1
`
`APPLE 1014
`
`1
`
`APPLE 1014
`
`

`

`THE MULTILAYER
`PRINTED CIRCUIT BOARD
`HANDBOOK
`
`Edited by
`J. A. SCARLETT
`
`j
`
`ELECTROCHEMICAL PUBLICATIONS LIMITED
`1985
`
`2
`
`

`

`ELECTROCHEMICAL PUBLICATIONS LIMITED
`8 Barns Street, Ayr, Scotland
`
`©
`Electrochemical Publications Ltd.
`1985
`
`All Rights Reserved
`No part of this book may be reproduced in any form
`without written authorisation from the publishers
`
`ISBN 0 901150 15 0
`
`Typesetting by Brian Robinson, North Marston, Bucks
`Printed and bound in Great Britain by
`Anchor Brendon Ltd, Tiptree, Essex
`
`inc
`int
`am
`oft
`
`bo
`an
`me
`ap
`all
`wt
`ffil
`gel
`.Pa
`WC
`of
`on
`SU
`
`as
`sp
`ex
`so
`th,
`nc
`ar,
`th
`
`to
`be
`ar
`m
`ar
`m
`
`3
`
`

`

`, J. A. Scarlett
`
`he
`so
`of
`,le
`es
`
`~4
`r.
`:ls
`
`,1
`·1
`
`l
`
`I
`
`i
`
`l
`I
`'
`l
`
`i
`,
`!
`k
`¥!
`f
`t
`
`CONTENTS
`
`PREFACE
`
`CHAPTER ONE
`Introduction
`
`1.1
`1.1.l
`1.1.2
`1.1.3
`1.1.4
`1.1.4.1
`1.1.4.2
`1.1.4.3
`1.1.4.4
`1.1.4.5
`1.1.4.6
`
`General
`Printed Circuit Boards
`History
`The Electrical Importance of Multilayer Boards
`Costs and Applications
`Costs of Boards
`Costs of Alternatives to Boards
`Choice of Board Type
`Thermal Problems
`System Architecture and Board Type
`Probable Need for Multilayers
`
`1.2
`1.2.1
`1.2.1.1
`1.2.1.2
`1.2.1.3
`1.2.2
`1.2.3
`1.2.4
`1.2.5
`1.2.6
`1.2.6.1
`1.2.6.2
`1.2.7
`1.2.8
`1.2.9
`1.2.10
`1.2.10.1
`1.2.10.2
`1.2.10.3
`1.2.10.4
`1.2.10.5
`
`1.3
`1.3 .1
`1.3.2
`1.3.2.1
`1.3.2.1.1
`1.3.2.1.2
`1.3.2.1.3
`1.3.2.1.4
`1.3.2.1.5
`
`' Types of Multilayer Board
`Access Hole Boards
`Access Hole Boards with Internal Connections
`Disadvantages of Access Hole Boards
`Solder Buttons
`Plated Pillar Boards
`Staked Boards
`Bonded Through-hole Plated Boards
`Buried Via-hole Boards
`Sequential Buried Via-hole Boards
`Two-level Buried Via Holes
`Multiple Level Buried Via Holes
`Double-double Boards
`Double-multilayer Boards
`Flexi-rigid Boards
`Other Forms of Multilayer Interconnects
`Etched and Welded Interconnects
`Three Dimensional Planar Co-axial Interconnects
`Etched and Filled Boards
`Moulded Boards
`Multi wire
`
`Production of Through-hole Plated Multilayers
`General
`Preparation of Inner Layers
`Film Work
`Incoming Photo Tools
`Film Types and Labels
`Step and Repeat
`Borders
`Environmental Control
`
`V
`
`1
`2
`3
`3
`3
`5
`6
`7
`8
`9
`
`11
`11
`12
`14
`14
`15
`16
`16
`17
`18
`18
`18
`19
`19
`20
`20
`20
`21
`22
`22
`23
`
`23
`23
`24
`24
`24
`25
`27
`28
`29
`
`4
`
`

`

`viii
`
`1.3.2.1.6
`1.3.2.2
`1.3.2.3
`1.3.2.4
`1.3.2.5
`1.3.2.6
`1.3.3
`1.3.4
`1.3.5
`1.3.6
`1.3.7
`
`1.4
`1.4.1
`1.4.2
`1.4.? 1
`1.4.2.2
`1.4.2.3
`1.4.3
`1.4.4
`1.4.5
`1.4.6
`1.4.7
`1.4.8
`
`1.5
`1.5.1
`1.5.2
`1.5.3
`1.5.3.1
`1.5.3.2
`1.5.3.3
`
`1.6
`1.6.1
`1.6.2
`1.6.3
`1.6.4
`l .G.5
`
`1.7
`1. 7 .1
`1.7.2
`1.7 .3
`1.7.3.1
`1.7.3.2
`1.7.4
`1.7 .5
`1.7.6
`1.7.6.1
`1.7 .6.2
`
`Contents
`
`Film Punching
`Planning
`Tape Making
`Laminate Preparation
`Inner Layer Printing and Etching
`Preparation for Bonding
`Bonding
`Drilling
`Smear Removal
`Through-hole Plating and Outer Layers
`Finishing
`
`Production Varian.ts
`Pillar Plated Boards
`BurieJ Via-hole Boards
`Inner Layer Plating
`Lay Up am.I BuuJing
`Pre-filling of Buried Holes
`Sequential Buried Via Holes
`Double Boards
`Flexi-rigids
`Mass Lamination
`Semi-additive Multilayers
`Bonding of Heat Ladders
`
`' Build and Thickness
`Prepreg Layers
`Board Thickness
`Practical Builds
`Four Layer Boards
`Higher Build Boards
`Buried Via-hole and Flexi-rigid Builds
`
`Handling Thin Laminates
`Storage and Transport
`Cutting
`Picking Up Thin Laminates
`Conveyorised Machines
`Plating Fixtures
`
`Reliability of Multilayer Boards
`Delamination
`Outgassing
`Short Circuits
`Design and Manufacturing Faults
`Growth of Short Circuits
`Carbonisation
`Warping
`Damage to Through-plated Holes
`Mechanical Damage
`Z-Plane Expansion
`
`CHAPTER TWO
`Laminates and Prepregs
`l. S. Saito
`
`2.1
`2.1.1
`
`2.2
`
`Introduction
`Use of Epoxy Materials in Laminate and Prepreg Manufacture
`
`Epoxy Materials
`
`30
`33
`33
`34
`34
`34
`34
`38
`38
`38
`41
`
`41
`41
`42
`42
`44
`44
`45
`45
`45
`46
`46
`46
`
`48
`48
`49
`50
`50
`50
`52
`
`52
`53
`53
`53
`54
`54
`
`54
`55
`55
`56
`56
`56
`58
`58
`58
`58
`59
`
`61
`61
`
`62
`
`5
`
`

