Printed circuit board design using AutoCAD

335 Pages·1998·15.318 MB·English

by  Chris Schroeder

Printed Circuit Board Desig n
Using AutoCAD
Chris Schroeder
Newnes
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Library of Congress Cataloging-in-Publication Data
Schroeder, Chris, 1954
Printed circuit board design using AutoCAD / Chris Schroeder.
p. cm. -- (The EDN series for design engineers)
Includes bibliographical references and index.
ISBN 0-7506-9834-9 (alk. paper)
1. Printed circuits--Design and construction--Data processing.
2. AutoCAD (Computer file) 3. Computer-aided design. I. Title.
II. Series.
TK7868.P7S344 1997
621.3815' 31--dc21 97-22001
CIP
British Library Cataloguing-in-Publication Data
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10 9 8 7 6 5 4 3 2 1
Printed in the United States of America
To Dr. Heinz Schroeder,
who encouraged his son's dreams
The EDN Series for Design Engineers
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F. Imdad-Haque Inside PC Card: CardBus and PCMCIA Design
C. Schroeder Inside OrCAD
J. Lenk Simplified Design of IC Amplifiers
J. Lenk Simplified Design of Micropower and Battery Circuits
J. Williams The Art and Science of Analog Circuit Design
J. Lenk Simplified Design of Switching Power Supplies
V. Lakshminarayanan Electronic Circuit Design Ideas
J. Lenk Simplified Design of Linear Power Supplies
M. Brown Power Supply Cookbook
B. Travis and I. Hickman EDN Designer's Companion
J.Dostal Operational Amplifiers, Second Edition
T. Williams Circuit Designer's Companion
R. Marston Electronics Circuits Pocketbook: Passive and Discrete Circuits (Vol. 2)
N. Dye and H. Granberg Radio Frequency Transistors: Principles and Practical
Applications
Gates Energy Products Rechargeable Batteries: Applications Handbook
T. Williams EMC for Product Designers
J. Williams Analog Circuit Design: Art, Science, and Personalities
R. Pease Troubleshooting Analog Circuits
I. Hickman Electronic Circuits, Systems and Standards
R. Marston Electronic Circuits Pocket Book: Linear ICs (Vol. 1)
R. Marston Integrated Circuit and Waveform Generator Handbook
I. Sinclair Passive Components: A User's Guide
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Content s
Preface xv
Chapter 1 . Introduction to PCB Design 1
PCB Classifications 1
PCB Manufacturing Considerations 4
Solder Mask over Bare Copper Process 6
Bare Board Electrical Test 1 4
Historical Overview of PCB Design Techniques 1 5
Introduction of Computer Aided Design and Manufacturing 1 6
Photoplotting of PCB Artwork 1 7
Numerically Controlled PCB Drilling 1 8
Evolution of PCB Design Tools 1 9
Impact of Manufacturing Requirements on PCB Design 21
Application of AutoCAD for PCB Design 22
Overview of the PCB Design Process Using AutoCAD 23
Floor Planning Metrics 23
PCB Design Rules 24
Trace Width and Spacing Requirements 28
Board Outline and Component Placement 30
Routing Connections 32
Final Steps in the Design Process and Postprocessing 35
Conclusion 35
Chapter 2. Schematic Drafting 37
Introduction to Electronic Schematics 37
Reference Designators 37
Part Descriptions 40
Symbols for Electronic Parts 43
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vi Contents
Special Schematic Symbols 56
Preferred Schematic Drafting Practices 59
Schematic Flow 59
Signal Naming Conventions 61
Title Block, Revision Block, and Notes 63
Hidden IC Power Pins 65
Schematic Organization and Planning 67
Schematic Drafting Tutorial Exercise 68
Drafting the Schematic 69
Generating the Bill of Materials 71
Importing Bill of Materials Files into Microsoft Excel 74
Importing Schematic Graphics into Microsoft Word 76
Guidelines for Drawing Schematics with AutoCAD 76
Conclusion 77
Chapter 3. Single Sided PCB Design 79
Introduction to the Tutorial Design 79
Structured Design Approach 83
Pad Blocks 86
Part Blocks 89
