IPC-7095C-2013.pdf - 第10页
9.2 Over-Collapse BGA Solder Ball Conditions .. 140 9.2.1 BGA Ball Shape without Heat Slug 500 µm Standof f Height .................................. 140 9.2.2 BGA Ball Shape with Heat Slug 375 µm Standof f Height ......…
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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9.2 Over-Collapse BGA Solder Ball Conditions .. 140
9.2.1 BGA Ball Shape without Heat Slug
500 µm Standoff Height .................................. 140
9.2.2 BGA Ball Shape with Heat Slug 375 µm
Standoff Height ................................................ 140
9.2.3 BGA Ball Shape with Heat Slug 300 µm
Standoff Height ................................................ 140
9.2.4 Critical Solder Paste Conditions ..................... 141
9.2.5 Overly Thick Paste Deposit ............................ 141
9.2.6 Void Determination Through X-Ray and
Cross-Section ................................................... 141
9.2.7 Voids and Uneven Solder Balls ...................... 141
9.2.8 Eggshell Void ................................................... 142
9.3 BGA Interposer Bow and Twist ...................... 142
9.3.1 BGA Interposer Warp ...................................... 142
9.3.2 Solder Joint Opens Due to Interposer Warp ... 143
9.4 Solder Joint Conditions ................................... 143
9.4.1 Target Solder Condition .................................. 143
9.4.2 Solder Balls with Excessive Oxide ................. 143
9.4.3 Evidence of Dewetting .................................... 144
9.4.4
Mottled Condition ............................................ 144
9.4.5
Tin/Lead Solder Ball Evaluation ..................... 144
9.4.6
SAC Alloy ........................................................ 144
9.4.7
Cold Solder Joint ............................................. 145
9.4.8 Incomplete Joining Due to Land
Contamination .................................................. 145
9.4.9
Deformed Solder Ball Contamination ............. 145
9.4.10
Deformed Solder Ball ...................................... 145
9.4.11 Insufficient Solder and Flux for Proper Joint
Formation ......................................................... 146
9.4.12
Reduced Termination Contact Area ................ 146
9.4.13
Solder Bridging ................................................ 146
9.4.14
Incomplete Solder Reflow ............................... 146
9.4.15
Missing Solder ................................................. 147
9.4.16
Nonwet Open (NWO) Solder Joint ................. 147
9.4.17
Head-on-Pillow (HoP) Solder Joint ................ 147
10 GLOSSARY AND ACRONYMS .......................... 148
11 BIBLIOGRAPHY AND REFERENCES ............... 150
Appendix A Process Control Characterization to
Reduce the Occurrence of Voids
..... 151
Figures
Figure 3-1
BGA Package Manufacturing Process ............. 3
Figure 3-2
Area Array I/O Position Comparisons .............. 5
Figure 3-3
Area Array I/O Position Patterns ...................... 5
Figure 3-4
MCM Type 2S-L-WB ......................................... 6
Figure 3-5
Conductor Width to Pitch Relationship ............ 7
Figure 3-6 Plastic Ball Grid Array, Chip Wire Bonded ....... 8
Figure 3-7 Ball Grid Array, Flip Chip Bonded .................... 8
Figure 3-8 BGA Warpage ................................................. 11
Figure 3-9 Examples of Pad Cratering ............................ 13
Figure 3-10 Various Possible Failure Modes for a BGA
Solder Joint ..................................................... 13
Figure 4-1 Termination Types for Area Array Packages .. 16
Figure 4-2 BOC BGA Construction .................................. 18
Figure 4-3 Top of Molded BOC Type BGA ...................... 18
Figure 4-4 Flip-Chip (Bumped Die) on BGA Substrate ... 19
Figure 4-5 JEDEC Standard Format for Package-on-
Package Components .................................... 22
Figure 4-6 Polymer Coated Sphere Interconnection ....... 23
Figure 4-7 Plastic Ball Grid Array (BGA) Package .......... 24
Figure 4-8 Cross-Section of a Thermally Enhanced
Ceramic Ball Grid Array (CBGA) Package ..... 25
Figure 4-9 Ceramic Ball Grid Array (CBGA) Package
with Molded Polymer Encapsulation .............. 25
Figure 4-10 Ceramic-Based Column Grid Array (CCGA)
Package .......................................................... 26
