HEAT TRANSFER T H E R M A L M A N AG E M E N T O F E L E C T RO N I C S K10756.indb 2 11/14/09 1:30:08 PM HEAT TRANSFER T H E R M A L M A N AG E M E N T O F E L E C T RO N I C S YOUNES SHABANY Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business K10756.indb 3 11/14/09 1:30:08 PM CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2010 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U. Government works Version Date: 20131118 International Standard Book Number-13: 978-1-4398-1468-0 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained.
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Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Visit the Taylor & Francis Web site at http://www.com and the CRC Press Web site at http://www.com To the loves of my life, Saeedeh and Arash K10756.indb 6 11/14/09 1:30:09 PM Contents Preface. xiii About the Author.1 Semiconductor Technology Trends.2 Temperature-Dependent Failures.1 Temperature-Dependent Mechanical Failures.2 Temperature-Dependent Corrosion Failures.3 Temperature-Dependent Electrical Failures.3 Importance of Heat Transfer in Electronics.4 Thermal Design Process. Energy, Energy Transfer, and Heat Transfer.1 Energy and Work.2 Macroscopic and Microscopic Energies.3 Energy Transfer and Heat Transfer.4 Equation of State.
Principle of Conservation of Energy.1 First Law of Thermodynamics.2 Energy Balance for a Control Mass.3 Energy Balance for a Control Volume. Heat Transfer Mechanisms.1 Conduction Heat Transfer.2 Convection Heat Transfer.1 Simplified Correlations for Convection Heat Transfer in Air.3 Radiation Heat Transfer.indb 7 11/14/09 1:30:09 PM viii Contents Chapter 5. Thermal Resistance Network.1 Thermal Resistance Concept.2 Series Thermal Layers.3 Parallel Thermal Layers.4 General Resistance Network.5 Thermal Contact Resistance.6 Thermal Interface Materials.7 Spreading Thermal Resistance.8 Thermal Resistance of Printed Circuit Boards (PCBs). Thermal Specification of Microelectronic Packages.1 Importance of Packaging.3 Thermal Specifications of Microelectronic Packages.1 Junction-to-Air Thermal Resistance.2 Junction-to-Case and Junction-to-Board Thermal Resistances.3 Package Thermal Characterization Parameters.4 Package Thermal Resistance Network.5 Parameters Affecting Thermal Characteristics of a Package.4 Device Power Dissipation.6 Board Size and Thermal Conductivity.
Fins and Heat Sinks.1 Infinitely Long Fin.2 Adiabatic Fin Tip.3 Convection and Radiation from Fin Tip.4 Constant Temperature Fin Tip.2 Fin Thermal Resistance, Effectiveness, and Efficiency.3 Fins with Variable Cross Sections.4 Heat Sink Thermal Resistance, Effectiveness, and Efficiency.5 Heat Sink Manufacturing Processes.indb 8 11/14/09 1:30:09 PM Contents ix Problems. Heat Conduction Equation.1 One-Dimensional Heat Conduction Equation for a Plane Wall.2 General Heat Conduction Equation.3 Boundary and Initial Conditions.1 Temperature Boundary Condition.2 Heat Flux Boundary Condition.3 Convection Boundary Condition.4 Radiation Boundary Condition.5 General Boundary Condition.6 Interface Boundary Condition.4 Steady-State Heat Conduction.1 One-Dimensional, Steady-State Heat Conduction.2 Two-Dimensional, Steady-State Heat Conduction.5 Transient Heat Conduction.1 Simple Lumped System Analysis.2 General Lumped System Analysis.3 Validity of Lumped System Analysis. Fundamentals of Convection Heat Transfer.1 Type of Flows.1 External and Internal Flows.2 Forced and Natural Convection Flows.3 Laminar and Turbulent Flows.4 Steady-State and Transient Flows.2 Viscous Force, Velocity Boundary Layer, and Friction Coefficient.3 Temperature Boundary Layer and Convection Heat Transfer Coefficient.5 Boundary Layer Equations. Forced Convection Heat Transfer: External Flows.1 Normalized Boundary Layer Equations.2 Reynolds Number, Prandtl Number, Eckert Number, and Nusselt Number.indb 9 11/14/09 1:30:10 PM x Contents 10.3 Functional Forms of Friction Coefficient and Convection Heat Transfer Coefficient.4 Flow over Flat Plates.1 Laminar Flow over a Flat Plate with Constant Temperature.2 Turbulent Flow over a Flat Plate with Uniform Temperature.3 Flow over a Flat Plate with Uniform Surface Heat Flux.5 Flow Across Cylinders.6 Cylindrical Pin-Fin Heat Sink.7 Procedure for Solving External Forced Convection Problems.
