R.J. Reynolds Vapor
`IPR2017-01117
`R.J. Reynolds Vapor v. Fontem
`Exhibit 1022-00001
`
`

`

`This book was set in Times Roman by Science Typographers, Inc.
`The editors were John Corrigan and John M. Morriss;
`the production supervisor was Louise Karam.
`The cover was designed by Tony Paccione.
`Project supervision was done by Science Typographers, Inc.
`Arcata Graphics/Halliday was printer and binder.
`
`PACKAGING OF ELE~ONIC SYSTEMS
`A Mechanical Engineering Approach
`
`Copyright © 1990 by McGraw-Hill, Inc. All rights reserved.
`Printed in the United States of America. Except as permitted under the
`United States Copyright Act of 1976, no part of this publication may be
`reproduced or distributed in any form or by any means, or stored in a data
`base or retrieval system, without the prior written permission of the
`publisher.
`
`1234567890 HAL HAL 9543210
`
`ISBN 0-07-015214-4
`
`Library of Congress Cataloging-in-Publication Data
`
`Dally, James W.
`Packaging of electronic systems: a mechanical engineering
`approach / James W. Dally.
`p. cm.--(McGraw-Hill series in mechanical engineering)
`Includes bibliographies and index.
`ISBN 0-07-015214-4
`1. Electronic packaging. I. Title. II. Series
`TKL7870.D25
`1990
`621.381’046--dc20
`
`89-12399
`
`Exhibit 1022-00002
`
`

`

`CONTENTS
`
`Preface
`List of Acronyms
`
`Part I Foundations of Mechanical Design
`of Electronic Systems
`
`Introduction
`1
`1.1 Goals and Objectives
`1.2 Mechanical Development in Design of Electronic Systems
`1.3 Mechanical Design Aspects of Packaging
`1.3.1 Connections
`1.3.2 Thermal Management
`1.3.3 Manufacturing
`1.3.4 Maintenance
`1.3.5 Shock and Vibration
`1.3.6 Ergonomics
`1.4 Range of Products
`1.5 Business Aspects
`References
`Exercises
`
`2 Electronic Components and Semiconductor
`Devices
`Introduction
`2.1
`2.2 Conductors, Insulators, and Semiconductors
`2.3 Extrinsic Semiconductors
`2.4 The P-N Junction
`
`ooo
`
`3
`
`3
`5
`7
`7
`9
`10
`11
`12
`13
`14
`15
`17
`17
`
`19
`
`19
`20
`22
`25
`
`vii
`
`Exhibit 1022-00003
`
`

`

`VIII CONTENTS
`
`2.5
`2.6
`
`2.7
`2.8
`2.9
`
`2.10
`2.11
`2.12
`2.13
`
`3
`3.1
`3.2
`3.3
`3.4
`3.5
`
`3.6
`3.7
`
`3.8
`3.9
`3.10
`3.11
`3.12
`3.13
`3.14
`
`Semiconductor Diodes
`Transistors
`2.6.1 Bipolar Transistors
`2.6.2 Metal Oxide Semiconductor Field Effect Transistors
`Comparison of Transistor Types
`Logic Gates
`Gate Technologies
`2.9,1 Bipolar Gates
`2.9.2 MOSFET Gates
`Power Delay Product
`¯ Scale of Integration
`I/O Count and Rent’s Rule
`Memory Devices
`References
`Exercises
`
`Circuit Analysis
`Introduction
`The Analog Method of Analysis
`Transmission Line Theory
`Sinusoidal Signal Propagation on a Transmission Line
`Termination of Transmission Lines
`3.5.1 Open Circuit Termination
`3.5.2 Short Circuit Termination
`3.5.3 Transmission Lines with Arbitrary Termination Impedance
`Pulse Propagation along a Low Loss Transmission Line
`Effect of Termination on Pulse Propagation
`3.7.1 Open-Ended Line
`3.7.2 Short Circuit at the Load End
`3.7.3 Arbitrary Resistive Load at the Line End
`Influence #f a Finite Rise Time on Pulse Shape
`Arbitrary Resistive Loads at Both Ends of the Line
`Reflections from Discontinuities
`,Characteristic Impedance of Conductors
`Transmission Lines on Circuit Boards
`Resistance of Printed Circuit Lines
`Logic Gate Characteristics
`References
`Exercises
`
`Part II
`
`Packaging
`
`4
`4.1
`4.2
`
`First Level Packaging--The Chip Carrier
`Introduction
`Types of Chip Carders
`4.2.1 Pin In-Hole Chip Carders
`4.2.2 Leaded Surface-Mounted Chip Carriers
`4.2.3 Leadless Surface-Mounted Chip Carriers
`
`,
`
`26
`28
`29
`33
`36
`37
`40
`40
`43
`44
`45
`47
`49
`52
`52
`
`55
`55
`56
`58
`60
`62
`62
`63
`64
`65
`66
`66
`67
`69
`71
`73
`76
`78
`80
`82
`83
`88
`88
`
`93
`
`95
`
`95
`97
`99
`103
`106
`
`Exhibit 1022-00004
`
`

