1、High-Speed Circuit BoardSignal IntegrityFor a listing of recent titles in the Artech House Microwave Library,turn to the back of this book.High-Speed Circuit BoardSignal IntegrityStephen C. ThieraufArtech House, Inc.Boston LLibrary of Congress Cataloguing-in-Publication DataA catalog record for this
2、 book is available from the U.S. Library of Congress.British Library Cataloguing in Publication DataA catalog record for this book is available from the British Library.Cover design by Igor Valdman 2004 ARTECH HOUSE, INC.685 Canton StreetNorwood, MA 02062All rights reserved. Printed and bound in the
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5、8053-131-810 9 8 7 6 5 4 3 2 1To Ann, Christopher, and KevinContentsPrefacexiiiCHAPTER 1Characteristics and Construction of Printed Wiring Boards11.1Introduction11.2Unit System11.3PWB Construction21.3.1Resins31.3.2Alternate Resin Systems31.3.3Reinforcements51.3.4Variability in Building Stackups61.3.
6、5Mixing Laminate Types71.4PWB Traces71.4.1Copper Cladding81.4.2Copper Weights and Thickness91.4.3Plating the Surface Traces91.4.4Trace Etch Shape Effects91.5Vias101.5.1Via Aspect Ratio131.6Surface Finishes and Solder Mask141.7Summary14References15CHAPTER 2Resistance of Etched Conductors172.1Introduc
7、tion172.2Resistance at Low Frequencies172.3Loop Resistance and the Proximity Effect202.3.1Resistance Matrix212.3.2Proximity Effect222.4Resistance Increase with Frequency: Skin Effect242.5Hand Calculations of Frequency-Dependent Resistance272.5.1Return Path Resistance282.5.2Conductor Resistance282.5.
8、3Total Loop Resistance292.6Resistance Increase Due to Surface Roughness292.7Summary30viiReferences30CHAPTER 3Capacitance of Etched Conductors313.1Introduction313.2Capacitance and Charge313.2.1Dielectric Constant323.3Parallel Plate Capacitor333.4Self and Mutual Capacitance353.5Capacitance Matrix373.6
9、Dielectric Losses393.6.1Reactance and Displacement Current403.6.2Loss Tangent403.6.3Calculating Loss Tangent and Conductance G413.7Environmental Effects on Laminate rand Loss Tangent433.7.1Temperature Effects443.7.2Moisture Effects443.8Summary45References45CHAPTER 4Inductance of Etched Conductors474
10、.1Introduction474.2Field Theory474.2.1Permeability484.2.2Inductance484.2.3Internal and External Inductance494.2.4Partial Inductance494.2.5Reciprocity Principal and Transverse Electromagnetic Mode504.3Circuit Behavior of Inductance514.3.1Inductive Voltage Drop534.3.2Inductive Reactance544.4Inductance
11、 Matrix554.4.1Using the Reciprocity Principle to Obtain theInductance Matrix from a Capacitance Matrix554.5Mutual Inductance554.5.1Coupling Coefficient564.5.2Beneficial Effects of Mutual Inductance574.5.3Deleterious Effects of Mutual Inductance594.6Hand Calculations for Inductance604.6.1Inductance o
12、f a Wire Above a Return Plane604.6.2Inductance of Side-by-Side Wires614.6.3Inductance of Parallel Plates614.6.4Inductance of Microstrip634.6.5Inductance of Stripline634.7Summary64References65viiiContentsCHAPTER 5Transmission Lines675.1Introduction675.2General Circuit Model of a Lossy Transmission Li
13、ne675.2.1Relationship Between L and R705.2.2Relationship Between C and G705.3Impedance715.3.1Calculating Impedance725.4Traveling Waves735.4.1Propagation Constant745.4.2Phase Shift, Delay, and Wavelength755.4.3Phase Constant at High Frequencies When R and G Are Small785.4.4Attenuation795.4.5Neper and
14、 Decibel Conversion805.5Summary and Worked Examples82References86CHAPTER 6Return Paths and Power Supply Decoupling876.1Introduction876.2Proper Return Paths876.2.1Return Paths of Ground-Referenced Signals896.2.2Stripline906.3Stripline Routed Between Power and Ground Planes906.3.1When Power Plane Volt
15、age Is the Same as Signal Voltage906.3.2When Power Plane Voltage Differs from Signal Voltage936.3.3Power System Inductance946.4Split Planes, Motes, and Layer Changes956.4.1Motes956.4.2Layer Changes986.5Connectors and Dense Pin Fields986.5.1Plane Perforation996.5.2Antipads996.5.3Nonfunctional Pads102
16、6.5.4Guidelines for Routing Through Dense Pin Fields1036.6Power Supply Bypass/Decoupling Capacitance1056.6.1Power Supply Integrity1066.6.2Distributed Power Supply Interconnect Model1106.7Connecting to Decoupling Capacitors1126.7.1Via Inductance1126.8Summary114References115CHAPTER 7Serial Communicati
17、on, Loss, and Equalization1177.1Introduction1177.2Harmonic Contents of a Data Stream117Contentsix7.2.1Line Spectra1197.2.2Combining Harmonics to Create a Pulse1207.2.3The Fourier Integral1227.2.4Rectangular Pulses with Nonzero Rise Times1237.3Line Codes1257.4Bit Rate and Data Rate1267.5Block Codes U
18、sed in Serial Transmission1287.6ISI1307.6.1Dispersion1307.6.2Lone 1-Bit Pattern1317.7Eye Diagrams1327.8Equalization and Preemphasis1347.8.1Preemphasis1347.8.2Passive Equalizers1377.8.3Passive RC Equalizer1397.9DC-Blocking Capacitors1407.9.1Calculating the Coupling Capacitor Value1427.10Summary145Ref
