Complete PCB Design Using OrCad Capture and Layout (eBook)

FRONT COVER 1
COMPLETE PCB DESIGN USING ORCAD CAPTURE AND LAYOUT 2
COPYRIGHT PAGE 3
TABLE OF CONTENTS 4
INTRODUCTION 16
ACKNOWLEDGMENTS 20
CHAPTER 1: INTRODUCTION TO PCB DESIGN AND CAD 22
Computer-Aided Design and the OrCAD Design Suite 22
Printed Circuit Board Fabrication 23
PCB cores and layer stack-up 23
PCB fabrication process 25
Photolithography and chemical etching 26
Mechanical milling 29
Layer registration 30
Function of OrCAD Layout in the PCB Design Process 32
Design Files Created by Layout 35
Layout format files (.MAX) 35
Postprocess (Gerber) files 35
PCB assembly layers and files 35
CHAPTER 2: INTRODUCTION TO THE PCB DESIGN FLOW BY EXAMPLE 38
Overview of the Design Flow 38
Creating a Circuit Design with Capture 38
Starting a new project 38
Placing parts 41
Wiring (connecting) the parts 44
Creating the Layout netlist in Capture 44
Designing the PCB with Layout 46
Starting Layout and importing the netlist 46
Making a board outline 50
Placing the parts 52
Autorouting the board 53
Manual routing 53
Cleanup 55
Locking traces 55
Performing a design rule check 56
Postprocessing the board design for manufacturing 56
CHAPTER 3: PROJECT STRUCTURES AND THE LAYOUT TOOL SET 60
Project Setup and Schematic Entry Details 60
Capture projects explained 60
Capture part libraries explained 63
Understanding the Layout Environment and Tool Set 64
Board technology files 64
The AutoECO utility 65
The session frame and Design window 67
The toolbar 68
Controlling the autorouter 78
Postprocessing and layer details 81
CHAPTER 4: INTRODUCTION TO INDUSTRY STANDARDS 86
Introduction to the Standards Organizations 87
Institute for Printed Circuits (IPC-Association Connecting Electronics Industries) 87
Electronic Industries Alliance (EIA) 87
Joint Electron Device Engineering Council (JEDEC) 87
International Engineering Consortium (IEC) 88
Military Standards 88
American National Standards Institute (ANSI) 88
Institute of Electrical and Electronics Engineers (IEEE) 88
Classes and Types of PCBs 89
Performance classes 89
Producibility levels 89
Fabrication types and assembly subclasses 90
OrCAD Layout design complexity levels—IPC performance classes 90
IPC land pattern density levels 91
Introduction to Standard Fabrication Allowances 91
Registration tolerances 91
Breakout and annular ring control 91
PCB Dimensions and Tolerances 92
Standard panel sizes 92
Tooling area allowances and effective panel usage 93
Standard finished PCB thickness 93
Core thickness 94
Prepreg thickness 94
Copper thickness for PTHs and vias 94
Copper cladding/foil thickness 95
Copper Trace and Etching Tolerances 96
Standard Hole Dimensions 97
Soldermask Tolerance 98
End Note 98
Suggested reading 98
Other items of interest 98
CHAPTER 5: INTRODUCTION TO DESIGN FOR MANUFACTURING 100
Introduction to PCB Assembly and Soldering Processes 100
Assembly Processes 100
Manual assembly processes 100
Automated assembly processes (pick and place) 101
Soldering Processes 102
Manual soldering 102
Wave soldering 103
Reflow soldering 105
Component Placement and Orientation Guide 106
Component Spacing for Through-hole Devices 107
Discrete THDs 107
Integrated circuit through-hole devices 107
Mixed discrete and IC through-hole devices 107
Holes and jumper wires 107
Component Spacing for Surface-Mounted Devices 107
Discrete SMDs 107
Integrated-circuit SMDs 107
Mixed discrete and IC SMDs 107
Mixed THD and SMD Spacing Requirements 107
Footprint and Padstack Design for PCB Manufacturability 115
Land Patterns for Surface-Mounted Devices 115
SMD padstack design 117
SMD footprint design 120
Land Patterns for Through-hole Devices 122
Footprint design for through-hole devices 122
Padstack design for through-hole devices 124
Hole-to-lead ratio 124
PTH land dimension (annular ring width) 125
