IPC-7095C-2013.pdf - 第8页
4.8.3 Solder Ball Attach Integrity .............................. 35 4.8.4 Package and Ball Coplanarity ........................... 35 4.8.5 Moisture Sensitivity (Baking, Storage, Handling, Rebaking) ....................…
Table of Contents
1 SCOPE ...................................................................... 1
1.1 Purpose ................................................................. 1
1.2 Intent .................................................................... 1
2 APPLICABLE DOCUMENTS .................................... 1
2.1 IPC ....................................................................... 1
2.2 JEDEC .................................................................. 2
3 SELECTION CRITERIA AND MANAGING BGA
IMPLEMENTATION
................................................... 2
3.1 Description of Infrastructure ............................... 3
3.1.1 Land Patterns and Circuit Board
Considerations ...................................................... 3
3.1.2 Technology Comparison ...................................... 5
3.1.3 Assembly Equipment Impact .............................. 8
3.1.4 Stencil Requirements ........................................... 8
3.1.5 Inspection Requirements ..................................... 9
3.1.6 Test ....................................................................... 9
3.2 Time-to-Market Readiness .................................. 9
3.3 Methodology ........................................................ 9
3.4 Process Step Analysis .......................................... 9
3.5 BGA Limitations and Issues ............................... 9
3.5.1 Visual Inspection ............................................... 10
3.5.2 Moisture Sensitivity ........................................... 10
3.5.3 Thermally Unbalanced BGA Design ................ 10
3.5.4 Rework ............................................................... 11
3.5.5 Cost .................................................................... 11
3.5.6 Availability ......................................................... 12
3.5.7 Voids in BGA ..................................................... 12
3.5.8 Pad Cratering ..................................................... 12
3.5.9 Standardization Issues ....................................... 12
3.5.10 Reliability Concerns .......................................... 13
3.5.11 Drivers for Lead-Free Technology .................... 14
4 COMPONENT CONSIDERATIONS ........................ 14
4.1 Semiconductor Packaging Comparisons and
Drivers ................................................................ 14
4.1.1 Package Feature Comparisons ........................... 14
4.1.2 BGA Package Drivers ....................................... 15
4.1.3
Cost Issues ......................................................... 15
4.1.4
Component Handling ......................................... 15
4.1.5
Thermal Performance ........................................ 17
4.1.6
Real Estate ......................................................... 17
4.1.7
Electrical Performance ....................................... 17
4.1.8
Mechanical Performance ................................... 17
4.2
Die Mounting in the BGA Package .................. 17
4.2.1 Wire Bond .......................................................... 18
4.2.2 Flip Chip ............................................................ 19
4.3 Standardization ................................................... 19
4.3.1 Industry Standards for BGA .............................. 19
4.3.2 Ball Pitch ........................................................... 20
4.3.3 BGA Package Outline ....................................... 21
4.3.4 Ball Size Relationships ...................................... 21
4.3.5 Package-on-Package BGA ................................. 22
4.3.6 Coplanarity ......................................................... 22
4.4
Component Packaging Style Considerations .... 23
4.4.1
Solder Ball Alloy ............................................... 23
4.4.2
Ball Attach Process ............................................ 24
4.4.3
Ceramic Ball Grid Array ................................... 24
4.4.4
Ceramic Column Grid Arrays ........................... 25
4.4.5
Tape Ball Grid Arrays ....................................... 25
4.4.6
Multiple Die Packaging ..................................... 25
4.4.7
System-in-Package (SiP) ................................... 26
4.4.8
3D Folded Package Technology ........................ 27
4.4.9
Ball Stack, Package-on-Package ....................... 27
4.4.10
Folded and Stacked Packaging Combination ... 28
4.4.11
Package-on-Package .......................................... 28
4.4.12
