Study of Miniaturization of a Silicon Vapor Chamber for Compact 3D Microelectronics, via a Hybrid Analytical and Finite Element Method

2019 ◽  
Vol 6 (5) ◽  
pp. 01-18
Author(s):  
Ma Yue ◽  
Shirazy Mahmoud ◽  
Coudrain Perceval ◽  
Colonna Jean-Phulippe ◽  
Souifi Abdelkader ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Numerical Models ◽  
Computational Cost ◽  
Vapor Chamber ◽  
Cooling Systems ◽  
Heat Spreaders ◽  
Operating Limits ◽  
Silicon Vapor ◽  
Core Height ◽  
Low Computational Cost

The interest in silicon vapor chambers (SVCs) has increased in the recent years as they have been identified as efficient cooling systems for microelectronics. They present the advantage of higher thermal conductivity and smaller form factor compared to conventional heat spreaders. This work aims to investigate the potential miniaturization of these devices, preliminary to integration on the backside of mobile device chips, located as close as possible to hotspots. While detailed numerical models of vapor chamber operation are developed, an easy modeling with low computational cost is needed for an effective parametric study.  Based on the study of the operating limits, this paper shows the thinning potential of a water filled micropillar for a device operating below 10 W and identify the corresponding vapour core height, and wick thickness.

scholarly journals Study of Miniaturization of a Silicon Vapor Chamber for Compact 3D Microelectronics, via a Hybrid Analytical and Finite Element Method

2019 ◽  
Vol 7 (6) ◽  
pp. 1-16
Author(s):  
Yue MA ◽  
M. R. S. Shirazy ◽  
Q. Struss ◽  
P. Coudrain ◽  
J.P. Colonna ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Numerical Models ◽  
Computational Cost ◽  
Vapor Chamber ◽  
Cooling Systems ◽  
Heat Spreaders ◽  
Operating Limits ◽  
Silicon Vapor ◽  
Core Height ◽  
Low Computational Cost

The interest in silicon vapor chambers (SVCs) has increased in the recent years as they have been identified as efficient cooling systems for microelectronics. They present the advantage of higher thermal conductivity and smaller form factor compared to conventional heat spreaders. This work aims to investigate the potential miniaturization of these devices, preliminary to integration on the backside of mobile device chips, located as close as possible to hotspots. While detailed numerical models of vapor chamber operation are developed, an easy modeling with low computational cost is needed for an effective parametric study.  Based on the study of the operating limits, this paper shows the thinning potential of a water filled micropillar for a device operating below 10 W and identify the corresponding vapour core height, and wick thickness.

Thermal Enhancement of an LED Light Engine for Automotive Exterior Lighting With Advanced Heat Spreader Technology

2016 ◽  
Author(s):  
Umut Zeynep Uras ◽  
Enes Tamdoğan ◽  
Mehmet Arık
Keyword(s):  
Thermal Conductivity ◽  
Numerical Models ◽  
Maximum Temperature ◽  
Vapor Chamber ◽  
Metal Core ◽  
Heat Spreader ◽  
Printed Circuit ◽  
Thermal Enhancement ◽  
Wide Range ◽  
Light Engine