`

`30
`33
`33
`34
`34
`34
`34
`38
`38
`38
`1-1
`
`1-1
`i1
`u
`i2
`i4
`l4
`l5
`l5
`l5
`l6
`l6
`l6
`
`l8
`l8
`l9
`;o
`;o
`;o
`;2
`
`;2
`;3
`;3
`;3
`;4
`i4
`
`i4
`i5
`i5
`i6
`i6
`i6
`;3
`;3
`;3
`8
`9
`
`1
`1
`
`2
`
`Contents
`
`Bisphenol-A Epichlorohydrin
`Addition of Epoxy Novolacs
`Control of Flow
`Glass Transition Temperature
`
`Non-epoxy Materials
`Polyimide
`B-Triazine
`Modified Epoxies
`Problems with Brominated Materials
`
`Glass Cloth
`
`Prepreg Manufacture
`Treater Types
`Mechanical Techniques
`Thermal Techniques
`OperaLiug ComliLiuus
`Process Control
`Prepreg Testing
`Gel Time Test
`Flow Test
`Scaled Flow Testing
`Resin Content Test
`Volatile Content Test
`Dicyaniamid Test
`Test for Ageing
`
`Laminate Manufacture
`Influential Parameters and Their Measurement
`Dimensiona1 Stability
`Copper Adhesion
`Dielectric Constant
`Thickness
`Solvent Resistance
`Baking
`Manufacturing Problems
`Smear Removal
`Drilling
`Degree of Cure
`Solutions to Laminate Problems
`General
`Use of Thin Copper Foil
`Methods of Promoting Adhesion
`Black Oxide
`Double Treatment of Copper
`
`2.2.1
`2.2.2
`2~.3
`2.2.4
`
`2.3
`2.3.1
`2.3.2
`2.3.3
`2.3.4
`
`2.4
`
`2.5
`2.5.1
`2.5.1.l
`2.5,1.2
`2.5.1.3
`2.5.2
`2.5.3
`2.5.3.1
`2.5.3.2
`2.5.3.3
`2.5.3.4
`2.5.3.5
`2.5.3.6
`2.5.3.7
`
`2.6
`2.6.1
`2.6.1.1
`2.6.1.2
`2.6.1.3
`2.6.1.4
`2.6.1.5
`2.6.1.6
`2.6.2
`2.6.2.1
`2.6.2.2
`2.6.2.3
`2.6.3
`2.6.3.1
`2.6.3.2
`2.6.4
`2.6.4.1
`2.6.4.2
`
`CHAPTER THREE
`The Manufacture of Woven Glass Fabrics
`D. J. Vaughan and C. G. Herschdorfer
`
`3.1
`
`3.2
`3.2.1
`3.2.2
`3.2.3
`3.2.4
`3.2.5
`3.2.6
`3.2.7
`
`Introduction
`
`Glass Fibre ProducLion
`Glass Composition
`Yarn
`Warping
`Slashing
`Entering
`Quilling
`Weaving
`
`IX
`
`62
`62
`, 62
`63
`
`63
`63
`63
`64
`64
`
`64
`
`64
`65
`65
`65
`65
`66
`66
`66
`67
`67
`68
`68
`68
`69
`
`69
`69
`69
`70
`71
`71
`71
`72
`72
`72
`72
`73
`73
`73
`74
`74
`74
`75
`
`76
`
`76
`79
`80
`83
`84
`84
`84
`86
`
`6
`
`

`

`X
`
`3.2.8
`
`3.3
`
`3.4
`
`3.5
`
`3.6
`
`Contents
`
`Heat Cleaning
`
`Finishing of Glass Fabric
`
`The Coupling Agent-resin Interface
`
`The Application of Finished Glass Fabric to Multilayer Prepreg and
`Circuit Laminates
`
`Conclusion
`
`CHAPTER FOUR
`Photoreslsts mu.l Plwtom~chanical Printinl!
`D. Simpkins
`
`4.1
`
`4.2
`4.2.1
`4.2.2
`4.2.3
`4.2.4
`4.2.5
`
`4.3
`4.3.1
`
`4.4
`4.4.1
`4.4.2
`4.4.3
`4.4.4
`4.4.5
`
`4.5
`4.5.1
`4.5.2
`4.5.3
`
`4.6
`4.6.1
`4.6.2
`4.6.3
`4.6.3.1
`4.6.3.2
`
`4.7
`4.7.1
`4.7.2
`4.7.3
`r1.7.4
`4.7.5
`
`4.8
`
`History and Philosophy
`
`The Materials
`Components
`Resins
`Sensitisers
`Additives
`Solvents
`
`Substrate Preparation
`Cleanliness Testing
`
`Application Methods
`Whirl Coating
`Dip Coating
`Spray Coating
`Roller Coating
`Curtain Coating
`
`Drying
`Air Drying
`Static Oven Drying
`Conveyorised Infra-red/ Air Ovens
`
`Exposure
`Fixed Source
`Travelling Source
`Exposure Time
`Using a Step Tablet
`Precautions
`
`Development
`Negative Resists
`Positive Resists
`Developing Equipment
`Tnspection and Touch-up
`Resist Removal·
`
`Future Developments
`
`CHAPTER FIVE
`Dry Film Photoresists
`L. R. Wallig
`
`5.1
`5: 1.1
`
`General
`Introduction
`
`86
`
`88
`
`90
`
`91
`
`93
`
`95
`
`96
`
`97
`98
`98
`98
`99
`99
`
`99
`100
`
`100
`100
`101
`101
`101
`103
`
`104
`104
`104
`104
`
`105
`105
`106
`106
`106
`107
`
`107
`107
`108
`108
`109
`109
`
`110
`
`111
`111
`
`7
`
`