Forced Convection Heat Transfer: Internal Flows.1 Mean Velocity and Mean Temperature.2 Laminar and Turbulent Pipe Flows.3 Entry Length and Fully Developed Flow.4 Pumping Power and Convection Heat Transfer in Internal Flows.5 Velocity Profiles and Friction Factor Correlations.6 Temperature Profiles and Convection Heat Transfer Correlations.7 Fans and Pumps.1 Types of Fans.2 Fan Curve and System Impedance Curve.4 Types of Pumps.8 Plate-Fin Heat Sinks. Natural Convection Heat Transfer.1 Buoyancy Force and Natural Convection Flows.2 Natural Convection Velocity and Temperature Boundary Layers.3 Normalized Natural Convection Boundary Layer Equations.1 Grashof and Rayleigh Numbers.2 Functional Form of the Convection Heat Transfer Coefficient.indb 10 11/14/09 1:30:10 PM Contents xi 12.4 Laminar and Turbulent Natural Convection over a Vertical Flat Plate.5 Natural Convection around Inclined and Horizontal Plates.6 Natural Convection around Vertical and Horizontal Cylinders.7 Natural Convection in Enclosures.8 Natural Convection from Array of Vertical Plates. Radiation Heat Transfer.1 Radiation Intensity and Emissive Power.3 Radiation Properties of Surfaces.4 Solar and Atmospheric Radiations.7 Radiation Heat Transfer between Black Bodies.8 Radiation Heat Transfer between Nonblack Bodies.9 Radiation Heat Transfer from a Plate-Fin Heat Sinks. Computer Simulations and Thermal Design.1 Heat Transfer and Fluid Flow Equations: A Summary.2 Fundamentals of Computer Simulation.1 Steady-State, One-Dimensional Heat Conduction.2 Steady-State, Two-Dimensional Heat Conduction.3 Transient Heat Conduction.4 Fluid Flow and Energy Equations.4 Solution of Finite-Difference Equations.5 Commercial Thermal Simulation Tools.1 Creating the Thermal Model.indb 11 11/14/09 1:30:10 PM xii Contents 14.2 Creating the Mesh.3 Solving Flow and Temperature Equations.4 Review the Results.5 Presenting the Results.6 Importance of Modeling and Simulation in Thermal Design.
Experimental Techniques and Thermal Design.1 Flow Rate Measurement Techniques.2 System Impedance Measurement.3 Fan and Pump Curve Measurements.4 Velocity Measurement Methods.5 Temperature Measurement Techniques.6 Acoustic Noise Measurements.7 Importance of Experimental Measurements in Thermal Design. Advanced Cooling Technologies.5 Other Heat Pipe Performance Limits.6 Heat Pipe Applications in Electronic Cooling.7 Heat Pipe Selection and Modeling.8 Thermosyphons, Loop Heat Pipes, and Vapor Chambers. 452 Appendix: Tables of Material Properties.indb 12 11/14/09 1:30:10 PM Preface Design and manufacturing of microelectronic devices and systems are multidisci- plinary engineering activities. With the continuous trend toward miniaturization and high power density systems, the dependency between different design disciplines has become even more pronounced.