Benefits of Multiple Die Packaging .................. 28
4.4.13 Solutions for Very Fine Pitch Array
Packaging ........................................................... 28
4.5
BGA Connectors and Sockets ........................... 29
4.5.1 Material Considerations for BGA
Connectors ......................................................... 29
4.5.2 Attachment Considerations for BGA
Connectors ......................................................... 29
4.5.3
BGA Materials and Socket Types ..................... 30
4.5.4 Attachment Considerations for BGA
Sockets ............................................................... 30
4.6
BGA Construction Materials ............................. 31
4.6.1
Types of Substrate Materials ............................. 31
4.6.2
Properties of Substrate Materials ...................... 33
4.7
BGA Package Design Considerations ............... 33
4.7.1
Power and Ground Planes ................................. 33
4.7.2
Signal Integrity .................................................. 34
4.7.3 Heat Spreader Incorporation Inside the
Package .............................................................. 34
4.8 BGA Package Acceptance Criteria and
Shipping Format ................................................ 34
4.8.1
Missing Balls ..................................................... 34
4.8.2
Voids in Solder Balls ......................................... 34
January 2013 IPC-7095C
v
Copyright IPC-Association Connecting Electronics Industries
Provided by IHS under license with IPC
Not for Resale
No reproduction or networking permitted without license from IHS
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4.8.3 Solder Ball Attach Integrity .............................. 35
4.8.4 Package and Ball Coplanarity ........................... 35
4.8.5 Moisture Sensitivity (Baking, Storage,
Handling, Rebaking) .......................................... 36
4.8.6 Shipping Medium (Tape and Reel, Trays,
Tubes) ................................................................. 37
4.8.7 Solder Ball Alloy ............................................... 37
5 PRINTED BOARDS AND OTHER MOUNTING
STRUCTURES
........................................................ 37
5.1 Types of Mounting Structures ........................... 37
5.1.1 Organic Resin Systems ...................................... 37
5.1.2 Inorganic Structures ........................................... 37
5.1.3 Layering (Multilayer, Sequential or
Build-Up) ........................................................... 37
5.2 Properties of Mounting Structures .................... 37
5.2.1 Resin Systems .................................................... 37
5.2.2 Reinforcements .................................................. 38
5.2.3 Laminate Material Properties ............................ 39
5.3 Surface Finishes ................................................. 40
5.3.1 Hot Air Solder Leveling (HASL) ..................... 41
5.3.2 Organic Surface Protection (Organic
Solderability Preservative) OSP Coatings ........ 42
5.3.3 Noble Platings/Coatings .................................... 42
5.4 Solder Mask ....................................................... 46
5.4.1 Wet and Dry Film Solder Masks ...................... 46
5.4.2 Photoimageable Solder Masks .......................... 47
5.4.3 Jettable Solder Mask ......................................... 47
5.4.4 Registration of Board to Panel Image for
Solder Mask ....................................................... 47
5.4.5 Via Protection .................................................... 47
5.5 Thermal Spreader Structure Incorporation
(e.g., Metal Core Boards) .................................. 48
5.5.1 Lamination Sequences ....................................... 48
5.5.2 Heat Transfer Pathway ...................................... 48
6 PRINTED CIRCUIT ASSEMBLY DESIGN
CONSIDERATION ................................................... 50
6.1 Component Placement and Clearances ............. 50
6.1.1
Pick and Place Requirements ............................ 50
6.1.2
Repair/Rework Requirements ............................ 50
6.1.3
Global Placement ............................................... 51
6.1.4 Alignment Legends (Silkscreen, Copper
Features, Pin 1 Identifier) .................................. 51
6.2
Attachment Sites (Land Patterns and Vias) ...... 52
6.2.1
Big vs. Small Land and Impact on Routing ..... 52
6.2.2 Solder Mask vs. Metal Defined Land
Design ................................................................ 52
6.2.3
Conductor Width ................................................ 53
6.2.4
Via Size and Location ....................................... 54
6.3 Escape and Conductor Routing Strategies ........ 54
6.3.1 Escape Strategies ............................................... 57