`

`Contents
`
`Dry Film Resist Structure
`How the Dry Film System Functions
`Comparison with Other Image Transfer Processes
`Dry Film Resist Cost
`
`Photopolymer Make-up
`Properties Determined by the Photoresist Composition
`Classification of Dry Film Resists
`The Dry Processable Photoresists
`Mechanism
`
`Selection of a Dry Film Resist Image Transfer System
`Solvent Processable Resisls
`Aqueous Processable Resist System
`
`Dry Film Photoresist Processing
`General
`
`The PCB Fabrication Process
`The Substrate
`Substrate Prelamination Cleaning
`The Copper Surface
`Resist Lamination
`Exposure (Photopolymerisation)
`Exposure Control/Measurement
`Effect of Actinic Intensity
`Spectral Sensitivity of the Resist
`Exposure Technology Trends
`Development of the Resist Image
`Development Mechanism
`Solvent Development
`Aqueous Development
`Future Trends
`Resist Removal (Stripping)
`
`Other Dry Film Resist Developments
`Dry Film Solder Mask
`Phototape
`Photo Chemical Machining (Chemical Milling)
`
`Dry Film Resist Processes
`Subtractive Processes
`Print and Etch
`Print, Plate and Etch
`Print and Etch with Copper Plated-through Holes (Tenting)
`Additive Processes
`Fully Additive Process
`Semi-additive Process
`
`Troubleshooting Guide
`
`5.1.2
`5.1.3
`5.1.4
`5.1.5
`
`5.2
`5.2.l
`5.2.2
`5.2.3
`5.2.3.1
`
`5.3
`5.3.1
`5.3.2
`
`5.4
`5.4.1
`
`5.5
`5.5.1
`5.5.2
`5.5.3
`5.5.4
`5.5.5
`5.5.5.1
`5.5.5.2
`5.5.5.3
`5.5.5.4
`5.5.6
`5.5.6.1
`5.5.6.2
`5.5.6.3
`5.5.6.4
`5.5.7
`
`5.6
`5.6.1
`5.6.2
`5.6.3
`
`5.7
`5.7 .1
`5.7.1.1
`5.7.1.2
`5.7.1.3
`5.7.2
`5.7.2.1
`5.7.2.2
`
`5.8
`
`CHAPTER SIX
`Accurate Screen Printing for Multilayer PCBs
`C. Wulter
`
`6.1
`
`6.2
`6.2.1
`6.2.2
`6.2.3
`
`Introduction
`
`Factors Influencing Printing Quality
`The Original Filmwork
`The Screen Frame
`Mesh Tension
`
`Xl
`
`111
`114
`114
`115
`
`115
`116
`117
`117
`117
`
`120
`Pl
`122
`
`l??.
`122
`
`123
`123
`123
`124
`125
`128
`129
`131
`132
`133
`133
`133
`135
`135
`136
`137
`
`138 0
`138
`138
`138
`
`139
`139
`139
`139
`140
`140
`140
`141
`
`142
`
`154
`
`155
`155
`156
`156
`
`7
`3
`3
`3
`}
`}
`
`}
`)
`
`)
`)
`l
`l
`l
`l
`
`i
`i
`i
`i
`
`5
`5
`5
`7
`
`7
`7
`3
`3
`}
`
`}
`
`)
`
`8
`
`

`

`xii
`
`6.2.4
`6.2.5
`6.2.5.1
`6.2.5.2
`6.2.5.3
`6.2.5.4
`6.2.6
`6.2.7
`6.2.8
`6.2.8.1
`
`6.J
`
`Contents
`
`The Mesh Itself
`Photomechanical Stencils
`Direct Stencils
`Indirect Stencils
`Direct/Indirect Stencils
`Summary of Stencil Types
`Exposure
`Setting Up
`The Ink
`Summary of Ink Mixing
`
`Conclusion
`
`CHAPTER SEVEN
`Etching, Ekhauts and Etching Machines
`Tfl. !Macleod Ross
`
`7.1
`
`7.2
`7.2.1
`7.2.2
`7.2.3
`7.2.4
`7.2.5
`7.2.6
`
`7.3
`
`7.4
`
`Introduction
`
`Etchants
`Ferric Chloride
`Ammonium Persulphate
`Chromic/Sulphuric Acid Mixtures
`Cupric Chloride
`Alkaline Etchants/ Ammoniacal Etchants
`Hydrogen Peroxide Etchants
`
`Etching Machines
`
`Conclusion
`
`CHAPTER EIGHT
`Lay-up and Bonding
`J. A. Scarlett
`
`8.1
`8.1.1
`8.1.1.1
`8.1.1.2
`8.1.1.3
`8.1.1.4
`8.1.1.5
`8.1.1.6
`8.1.2
`8.1.2.1
`8.1.2.2
`8.1.2.3
`8.1.2.4
`8.1.3
`8.1.4
`8.1.4.1
`8.1.4.2
`8.1.4.3
`8.1.4.4
`8.1.4.5
`
`8.2
`8.2.1
`8.2.2
`8.2.3
`
`Inner Layer Preparation
`Plain Multilayer Boards
`Tooling Holes for Printing
`Tooling Holes for Bonding
`Milling or Punching Tooling Slots
`Film Tooling Set
`Location of Films
`Copper Around Tooling Holes
`Buried Via-hole and Sequential Multilayer Boards
`Panel Plating
`Pattern Plating
`Hole Filling
`Surface Dressing
`Single-sided Layers
`Oxidation
`Need for Oxidation
`Bond Strength
`Oxidising
`Cleaning and Drying
`Conveyorised Spray Oxidising
`
`Prepreg Preparation
`Storage
`Cutting and Testing
`Punching
`
`158
`159
`159
`160
`160
`. 160
`161
`161
`163
`164
`
`165
`
`166
`
`168
`168
`170
`170
`171
`171
`172
`
`174
`
`179
`
`181
`181
`181
`182
`183
`183
`184
`185
`185
`185
`185
`186
`186
`187
`187
`187
`187
`188
`188
`189
`
`189
`189
`190
`190
`
`9
`
`