Chip designers, hardware engineers, mechanical engineers, test engineers, reliability engineers, and thermal engineers can no longer work in their own solo environments. They are now expected to interact with each other and ensure that a proposed design from one discipline does not violate the requirements of other disciplines. Some microelectronic companies have gone a step further and looked for multidisciplinary engineers who have knowledge and expertise in multiple design disciplines. These engineers can move the design process through multiple disciplines in parallel, and will reduce the risk of a product being optimized in one aspect while not meeting the requirements of the others.
Thermal engineering is one of the disciplines involved in the design and manu- facturing of electronic systems. Appropriate thermal design has become one of the enabling factors for the realization of high power density electronic equipment. In addition to preventing the failures that may result from high temperature, smart and innovative thermal designs will increase the life expectancy of a system; may reduce its emitted acoustic noise, cost, time to market, and energy consumption; and can create significant market differentiations compared to similar products. I have worked in the field of thermal management of electronics for over 10 years.
Most of the mechanical, electrical, hardware, power, and industrial engineers I have worked with have had little to no knowledge of thermal management. I have also been teaching a course on heat transfer in electronics to undergraduate students in electrical and computer engineering majors for over eight years. These students have little or no background in thermodynamics and heat transfer principles. Although there is a general consensus that the engineers who work on the hardware side of the electronic industry will benefit from basic knowledge of thermal engineering, there is no heat transfer book that is written for this group.
The target audience for this book is current and future engineers, with careers in the electronic industry. It educates those engineers on the basics of thermal man- agement of electronics, broadens their engineering knowledge and expertise, and moves them a step closer to being multidisciplinary engineers. It assumes no previ- ous exposure to the sciences of heat transfer and thermodynamics and introduces all the relevant principles accordingly. This book is structured so that the first seven chapters give readers a basic knowl- edge of thermal management of electronics such that they will be able to analyze and solve simple electronic cooling problems.
Chapters 8 through 13 go into the details of heat transfer fundamentals and may be used by those who are interested in a deeper understanding of the physics of heat transfer. Chapters 14 and 15 discuss computational and experimental methods and tools used in a typical thermal design process. Finally, some advanced cooling techniques are introduced in Chapter 16.indb 13 11/14/09 1:30:10 PM xiv Preface Chapters 1 through 7 and selected parts of Chapters 8 through 13 constitute enough topics for a semester-long undergraduate course in thermal management of electronics, or heat transfer in electronics, for nonmechanical engineering majors. Chapters 1, 6, 7, 14, 15, 16, and selected parts of the other chapters contain enough topics for an undergraduate course in thermal management of electronics for mechanical engineering students who have already taken courses in thermodynam- ics and heat transfer.
Chapters 1 through 7 and 14 through 16 can be used as a supplement to a work- shop on thermal management of electronics for mechanical, electrical, and power engineers and for project managers who are currently working in the electronics design and manufacturing industry. I would like to express my sincere thanks to the following reviewers for their many helpful comments and suggestions: Kaveh Azar, Advanced Thermal Solutions; David Copeland, Sun Microsystems; Paul Durbin, Iowa State University; Marc Hodes, Tufts University, Nicole Okamoto, San Jose State University; Sadegh Sadeghipour, Luminant; Yizhang Yang, Advanced Micro Devices; Ross Wilcoxon, Rockwell Collins; and Michael Yovanovich, University of Waterloo. I am grateful to my wife, Saeedeh, who was my main supporter in this project, and my son, Arash, who gives me the motivation for almost everything I do. I need to thank them for allowing me to spend a lot of time writing this book that I should have spent with them.
I cannot make up for those precious times. However, I hope this book will save its readers some time such that they can spend more time with their families.indb 14 11/14/09 1:30:11 PM About the Author Younes Shabany was born in Rasht in northern Iran, but lived most of his life in Tehran where he went to school until he received his BS in mechanical engineering from Sharif University of Technology in 1991. He then went to Vancouver, Canada where he obtained his MS in mechanical engineering from the University of British Columbia in 1994.