19、erences146CHAPTER 8Single-Ended and Differential Signaling and Crosstalk1498.1Introduction1498.2Odd and Even Modes1498.2.1Circuit Description of Odd and Even Modes1508.2.2Coupling Coefficient1538.2.3Stripline and Microstrip Odd- and Even-Mode Timing1558.2.4Effects of Spacing on Impedance1578.3Multic
20、onductor Transmission Lines1588.3.1Bus Segmentation for Simulation Purposes1598.3.2Switching Behavior of a Wide Bus1608.3.3Simulation Results for Loosely Coupled Lines1618.3.4Simulation Results for Tightly Coupled Lines1628.3.5Data-Dependent Timing Jitter in MulticonductorTransmission Lines1648.4Dif
21、ferential Signaling, Termination, and Layout Rules1658.4.1Differential Signals and Noise Rejection1658.4.2Differential Impedance and Termination1668.4.3Reflection Coefficient and Return Loss1708.4.4PWB Layout Rules When Routing Differential Pairs1728.5Crosstalk1738.5.1Coupled-Line Circuit Model1758.
22、5.2NEXT and FEXT Coupling Factors1778.5.3Using Kbto Predict NEXT1788.5.4Using Kfto Predict FEXT1798.5.5Guard Traces1798.5.6Crosstalk Worked Example180 xContents8.5.7Crosstalk Summary1828.6Summary182References183CHAPTER 9Characteristics of Printed Wiring Stripline and Microstrips1859.1Introduction185
23、9.2Stripline1859.2.1Time of Flight1869.2.2Impedance Relationship Between Trace Width,Thickness, and Plate Spacing1879.2.3Mask Biasing to Obtain a Specific Impedance1899.2.4Hand Calculation of Zo1899.2.5Stripline Fabrication1919.3Microstrip1939.3.1Exposed Microstrip1949.3.2Solder Mask and Embedded Mi
24、crostrip1969.4Losses in Stripline and Microstrip1979.4.1Dielectric Loss1999.4.2Conductor Loss1999.5Microstrip and Stripline Differential Pairs2019.5.1Broadside Coupled Stripline2019.5.2Edge-Coupled Stripline2049.5.3Edge-Coupled Microstrip2059.6Summary206References207CHAPTER 10Surface Mount Capacitor
25、s20910.1Introduction20910.2Ceramic Surface Mount Capacitors20910.2.1Dielectric Temperature Characteristics Classification20910.2.2Body Size Coding21110.2.3Frequency Response21210.2.4Inductive Effects: ESL21410.2.5Dielectric and Conductor Losses: ESR21510.2.6Leakage Currents: Insulation Resistance218
26、10.2.7Electrical Model21910.2.8MLCC Capacitor Aging22010.2.9Capacitance Change with DC Bias and Frequency22110.2.10MLCC Usage Guidelines22210.3SMT Tantalum Capacitors22310.3.1Body Size Coding22310.3.2Frequency Response22410.3.3Electrical Model22510.3.4Aging22510.3.5Effects of DC Bias, Temperature, a
27、nd Relative Humidity225Contentsxi10.3.6Failure of Tantalum Capacitors22610.3.7ESR and Self Heating: Voltage and Temperature Derating22710.3.8Usage Guidelines22710.4Replacing Tantalum with High-Valued Ceramic Capacitors228References230Appendix: Conversion Factors231About the Author233Index235xiiConte
28、ntsPrefaceThis is a book for engineers designing high-speed circuit boards. To the signal integ-rity engineer, this book will be a handbook of formulas and terminology as well as arefresher of basic electrostatic and electromagnetic principals. The high-speed cir-cuit designer will find this book an
29、 easy entry into the electromagnetics and physicsof high-speed signaling. It introduces concepts fundamental to high-speed signaling,such as lossy transmission line behavior, skin effect, and the characteristics of lami-nates and surface mount capacitors. The focus throughout is on the effects of di
30、elec-tric and conductor loss on signal quality, with a particular emphasis on serialdifferential signaling. Coupling between transmission lines (especially in the contextof crosstalk and odd/even modes) is discussed. Besides being useful in serial signal-ing, this has application to multiconductor b
31、usses.Reflections on transmission lines are only superficially covered in this text. Thistopic has been extensively covered in the literature, and the reader of this book isassumed to be familiar with the creation and mitigation of reflections on transmis-sion lines. However, the proper routing and
32、termination of differential pairs has notbeen as well covered in the literature and so is discussed in Chapter 8.Similarly, power supply decoupling has been thoroughly discussed elsewhere,so the coverage in this book is brief. Instead, the focus here is on managing returnpaths (something often not w
33、ell covered) and the electrical characteristics andbehavior of capacitors. The material in Chapter 10 is a concise catalog of essentialelectrical characteristics of discrete capacitors, with a focus on surface mounttechnology.The fundamentals of resistance, capacitance, inductance, and loss calculat
34、ionspresented in Chapters 25 are illustrated with practical worked examples that maybe used as templates to solve similar problems.Many simple formulas are presented to allow hand calculation of resistance,capacitance, inductance, and impedance. These types of calculations are helpful indeveloping i