Clearance between plane layers and PTHs 127
Soldermask and solder paste dimensions 128
CHAPTER 6: PCB DESIGN FOR SIGNAL INTEGRITY 130
Circuit Design Issues Not Related to PCB Layout 130
Noise 130
Distortion 131
Frequency response 132
Issues Related to PBC Layout 132
Electromagnetic Interference and Cross Talk 132
Magnetic fields and inductive coupling 133
Loop inductance 136
Electric fields and capacitive coupling 138
Ground Planes and Ground Bounce 140
What ground is and what it is not 140
Ground (return) planes 143
Ground bounce and rail collapse 144
Split power and ground planes 146
PCB Electrical Characteristics 148
Characteristic impedance 148
Reflections 154
Ringing 158
Electrically long traces 160
Critical length 163
Transmission line terminations 164
PCB Routing Topics 165
Parts placement for electrical considerations 166
PCB layer stack-up 167
Bypass capacitors and fanout 172
Trace width for current carrying capability 172
Trace width for controlled impedance 174
Trace spacing for voltage withstanding 184
Trace spacing to minimize cross talk (3w rule) 184
Traces with acute and 90º angles 185
CHAPTER 7: MAKING AND EDITING CAPTURE PARTS 188
The Capture Part Libraries 188
Types of Packaging 189
Homogeneous parts 189
Heterogeneous parts 190
Pins 190
Part Editing Tools 191
The Select tool and settings 191
The pin tools 191
The graphics tools 192
The zoom tools 192
Constructing Capture Parts 192
Method 1: Constructing Parts Using the New Part Option (Design Menu) 193
Design example for a passive, homogeneous part 193
Design example for an active, multipart, homogeneous component 201
Assigning power pin visibility 204
Design example for a passive, heterogeneous part 205
Method 2: Constructing Parts with Capture Using the Design Spreadsheet 208
Method 3: Constructing Parts Using Generate Part from the Tools Menu 211
Method 4: Generating Parts with the PSpice Model Editor 213
Generating a Capture part library from a PSpice model library 214
Making and/or Obtaining PSpice Libraries for Making New Capture Parts 215
Downloading libraries and/or models from the Internet 216
Making a PSpice model from a Capture project 217
Adding PSpice templates (models) to preexisting Capture parts 227
Constructing Capture Symbols 229
CHAPTER 8: MAKING AND EDITING LAYOUT FOOTPRINTS 232
Introduction to the Library Manager 232
Introduction to Layout's Footprint Libraries and Naming Conventions 233
Layout's footprint libraries 234
Naming conventions 234
The Composition of Footprints 238
Padstacks 238
Obstacles 239
Text 241
Datums and insertion origins 241
The Basic Footprint Design Process 242
Working with Padstacks 247
Accessing existing padstacks 248
Editing padstack properties from the spreadsheet 249
Saving footprints and padstacks 250
Footprint Design Examples 252
Design example 1: a surface-mount footprint design 253
Design example 2: a modified through-hole footprint design 258
Using the Pad Array Generator 264
Introduction 264
Footprint design for PGAs 264
Footprint design for BGAs 269
Blind, buried, and microvias 279
Mounting holes 280
Printing a catalog of a footprint library 282
CHAPTER 9: PCB DESIGN EXAMPLES 284
Overview of the Design Flow 285
Example 1: Dual Power Supply, Analog Design 287
Initial design concept and preparation 288
Project setup and design in Capture 289
Defining the board requirements 306
Importing the design into Layout 309
Setting up the board 310
Prerouting the board 327
Autorouting the board 337
Finalizing the design 339
Example 2: Mixed Analog/Digital Design Using Split Power, Ground Planes 343
Mixed-signal circuit design in Capture 343
Power and ground connections to digital and analog parts 345
Connecting separate analog and digital grounds to a split plane 345
Using busses for digital nets 348