`

`4.3 Chip-to-Chip Cartier Mounting
`4.4 Chip-to-Chip Carrier Connections
`4.4.1 Automated Wire Bonding
`4.4.2 Tape-Automated Bonding
`4.4.3 Flip-Chip Connections to the Chip Carrier
`4.5 Multichip Packages
`4.5.1 Hybrids
`4.5.2 The Thermal Conduction Module
`4.6 First Level Packaging for Other Components
`4.6.1 Resistors
`4.6.2 Capacitors
`4.6.3 Diodes
`References
`Exercises
`
`,
`
`5 Second Level Packaging--Circuit Boards
`Introduction
`5.1
`5.2 Types of Printed Circuit Boards
`5.3 Circuit Board Materials
`5.3.1 Copper Foil
`5.4 Footprint Design
`5.5 Component Placement
`5.5.1 Placement for Enhanced Wirability
`5.5.2 Placement for F~nhanced Reliability
`5.6 Routing Methods
`5.6.1 Surface Organization
`5.6.2 Design Rules for Routing
`5.6.3 Automatic Routing Programs
`5.6.4 Wiring Algorithms
`References
`Exercises
`
`6
`6.1
`6.2
`
`Production of Printed Circuit Boards
`Overview of the Production Process
`Preparation of Master Layouts
`6.2.1 Manual Preparation of the Artwork
`6.2.2 Automated Artwork by Photoplotting
`6.3 Lithography
`6.3.1 Photoresist Printing
`6.3.2 Etching
`6.4 Drilling and Punching
`6.5 Lamination
`Plating
`6.6
`6.6.1 Plated through Holes
`6.6.2 Panel and Pattern Plating
`6.6.3 Tin-Lead or Solder Plating
`6.6.4 Gold Plating
`Solder Masks
`Pretinning
`
`6.7
`6.8
`
`CONTENTS
`
`107
`108
`109
`113
`113
`115
`115
`116
`119
`119
`123
`125
`126
`126
`
`129
`129
`134
`135
`143
`144
`148
`149
`153
`158
`158
`162
`166
`168
`175
`176
`
`182
`182
`184
`184
`186
`187
`187
`190
`192
`195
`197
`198
`198
`201
`202
`202
`204
`
`Exhibit 1022-00005
`
`