In recent years, light emitting diodes (LEDs) have become an attractive technology for general and automotive illumination systems. LEDs have been preferable for automobile lighting due to its numerous advantages such as long life, low power consumption, optical control and light quality as well as robustness for high vibration. Thermal management is one of the main issues due to severe ambient conditions and compact volume. Conventionally, tightly packaged double sided FR4 based printed circuit boards are utilized for both driver electronics components and LEDs. In fact, this approach will be a leading trend for advanced Internet of Things (IOT) applications in near future. A series of numerical models are developed to determine the local temperature distribution on both sides of a light engine. Results showed that FR4 PCB has a temperature gradient of over 63°C while the maximum temperature is 105°C. This causes a significant degradation of lifetime and lumen extraction as many LEDs are recommended to be operated below 100°C. In addition to FR4, Aluminum metal core and vapor chamber based advanced heat spreader substrates are developed to obtain thermal impact on the substrate due to a wide range of thermal conductivity of three boards. To mimic real application, two special flex circuits are developed for LEDs and driver circuit. 10 red and 6 amber LEDs at one flex-PCB, and driver components are populated on the other flex-PCB are mounted. Both flex circuits are attached each side of the substrate. Experimental results showed that the local hotspots occurred at FR4 PCB due to low thermal conductivity. Later, a metal core printed circuit board is investigated to minimalize local hot spots. High conductivity metal core PCB showed a 19.9% improvement over FR4 based board. A further study has been performed with an advanced heat spreader based on vapor chamber technology. Results showed that a thermal enhancement of 7.4% and 25.8% over Al metal core and FR4 based boards with an advanced vapor chamber substrate.

scholarly journals Tsunami propagation kernel and its applications

2021 ◽  
Author(s):  
Takenori Shimozono
Keyword(s):  
Kernel Method ◽  
Numerical Models ◽  
Computational Cost ◽  
Specific Area ◽  
Tsunami Propagation ◽  
Kernel Convolution ◽  
Damping Parameter ◽  
Tsunami Risk ◽  
Convolution Kernels ◽  
Low Computational Cost

Abstract. Tsunamis rarely occur in a specific area, and their occurrence is highly uncertain. Generated from their sources in deep water, they occasionally undergo tremendous amplification over decreasing water depth to devastate low-lying coastal areas. Despite the advancement of computational power and simulation algorithms, there is a need for novel and rigorous approaches to efficiently predict coastal amplification of tsunamis during different disaster management phases, such as tsunami risk assessment and real-time forecast. This study presents convolution kernels that can instantly predict onshore waveforms of water surface elevation and flow velocity from observed/simulated wavedata apart from the shore. Kernel convolution involves isolating an incident-wave component from the offshore wavedata and transforming it into the onshore waveform. Moreover, unlike previous derived ones, the present kernels are based on shallow-water equations with a damping term and can account for tsunami attenuation on its path to the shore with a damping parameter. Kernel convolution can be implemented at a low computational cost compared to conventional numerical models that discretise the spatial domain. The prediction capability of the kernel method was demonstrated through application to real-world tsunami cases.

Numerical Analysis of Conduction in a Foam

2002 ◽  
Author(s):  
A. M. Druma ◽  
M. K. Alam ◽  
C. Druma
Keyword(s):  
Thermal Conductivity ◽  
Porous Medium ◽  
Numerical Models ◽  
High Porosity ◽  
Material Microstructure ◽  
Element Analysis ◽  
Empirical Parameter ◽  
Bulk Properties ◽  
Heat Spreaders ◽  
Homogeneous Models

Porous organic materials are being developed for use as insulation, heat spreaders, and compact heat exchanger cores. The bulk properties of such a porous medium are difficult to determine analytically, particularly for the case of high porosity or when the porous material is not isotropic or homogeneous. Models that predict thermal conductivity of foams often use an empirical parameter to account for the effect of pore shape and material microstructure on the conduction process. A finite element analysis has been developed to calculate the thermal conductivity of a porous medium containing micropores. The effective thermal conductivity and the empirical conduction parameter are evaluated by comparing the results of the analytical and numerical models.

