is achieved. CuO nanofluid and high-porosity low-pore-density metal foam provided the optimum results, namely a base temperature of 314 K, compared to 341 K, with a pressure drop of 130 Pa. A trade-off was achieved between the temperature reduction and pumping power, as higher concentrations of nanofluid provided better thermal management and resulted in a large pressure drop.

Numerical Study on Heat Propagation in Laptop Cooling System

Thermal management of microelectronic devices has become increasingly important to maintain their performance and prolonging the lifespan of the devices. In this study, numerical simulation has been conducted to investigate the heat propagation for high performance microelectronic device of laptop. Two models are constructed and Ansys Fluent is used for the Computational Fluid Dynamics (CFD) simulation, source term is applied at the heat source, heat sink and two different material heat pipes are the main cooling components in the system. The results show that the improved design model is a better design for laptop cooling systems, and the increasing number of air vents, thermal conductivity, and length of heat pipes can effectively cool the high-powered microchip effectively. Transient simulation, considering the wick structure and working fluid in the simulation, is suggested for future work.

Interfacial template-engineered eco-friendly nanocomposites towards rapid thermal conduction

Heat conductive polymer composites are widely applied in the thermal management of microelectronic devices, while most polymers as heat conductive composite substrates are difficult to degrade in natural conditions. To alleviate the increasingly severe environmental problems, herein, we elaborately design novel eco-friendly nanocomposites with high thermal conductivity through a facile interface-enhancement-template (IET) strategy, which was composited of poly (butylene succinate) (PBS) and chitosan-coated hexagonal boron nitride (CS/h-BN). The melt blending h-BN/PBS nanocomposites were only 1.40 W m−1 K−1 at 40 wt% in thermal conductivity, while the CS/h-BN/PBS-* nanocomposites prepared by the IET strategy can reach 2.72 W m−1 K−1 in the same loading. Besides, when pristine PBS was used as thermal interface material between LED chips and Cu heat sink, the run temperature of LED chips can reach 106.0 °C at 120 s. However, the CS/h-BN/PBS-* nanocomposites were only 47.3 °C under the same conditions, and the run temperature of LED chips remained relatively constant during the 8 cycles, exhibiting excellent sustained heat dissipation. This work provides a new strategy for the preparation of eco-friendly nanocomposites with high thermal conductivity.

Paving 3D interconnected Cring-C3N4@rGO skeleton for polymer composites with efficient thermal management performance yet high electrical insulation

Polymer-based thermal interface materials (TIMs) with good electrical insulation property is essential in the thermal management of microelectronic devices. A common approach to increasing the polymer's low intrinsic thermal conductivity is to introduce thermally conductive fillers. In most cases, those fillers are also electrically conductive, which destroys the origin electrical insulation property. In this work, we develop a novel heterogeneous two-dimensional hybrid filler by assembling circular carbon nitride (Cring-C3N4) and graphene oxide (GO), aiming to bring the insulation property via Cring-C3N4. With an ordered 3D interconnected structure, the assembled filler shows enlarged sheet size and compact sheet stacking, which facilitates heat conduction. Additionally, the adopted ice-templated method further arranges the filler with the largest thermal conductivity reaching 4.12 W/mK. Meanwhile, it also shows a lower electrical conductivity of 3.6 × 10−7 S/m, meeting most electrical insulation required occasions. Practical heat dissipation performance tests reveal that both larger temperature change rate and maximum attainable temperature are observed for ice-templated treated composite, indicating the reduced thermal contact resistance (TCR) is responsible for the overall improved heat conduction process. This viewpoint is also supported by the practical application of the material functioning as TIMs from both experimental and simulative aspects.

Thermal interface materials for cooling microelectronic systems: present status and future challenges

Thermal management has become a challenging aspect particularly in the field of microelectronics due to rapid miniaturization and massive scale integration. This has resulted in the generation of enormous amounts of heat that needs to be efficiently transferred from microelectronic devices to ensure longer life cycles. The efficient transfer of heat offers advantages such as achieving higher operating temperatures and prevents component failure. A device engineer has to, therefore, identify methods that would facilitate the efficient transfer of heat from the systems. The existence of an interface between the heat source and the heat sink impedes the efficient transfer of heat. Over the years, researchers have identified techniques that could be employed to reduce the interface impediments. Among these techniques, the application of thermal interface materials (TIMs) at the interface is the most promising and has become an integral part of applications where an efficient transfer of heat across interfaces is desirable. In the present paper, the assessment of contact resistance, properties of interface materials and thermal management of microelectronic devices using TIMs are discussed. The present status of TIMs is critically reviewed and the future challenges are highlighted.