`

`l
`
`X CONTENTS
`
`6.9
`6.10
`6.11
`
`6.12
`6.13
`
`Assembly
`Solder and Solder Fluxes
`Solder Methods
`6.11.1 Solder Pots and Wave Soldering
`6.11.2 Vapor Phase Soldering
`Cleaning and Coating
`Ceramic Circuit Boards
`6.13.1 Ceramic Substrate Materials and Processes
`6.13.2 Metallization
`6.13.3 Glasses as Dielectrics and Seals
`References
`Exercises
`
`7 Third Level Packaging
`7.1
`Introduction
`7.2 Connectors
`7.2.1 Connector Pins, Contacts, and Inserts
`7.2.2 Connector Resistance and Plating Materials
`7.2.3 Connector Forces
`7.3 Back Panel, Wire Wrap Boards, and Cable Connections
`7.3.1 Back Panels
`7.3.2 Wire Wrap Panels
`7.3.3 Cable Connected Boards
`7.4 Power Supplies and Bus Bars
`7.4.1 Batteries as Power Supplies
`7.4.2 Power Supplies
`7.4.3 Bus Bars
`7.5 Card Racks
`7.5.1 Card Guides and Retainers
`7.6 Electronic Enclosures
`7.6.1 Commercial Enclosures
`7.6.2 Military Enclosures
`7.7 Wires and Cabling
`7.7.1 Wire Conductors
`7.7.2 Wire Insulation
`7.7.3 Wire to Cable
`7.7.4 Wire Shielding
`7.8 Fans and Cold Plates
`7.8.1 Fans and Fan Noise
`7.8.2 Cold Plates and Cold Rails
`References
`Exercises
`
`Part III
`8
`8.1
`8.2
`
`Analysis Methods
`
`Thermal Analysis Methods-- Conduction
`Introduction
`Reliability
`8.2.1 Failure Rate
`
`204
`208
`210
`211
`212
`213
`214
`215
`217
`219
`220
`221
`
`224
`
`224
`225
`227
`233
`239
`241
`241
`243
`246
`248
`248
`249
`250
`253
`254
`256
`256
`259
`264
`265
`267
`270
`272
`273
`275
`278
`278
`279
`
`285
`
`287
`
`287
`288
`288
`
`Exhibit 1022-00006
`
`

`

`CONTENTS
`
`xi
`
`8.3
`
`8.2.2 Component ReLiability
`8.2.3 System ReLiabiLity
`Steady State Heat Transfer by Conduction
`8.3.1 One-Dimensional Heat Transfer
`8.3.2 General Equations Governing Conduction
`8.3.3 Heat Flow in Cylindrical Packages
`8.3.4 Heat Flow through Layered Composites
`8.3.5 Heat Transfer by Convection and Conduction
`8.3.6 Contact Resistance
`8.3.7 Conduction from Small Area Heat Sources
`8.4 Transient Conduction
`8.5 Heat Transfer from Chip to Chip Carrier
`8.5.1 Commercial Description of Heat Transfer in Chip Carriers
`8.6 Conduction in Circuit Cards
`8.6.1 Conduction in the Plane of the Circuit Board
`8.6.2 Conduction through the Thickness of a Circuit Board
`8.6.3 Conduction Cooling with a Heat Frame
`8.7 Cold Plates and Cold Rails
`8.8 Advanced CooLing Methods
`8.8.1 The Thermal Conduction Module
`8.8.2 Pease and Tuckerman Experiments
`References
`Exercises
`
`291
`292
`296
`296
`299
`300
`301
`302
`303
`305
`308
`311-
`315
`317
`317
`318
`321
`324
`326
`328
`329
`329
`329
`
`9.1
`9.2
`
`9 Thermal Analysis Methods-- Radiation
`and Convection
`Introduction
`Laws Governing Heat Transfer by Radiation
`9.2.1 Shape Factors and Energy Exchange
`9.2.2
`Influence of Surface Emmissivity on Radiation Heat Transfer
`9.2.3 The Radiation Heat Transfer Coefficient
`9.3 Convection Heat Transfer
`9.4
`Free or Natural Convection
`9.4.1 Free Convection on a Vertical Plate with Laminar Flow
`9.4.2 Free Convection on a Vertical Plate with Turbulent Flow
`9.4.3 An Approximate Relation for Free Convection for the
`Vertical Plate
`9.4.4 Free Convection Heat Transfer with Other Shapes
`Forced Air Convection Coefficients
`9.5.1 Laminar Flow over a Flat Plate
`9.5.2 Turbulent Flow over a Flat Plate
`9.5.3 Combined Laminar and Turbulent Flow over a Flat Hate
`9.5.4 Convection from a Flat Plate with a Uniform Heat Flux
`Forced Convection with Internal Flow--Ducts
`9.6.1 Average Velocity and Temperature
`9.6.2 Temperature Difference
`9.7 Heat Transfer and Friction Coefficients for Duct Flow
`9.7.1 Summary
`
`9.5
`
`9.6
`
`334
`334
`335
`335
`339
`342
`344
`345
`348
`349
`
`350
`350
`352
`352
`355
`356
`357
`357
`359
`361
`362
`364
`
`Exhibit 1022-00007
`
`