Thermal Performance of Natural Graphite Heat Spreaders With Embedded Thermal Vias

2007 ◽  
Author(s):  
Martin Smalc ◽  
Prathib Skandakumaran ◽  
Julian Norley
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Thermal Performance ◽  
Numerical Models ◽  
Accelerated Aging ◽  
High Heat ◽  
High Heat Flux ◽  
Natural Graphite ◽  
Heat Spreaders ◽  
Graphite Heat

Natural graphite heat spreaders are in use in electronic cooling applications where heat flux density is low. Natural graphite is an anisotropic material, with a high thermal conductivity in the plane of the spreader combined with a much lower thermal conductivity through its thickness. This low through-thickness thermal conductivity poses a problem when attempting to cool heat sources with relatively high heat flux densities. This problem can be overcome by embedding a thermal via in the graphite material. This via is made from an isotropic material with a thermal conductivity significantly higher than the through-thickness graphite conductivity. This paper examines the thermal performance of a natural graphite heat spreader with an embedded thermal via. The work is primarily experimental although numerical models were used to guide the experiments. The thermal performance of these spreaders is compared to that of spreaders made from conventional isotropic materials. The effect of accelerated aging tests on the performance of these graphite spreaders is reviewed. Finally, two applications are examined; first cooling an ASIC module and second, cooling an FB-DIMM memory card.

Model of Multiscale Transport in Carbon Foams

2003 ◽  
Author(s):  
C. Druma ◽  
M. K. Alam ◽  
A. M. Druma
Keyword(s):  
Thermal Conductivity ◽  
Numerical Models ◽  
Carbon Foam ◽  
Compact Heat Exchanger ◽  
High Concentration ◽  
Element Analysis ◽  
Bulk Properties ◽  
Heat Spreaders ◽  
Carbon Foams ◽  
Different Shapes

A number of carbon foam products are being developed for use as insulation, heat spreaders, and compact heat exchanger cores. Such foams have voids that are typically of the order 100 microns, and pore walls are about 10 microns. Within the walls of the pores, the graphene planes are arranged anisotropically so that the thermal transport is highly dependent on the orientation of the bulk foam. This results in bulk conductivities that range from 1 W/mK to 200 W/mK. The bulk properties of such a porous medium are difficult to determine analytically, particularly for the case of high concentration of non-spherical pores, or when the porous material is anisotropic or non-homogeneous. A finite element analysis has been developed to calculate the bulk thermal conductivity of carbon foams containing micropores of different shapes. The effective thermal conductivity is then evaluated by comparing the results of the analytical and numerical models.

Practical analytical steady-state temperature solution for annealed pyrolytic graphite heat spreader

2017 ◽  
Vol 27 (1) ◽  
pp. 174-188 ◽  
Author(s):  
Nhat Minh Nguyen ◽  
Eric Monier-Vinard ◽  
Najib Laraqi ◽  
Valentin Bissuel ◽  
Olivier Daniel
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Steady State ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Pyrolytic Graphite ◽  
Heat Spreader ◽  
Content Type ◽  
Heat Spreaders ◽  
Operating Limits

Purpose The purpose of this paper is to supply an analytical steady-state solution to the heat transfer equation permitting to fast design investigation. The capability to efficiently transfer the heat away from high-powered electronic devices is a ceaseless challenge. More than ever, the aluminium or copper heat spreaders seem less suitable for maintaining the component sensitive temperature below manufacturer operating limits. Emerging materials, such as annealed pyrolytic graphite (APG), have proposed a new alternative to conventional solid conduction without the gravity dependence of a heat-pipe solution. Design/methodology/approach An APG material is typically sandwiched between a pair of aluminium sheets to compose a robust graphite-based structure. The thermal behaviour of that stacked structure and the effect of the sensitivity of the design parameters on the effective thermal performances is not well known. The ultrahigh thermal conductivity of the APG core is restricted to in-plane conduction and can be 200 times higher than its through-the-thickness conductivity. So, a lower-than-anticipated cross-plane thermal conductivity or a higher-than-anticipated interlayer thermal resistance will compromise the component heat transfer to a cold structure. To analyse the sensitivity of these parameters, an analytical model for a multi-layered structure based on the Fourier series and the superposition principle was developed, which allows predicting the temperature distribution over an APG flat-plate depending on two interlayer thermal resistances. Findings The current work confirms that the in-plane thermal conductivity of APG is among the highest of any conduction material commonly used in electronic cooling. The analysed case reveals that an effective thermal conductivity twice as higher than copper can be expected for a thick APG sheet. The relevance of the developed analytical approach was compared to numerical simulations and experiments for a set of boundary conditions. The comparison shows a high agreement between both calculations to predict the centroid and average temperatures of the heating sources. Further, a method dedicated to the practical characterization of the effective thermal conductivity of an APG heat-spreader is promoted. Research limitations/implications The interlayer thermal resistances act as dissipation bottlenecks which magnify the performance discrepancy. The quantification of a realistic value is more than ever mandatory to assess the APG heat-spreader technology. Practical implications Conventional heat spreaders seem less suitable for maintaining the component-sensitive temperature below the manufacturer operating limits. Having an in-plane thermal conductivity of 1,600 W.m−1.K−1, the APG material seems to be the next paradigm for solving endless needs of a thermal designer. Originality/value This approach is a practical tool to tailor sensitive parameters early to select the right design concept by taking into account potential thermal issues, such as the critical interlayer thermal resistance.