`

`Contents
`
`Tooling
`Bonding Pins
`Pin Patterns
`Material Movement
`Pin Sizes
`Press Plates
`Liners
`
`Stacking
`The Lay-up Area
`Lay-up
`Single Board
`Multiple Boards
`Hamlliug of Laminates and l'rcprcgs
`
`Packing
`Krafl Paµe1
`Conformal Sheet
`Blotting Paper
`Bonding Under Vacuum
`
`The Action of Prepreg During Bonding
`The Bonding Operation
`Inter-relation of Bonding Parameters
`Board Thickness
`Filling Low Areas
`
`Bonding Defects
`Types of Defects
`Telegraphing
`Unbonded Voids
`Air Inclusions
`Delamination
`Surface Defects
`Flatness of Boards
`Thickness Variations
`Bowing, Warping or Twisting
`Measling and Crazing
`Avoidance of Defects
`
`8.3
`8.3.1
`8.3.1.l
`8.3.1.2
`8.3.1.3
`8.3.2
`8.3.3
`
`8.4
`8.4.1
`8.4.2
`8.4.2. l
`8.4.2.2
`8.4.3
`
`8.5
`8.:5.1
`8.5.2
`8.5.2.1
`8.5.2.2
`
`8.6
`8.6.1
`8.6.2
`8.6.3
`8.6.3.1
`
`8.7
`8.7 .1
`8.7. l.l
`8.7.1.2
`8.7.1.3
`8.7.1.4
`8.7.1.5
`8.7.2
`8.7.2.1
`8.7.2.2
`8.7.2.3
`8.7.3
`
`CHAPTER NINE
`Presses and Press Cycles
`J. A. Scarlett and C. T. Morrisroe
`
`9.1
`9.1.1
`9.1. l.l
`9.1.1.2
`9.1.1.3
`9.1.1.4
`9.1.2
`9.1.2.1
`9.1.2.2
`9.1.2.3
`9.1.3
`9.1.3.1
`9.1.3.2
`9.1.3.3
`9.1.3.4
`9.1.4
`
`Presses
`Introduction
`General Press Features
`Press Plattens
`Press Frame
`Installation of a Press
`Heating
`Electric Heating
`Steam Heating
`Oil Heating
`Cooling
`Water Cooling
`Air Purging
`Chilled Oil Cooling
`Summary of Heating and Cooling Methods
`Pressing
`
`I
`
`l
`
`Xlll
`
`191
`191
`191
`192
`192
`193
`194
`
`195
`195
`195
`19'5
`196
`196
`
`196
`196
`198
`198
`198
`
`199
`199
`199
`200
`200
`
`201
`201
`201
`201
`202
`202
`202
`202
`202
`203
`204
`204
`
`205
`205
`205
`206
`206
`208
`208
`208
`209
`209
`210
`211
`212
`213
`213
`213
`
`10
`
`

`

`xiv
`
`9.1.4.1
`9.1.4.2
`9.1.5
`9.1.6
`
`9.2
`9.2.1
`9.2.1.1
`9.2.1.2
`9.2.1.3
`9.2.2
`9.2.2.1
`9.2.2.2
`9.2.2.3
`9.2.2.4
`9.2.3
`9.2.4
`9.2.4.1
`9.2.4.2
`
`9.3
`9.3.1
`9.3.2
`
`9.4
`9.4.1
`9.4.2
`9.4.2.1
`9.4.2.2
`9.4.2.3
`9.4.2.4
`9.4.3
`9.4.3.1
`9.4.3.2
`
`Contents
`
`"
`
`Hydraulic System
`Intermediate Plattens
`Instrumentation
`Loading and Unloading
`
`Press Cycles
`General
`Resin Behaviour
`Kiss Pressure Cycles
`Single Pressure Cycles
`Temperature Cycles
`Cold Start Cycles.
`HoL SLa1 l Cycles
`Packing
`Post Cure Baking
`Automation of Press Cycles
`Misunderstandings
`Temperature
`Pressure
`
`Transfer Presses
`General
`Transfer Press Construction
`
`Press Capacity and Use
`Durability and Flexibility
`Capacity
`Board Size
`Number of Blanks Bonded Per Cycle
`Multiple Imaging of Boards
`Overall Cycle
`Unstacking
`Removing Tooling Pins
`Opening the Press Plates
`
`CHAPTER TEN
`Machining Multilayer Circuit Boards
`I K HaggP anrl .T. C. Mather
`
`10.l
`
`10.2
`
`10.3
`10.3 .1
`10.3.2
`10.3.3
`10.3.4
`10.3.5
`10.3.6
`
`Introduction
`
`Fundamental Considerations
`
`Detailed Considerations
`Tool Geometry
`Tool Material
`Design Properties of the Tool
`Chip Removal
`Workpiece Materials
`Equipment
`
`10.4
`10.4.1
`10.4.1.1
`10.4.1.2
`10.4.1.3
`10.4.1.3.1
`10.4.1.3.2
`10.4.1.3.3
`10.4.1.4
`10.4.1.5
`
`Machining to Establish Geometry
`Co11lou1 Ruuting
`Acceptability Criteria
`Conclusions from Machining Theory
`Routing Bits
`Materials
`Geometry
`Tool Life
`Contour Routing Equipment
`Workoiece
`
`213
`213
`214
`214
`
`218
`218
`218
`220
`221
`222
`222
`222
`224
`225
`226
`226
`226
`227
`
`228
`228
`231
`
`232
`232
`232
`232
`233
`234
`234
`234
`234
`235
`
`236
`
`236
`
`238
`238
`239
`241
`241
`241
`242
`
`243
`243
`243
`244
`247
`247
`248
`248
`249
`250
`
`11
`
`