Starting the Tutorial Exercise 91
Setting Up Layers 92
Drawing the Board Outline 93
Placing Components 94
Trace Routing 96
Introduction to the AutoPADS Utilities 99
Manufacturing Documentation 99
Extracting NC Drill Data 99
Running AutoDRIL to Generate Excellon Data 102
AutoDRIL Conversion Options 102
X and Y Offset Entry 103
CDF Filename Entry 103
AutoDRIL Error Messages 104
AutoDRIL Limitations 104
Examining the Excellon NC Drill Data File 104
Drill Detail Drawing 105
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Contents vii
Assembly Drawing 107
Board Artwork 107
AutoCAD Configuration 109
AutoCAD Limitations 110
AutoCAD Binary ADI Plotting Considerations 11 1
Gerber Output from AutoPADS 11 1
Aperture Assignments 112
Plotting and Conversion Considerations 112
Generating the Binary ADI Plot Files 113
Silkscreen Artwork 114
Solder Side Artwork 114
Solder Mask Artwork 114
Running AutoPADS to Generate Gerber Data 115
ADI Resolution Setup 115
Binary ADI Plot Filename Entry 116
AutoPADS Error Messages 116
Converting the Plot Files with AutoPADS 116
Sending Files to a Service Bureau 117
Drill Detail Drawing File 118
PCB README.DOC File 118
Compressing Files with PKZIP 120
Conclusion 120
Chapter 4. Double Sided PCB Design 121
Introduction to the Tutorial Design 121
Structured Design Approach 125
Starting the Tutorial Exercise 126
Rules for Lead Spacing, Hole Diameter,and Pad Size 127
Creating a New Pad Block 129
Creating a New Part Block 134
Setting Up Layers 137
Drawing the Board Outline 138
Placing Components 138
Trace Routing 141
Using the AutoPADS Utilities 144
Manufacturing Documentation 145
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viii Contents
Extracting NC Drill Data and Running AutoDRIL 145
Drill Detail and Assembly Drawings 145
Board Artwork 148
Preparing Files for a Service Bureau 149
Conclusion 151
Chapter 5. Surface Mount PCB Design 153
Introduction to the Tutorial Design 155
Structured Design Approach for SMT 157
SMT Pads 160
SMT Part Blocks 165
Recommended SMT Design Practices 166
Starting the Tutorial Exercise 168
Setting Up Layers 168
Drawing the Board Outline 169
Placing Components 170
Trace Routing 172
Using the AutoPADS Utilities 175
Manufacturing Documentation 176
Extracting NC Drill Data and Running AutoDRIL 176
Drill Detail and Assembly Drawings 176
Board Artwork 179
Silkscreen Artwork 181
Component and Solder Side Artwork 181
Solder Mask Artwork 182
SMT Solder Paste Artwork 182
Preparing Files for a Service Bureau 183
Conclusion 185
Chapter 6. Importing Gerber Files for
Manufacturing Documentation 187
Obtaining Gerber Data 187
AutoCAD DXB and DXF Format 188
Starting the DXB Tutorial Exercise 189
Using the GBR2DXB Conversion Utility 190
Gerber Format Setup 191
Contents ix
AutoCAD Layer Setup 191
Layer Names by D Code Option 191
Gerber Filename Entry 191
Conversion Process 191
Batch Conversion 192
Stopping the Program 192
Error Messages 192
Common Problems 193
Scale Factor Problems 193
Correcting the Origin for Imported Data 193
Editing Text in Imported Data 193
Accuracy Limitations 193
Completing the DXB Tutorial Exercise 194
Preparing the Drill Detail Drawing from DXB Data 195
Preparing the Assembly Drawing from DXB Data 197
Starting the DXF Tutorial Exercise 199
Using the GBR2DXF Conversion Utility 200
Aperture Assignments 201
Creating a New Aperture File 201
Editing an Aperture File 201
Gerber Format Setup 202
Gerber Filename Entry 202
AutoCAD Layer Setup 203
Conversion Options 203
Conversion Process 203
Stopping the Program 203
Error Messages 204
Common Problems 204
Scale Factor Problems 204
Correcting the Origin for Imported Data 205
Editing Text in Imported Data 205
Accuracy Limitations 205
Completing the DXF Tutorial Exercise 205
Preparing the Drill Detail Drawing from DXF Data 207
Preparing the Assembly Drawing from DXF Data 209
Conclusion 209