`

`CONTENTS
`
`9.8 Air Flow in Electronic Enclosures
`9.8.1 Fluid Statics
`9.8.2 Enclosure Impedance and Fan Characteristics ¯
`9.8.3 Fan Placement in the Enclosure
`9.8.4 An Electrical Analogy for Head Loss Determination
`References
`Exercises
`
`lO
`10.1
`10.2
`
`10.3
`10.4
`10.5
`10.6
`
`10.7
`
`10.8
`10.9
`
`10.10
`
`10.11
`
`Analysis of Vibration of Electronic Equipment
`Introduction
`Vibrating Systems with a Single Degree of Freedom
`10.2.1 Free Vibrations
`10.2.2 Forced Vibrations
`10.2.3 Transmission Coefficients
`Isolation of Systems from Exciting Forces
`Vibration of Axial Leaded Components
`Fatigue Analysis of Component Leads
`Vibration of Circuit Boards
`10.6.1
`Improving the Vibration Behavior of Circuit Boards
`10.6.2 Stresses in Circuit Boards Due to Vibration
`10.6.3 Stresses in Copper Signal Traces
`Lead Wire Failures on Vibrating Printed Circuit Boards
`10.7.1 Stresses in Solder Joints
`The Theorem of Castigliano
`Fasteners
`10.9.1 Strength of Fasteners
`10.9.2 Bolt Preload
`Fastened Joints Loaded in Tension
`10.10.1 Stress and Fatigue Analysis
`Fastened loints Loaded in Shear
`References ,
`Exercises
`
`Index
`
`365
`365
`367
`370
`373
`375
`376
`
`382
`382
`386
`386
`390
`391
`394
`399
`401
`404
`408
`410
`412
`413
`417
`419
`421
`424
`425
`425
`426
`428
`430
`430
`
`437
`
`Exhibit 1022-00008
`
`

`

`CHAPTER
`
`1
`
`INTRODUCTION
`
`1.1 GOALS AND OBJECTIVES
`
`This book has been prepared to serve as a text for students and entry level
`persons beginning to design electronic systems. The coverage begins at the
`interface between electronic engineering and mechanical engineering and pertains
`to the mechanical and manufacturing issues that arise in developing a new
`electronic system. The treatment is quite broad, starting with the integrated
`circuits (the chip) and proceeding through the many levels of packaging involved
`in developing a complete electronic system. The material is often highly descrip-
`tive, particularly when compared to the mathematical treatments presented in
`more mature subjects in mechanics or mechanical design. However, the descrip-
`tive material is important to introduce the essential vocabulary, which is full of
`acronyms, and to present the wide array of electronic components that the
`mechanical or electrical engineer must deal with in the design process.
`To organize the material and to facilitate understanding by the reader, this
`book is divided into three parts. Part 1 covers background material including
`semiconductor physics, analog circuit theory, digital circuit theory and transmis-
`sion line theory. The objective of this background information is to give the
`engineers involved in packaging the basic understanding as to why and how
`electronic circuits operate. Experience has shown that this background informa-
`tion greatly enhances communication between the mechanical and electrical
`engineering functions in a development project and enhances the opportunity for
`parallel product development instead of sequential development.
`Part 2 involves packaging beginning at the first level where the chip is
`housed in its carrier and extending through the higher levels to the design of the
`cabinets and instrument panels. The word "packaging" is poorly understood by
`
`3
`
`Exhibit 1022-00009
`
`