`

`Contents
`
`Material Properties
`MLCB Design
`Support and Rigidity
`Operating Parameters
`Troubleshooting Contour Routing Problems
`Chamfering
`
`Machining to Establish Interconnection
`Drilling
`Acceptability Criteria ·
`Conclusions from Drilling Theory
`Drill Bits
`Drill Bit Materials
`Drill Geometry
`Tool Life
`Drilling Equipment
`Workpiece
`Materials
`MLCBDesign
`Support
`Operating Parameters
`Finishing Operations
`Troubleshooting Drilling Problems
`Dielectric Smear
`Inner Pad Distortion
`Drill Withdrawal Distortion
`Entry and Exit Copper Burrs
`Rough Hole Walls
`Fishbowl Hole Walls
`Drilling Delamination
`Nailhead
`Pad Ripout
`Dielectric Tearout
`Troubleshooting Summary
`Counter boring.
`
`Advanced Machining Techniques
`Mechanical Methods
`Chemical Methods
`Laser Methods
`. ArlaptivP C-:ontrol
`
`10.4.1.5.l
`10.4.1.5.2
`10.4.1.5.3
`10.4.1.6
`10.4.1.7
`10.4.2
`
`10.5
`10.5.1
`10.5.1.1
`10.5.1.2
`10.5.1.3
`10.5.1.3.1
`10 . .5.1.3.2
`10.5.1.3.3
`10.5.1.4
`10.5.1.5
`10.5.1.5.l
`10.5.1.5.2
`10.5.1.5.3
`10.5.1.6
`10.5.1.7
`10.5.1.8
`10.5.1.8.1
`10.5.1.8.2
`10.5.1.8.3
`10.5.1.8.4
`10.5.1.8.5
`10.5.1.8.6
`10.5.1.8.7
`10.5.1.8.8
`10.5.1.8.9
`10.5.1.8.10
`10.5.1.9
`10.5.2
`
`10.6
`10.6.1
`10.6.2
`10.6.J
`10.6.4
`
`CHAPTER ELEVEN
`Smear Removal Methods
`D.R. Witherell
`
`11.1
`11.1.1
`11.1.2
`11.1.3
`11.1.4
`
`11.2
`11.2. l
`11.2.2
`11.2.3
`
`Introduction
`Definition of Drill Smear
`Causes of Smear Formation
`Materials Subject to Smear
`Procedures Leading to a Reduction in Hole Wall Smearing
`
`Criteria for Selection of a Smear Removal. Process
`LarninaLe MaLerial
`Process Capabilities
`Customer Preference
`
`11.3
`11.3.1
`11.3.1.1
`11.3.1.1.1
`
`Smear Removal Methods
`Chemical Methods for Smear Removal
`Sulphuric Acid Systems
`Mechanism of Removal
`
`r ..
`
`l
`
`xv
`
`250
`252
`252
`252
`254
`257
`
`258
`258
`258
`261
`265
`1,6:,
`265
`267
`268
`268
`268
`269
`271
`271
`273
`274
`275
`275
`275
`277
`278
`281
`281
`282
`285
`286
`286
`287
`
`288
`289
`289
`289
`290
`
`292
`292
`292
`293
`293
`
`293
`293
`294
`295
`
`295
`295
`295
`296
`
`12
`
`

`

`xvi
`
`11.3.1.1.2
`11.3.1.1.3
`11.3.1.1.4
`11.3.1.1.5
`11.3.1.2
`11.3.1.3
`11.3.2
`11.3.3
`11.3.3.1
`11.3.3.2
`11.3.3.3
`11.3.3.4
`
`11.4
`
`11.5
`
`Contents
`
`Equipment Required
`Typical Process Procedure
`Process Parameters
`Control Procedures
`Chromic Acid Systems
`Strong Base Systems
`Mechanical Methods for Smear Removal
`Gas Plasma
`Principles of Operation
`Materials Subject to Plasma Etch
`Equipment Requirements
`Typical Process Procedures
`
`Inspection Methods
`
`Summary
`
`CHAPTER TWELVE
`Electroless Plating
`D. A. Luke
`
`12.1
`
`12.2
`
`12.3
`
`12.3.1
`12.3.2
`12.3.3
`12.3.4
`12.3.5
`
`12.3.6
`
`12.4
`12.4.1
`12.4.2
`
`12.5
`
`12.6
`12.6.1
`12.6.2
`12.6.3
`12.6.3.1
`12.6.3.2
`12.6:3.3
`
`12.7
`12. 7 .1
`12.7.2
`12.7 .3
`12. 7.4
`12.7.5
`
`Introduction
`
`History of Through-hole Plating of Multilayer Printed Circuits
`
`Special Problems Posed by Multilayer Circuits Compared with
`Conventional Double-sided Boards
`Drill Smear on Innerlayer Connections
`Over Etching of lnnerlayers
`Surface which Rejects Catalyst
`Bleaching of Black Oxide Layers
`Thick Boards Requiring High Throwing Power Electroplating
`Solutions
`Thermal Shock of Plated Deposits
`
`Alternative to Through-hole Plating for Multilayer Printed Circuits
`Vacuum Metallising
`Consecutive Deposition of Metal and lnsulant
`
`Special Laminates and Composites
`
`Typical Sequences for Electroless Plating
`Special Conditioners for Epoxy-glass which has been Back-etched
`Pre-etch
`Activation
`Two-stage Activation
`Single-stage Activation
`Catalyst Coverage
`
`Electroless Copper Deposition
`Basic Constituents
`Available Processes
`Analysis
`Deposit Properties
`Plant
`
`CHAPTER 13
`Electroplating
`D. A. Luke
`
`13 .1
`
`Copper Plating
`
`296
`297
`299
`300
`300
`301
`301
`302
`302
`302
`302
`102
`
`303
`
`304
`
`306
`
`306
`
`307
`307
`308
`308
`309
`
`309
`309
`
`310
`310
`310
`
`310
`
`311
`311
`313
`315
`315
`316
`318
`
`321
`321
`322
`323
`324
`324
`
`326
`
`13
`
`

