Effects of Substrate Conductivity on Convective Cooling of Electronic Components

1994 ◽  
Vol 116 (3) ◽  
pp. 198-205 ◽  
Author(s):  
C. Y. Choi ◽  
S. J. Kim ◽  
A. Ortega
Keyword(s):  
Heat Transfer ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Maximum Temperature ◽  
Dimensionless Temperature ◽  
Heat Sources ◽  
Flow Conditions ◽  
Conductive Materials ◽  
Simple Boundary ◽  
Transfer Problems

The coupled conduction and forced convection transport from substrate-mounted modules in a channel is numerically investigated to identify the effects of the substrate conductivity. The results presented apply to air and two-dimensional laminar flow conditions. It was found that recirculating cells as well as streamwise conduction through the substrate play an important role in predicting convective heat transfer from the printed circuit board (PCB) and modules and in determining the temperature distributions in the PCB, modules, and fluid. The dimensionless temperature and the local Nusselt number along the interface between the fluid and the module or PCB are rather complicated, and therefore, predetermined simple boundary conditions along the solid surface may be inappropriate in many conjugate heat transfer problems. In general, the results show that the maximum temperature within heat sources can be greatly reduced by increasing the conductivity of the PCB. The effectiveness of the use of highly conductive materials for PCB, however, depends on the distance between the heat generating modules on the PCB. In addition, finite thermal resistance between the module and the PCB would serve to diminish the PCB conduction effects, thereby reducing the effectiveness of the enhancement afforded by increased conductivity.

Thermal Performance Analysis and Heat Transfer Enhancement Study in an Antminer Mining Machine

2020 ◽  
Vol 13 (2) ◽  
Author(s):  
Wen-Xiao Chu ◽  
Yao-Wen Chang ◽  
Yi-Yu Hu ◽  
Chi-Chuan Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Printed Circuit Board ◽  
Hot Spot ◽  
Flow Direction ◽  
Heat Sinks ◽  
Circuit Board ◽  
Maximum Temperature ◽  
Mining Machine ◽  
Temperature Operating

Abstract In this paper, the thermal performance of an AntMiner mining machine containing 189 chips on three printed circuit board (PCBs) is experimentally studied. The numerical method is applied to analyze the local airflow and thermal distribution alongside the flow direction and shows a good agreement with the experimental results. Some hot-spot regions are identified where chips might suffer under high-temperature operating condition. Meanwhile, the highly compact arrangement may result in pronounced bypass and jeopardize the thermal performance of the mining machine rapidly; thereby, the airflow management strategy for such confined compartment is implemented. The result shows that the flowrate distribution can be notably improved. Although the total flowrate is slightly reduced by 4.4%, the maximum chip temperature on three PCBs can be reduced by 3.2 °C, 3.5 °C, and 3.0 °C, and the corresponding improvement on thermal performance reaches 13.3%, 15.6%, and 13.0%, respectively. Furthermore, the maximum temperature of the downstream chips will be reduced by 2.5 °C when incorporating the “partial bypass” design by the removal of 12 backside heat sinks. The corresponding heat transfer performance is improved by 8.9–13.9%.

Separation of Natural Convection and Radiation by Changing Rotational Acceleration

Volume 1 ◽  
2004 ◽  
Author(s):  
Arnout Willockx ◽  
Gilbert De Mey ◽  
Michel De Paepe ◽  
Boguslaw Wiecek ◽  
Mariusz Felczak ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Centripetal Force ◽  
Rotational Acceleration ◽  
Governing Equations ◽  
Total Heat Transfer ◽  
Closed Cavity ◽  
Printed Circuit

The objective is to separate natural convection and radiation experimentally. Therefore a heat source is placed inside a closed cavity and the acceleration inside the cavity can be changed. A centrifuge is used to change the acceleration. A flat resistor etched on a printed circuit board of 10mm × 48mm, is placed in a hermetically sealed cylinder, which hangs under the arm of the centrifuge. The resistor is powered by a battery, dissipates 0,35W and has a surface temperature of 60°C at 1g. Natural convection is maintained inside the cylinder. Conduction is reduced to a negligible amount by construction of the experiment, thus convection and radiation are the main modes of heat transfer. The rotational speed of the centrifuge determines the centrifugal force in the cylinder. When the centripetal force increases, the temperature of the resistor decreases due to the increase of natural convection. The amount of radiation and total heat transfer can be determined from the experiment, so the amount of natural convection can also be determined. The experimental results are compared with the governing equations to validate the experiment. The reproducibility of the experiment is also checked.