`

`4
`
`FOUNDATIONS OF MECHANICAL DESIGN OF ELECTRONIC SYSTEMS
`
`Wafer
`
`Edge connector
`
`Substrate
`
`/,,s
`
`Back panel
`
`~Chip Carrier
`
`Printed
`circuit
`board
`
`Chassis
`
`Cabinet
`
`FIGURE 1.1
`A schematic illustration of several levels of packaging involved in an electronic system.
`
`the engineering community where it is often confused with the design of a
`container to prevent damage during shipment of a product. Packaging of elec-
`tronic systems refers to the placement and connection of many electronic and
`electromechanical components (sometimes thousands) in an enclosure that pro-
`tects the system from the environment and provides easy access for routine
`maintenance. An example, which describes some of the important features of
`packaging, is illustrated in Fig. 1.1. Note that the packasing process starts with
`the chip, which has been fabricate on a wafer of silicon. After testing, the chip is
`housed in a chip carder and small wires are used to electrically connect the chip
`to the carrier (the first level of connections). Next, the chip carriers are placed on
`a circuit board and connected together (second level) with wiring traces that have
`been formed by photoetching the circuit board. Connectors on the circuit boards
`are then inserted into contacts on a back panel, which carries the higher level
`connections that permit communication from one circuit board to the next.
`Cables are shown that connect the power supply to the back panel and that bring
`the input and output (I/O) signal into the unit. Finally, the entire array of circuit
`boards, back panels, power supplies and cables are housed in a cabinet. The
`packaging aspect of the design of an electronic system is extremely important
`
`Exhibit 1022-00010
`
`

`

`INTRODUCrlON ~
`
`because about one-half of the cost of a system is involved in packaging and the
`other half of the cost is for the individual electronic devices.
`Part 3 deals with the environmental aspect of packaging. In addition to
`carefully packing thousands of electronic components into a stylish and func-
`tional cabinet, packaging involves the protection of these components from the
`environment. Heat management is perhaps the most important of the environ-
`mental considerations because the operating temperature of the chips markedly
`affects the reliability of the circuit board and the availability of a system. For
`electronic systems destined for use in the field by either the military or by
`industry, shock and vibration represent harsh environments that must be accom-
`modated in the design of the hardware. Finally, noise is an important considera-
`tion, particularly in air-cooled equipment where one or more fans are used to
`move significant volumes of air.
`In this presentation, simple examples that emphasize basic theoretical
`approaches and which illustrate sound design concepts will be selected. In actual
`practice, the real problems will be much more complex but the applicable theory
`and the design concepts are the same. In many design offices special codes or
`software exists for handling some of the complexity associated with very large
`electronic systems. We will recognize some of these codes in this book but we will
`not describe them in any detail becat~se they change rapidly with time.
`
`1.2 MECHANICAL DEVELOPMENT
`IN DESIGN OF ELECI’RONIC SYSTEMS
`
`A mechanical development department is usually responsible for packaging
`electronic systems in most industrial firms involved in producing an extensive line
`of electronic products. Because an electronic system is usually quite complex,
`involving several different disciplines, multidepartment organi:,ations are usually
`established to handle the logical flow of paper, CAD tapes and other information
`generated in a typical development. An example of one organization is shown in
`Fig. 1.2. The development process is initiated (in large firms at least) by corporate
`planners who identify customer needs and predict market trends and technologi-
`cal advances. With this information as a basis they prepare the specifications for
`
`Corporate
`~tanning
`
`Test and
`development development manufacture ~- Shipping
`integrate
`
`Software
`development
`
`FIGURE 1.2
`Typical development organiTation showing information flow and discipline interfaces.
`
`Exhibit 1022-00011
`
`