`

`Contents
`
`Typical Pattern Plating Sequence
`Soak Cleaner
`Mild Etch
`Acid Dip
`Rinses
`Copper Plating Solutions Available
`Pyrophosphate Solution
`Acid Sulphate Solution
`Throwing Power Considerations f9r Thick Boards
`Throwing Power Measurement
`Distribution
`Anode Positions
`Anode Masks
`Power Suµµlit:s tv Ano,:k·s
`Agitation
`Solution Constituents
`Robbing Strips
`Plating of Internal Layers
`Stress Considerations
`Stress Measurements
`Elongation Deposits
`Hardness
`Electrical Conductivity
`Contamination
`Causes and Effects of Organic Contamination
`Metallic Contamination
`
`Tin-lead Plating
`Considerations for High Throwing Power Tin-lead Process
`Throwing Power and Plate Distribution
`Changes of Alloy with Processing Conditions
`Interference from Organic Matter
`Fusion Time
`Out gassing
`Surface Effects
`Estimation
`Corrosion Resistance
`
`Nickel and Nickel Alloys
`Nickel
`Tin-nickel
`Palladium-nickel
`
`Gold
`Substrate Preparation
`Preparation and Methods of Reducing Porosity
`Porosity
`Pretreatment
`Cathode Efficiency
`Distribution
`Internal Stress
`Elongation
`Wear
`Hardness
`Porosity Measurement
`
`13.1.l
`13.1.l.l
`13.1.1.2
`13.1.1.3
`13.1.1.4
`13.1.2
`13.1.2.1
`13.1.2.2
`13.1.3
`13.1.3.1
`13.1.4
`13.1.4.1
`13.1.4.2
`LU.4.3
`13.1.4.4
`13.1.4.5
`13.1.4.6
`13.1.5
`13.1.5.1
`13.1.5.2
`13.1.5.3
`13.1.5.4
`13.1.5.5
`13 .1.6
`13.1.6.1
`13.1.6.2
`
`13.2
`13.2.1
`13.2.1.1
`13.2.2
`13.2.3
`13.2.3.1
`13.2.3.2
`13.2.3.3
`13.2.3.4
`13.2.4
`
`13.3
`13 .3.1
`13.3.2
`13.3.3
`
`13.4
`13 .4.1
`13.4.1.l
`13.4.1.2
`13.4.1.3
`13.4.2
`13.4.3
`13 .4.4
`134.'i
`lJ .4.6
`13 .4. 7
`13.4.8
`
`CHAPTER FOURTEEN
`Cleaning and Preparation of Exposed Copper Surfaces in MLB Manufacture
`G. D. M. Menzies
`
`14.1
`
`Introduction
`
`XVII
`
`326
`327
`327
`327
`327
`328
`328
`330
`331
`331
`332
`333
`333
`333
`333
`334
`334
`334
`334
`335
`336
`338
`338
`339
`339
`339
`
`340
`340
`340
`341
`343
`343
`343
`343
`344
`344
`
`345
`345
`347
`347
`
`347
`348
`348
`348
`349
`350
`351
`351
`353
`354
`354
`354
`
`356
`
`14
`
`

`

`XVlll
`
`14.2
`14.2.1
`14.2.2
`14.2.3
`14.2.4
`14.2.5
`14.2.6
`14.2.7
`
`Contents
`
`Cleaning Methods
`The Importance of Rinsing
`Purposes of Surface Preparation
`Cleaning Processes Used and Associated Problems·
`Results of Inadequate Cleaning
`Surface Smoothing
`Preparation of Boards with Gold-plated Edge Connectors
`Cleaning Sequence
`
`CHAPTER FIFTEEN
`Solder Finishes
`D. S. Kingsley
`
`15 .1
`
`15.2
`15 .2.1
`15.2.2
`15.2.3
`15.2.4
`15.2.5
`15.2.6
`15.2.7
`15.2.8
`
`15 .3
`
`Introduction
`
`Types of Finish
`Roller Tinning
`Electrodeposited Tin-lead
`Flow Melting
`Hydro-squeegee
`Hot Oil Fusing
`Infra-red Fusing
`Condensation Reflow
`Hot Air Levelling
`
`Conclusion
`
`CHAPTER SIXTEEN
`Quality and Inspection
`J. A. Scarlett
`
`16.1
`16.1.1
`16.1.2
`16.1.3
`16.1.4
`
`16.2
`16.2.1
`16.2.1.1
`16.2.1.2
`16.2.1.3
`16.2.2
`16.2.2.1
`16.2.2.2
`16.2.3
`16.2.4
`16.2.4.1
`16.2.5
`16.2.5.1
`16.2.S.2
`16.2.5.3
`
`16.3
`16.3.1
`16.3.1.1
`16.3.1.2
`16.3.2
`16.3.2.1
`16.3.2.2
`
`Quality
`Quality
`Quality Control
`Quality Assurance
`Acceptable Quality Level
`
`On-line Quality Control
`Preliminary Controls
`Filmwork
`Drill and Router Tapes
`Raw Materials
`Quality Control on Inner Layers
`Printing
`Etching and Oxidising
`Quality Control of Bonding
`Quality Control of Drilling
`Smear Removal and Etch Back
`Quality Control of Plating and Outer Layer Processing
`Electroless Copper
`Electroplating
`Printing and Etching
`
`Final Inspection , .
`Test Coupons
`Need for Test Coupons
`Features of Test Coupons
`Visual Inspection
`General Examination
`Pads and Holes
`
`356
`356
`357
`357
`360
`362
`362
`365
`
`367
`
`367
`367
`368
`368
`369
`370
`370
`371
`371
`
`372
`
`374
`374
`374
`375
`375
`
`376
`377
`377
`379
`379
`379
`379
`380
`380
`381
`381
`382
`382
`382
`382
`
`382
`383
`383
`384
`385
`385
`386
`
`15
`
`

`

`Contents
`
`Tracks and Clearances
`Solder Resist, Legend and Profile
`Aids to Visual Inspection
`Destructive Tests
`Track Tests
`Hole Barrel Strength
`Solderability
`Solder Float Test
`Flexing
`Thermal Tests
`
`Microsections
`Cutting Samples
`Encapsulation
`Resins
`Preparation
`Viewing
`Photographic Records
`Evaluation of Microsections
`Surface Features
`General Internal Features
`Holes
`Evaluation After Thermal Testing
`Interpretation of Microsections of Holes
`
`Electrical Testing
`Tests on Test Coupons
`Manual Testing for Continuity
`Automatic Continuity Testing
`Test Fixtures
`Individual Heads
`Grid Based Heads
`Translation Boards
`Flexible Probe Heads
`Simulated Component Test Heads
`Edge Connectors and Buried Via Holes
`Test Programmes
`Comparative Testing
`Testing to Circuit Diagram
`Limitations of Automatic Continuity Testing
`
`16.3.2.3
`16.3.2.4
`16.3.2.5
`16.3.3
`16.3.3.1
`16.3.3.2
`16.3.3.3
`16.3.3.4
`16.3.3.5
`16.3.3.6
`
`16.4
`16.4.1
`16.4.2
`16.4.2.1
`16.4.3
`16.4.4
`16.4.4.1
`16.4.5
`16.4.5.1
`16.4.5.2
`16.4.5.3
`16.4.5.4
`16.4.6
`
`16.5
`16.5.1
`16.5.2
`16.5.3
`16.5.3.1
`16.5.3.1.1
`16.5.3.1.2
`16.5.3.1.3
`16.5.3.1.4
`16.5.3.1.5
`16.5.3.1.6
`16.5.3.2
`16.5.3.2.1
`16.5.3.2.2
`16.5.3.3
`
`CHAPTER SEVENTEEN
`Laminate Stability
`N. C. J. Parry
`
`17 .1
`17.1.1
`17 .1.2
`
`17 ?,
`17 .2.1
`1/.l.1.1
`17.2.1.2
`17.2.1.3
`17.2.2
`17.2.2.1
`17 .2.2.2
`
`Introduction
`X and Y Shift
`Z-Axis Changes
`
`(:,i 11 ses
`Raw Materials
`Woven Glass Fabric
`Resin
`Copper Foil
`Laminate Production Processes
`Impregnation
`Pressing
`
`17 .3
`
`Quantifying the (In)Stability
`
`XIX
`
`386
`387
`387
`389
`389
`389
`390
`390
`390
`392
`
`194
`394
`395
`395
`396
`396
`396
`396
`397
`398
`398
`399
`400
`
`401
`402
`402
`403
`403
`403
`403
`404
`404
`405
`406
`406
`406
`407
`407
`
`409
`409
`409
`
`410
`410
`410
`410
`414
`414
`414
`414
`
`415
`
`16
`
`