Measurements of Sheath Temperature Profiles in Bruce LVRF Bundles Under Post-Dryout Heat Transfer Conditions in Freon

2006 ◽  
Author(s):  
Y. Guo ◽  
D. E. Bullock ◽  
I. L. Pioro ◽  
J. Martin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Uranium ◽  
Outer Ring ◽  
Maximum Temperature ◽  
Experimental Program ◽  
Uniform Heat Flux ◽  
Flow Conditions ◽  
Channel Power ◽  
Ring Element

An experimental program has been completed to study the behaviour of sheath wall temperatures in the Bruce Power Station Low Void Reactivity Fuel (shortened hereafter to Bruce LVRF) bundles under post-dryout (PDO) heat-transfer conditions. The experiment was conducted with an electrically heated simulator of a string of nine Bruce LVRF bundles, installed in the MR-3 Freon heat transfer loop at the Chalk River Laboratories (CRL), Atomic Energy of Canada Limited (AECL). The loop used Freon R-134a as a coolant to simulate typical flow conditions in CANDU® nuclear power stations. The simulator had an axially uniform heat flux profile. Two radial heat flux profiles were tested: a fresh Bruce LVRF profile and a fresh natural uranium (NU) profile. For a given set of flow conditions, the channel power was set above the critical power to achieve dryout, while heater-element wall temperatures were recorded at various overpower levels using sliding thermocouples. The maximum experimental overpower achieved was 64%. For the conditions tested, the results showed that initial dryout occurred at an inner-ring element at low flows and an outer-ring element facing internal subchannels at high flows. Dry-patches (regions of dryout) spread with increasing channel power; maximum wall temperatures were observed at the downstream end of the simulator, and immediately upstream of the mid-bundle spacer plane. In general, maximum wall temperatures were observed at the outer-ring elements facing the internal subchannels. The maximum water-equivalent temperature obtained in the test, at an overpower level of 64%, was significantly below the acceptable maximum temperature, indicating that the integrity of the Bruce LVRF will be maintained at PDO conditions. Therefore, the Bruce LVRF exhibits good PDO heat transfer performance.

Thermal Performance of Microelectronic Substrates With Submillimeter Integrated Vapor Chamber

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Sangbeom Cho ◽  
Yogendra Joshi
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Printed Circuit Board ◽  
Mechanical Design ◽  
Three Dimensional ◽  
Circuit Board ◽  
Working Fluid ◽  
Vapor Chamber ◽  
Conduction Model ◽  
Printed Circuit

We develop a vapor chamber integrated with a microelectronic packaging substrate and characterize its heat transfer performance. A prototype of vapor chamber integrated printed circuit board (PCB) is fabricated through successful completion of the following tasks: patterning copper micropillar wick structures on PCB, mechanical design and fabrication of condenser, device sealing, and device vacuuming and charging with working fluid. Two prototype vapor chambers with distinct micropillar array designs are fabricated, and their thermal performance tested under various heat inputs supplied from a 2 mm × 2 mm heat source. Thermal performance of the device improves with heat inputs, with the maximum performance of ∼20% over copper plated PCB with the same thickness. A three-dimensional computational fluid dynamics/heat transfer (CFD/HT) numerical model of the vapor chamber, coupled with the conduction model of the packaging substrate is developed, and the results are compared with test data.

An Experimental Assessment of Numerical Predictive Accuracy for Electronic Component Heat Transfer in Forced Convection—Part II: Results and Discussion

2003 ◽  
Vol 125 (1) ◽  
pp. 76-83 ◽  
Author(s):  
Peter J. Rodgers ◽  
Vale´rie C. Eveloy ◽  
Mark R. Davies
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Printed Circuit Board ◽  
Predictive Accuracy ◽  
Numerical Models ◽  
Circuit Board ◽  
Junction Temperature ◽  
Electrical Performance ◽  
Test Cases ◽  
Computational Fluid Dynamics Cfd

Numerical predictive accuracy is assessed for component-printed circuit board (PCB) heat transfer in forced convection using a widely used computational fluid dynamics (CFD) software. In Part I of this paper, the benchmark test cases, experimental methods and numerical models were described. Component junction temperature prediction accuracy for the populated board case is typically within ±5°C or ±10%, which would not be sufficient for temperature predictions to be used as boundary conditions for subsequent reliability and electrical performance analyses. Neither the laminar or turbulent flow model resolve the complete flow field, suggesting the need for a turbulence model capable of modeling transition. The full complexity of component thermal interaction is shown not to be fully captured.