Defining the layer stack-up for split planes 349
Establishing a primary power plane 351
Creating split ground planes 355
Creating nested power planes with copper pours 357
Using anti-copper on plane layers 359
Setting up and running the autorouter 361
Moving a routed trace to a different layer 363
Adding ground planes and guard traces to routing layers 363
Defining vias for flood planes/pours 366
Setting the copper pour spacing 368
Stitching a ground plane manually 369
Using anti-copper obstacles on copper pours 370
Routing guard traces and rings 370
Example 3: Multipage, Multipower, and Multiground Mixed A/D PCB Design with PSpice 373
Project setup for PSpice simulation and Layout 375
Adding schematic pages to the design 377
Using off-page connectors with wires 379
Using off-page connectors with busses 380
Setting up multiple-ground systems 380
Setting up PSpice sources 381
Performing PSpice simulations 382
Preparing the simulated project for Layout 385
Assigning a new technology file 386
Placing parts on the bottom (back) of a board 386
Layer stack-up for a multiground system 386
Net layer assignments 388
Through-hole and blind via setup 388
Fanning out a board with multiple vias 388
Overriding known errors in Layout 391
Autorouting with the DRC/route box 391
Using forced thermals to connect ground planes 393
Using the AutoECO to update a board from Capture 393
Example 4: High-Speed Digital Design 397
Layer setup for microstrip transmission lines 401
Via design for heat spreaders 402
Constructing a heat spreader with copper area obstacles 403
Using free vias as heat pipes 403
Determining critical trace length of transmission lines 408
Routing controlled impedance traces 409
Moated ground areas for clock circuits 411
Routing curved traces 411
Gate and pin swapping 413
Stitching a ground plane with the free via matrix 416
Miscellaneous Items 418
Fixing bad pad exits 418
Design cache—cleanup, replace, update 419
Adding test points 421
Types of AutoECOs 422
Making a custom Capture template 424
Making a custom Layout technology/template file 424
Using the Stackup Editor 425
Using the Stackup Editor with an active board design 425
Using the Stackup Editor to set up a custom technology or template file 428
Submitting stack-up drawings with Gerber files 429
Adding solder thieves 429
Printing a footprint catalog from a PCB design 430
CHAPTER 10: POSTPROCESSING AND BOARD FABRICATION 432
The Circuit Design with OrCAD 432
Schematic design in Capture 432
The board design with Layout 434
Postprocessing the design with Layout 435
Fabricating the Board 438
Choosing a board house 438
Setting up a user account 438
Submitting Gerber files and requesting a quote 439
Annotating the layer types and stack-up 440
Receipt inspection and testing 443
Nonstandard Gerber files 443
CHAPTER 11: ADDITIONAL TOOLS 444
Using PSpice to Simulate Transmission Lines 444
Simulating digital transmission lines 445
Simulating analog signals 448
Using Microsoft Excel with a Bill of Materials Generated by Capture 448
Using the SPECCTRA Autorouter with Layout 450
Introduction to GerbTool 458
Opening a Layout-generated Gerber file with GerbTool 458
Making a .DRL file for a CNC machine 459
Panelization 464
Using the IPC-7351 Land Pattern Viewer 470
Using CAD Tools to 3-D Model a PCB 473
APPENDICES 476
Appendix A: Layout Technology Files 476
Appendix B: List of Design Standards 478
Appendix C: A Partial List of Packages and Footprints and Some of the Footprints Included in OrCAD Layout 480
Appendix D: Rise and Fall Times for Various Logic Families 492
Appendix E: Drill and Screw Dimensions 494
Appendix F: References by Subject 496
BIBLIOGRAPHY AND REFERENCES 512
INDEX 516
A 516
B 516
C 517
D 518
E 519
F 520
G 521
H 521
I 522
J 522
L 522
M 523
N 523
O 523
P 524
Q 525
R 525
S 526
T 527
U 528
V 528
W 528
X 529
Y 529
Z 529