6.3.2 Surface Conductor Details ................................. 58
6.3.3 Dog Bone Through Via Details ........................ 58
6.3.4 Design for Mechanical Strain ........................... 58
6.3.5 Uncapped Via-in-Pad and Impact on
Reliability Issues ................................................ 59
6.3.6 Fine Pitch BGA Microvia in Pad Strategies ..... 60
6.3.7 Power and Ground Connectivity ....................... 61
6.4 Impact of Wave Solder on Top Side BGAs ..... 61
6.4.1 Top Side Reflow ................................................ 61
6.4.2 Impact of Top Side Reflow ............................... 61
6.4.3 Methods of Avoiding Top Side Reflow ............ 62
6.4.4 Top Side Reflow for Lead-Free Boards ............ 64
6.5 Testability and Test Point Access ...................... 64
6.5.1 Component Testing ............................................ 64
6.5.2 Damage to the Solder Balls During Test and
Burn-In ............................................................... 64
6.5.3 Bare Board Testing ............................................ 65
6.5.4 Assembly Testing ............................................... 66
6.6 Other Design for Manufacturability Issues ....... 68
6.6.1 Panel/Pallet Design ............................................ 68
6.6.2 In-Process/End Product Test Coupons .............. 68
6.7 Thermal Management ........................................ 69
6.7.1 Conduction ......................................................... 70
6.7.2
Radiation ............................................................ 70
6.7.3
Convection ......................................................... 70
6.7.4
Thermal Interface Materials .............................. 71
6.7.5
Heat Sink Attachment Methods for BGAs ....... 72
6.8
Documentation and Electronic Data Transfer ... 73
6.8.1
Drawing Requirements ...................................... 74
6.8.2
Equipment Messaging Protocols ....................... 74
6.8.3
Specifications ..................................................... 75
7 ASSEMBLY OF BGAS ON PRINTED CIRCUIT
BOARDS
................................................................. 76
7.1
SMT Assembly Processes .................................. 76
7.1.1
Solder Paste and Its Application ....................... 76
7.1.2
Component Placement Impact ........................... 78
7.1.3
Vision Systems for Placement ........................... 78
7.1.4
Reflow Soldering and Profiling ......................... 79
7.1.5
Material Issues ................................................... 84
7.1.6
Vapor Phase ....................................................... 84
7.1.7
Cleaning vs. No-Clean ...................................... 84
7.1.8
Package Standoff ............................................... 85
7.2
Post-SMT Processes .......................................... 86
7.2.1
Conformal Coatings ........................................... 86
IPC-7095C January 2013
vi
Copyright IPC-Association Connecting Electronics Industries
Provided by IHS under license with IPC
Not for Resale
No reproduction or networking permitted without license from IHS
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7.2.2 Use of Underfills and Adhesives ....................... 86
7.2.3 Depaneling of Boards and Modules ................. 90
7.3 Inspection Techniques ........................................ 91
7.3.1 X-Ray Usage ...................................................... 91
7.3.2 X-Ray Image Acquisition .................................. 91
7.3.3 Definition and Discussion of X-Ray System
Terminology ....................................................... 92
7.3.4 Analysis of the X-Ray Image ........................... 95
7.3.5 Scanning Acoustic Microscopy ......................... 97
7.3.6 BGA Standoff Measurement ............................. 97
7.3.7 Optical Inspection .............................................. 97
7.3.8 Destructive Analysis Methods ........................... 99
7.4 Testing and Product Verification ..................... 100
7.4.1 Electrical Testing ............................................. 100
7.4.2 Test Coverage .................................................. 101
7.4.3 Burn-In Testing ................................................ 101
7.4.4 Product Screening Tests .................................. 101
7.5 Void Identification ........................................... 101
7.5.1 Sources of Voids .............................................. 101
7.5.2 Void Classification ........................................... 102
7.5.3 Voids in BGA Solder Joints ............................ 102
7.6 Void Measurement ........................................... 104
7.6.1 X-Ray Detection and Measurement
Cautions ........................................................... 104
