IPC-7095C-2013.pdf - 第11页
Figure 4-31 Ball Contact Positional T olerance ................... 36 Figure 5-1 Examples of Different Build-Up Constructions .................................................. 38 Figure 5-2 Expansion Rate Above T g ....…
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
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Figure 7-14 Example of Partial Underfill - package was
pulled from the PCB and dark underfill can
be seen in the corners ................................... 89
Figure 7-15 Corner Applied Adhesive ................................ 90
Figure 7-16 Critical Dimension for Application of
Prereflow Corner Glue .................................... 90
Figure 7-17 Typical Corner Glue Failure Mode in Shock
if Glue Area is Too Low - Solder Mask Rips
Off Board and Does Not Protect the Solder
Joints .............................................................. 90
Figure 7-18 Fundamentals of X-Ray Technology .............. 92
Figure 7-19 X-Ray Example of Missing Solder Balls ........ 92
Figure 7-20 X-ray Example of Voiding in Solder Ball
Contacts .......................................................... 92
Figure 7-21 Manual X-Ray System Image Quality ............ 92
Figure 7-22 Example of X-Ray Pin Cushion Distortion
and Voltage Blooming .................................... 93
Figure 7-23 Transmission image (2D) ............................... 93
Figure 7-24 Tomosynthesis image (3D) ............................. 93
Figure 7-25
Laminographic Cross-Section Image (3D) ..... 94
Figure 7-26
Transmission Example ................................... 94
Figure 7-27
Oblique Viewing Board Tilt ............................. 94
Figure 7-28
Oblique Viewing Detector Tilt ......................... 94
Figure 7-29
Top Down View of FBGA Solder Joints .......... 95
Figure 7-30
Oblique View of FBGA Solder Joints ............. 95
Figure 7-31
Tomosynthesis ................................................ 96
Figure 7-32
Scanned Beam X-Ray Laminography ............ 96
Figure 7-33
Scanning Acoustic Microscopy ....................... 97
Figure 7-34
Endoscope Example ....................................... 98
Figure 7-35 Lead-Free 1.27 mm Pitch BGA Reflowed
in Nitrogen and Washed Between SMT
Passes ............................................................ 98
Figure 7-36 Lead-Free BGA Reflowed in Air and
Washed Between SMT Passes ...................... 98
Figure 7-37
Engineering Crack Evaluation Technique ....... 99
Figure 7-38 A Solder Ball Cross Sectioned Through
a Void in the Solder Ball ............................... 100
Figure 7-39 Cross-Section of a Crack Initiation at the
Ball/Pad Interface ......................................... 100
Figure 7-40
No Dye Penetration Under the Ball .............. 100
Figure 7-41 Corner Balls have 80-100% Dye
Penetration Which Indicate a Crack ............. 100
Figure 7-42 Small Voids Clustered in Mass at the
Ball-to-Land Interface ................................... 102
Figure 7-43 Typical Size and Location of Various
Types of Voids in a BGA Solder Joint .......... 103
Figure 7-44 X-Ray Image of Solder Balls with Voids
at 50 kV (a) and 60 kV (b) ........................... 104
Figure 7-45
Examples of Suggested Void Protocols ....... 105
Figure 7-46 Example of Voided Area at Land and
Board Interface ............................................. 108
Figure 7-47
X-Ray Image Showing Uneven Heating ....... 110
Figure 7-48 X-Ray Image at 45° Showing Insufficient
Heating in One Corner of the BGA ............... 110
Figure 7-49 Example of Head-on-Pillow Showing Ball
and Solder Paste have not Coalesced ......... 110
Figure 7-50 Head-on-Pillow Process Sequence
Occurrences .................................................. 111
Figure 7-51 HoP Due to High Package Warpage ............ 111
Figure 7-52 Example of Liquidus Time Delay .................. 111
Figure 7-53 Solder Particles on Board Noncoalesced
After Reflow ................................................... 111
Figure 7-54 Hanging Ball Examples ................................. 112
Figure 7-55 X-Ray Image of Popcorning ......................... 112
Figure 7-56 X-Ray Image Showing Warpage in a BGA .. 113
Figure 7-57 BGA/Assembly Shielding Examples ............. 114
Figure 8-1 BGA Solder Joint of Eutectic Tin/Lead Solder
Composition Exhibiting Lead Rich (Dark)
Phase and Tin Rich (Light) Phase Grains ... 120
Figure 8-2 Socket BGA Solder Joints of SnAgCu
Composition, Showing the Solder Joint
Comprised of 6 Grains (Top Photo) and
a Single Grain (Bottom Photo). .................... 120
Figure 8-3 Thermal-Fatigue Crack Propagation
in Eutectic Tin/Lead Solder Joints in
a CBGA Module ............................................ 120
Figure 8-4 Thermal-Fatigue Crack Propagation
in Sn-3.8Ag-0.7Cu Joints in a CBGA
Module .......................................................... 120
Figure 8-5 Incomplete Solder Joint Formation for
1% Ag Ball Alloy Assembled at Low
End of Typical Process Window ................... 122
Figure 8-6 Solder Joint Failure Due to Silicon and
Board CTE Mismatch ................................... 123
Figure 8-7 Grainy Appearing Solder Joint ..................... 124
Figure 8-8 Nonsolderable Land (Black Pad) ................. 124
Figure 8-9 Land Contamination (Solder Mask
Residue) ....................................................... 124
Figure 8-10 Solder Ball Drop ........................................... 124
Figure 8-11 Missing Solder Ball ....................................... 125
Figure 8-12 Example of Dynamic Warpage of Flip
Chip BGA Packages and PCBs ................... 125
Figure 8-13 Example of a Severely Warped BGA
Package and PCB After Reflow Soldering
in an Un-Optimized SMT Process ................ 125
Figure 8-14 Examples of Acceptable Convex Solder
Joints with Solder Joint Surface Tangents
Shown in the Top Left Photo ........................ 126
Figure 8-15 Example of an Acceptable Columnar
Solder Joint ................................................... 126
Figure 8-16 Two Examples of Pad Cratering (Located
at Corner of BGA) ........................................ 127
Figure 8-17 Pad Crater Under 1.0 mm Pitch Lead-
Free Solder Ball. Crack in Metal Trace
Connected to the Land is Clear; However,
the Pad Crater is Difficult to See in Bright
Field Microscopy. .......................................... 127
Figure 8-18 Cross-Section Photographs Illustrating
Insufficient Melting of Solder Joints During
Reflow Soldering. These Solder Joints are
Located Below the Cam of a Socket. .......... 128
Figure 8-19 Solder Mask Influence .................................. 129
IPC-7095C January 2013
x
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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