Figure 4-11 Polyimide Film-Based Lead-Bond µBGA
Package Substrate Furnishes Close
Coupling Between Die Pad and Ball
Contact ........................................................... 26
Figure 4-12 Comparing In-Package Circuit Routing
Capability of the Single Metal Layer
Tape Substrate to Two Metal Layer
Tape Substrate ............................................... 26
Figure 4-13 Single Package Die-Stack BGA ..................... 27
Figure 4-14 Custom Eight Die (Flip-Chip and
Wire-Bond) SiP Assembly .............................. 27
Figure 4-15 Folded Multiple-Die BGA Package ................. 27
Figure 4-16 Eight Layer Ball Stack Package ..................... 27
Figure 4-17 SO-DIMM Memory Card Assembly ................ 28
Figure 4-18 Folded and Stacked Multiple Die
BGA Package ................................................. 28
Figure 4-19 Package-on-Package Assembly ..................... 28
Figure 4-20 Semiconductors Packaged with
µPILR Substrate ............................................. 29
Figure 4-21 Solder Interface Between µPILR-Configured
Substrate Interposer and Circuit Board .......... 29
Figure 4-22 BGA Connector ............................................... 29
Figure 4-23 PGA Socket Pins ............................................ 30
Figure 4-24 PGA Socket With and Without Pick and
Place Cover .................................................... 30
Figure 4-25 LGA Contact Pin ............................................. 31
Figure 4-26 LGA Socket With and Without Pick and
Place Cover .................................................... 31
Figure 4-27 Example of Missing Balls on a BGA
Component ..................................................... 35
Figure 4-28 Example of Voids in Eutectic Solder Balls
at Incoming Inspection ................................... 35
Figure 4-29 Examples of Solder Ball/Land Surface
Conditions ....................................................... 35
Figure 4-30
Establishing BGA Coplanarity Requirement ... 36
IPC-7095C January 2013
viii
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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Figure 4-31 Ball Contact Positional Tolerance ................... 36
Figure 5-1 Examples of Different Build-Up
Constructions .................................................. 38
Figure 5-2 Expansion Rate Above T
g
.............................. 40
Figure 5-3 Hot Air Solder Level (HASL) Surface
Topology Comparison ..................................... 42
Figure 5-4 Black Pad Related Fracture Showing Crack
Between Nickel & Ni-Sn Intermetallic Layer .. 43
Figure 5-5 Crack Location for a) Black Pad Related
Failure and (b) Interfacial Fracture When
Using ENIG Surface Finish ............................ 43
Figure 5-6 Typical Mud Crack Appearance of Black
Pad Surface .................................................... 44
Figure 5-7 A Large Region of Severe Black Pad with
Corrosion Spikes Protruding into Nickel
Rich Layer through Phosphorus Rich
Layer Underneath Immersion Gold
Surface ........................................................... 44
Figure 5-8 Gold Embrittlement ......................................... 45
Figure 5-9 Graphic Depiction of Electroless Nickel/
Electroless Palladium/Immersion Gold ........... 45
Figure 5-10 Graphic Depiction of Directed Immersion
Gold ................................................................ 45
Figure 5-11 Example of Micro Voids .................................. 46
Figure 5-12 Via Plug Methods ........................................... 49
Figure 5-13 Metal Core Board Construction Examples ..... 50
Figure 6-1 BGA Alignment Marks .................................... 51
Figure 6-2 Solder Lands for BGA Components ............... 53
Figure 6-3 Metal Defined Land Attachment Profile .......... 53
Figure 6-4 Solder Mask Stress Concentration ................. 53
Figure 6-5 Solder Joint Geometry Contrast ..................... 54
Figure 6-6 Good/Bad Solder Mask Design ...................... 55
Figure 6-7 Examples of Metal-Defined Land ................... 55
Figure 6-8 Quadrant Dog Bone BGA Pattern .................. 55
Figure 6-9 Square Array ................................................... 56
Figure 6-10 Rectangular Array ........................................... 56
Figure 6-11 Depopulated Array .......................................... 56