35、ntuition and in approximating beforehand the results to be expectedfromfieldsolvingsoftware,circuitsimulationtools,andlaboratorymeasurements.Extensive references are given at the end of each chapter, providing the inter-ested reader the opportunity to dig deeper. The references intentionally span cl
36、assic,older works (some of which were written in the 1950s, but most of the older onesare from the 1960s and 1970s) as well as modern works. The older references arevaluable, as they are the original works often cited by others, sometimes without theproper context. Although long out of print, the se
37、lected older references are gener-ally available secondhand and are worthy additions to the signal integrity engineerslibrary. Particular mention is made of Johnsons Transmission Lines and Networksxiii(published in 1950, referenced in Chapter 2) and Skillings Electrical EngineeringCircuits (1965, se
38、e the references in Chapter 3) and Transient Electric Currents(1952). These books are succinct and in my view remain unmatched. Miners Linesand Electric Fields for Engineers (1996, first referenced in Chapter 3) is the one elec-tromagnetics textbook every signal integrity engineer should have in his
39、 or herlibrary.Im indebted to my friends and coworkers for their support, encouragement,and help during the creation of this book. Special mention must be made of the assis-tance, perspective, and advice provided by my colleagues Jeff Cooper, Ernie Grella,and Tim Haynes. Special thanks also goes to
40、Fahrudin Alagic for his many monthsof precise laboratory measurements that support the material appearing in Chapters57. Im grateful to all of those who suffered through early versions of the manu-script for their constructive remarks. Im also obliged to the anonymous reviewer forhis insightful comm
41、ents. All of these comments were most helpful and have resultedin an improved text. Of course, any inaccuracies or errors that made it into the textare my doing and in no way reflect on the reviewers.Finally, Im especially grateful to my wife Ann for her understanding, patience,encouragement, and un
42、flagging support throughout the many long hours it took tocreate this work. This book would not have been possible without her.xivPrefaceC H A P T E R1Characteristics and Construction ofPrinted Wiring Boards1.1IntroductionThis is a book about high-speed signaling on printed wiring boards (PWBs). The
43、physical construction of PWBs determines the conductors resistance (discussed inChapter 2), its self capacitance (covered in Chapter 3) and inductance (Chapter 4),and the coupling to neighboring conductors (Chapters 5 and 9). At the high fre-quencies of interest in this book, these electrical primit
44、ives appear on a PWB as dis-tributed rather than lumped elements, giving rise to transmission line behavior.It is thus necessary for the high-speed circuit designer to have an understandingof how PWBs are constructed and a sense of the trade-offs fabricators must makewhen manufacturing high-density,
45、 high-layer count PWBs. This chapter summa-rizes those characteristics impacting the electrical characteristics of PWBs and intro-duces some of the terminology used in the PWB design industry.The larger PWB fabricators provide design for manufacturability (DFM) docu-ments (see 1, 2 to cite just two
46、examples) that detail the dimensional and many ofthe practical requirements necessary to create PWB artwork for their facility. Thesedocuments are helpful in understanding the practical state of the art in such thingsas via size, layer count, and trace width and spacing and can act as a primer to th
47、oseunfamiliar with PWB technology. Additional underlying detail that is somewhatgeneral in nature may be found in 3, 4.1.2Unit SystemThe PWB industry nearly universally uses an inched-based measuring system ratherthan the metric system. Trace width and length and dielectric thickness are thusspecifi
48、ed in decimal fractions of an inch, as are most component dimensions. How-ever, many micopackage dimensions (most notably the pin or ball pitch) are speci-fied with metric millimeters, and the trace thickness is specified in ounces (relatingto the amount of copper plating, as described in Section 1.
49、4). The Appendix tabu-lates some common conversion factors, but here its noted that 1m = 39.37008 inand 1 mil = 0.001 in. Therefore, 1 mil = 0.002539 0.00254 cm = 0.02539 0.0254 mm.Example 1.1A ball grid array micropackage (BGA) has solder balls on a 1-mm pitch. What is thepitch in mils?1SolutionRef
50、erring to Appendix A, to convert from inches to millimeters, the value in inches ismultiplied by 25.4. The 1-mm ball pitch therefore is equivalent to:125 4mm.mm/in=39.37 103in = 39.37 mils. As there are not precisely 39.37 in per meter, the con-version factor is not precisely 25.4 mm/in. This error
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