Thermal Performance of Natural Graphite Heat Spreaders

2005 ◽  
Author(s):  
Martin Smalc ◽  
Gary Shives ◽  
Gary Chen ◽  
Shrishail Guggari ◽  
Julian Norley ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Management ◽  
Numerical Models ◽  
Laptop Computer ◽  
Natural Graphite ◽  
Heat Spreader ◽  
Graphite Sheet ◽  
Cooling Fan ◽  
Heat Spreaders ◽  
Graphite Heat

Heat spreaders can be made from natural graphite sheet materials. These spreaders take advantage of the anisotropic thermal properties of natural graphite. Natural graphite exhibits a high thermal conductivity in the plane of the sheet combined with a much lower thermal conductivity through the thickness of the sheet. As a result, a natural graphite sheet can function as both a heat spreader and an insulator and can be used to eliminate localized hot spots in electronic components. In some cases, a natural graphite heat spreader can replace a conventional thermal management system consisting of a heat sink and cooling fan. This paper examines the properties of natural graphite heat spreaders and the application of these spreaders to thermal management problems in laptop computers. The thermal and mechanical properties of natural graphite heat spreaders are presented along with a discussion of how those properties are measured. The use of a natural graphite heat spreader to reduce the touch temperature in a laptop computer is presented. Both experimental techniques and numerical models are used to examine performance of the heat spreader in this application.

scholarly journals Computing Expectiles Using k-Nearest Neighbours Approach

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 645
Author(s):  
Muhammad Farooq ◽  
Sehrish Sarfraz ◽  
Christophe Chesneau ◽  
Mahmood Ul Hassan ◽  
Muhammad Ali Raza ◽  
...  
Keyword(s):  
Computational Cost ◽  
Real Life ◽  
Distance Measures ◽  
Computational Time ◽  
High Dimensional ◽  
Test Error ◽  
Nearest Neighbours ◽  
Comparable Performance ◽  
Asymmetric Least Squares ◽  
Low Computational Cost

Expectiles have gained considerable attention in recent years due to wide applications in many areas. In this study, the k-nearest neighbours approach, together with the asymmetric least squares loss function, called ex-kNN, is proposed for computing expectiles. Firstly, the effect of various distance measures on ex-kNN in terms of test error and computational time is evaluated. It is found that Canberra, Lorentzian, and Soergel distance measures lead to minimum test error, whereas Euclidean, Canberra, and Average of (L1,L∞) lead to a low computational cost. Secondly, the performance of ex-kNN is compared with existing packages er-boost and ex-svm for computing expectiles that are based on nine real life examples. Depending on the nature of data, the ex-kNN showed two to 10 times better performance than er-boost and comparable performance with ex-svm regarding test error. Computationally, the ex-kNN is found two to five times faster than ex-svm and much faster than er-boost, particularly, in the case of high dimensional data.

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