Figure 6-12 Square Array with Missing Balls ..................... 56
Figure 6-13 Interspersed Array .......................................... 57
Figure 6-14 Conductor Routing Strategy ........................... 58
Figure 6-15 BGA Dogbone Land Pattern Preferred
Direction for Conductor Routing ..................... 59
Figure 6-16 Preferred Screw and Support Placement ...... 59
Figure 6-17 Connector Screw Support Placement ............ 59
Figure 6-18 Cross Section of 0.75 mm Ball with Via-in-
Pad Structure (Indent to the Upper Left of
the Ball is an Artifact.) .................................... 59
Figure 6-19 Cross Section of Via-in-Pad Design
Showing Via Cap and Solder Ball .................. 60
Figure 6-20 Via-in-Pad Process Descriptions .................... 60
Figure 6-21 Microvia Example ........................................... 61
Figure 6-22 Microvia-in-Pad Voiding .................................. 61
Figure 6-23 Ground or Power BGA Connection ................ 61
Figure 6-24 Example of Top Side Reflow Joints ................ 62
Figure 6-25 Example of Wave Solder Temperature
Profile of Topside of Mixed Component
Assembly ........................................................ 62
Figure 6-26 Heat Pathways to BGA Solder Joint During
Wave Soldering .............................................. 63
Figure 6-27 Methods of Avoiding BGA Topside Solder
Joint Reflow .................................................... 63
Figure 6-28 An Example of a Side Contact Made with
a Tweezers Type Contact ............................... 64
Figure 6-29 Pogo-Pin Type Electrical Contact
Impressions on the Bottom of a
Solder Ball ...................................................... 65
Figure 6-30 Area Array Land Pattern Testing .................... 66
Figure 6-31 Board Panelization ......................................... 69
Figure 6-32 Comb Pattern Examples ................................ 70
Figure 6-33 Heat Sink Attached to a BGA with an
Adhesive ......................................................... 72
Figure 6-34 Heat Sink Attached to a BGA with a Clip
that Hooks onto the Component Substrate .... 72
Figure 6-35 Heat Sink Attached to a BGA with a Clip
that Hooks into a Through-Hole on the
Printed Circuit Board ...................................... 72
Figure 6-36 Heat Sink Attached to a BGA with a Clip
that Hooks onto a Stake Soldered in the
Printed Circuit Board ...................................... 73
Figure 6-37 Heat Sink Attached to a BGA by Wave
Soldering Its Pins in a Through-Hole in
the Printed Circuit Board ................................ 73
Figure 7-1 Aspect and Area Ratios for Complete
Paste Release ................................................ 77
Figure 7-2 High Lead and Eutectic Solder Ball and
Joint Comparison ............................................ 78
Figure 7-3 Example of Peak Reflow Temperatures at
Various Locations at or Near a BGA .............. 79
Figure 7-4 Schematic of Reflow Profile for Tin/Lead
Assemblies ..................................................... 81
Figure 7-5 An Example of Tin/Lead Profile with
Multiple Thermocouples .................................. 81
Figure 7-6 Schematic of Reflow Profile for Lead-Free
Assemblies ..................................................... 81
Figure 7-7 Examples of Lead-Free Profiles with Soak
(Top) and Ramp to Peak (Bottom) with
Multiple Thermocouples. The Profiles
with Soak Tend to Reduce Voids in
BGAs. ............................................................. 82
Figure 7-8 Locations of Thermocouples on a Board
with Large and Small Components ................ 82
Figure 7-9 Recommended Locations of Thermocouples
on a BGA ........................................................ 82
Figure 7-10 Effect of Having Solder Mask Relief Around
the BGA Lands of the Board .......................... 86
Figure 7-11 Map of Underfill Adhesive Usage for BGA
and Other Packages ....................................... 88
Figure 7-12 Flow of Underfill Between Two Parallel
Surfaces .......................................................... 88
Figure 7-13 Examples of Underfill Voids - small, medium
and large; upper left, lower left and left of
solder balls, respectively ................................ 89
January 2013 IPC-7095C
ix
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
--`,,```,,,,````-`-`,,`,,`,`,,`---