`

`xx
`
`17.4
`17.4.1
`17.4.2
`
`17 .5
`
`17.6
`
`Contents
`
`Improving Stability
`The Laminator's Task
`M/L Designer and Fabricator's Task
`
`The Future
`
`Conclusion
`
`CHAPTER EIGHTEEN
`The Use of Radiography in the Inspection of Multilayer Boards
`n. S. Kingsley
`Introduction
`18 .1
`
`18.2
`
`I 8.3
`
`18.4
`
`18.5
`
`18.6
`
`Busic Principles
`
`Pilm Image
`
`Choice of Equipment
`
`Safety Requirements
`
`Basic Specification
`
`CHAPTER NINETEEN
`Multilayer Board Repair
`D. S. Kingsley
`Introduction
`
`19.1
`
`19.2
`19.2.1
`19.2.2
`19.2.3
`
`19.3
`
`19.4
`
`19.5
`19.5 .1
`19.5.2
`
`19.6
`19.6.1
`19.6.2
`19.6.3
`19.6.4
`19.6.5
`19.6.5.1
`19.6.5.2
`19.6 . .'.i.3
`19.6.6
`19.6.7
`19.6.8
`19.6.9
`19.6.10
`19.6.11
`19.6.11.1
`
`Specifications
`Rework
`Repair
`Modification
`
`Quality Control of Rework
`
`Repair Technician
`
`The Repair Section
`The Track Cutting Machine
`Other Equipment
`
`Repair Methods
`Removal of Inclusions
`Lifted Pads and/or Conductors
`Internal Short Circuit
`Replacement of Missing Surface Pads
`Repair of Damaged Conductors on Internal Layers Prior to Lamination
`Conductive Compound
`Tinned Copper Foil Bridge
`Parallel Gap \Velding Tec:-hni<Jllf'.
`Refurbishing Edge Contacts
`Repair of Damaged Conductor, nn External Layers
`Complete Replacement of Edge Contacts
`Removal of Short Circuits and/or Excess Metal, External Layers
`Repair of Open Circuits After Lamination (Inner Layer)
`Re-establishment of Solder Pad
`Method A
`
`419
`419
`420
`
`421
`
`422
`
`423
`
`423
`
`425
`
`426
`
`428
`
`429
`
`430
`
`431
`431
`431
`431
`
`432
`
`432
`
`4JJ
`434
`435
`
`437
`438
`440
`441
`441
`441
`441
`4-42
`442
`442
`443
`443
`443
`443
`444
`444
`
`17
`
`

`

`Contents
`
`19.6.11.2
`19.6.11.2.1
`19.6.11.2.2
`19.6.12
`
`Methods B and C
`Method B
`Method C
`Local Through-hole Plating of Holes
`
`CHAPTER TWENTY
`Flexi-rigid Boards
`J. A. Scarlett
`
`20.1
`
`20.2
`
`20.3
`
`20.4
`20.4.1
`
`20.5
`20.5.1
`20.5.2
`20.5.2.1
`20.5.2.2
`20.5.3
`20.5.3.1
`20.5.3.2
`
`20.6
`20.6.1
`20.6.2
`
`Construction of Flexi-rigid Boards
`
`Types of Flexi-rigid Boards
`
`The Design of Flexi-rigid Boards
`
`Applications for Flexi-rigid Boards in Digital Systems
`Advantages and Disadvantages of Flcxi-rigid Boards
`
`Manufacture of Flexi-rigids
`Laminate Stability
`Cover Coat and Plated Holes in Tails
`Cover Coat
`Plated Holes in Tails
`Final Bonding, Through-plating and Profiling
`Plating and Bonding
`Profiling
`
`Design of Pads in Tails
`Unplated Tails
`Plated Tails
`
`CHAPTER TWENTY-ONE
`Desoldering Multilayer Boards without Damage
`J. A. Scarlett
`
`21.1
`21.1.1
`21.1.2
`21.1.3
`21.1.4
`
`21.2
`21.2.1
`21.2.2
`
`21.3
`21.3.1
`21.3.1.1
`21.3.1.2
`21.3.1.3
`21.3.2
`
`21.4
`7.1.4.1
`1.1.4.2
`
`21.5
`21.5.1
`21.5.2
`
`21.6
`
`Introduction
`Solderability
`Unplated and Plated Holes
`Repair Kits
`Damage to Holes
`
`Types of Joints
`Non-plated Holes
`Through-plated Holes
`
`Removal of Components
`Single Leads
`Removal of Solder
`Softening of Resin
`Damage to Holes
`Multiple Leads
`
`Correct Techniques for Lead Removal
`Simnlt;ineous Desoldering
`Lead Cutting
`
`Crimping
`Damage Caused by Crimped Leads
`Assembly Without Crimping
`
`Avoidance of Damage to Holes
`
`XXI
`
`444
`444
`446
`447
`
`450
`
`451
`
`454
`
`455
`!J58
`
`459
`459
`462
`462
`462
`466
`466
`470
`
`472
`472
`474
`
`478
`478
`478
`479
`479
`
`480
`480
`480
`
`481
`481
`481
`483
`484
`484
`
`484
`484
`485
`
`485
`485
`486
`
`486
`
`l
`l
`l
`3
`i
`i
`
`18
`
`