`

`CHAPTER
`
`5
`
`SECOND
`LEVEL
`PACKAGING,
`CIRCUIT
`BOARDS
`
`5.1 INTRODUCTION
`
`The circuit board is a major element in the mechanical design of an electronic
`system because it is the primary field replaceable unit that embodies many very
`important functions which include:
`
`1. A mounting surface for most of the components.
`2. Soldering pads to facilitate first to second level and second to third level
`connections. These pads also provide the mounting areas for attaching the
`components to the board.
`3. Wiring channels to provide conduits for chip-to-chip connections.
`4. A test bed to provide accessible and organized points which are probed in
`making circuit checks.
`5. A marking surface to assist in identification of the components placed on the
`board in assembly. Other board markings support manufacturing operations.
`6. A controlled profile on one side of the card with additional markings to
`support field maintenance and service.
`
`129
`
`Exhibit 1022-00012
`
`

`

`l~0
`
`PACKAGING
`
`Each of these functions of the circuit board will be discussed individually.
`The circuit board serves as a mounting plane for the various components such as
`ICs, resistors, capacitors and diodes. The board provides a method of fixation,
`either pin in-hole or surface mount, for the component attachment to the board.
`This attachment essentially fixes the position of each component for the life of
`the product. The board acting as a planar mounting structure also mitigates
`shock and vibration forces that are transmitted to the components through the
`board. In this sense the PCB, like the chip carrier, acts to protect the compo-
`nents. As the circuit boards are usually relatively thin planes with large lateral
`dimensions, the weight of the components that can be supported is limited.
`Usually heavy components, like transformers and displays, are mounted directly
`on the chassis since they can impart forces large enough to damage the board in a
`shock or vibratory environment.
`The circuit board is usually a laminate with a copper cladding on one or
`both sides. The cladding is configured by an etching process to any shape
`required to provide attachment pads and the wiring for the electronic compo-
`nents. Footprints etched from the copper cladding, as illustrated in Fig. 5.1,
`provide soldering surfaces that are precisely aligned to match the corresponding
`
`0,025
`
`0.020
`
`~~"-" typ ~
`
`0. 5
`
`~ 0.075
`
`0.030
`typ
`
`~ 0.075
`
`0.550
`
`0.350
`
`0.105
`
`FIGURE 5.1
`Footprint showing etched copper pads
`positioned on the circuit board to provide
`soldering surfaces for an 18 J leaded chip
`carrier. (Courtesy of Texas Instruments,
`Inc.) "
`
`Exhibit 1022-00013
`
`

`

`SECOND-LEVEL PACKAGING--CIRCUIT BOARDS 131
`
`through hole
`
`Copper foil land
`for solder surface
`
`g
`
`channel
`
`5.2
`channels are formed between etched copper leads.
`
`or pads from the components. The size and shape of these soldering pads
`to a large degree the formation and geometry of the solder joints
`the chip cartier leads to the board. Other solder pads are provided to
`to the leads for the I/O cables or connectors that carry power or signals to
`PCBs in the system.
`The circuit board also supports the wiring traces that lead between the
`located on the board. These wiring traces are arranged in wiring
`as illustrated in Fig. 5.2. The wiring traces are etched from the copper
`and a typical circuit board may support 1000 to 10,000 individual traces
`from one wiring point to another. Wiring traces include conductors for
`signal, which are small in cross-sectional area because of the low currents
`in switching the logic gates. Traces for conducting the power to the
`are much larger in width to accommodate the higher currents
`to operate each device. For some circuit boards that contain several
`layers, the wiring planes are embedded on interior layers. The power
`ground wiring (V÷ and V-), in multilayer construction, is provided with
`solid copper planes dedicated to supplying the required current. The
`and ground planes also serve to control the characteristic impedance of the
`lines located on adjacent signal planes.
`When the circuit board is completely assembled, as shown in Fig. 5.3, it
`many different types of components and perhaps 100 or more devices.
`failure of at least one of these devices over the life of the product is
`it is important that the circuit board be field replaceable. The defective
`should be removable and easy to repair with equipment found at a service
`
`Exhibit 1022-00014
`
`