7.6.2 Impact of Voids ................................................ 104
7.6.3 Void Protocol Development ............................ 104
7.6.4 Sampling Plans for Void Evaluation ............... 105
7.7 Process Control for Void Reduction ............... 106
7.7.1 Process Parameter Impact on Void
Formation ......................................................... 106
7.7.2 Process Control Criteria for Voids in
Solder Balls ...................................................... 108
7.7.3
Process Control Criteria .................................. 109
7.8
Solder Defects .................................................. 109
7.8.1
Solder Bridging ................................................ 109
7.8.2
Cold Solder ...................................................... 109
7.8.3
Opens ............................................................... 109
7.8.4
Insufficient/Uneven Heating ............................ 109
7.8.5
Head-on-Pillow ................................................ 110
7.8.6
Hanging Ball/Non-Wet Open (NWO) ............. 112
7.8.7
Component Defects .......................................... 112
7.8.8
Defect Correlation/Process Improvement ....... 113
7.9
Repair Processes .............................................. 113
7.9.1
Rework/Repair Philosophy .............................. 113
7.9.2
Removal of BGA ............................................. 113
7.9.3
Replacement ..................................................... 114
8 RELIABILITY ......................................................... 117
8.1 Reliability Drivers for BGAs .......................... 117
8.1.1 Cyclic strain ..................................................... 117
8.1.2 Fatigue .............................................................. 117
8.1.3 Creep ................................................................ 118
8.1.4 Creep and Fatigue Interaction ......................... 118
8.1.5 Mechanical reliability ...................................... 119
8.2 Damage Mechanisms and Failure of Solder
Attachments ...................................................... 119
8.2.1 Comparison of Thermal Fatigue Crack
Growth Mechanism in SAC vs. Tin/Lead
BGA Solder Joints ........................................... 119
8.2.2 Mixed Alloy Soldering .................................... 121
8.3 Solder Joints and Attachment Types ............... 122
8.3.1 Global Expansion Mismatch ........................... 123
8.3.2 Local Expansion Mismatch ............................. 123
8.3.3 Internal Expansion Mismatch .......................... 123
8.4 Solder Attachment Failure ............................... 123
8.4.1 Solder Attachment Failure Classification ........ 123
8.4.2 Failure Signature-1: Cold Solder .................... 123
8.4.3 Failure Signature-2: Land, Nonsolderable ...... 124
8.4.4 Failure Signature-3: Ball Drop ........................ 124
8.4.5 Failure Signature-4: Missing Ball ................... 124
8.4.6 Failure Signature-5: PCB and BGA Stack
Warpage ............................................................ 124
8.4.7 Failure Signature-6: Mechanical Failure ......... 126
8.4.8 Failure Signature-7: Insufficient Reflow ......... 127
8.5 Critical Factors to Impact Reliability ............. 127
8.5.1 Package Technology ........................................ 127
8.5.2 Stand-Off Height .............................................. 128
8.5.3 PCB Design Considerations ............................ 129
8.5.4 Reliability of Solder Attachments of
Ceramic Grid Array ......................................... 129
8.5.5 Lead-Free Soldering of BGAs ........................ 129
8.6 Design for Reliability (DfR) Process .............. 135
8.7 Validation and Qualification Tests .................. 135
8.8 Screening Procedures ....................................... 136
8.8.1 Solder Joint Defects ......................................... 136
8.8.2 Screening Recommendations ........................... 136
8.9 Accelerated Reliability Testing ....................... 136
9 DEFECT AND FAILURE ANALYSIS CASE
STUDIES ............................................................... 138
9.1 Solder Mask Defined BGA Conditions ........... 138
9.1.1 Solder Mask Defined and Nondefined
Lands ................................................................ 138
9.1.2 Solder Mask Defined Land on Product
Board ................................................................ 139
9.1.3
Solder Mask Defined BGA Failures ............... 139
January 2013 IPC-7095C
vii
Copyright IPC-Association Connecting Electronics Industries
Provided by IHS under license with IPC
Not for Resale
No reproduction or networking permitted without license from IHS
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