`

`Contents
`
`xxii
`
`21.7
`
`Summary
`
`CHAPTER TWENTY-TWO
`Documentation and Standards
`W. Macleod Ross
`
`22.1
`
`22.2
`
`22.2.1
`22.2.2
`22.2.3
`
`22.3
`
`Introduction
`
`International Standards and Specifications for Multilayer
`Materials and Circuits
`European Standards and Specifications
`United Kingdom Standards and Specifications
`Amencan Standartls am\ ,SpP.cifications
`
`In-huu~e Standards and Spec1tications
`
`CHAPTER TWENTY-THREE
`Design
`J. A. Scarlett
`
`23.1
`
`23.2
`23.2.1
`23.2.2
`23.2.3
`23.2.3.1
`23.2.3.2
`23.2.3.3
`23.2.4
`23.2.5
`
`23.3
`23.3.1
`23.3.2
`23.3.3
`23.3.4
`23.3.5
`23.3.5.1
`23.3.5.2
`23.3.5.3
`23.3.6
`23.3.7
`23.3.8
`
`23.4
`
`23.5
`
`23.6
`23.6.1
`23.6.2
`
`23.7
`
`23.8
`
`When to use Multilayer Boards
`
`0
`
`Electrical Properties in Design
`Current Carrying Capacity
`Voltage Breakdown
`Characteristic Impedance
`Reflections and Surge Currents
`Propagation Delay
`Effect of Low Characteristic Impedance
`Capacitance
`Crosstalk
`
`Mechanical Aspects of Design
`Balance
`Build
`Overall Thickness
`Laminate Thickness and Stability
`Feature Sizes
`Track and Gap Widths
`Hole and Pad Sizes
`Pad Size and Reliability
`Location of Features
`Planes and Pads
`Outer Layers and Finishes
`
`Layer Numbering
`
`Solder Resist and Legends
`
`Designing Multilayer Boards _
`The Seit-defeating MulLilayer Doard
`Placinr. Vi:=i Holes
`
`Buried Via-hole and Double-double Boards
`
`Filmwork for Multilayer Boards
`
`486
`
`. 489
`
`490
`491
`492
`494
`
`499
`
`500
`500
`501
`501
`503
`503
`503
`504
`504
`
`507
`507
`507
`509
`509
`510
`510
`511
`512
`513
`513
`520
`
`521
`
`522
`
`522
`52,2
`523
`
`524
`
`524
`
`19
`
`

`

`Contents
`
`xxiii
`
`CHAPTER TWENTY-FOUR
`Multiwire
`R. P. Burr and G. Messner
`
`24.1
`
`24.2
`24.2.1
`24.2.2
`
`24.3
`24.3. l
`24.3.2
`24.3.2.1
`24.3.2.2
`24.3.2.3
`24.3.2.3.1
`24.3.2.4
`24.3.3
`24.3.3.1
`24.3.3.2
`24.3.3.3
`24.3.3.4
`24.3.3.5
`24.3.4
`24.3.5
`
`24.4
`24.4.1
`24.4.2
`24.4.3
`24.4.4
`24.4.5
`
`24.5
`24.5.1
`24.5.1.1
`24.5.1.2
`24.5.1.2.1
`24.5 .1.2.2
`24.5.1.2.3
`24.5.2
`24.5.2.1
`24.5.2.2
`24.5.2.2.1
`24.5.2.2.2
`24.5.2.2.3
`24.5.2.3
`24.5.3
`24.5.3.1
`24.5.3.2
`
`24.6
`24.6.1
`24.6.2
`24.6.3
`24.6.4
`
`Introduction
`
`Multiwire Product and Process Overview
`The Multiwire Board
`The Multiwire Process
`
`Multiwire Manufacturing System
`Format Preparation
`1
`Wiring Process
`Wiring Machine Struclure
`Wirtpg Machine Operation
`Wiring Machine Performance
`\\Tiring Speed and Productivity
`Multilevel Wiring
`Termination Process
`Protection of Board Surface
`Hole Drilling
`Hole Cleaning
`Hole Metallisation
`Alternative Processes
`Final Fabrication
`Testing
`
`Multilayer Design (MDT) System
`Design System Function
`System Data Interface
`Input Conversion
`Routing
`Hardware and Performance
`
`Multiwire Product Characteristics
`Reliability
`Electrical Insulation
`Termination (Hole-to-wire) Interface Reliability
`Effects of Multi wire Pattern Formation Technology
`Effects of Wire-hole Interface Formation Process
`Effects of Multi wire Structural Materials
`High Frequency Characteristics
`Characteristic Impedance
`Effects of Wire Crossovers
`Crossover Capacitance
`Intcrwire Capacitance Coupling
`Crossover Capacitance Loading Effects
`Crosstalk
`Special Product Characteristics
`Improved Thermal Conductivity
`Options for Surface Attachment
`
`!Vlultiwire Market and Applicalions
`Typical Production Configur a Li um
`Direction of Product Applications
`Commercial Status
`Summary
`
`528
`
`530
`
`530
`531
`532
`
`533
`533
`535
`535
`536
`)41
`541
`542
`543
`543
`543
`544
`544
`545
`545
`546
`
`547
`547
`548
`548
`550
`553
`
`554
`554
`555
`557
`557
`558
`560
`560
`561
`563
`563
`564
`565
`566
`569
`569
`570
`
`572
`572
`573
`577
`577
`
`i
`
`1
`
`20
`
`

`

`Chapter 1
`
`INTRODUCTION
`
`J. A. SCARLETT
`
`STC Exacta Ltd., Selkirk, Scotland
`
`1.1 GENERAL
`
`1.1.1 Printed Circuit Boards
`
`Printed circuit boards (PCBs) are key components in almost all electronic
`assemblies. Their basic concept is simple enough. A pattern of metal tracks
`which serve to interconnect the components is bonded onto an insulated
`plastic substrate which provides mechanical support for the components.
`When the density of the interconnect is such that all the tracks required
`cannot be fitted onto one side of the plastic substrate, the second side can
`also be used. When the tracking on two sides becomes inadequate, a
`multilayer structure of alternating layers of plastic and patterned metal
`tracking is used. Components can be mounted with their leads through
`holes in the board and their leads soldered to pads around the holes on the
`interconnect tracking or they can be re-flow soldered to pads on the surface.
`The functions of a board can be summarised as:
`
`l To provide a mechanical support for the components;
`2 To provide an electrical interconnect for the components;
`3 To provide a safe working environment for the components.
`
`All of these can be provided in other ways, but only a printed circuit board
`can off er the user the advantages of:
`
`(i) predictability of electrical performance;
`(ii) repeatability of manufacture (if all the interconnections are right on
`the prototype, th