Heat transfer and flow characteristics of novel patterns of chevron minichannel heat sink: An insight into thermal management of microelectronic devices

In this study, novel patterns of chevron minichannel are introduced to mitigate the thermal resistance in microelectronic devices that receive uniform heat flux. The models are classified into four categories, which are Case A (without curvature), Case B (curvature on one side), Case C (curvature on two sides), and Case D (curvature on three sides). The analysis is carried out numerically, and its validation is checked with an experimental study. The comparison confirms the reliability of the obtained results as the deviations are less than 10%. The results show that the use of curvatures can improve the thermal performance of chevron minichannels, so the fundamental mechanisms are discussed. It is found that recirculation zones and jet-like impingement flows are the main flow features in the enhanced models. Also, thermal performance improves as the number of curvatures is increased. Higher heat absorptions are achieved by introducing curvatures on the sides of the chevron minichannel, with augmentations in the range of 1.57–3.27 times with respect to the number and position of curvatures. The model with curvature on three sides (Case D) shows the best performance as it presents the lowest values of the thermal resistance at the same pumping powers.

Constructing reduced graphene oxide/boron nitride frameworks in melamine foam towards synthesizing phase change materials applied in thermal management of microelectronic devices.

Phase change materials (PCMs) exhibit wide application prospects in many fields related to energy utilization and management and attract increasing interest. In this work, through the graphene oxide (GO)-assisted dispersion technology, GO/boron nitride (BN) nanosheets were incorporated into melamine foam and successfully deposited on the surface of the foam framework after hydrothermal reaction. Through the following freeze-drying and carbonization treatment, the composite MF/rGO/BN aerogels were obtained with integrated hybrid rGO/BN frameworks. The composite PCMs were prepared through encapsulating polyethylene glycol (PEG) within the hybrid aerogels. The encapsulation stability and thermal properties of the composite PCMs were systematically investigated. The composite PCM sample containing the highest content of rGO/BN exhibited excellent encapsulation stability, high thermal conductivity (up to 0.79 W m-1 K-1), high phase change enthalpy (160.7 J g-1) with the retention of 90.8% of the pure PEG, and excellent chemical and thermal stability. Further results clearly showed that the composite PCMs had excellent light-to-heat energy transition ability and could be used as a thermal management component to suppress the overheating of devices during the operation process, or to supply energy for thermoelectric devices under emergency conditions to ensure a continuous power supply sustained for a certain time until the safeguard procedures are adopted.

Photo- and electro-responsive phase change materials based on highly anisotropic microcrystalline cellulose/graphene nanoplatelet structure

Phase change materials (PCMs) exhibit great potential applications in many fields, such as energy-saving building, solar energy harvesting, waste heat utilization, constant temperature protection and thermal management of microelectronic devices. In this work, we proposed a facile and novel method to prepare the composite PCMs. Through the combination of pre-refrigeration and freeze-drying techniques using the microcrystalline cellulose (MCC)/graphene nanoplatelets (GNPs) hydrogels, which were firstly prepared through solution compounding, gelling and solvent exchanging successively, the porous MCC/GNP aerogels with highly oriented stacking of MCC/GNP were successfully obtained. The composite PCMs based on the highly anisotropic MCC/GNP aerogel and polyethylene glycol (PEG) exhibited relatively high thermal conductivity (1.03 W/mK) at low GNP content (1.51 wt%), high latent heat (182.6 J/g) which was 99.84% of pure PEG, excellent encapsulation ability and mechanical stability. Further results showed that the composite PCMs exhibited excellent solar energy harvesting/electrical energy transformation, storage and release abilities. In addition, a simple heating device was designed to verify the application of the composite PCMs as the temperature protection element. The measurements showed that the presence of the PCMs prevented the rapidly rising of temperature during the heating process while maintained the temperature at relatively high level in a long time during the cooling process.

Thermal management of microelectronic devices using micro-hole cellular structure and nanofluids

We investigated the thermal performance of micro-hole cellular structure using Al2O3–H2O and CuO–H2O nanofluids with 0.67% and 0.4%, respectively, of volumetric concentration numerically and then validated these numerical results with the experimental results at a heating power of 345 W. We found that the thermal conductivities of Al2O3–H2O and CuO–H2O nanofluids were enhanced by 2% and 1.19%, respectively, as compared to the base fluid (water). Using Al2O3–H2O nanofluids, we achieved the minimum base temperature of 24.5 °C and 26.6 °C numerically and experimentally, respectively, for the micro-hole cellular structure. Using CuO–H2O nanofluids, we achieved the minimum base temperature of 25.5 °C and 27.7 °C numerically and experimentally, respectively. The estimated errors between obtained numerical and experimental results were 8.8% and 8.5% for Al2O3–H2O and CuO–H2O, respectively. Experimentally, we achieved the lowest base temperature of 26.6 °C and 27.7 °C using Al2O3–H2O and CuO–H2O nanofluids, respectively, which was about 17.6% and 14.5% lower than the reported temperature value of 32.3 °C using water (Tariq et al. in Therm Sci, 2018. http://www.doiserbia.nb.rs/Article.aspx?ID=0354-98361800184T ).