`

`FIGURE 5.3
`An assembled circuit board with a wide variety of components that can be probed in testing.
`
`(Courtesy of Eldre Components, Inc.)
`
`center. In repairing ~e board, it is necessary to test many different locations on
`the board with a voltmeter or an oscilloscope probe to ascertain which, if any, of
`the components have failed. To facilitate probing and subsequent repair, the
`devices should have lead structures that are accessible to a voltage probe. Also,
`the leads should be accessible for specialized soldering tools that can melt the
`solder at all of the chip carrier joints simultaneously to permit rapid removal of
`the devices without damage to the board and the remaining devices.
`Since the copper cladding on the circuit board material can be etched to
`any configuration, it is easy to mark the circuit card to facilitate the manufactur-
`ing process. The example presented in Fig. 5.4a shows markings identifying the
`location various ICs employed in assembling this board. The markings illustrated
`in Fig. 5.4b indicate the part number, revisions and the date of circuit board
`production. It is clearly easy to mark the board with component outlines, part
`numbers, production dates, lot numbers or any other information that will assist
`in production control, component assembly and inventory control.
`To facilitate maintenance, the shape of the card is modified to prevent
`
`improper substitution in field substitution and replacement. The profile of the
`circuit card along the edge where the connector pads are located is usually slotted
`or notched (see Fig. 5.4c). These slots act as keys and permit the correct board to
`
`Exhibit 1022-00015
`
`

`

`SECOND-LEVEL PACKAGING--CI~.CUIT BOARDS 133
`
`FIGURE 5.4
`Circuit board marking and profiling
`to assist in manufacturing and main-
`tenance. (a) Markings show IC
`numbers and locations. (b) Mark-
`ings showing part number and date
`of production. (c) Profiled edge of
`the card forms a key insuring inser-
`tion of only the correct card.
`(Courtesy of Gerber Scientific Instru-
`ment Co.)
`
`(c)
`
`Exhibit 1022-00016
`
`

`

`134 PACKAGING
`
`be inserted into the edge connector but prohibit the incorrect substitution of the
`wrong part number. Markings of the part number and the probe sites with
`reference voltages can also be placed on the card to assist maintenance personnel
`in servicing the card either in the field or in the repair facility.
`
`5.2 TYPES OF PRINTED CIRCUIT BOARDS
`
`There are three common types of printed circuit boards in use today including
`the single-sided, double-sided and multilayer board. These three types of boards
`can be fabricated from polymeric composites or from ceramics. The selection of a
`specific type of board depends to a large degree on circuit density and the
`number of connections that must be made between the components mounted on
`
`the board. For low density product where only 10-20 components with limited
`I/O are involved, low cost, polymeric composite, single-sided boards, which have
`circuit lines on only one side, are often used. Holes are drilled or punched into
`these laminates to support pins from the components; however, these holes are
`not plated and the solder joint is limited in size to the region between the pin and
`the top surface soldering pad.
`For intermediate density product, double-sided boards are employed, which
`incorporate circuit lines on both the top and bottom surface of the laminate. The
`circuits on the opposite sides of the board are connected as necessary by plated
`through holes (PTHs) that serve as transverse conductors (called vias) through
`the thickness of the board. An example of a plated through hole is shown in Fig.
`5.5. The PTH is also used to contain the pins for components that use pin
`in-hole-type mounting. In these cases the pin and the hole wall are soldered
`together and the solder joint encompasses the top and bottom solder pads and
`fills the entire hole.
`Multilayer boards (MLBs) are fabricated from polymeric composites con-
`taining several layers of laminates, each layer having two wiring planes. Typical
`construction of the multilayer board is shown in Fig. 5.6. The layers are prepared
`in a sandwich with a pre-impregnated epoxy-glass sheet, known as prepreg,
`positioned between each layer. The epoxy in the prepreg at this stage is only
`
`Di~ :ectric
`laminate
`
`Copper plating
`
`Copper soldering pad
`
`FIGURE 5.5
`Plated through hole connecting the top and bottom surfaces of a double-sided circuit board.
`
`Exhibit 1022-00017
`
`