Natural Convection and Passive Heat Rejection from Two Heat Sources Maintained at Different Temperatures on a Printed Circuit Board

2004 ◽  
Vol 126 (1) ◽  
pp. 14-21 ◽  
Author(s):  
Randy D. Weinstein ◽  
Amy S. Fleischer ◽  
Kimberly A. Krug
Keyword(s):  
Natural Convection ◽  
Power Dissipation ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Heat Sources ◽  
Circuit Boards ◽  
Vertical Orientation ◽  
Heat Rejection ◽  
Different Temperatures ◽  
Independent Heat

Natural convection and passive heat rejection from two independent heat sources maintained at different temperatures (60°C and 100°C above ambient) on single circuit boards (FR4 and copper clad FR4) are experimentally studied. The effect of heat source location on maximum power dissipation is presented for both horizontal and vertical orientations. Heat losses due to radiation, natural convection and board conduction are quantified. As long as the heat sources are more than 2 cm apart, they do not influence each other on the FR4 board. Vertical orientation increases the power dissipation in the components by up to 30% for the FR4 board and 15% for the copper clad board. Two ounces of copper cladding increases the overall power dissipation by 150–190%.

Heat in Computers: Applied Heat Transfer in Information Technology

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Wataru Nakayama
Keyword(s):  
Heat Transfer ◽  
Integrated Circuits ◽  
Printed Circuit Board ◽  
Cfd Simulation ◽  
Coolant Flow ◽  
Energy Utilization ◽  
Utilization Efficiency ◽  
Circuit Board ◽  
Evolutionary Trend ◽  
Simulation Code

Since the advent of modern electronics technology, heat transfer science and engineering has served in the development of computer technology. The computer as an object of heat transfer research has a unique aspect; it undergoes morphological transitions and diversifications in step with the progress of microelectronics technology. Evolution of computer's hardware manifests itself in increasing packing density of electronic circuits, modularization of circuit assemblies, and increasing hierarchical levels of system internal structures. These features are produced by the confluence of various factors; the primary factors are the pursuit of ever higher processing performance, less spatial occupancy, and higher energy utilization efficiency. The cost constraint on manufacturing also plays a crucial role in the evolution of computer's hardware. Besides, the drive to make computers ubiquitous parts of our society generates diverse computational devices. Concomitant developments in heat generation density and heat transfer paths pose fresh challenges to thermal management. In an introductory part of the paper, I recollect our experiences in the mainframe computers of the 1980s, where the system's morphological transition allowed the adoption of water cooling. Then, generic interpretations of the hardware evolution are attempted, which include recapturing the past experience. Projection of the evolutionary trend points to shrinking space for coolant flow, the process commonly in progress in all classes of computers today. The demand for compact packaging will rise to an extreme level in supercomputers, and present the need to refocus our research on microchannel cooling. Increasing complexity of coolant flow paths in small equipment poses a challenge to a user of computational fluid dynamics (CFD) simulation code. In highly integrated circuits the paths of electric current and heat become coupled, and coupled paths make the electrical/thermal codesign an extremely challenging task. These issues are illustrated using the examples of a consumer product, a printed circuit board (PCB), and a many-core processor chip.

Optimal Distribution of Discrete Heat Sources Under Mixed Convection—A Heuristic Approach

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Tapano Kumar Hotta ◽  
C. Balaji ◽  
S. P. Venkateshan
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Optimal Configuration ◽  
Surface Radiation ◽  
Horizontal Wind ◽  
Maximum Temperature ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Temperature Excess ◽  
Effect Of Surface

Steady state experiments are conducted in a low speed horizontal wind tunnel under mixed convection for five discrete heat sources (aluminum) of nonidentical sizes arranged at different positions on a substrate board (bakelite) to determine the optimal configuration. The optimal configuration is one for which the maximum temperature excess (difference between the maximum temperature among the heat sources of that configuration, and the ambient temperature) is the lowest among all the other possible configurations and is determined by a heuristic nondimensional geometric parameter λ. The maximum temperature excess is found to decrease with λ, signifying an increase in heat transfer coefficient. In view of this, the configuration with highest λ is deemed to be the optimal one. The effect of surface radiation on the heat transfer characteristic of heat sources is also studied by painting their surface with black, which reduces their temperature by as much as 12%. An empirical correlation is developed for the nondimensional maximum temperature excess (θ) in terms of λ, by taking into account the effect of surface radiation. The correlation when applied for highest λ of the configuration returns the minimum value of θ at the optimal condition, which is a key engineering quantity that is sought in problems of this class.

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