A carbon fiber solder matrix composite for thermal management of microelectronic devices

A novel carbon fiber solder matrix composite for thermal management of microelectronic devices.

Microjet cooling devices for thermal management of electronics

This research is an effort to demonstrate the applicability of miniaturized synthetic jet (microjet) technology to the area of thermal management of microelectronic devices. Synthetic jets are jets which are formed from entrainment and expulsion of the fluid in which they are embedded. Design issues of microjet cooling devices are discussed along with characterization of excitation elements and the turbulent synthetic jets produced thereby. Geometrical parameters of the microjet cooling devices were empirically optimized with regards to cooling performance. The cooling performance of the optimized microjets was compared with previous theoretical and empirical studies of conventional jet impingement. The cooling performance of the microjet devices has been investigated in an open environment as well as in a vented and closed case environment. In such experiments, the synthetic jet impinges normal to the surface of a packaged thermal test die, comprising a heater and a diode-based temperature sensor. This test assembly allows simultaneous heat generation and temperature sensing of the package, thereby enabling assessment of the performance of the synthetic jet. Using microjet cooling devices, a thermal resistance of 30.1/spl deg/C/W has been achieved (when unforced cooling is used, thermal resistance is 59.6/spl deg/C/W) when the test chip is located at 15mm spacing from the jet exit plane. In order to more directly compare and scale the cooling results, a preliminary study on heat transfer correlations of the microjet cooling device has been performed. Finally, a comparison of the performance of the microjet cooler with standard cooling fans is given.

Thermal conductivity and the microstructure of state-of-the-art chemical-vapor-deposited (CVD) diamond

Two new techniques have been developed for making high-accuracy measurements of the thermal conductivity κ in chemical-vapor-deposited (CVD) diamond films: (1) a steady state technique for measuring κ ∥ (heat flowing in a direction parallel to the plane of the sample) and (2) a laser flash technique for measuring κ ⊥ (heat flowing perpendicular to the plane of the film). By measuring κ ∥ and κ ⊥ for a series of high-quality CVD diamond films of different thicknesses, we are able to extract local values for these variables as a function of height z above the substrate surface. Both show a large gradient with respect to z, with κ local ⊥ rising more rapidly with z than κ local a for approximately the first 200 μm. This is consistent with phonon scattering from impurities and defects if they are preferentially located near grain boundaries of the columnar structure. For z ⪆ 300 μ m , the local conductivity is nearly isotropic with the very high value of 23–24 W cm −1°C −1 at 25°C, to be compared with 22 W cm −1°C −1 for the best type IIa single-crystal diamond so far reported. These results have direct implications for the thermal management of microelectronic devices if the remarkable conductivity of diamond is to be used most effectively.

Anisotropic thermal conductivity in chemical vapor deposition diamond

The thermal conductivity of thick-film diamond prepared by chemical vapor deposition (CVD) has been measured with heat flowing in a direction perpendicular to the plane of the film. A laser flash technique with fast infrared detection has been devised for measurement of thin samples with high conductivity. The conductivity perpendicular to the plane is observed to be at least 50% greater than with heat flowing parallel to the plane. This anisotropy is attributed to low-quality grain boundaries in the columnar microstructure. The observed dependence of the thermal conductivity on microstructure has important implications for thermal management of microelectronic devices with CVD diamond.

Unusually high thermal conductivity in diamond films

Chemical-vapor-deposited (CVD) polycrystalline diamond films have recently been reported with a thermal conductivity that is only 25% less than that of high quality single-crystal natural diamond. By studying a series of such films of various thicknesses grown under virtually identical conditions, we have discovered a significant (factor of four) through the thickness gradient in thermal conductivity. The observed gradient is attributed mainly to phonon scattering by the roughly cone-shaped columnar microstructure. For 350 μm films, the material near the top (growth) surface has a conductivity of at least 21 W/cm °C, i.e., comparable to the best single crystals. This remarkable dependence of thermal conductivity on microstructure has important implications for thermal management of microelectronic devices using CVD diamond.