IPC-7095C-2013.pdf - 第12页

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 ..........................…

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

.............................. 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

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

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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Figure 8-20 Reliability Test Failure Due to Very Large

Void ............................................................... 129

Figure 8-21 Comparison of a Lead-Free (SnAgCu)

and Tin/Lead (SnPb) BGA Reﬂow

Soldering

Proﬁles .......................................................... 132

Figure 8-22 Endoscope Photo of a SnAgCu BGA

Solder Ball .................................................... 133

Figure 8-23 Comparison of Reﬂow Soldering Proﬁles

for Tin/Lead, Backward Compatibility and

Total Lead-Free Board Assemblies .............. 134

Figure 8-24 Micrograph of a cross-section of a BGA

SnAgCu solder ball, assembled onto a

board with tin/lead solder paste using the

standard tin/lead reﬂow soldering proﬁle.

The SnAgCu solder ball does not melt;

black/grey interconnecting ﬁngers are

lead-rich grain boundaries; rod shape

particles are Ag3Sn IMCs; grey particles

are Cu6Sn5 IMCs. ........................................ 134

Figure 8-25 Micrograph of a cross-section of a BGA

SnAgCu solder ball, assembled onto a

board with tin/lead solder paste using a

backward compatibility reﬂows soldering

proﬁle. The SnAgCu solder ball has

melted. .......................................................... 134

Figure A-1 Typical Flow Diagram for Void

Assessment .................................................. 151

Figure A-2 Voids in BGAs with Crack Started at

Corner Lead .................................................. 155

Figure A-3

Void Diameter Related to Land Size ............ 155

Tables

Table 3-1

Multichip Module Deﬁnitions ............................... 6

Table 3-2 Number of Escapes vs.

Array Size on Two Layers of Circuitry ................ 6

Table 3-3 Potential Plating or Component Termination

Material Properties ............................................ 10

Table 3-4

Example of Semiconductor Cost Predictions ... 12

Table 4-1 JEDEC Standard JEP95-1/5

Allowable Ball Diameter Variations for FBGA ... 20

Table 4-2

Ball Diameter Sizes for PBGAs ........................ 20

Table 4-3

Future Ball Size Diameters for DSPBGAs ........ 21

Table 4-4

Land Size Approximation .................................. 21

Table 4-5 Land-to-Ball Calculations for Current and

Future BGA Packages (mm) ............................. 22

Table 4-6 Examples of JEDEC Registered BGA

Outlines ............................................................. 22

Table 4-7

Pb-Free Alloy Variations .................................... 24

Table 4-8 IPC-4101C FR-4 Property Summaries -

Speciﬁcation Sheets Projected to Better

Withstand Lead-Free Assembly ........................ 32

Table 4-9 Typical Properties of Common

Dielectric Materials for BGA Package

Substrates ......................................................... 34

Table 4-10

Moisture Classiﬁcation Level and Floor Life ..... 36

Table 5-1 Environmental Properties of Common

Dielectric Materials ............................................ 39

Table 5-2 Key Attributes for Various Board Surface

Finishes ............................................................. 41

Table 5-3 Via Filling/Encroachment to Surface Finish

Process Evaluation ........................................... 48

Table 5-4 Via Fill Options .................................................. 50

Table 6-1 Number of Conductors Between Solder

Lands for 1.27 mm Pitch BGAs ........................ 52

Table 6-2 Number of Conductors Between Solder

Lands for 1.0 mm Pitch BGAs .......................... 52

Table 6-3 Maximum Solder Land to Pitch Relationship .... 53

Table 6-4 Escape Strategies for Full Arrays ..................... 57

Table 6-5 Conductor Routing - 1.27 mm Pitch ................. 58

Table 6-6 Conductor Routing - 1.0 mm Pitch ................... 58

Table 6-7 Conductor Routing - 0.8 mm Pitch ................... 58

Table 6-8 Conductor Routing - 1.27 mm Pitch ................. 58

Table 6-9 Conductor Routing - 1.0 mm Pitch ................... 58

Table 6-10 Conductor Routing - 0.8 mm Pitch ................... 58

Table 6-11 Effects of Material Type on Conduction ............ 71

Table 6-12 Emissivity Ratings for Certain Materials ........... 71

Table 7-1 Particle Size Comparisons ................................ 76

Table 7-2 Example of Solder Paste Volume

Requirements for Ceramic Array Packages ..... 78

Table 7-3 Proﬁle Comparison Between SnPb and SAC

Alloys ................................................................. 80

Table 7-4 Inspection Usage Application

Recommendations ............................................ 91

Table 7-5 Field of View for Inspection .............................. 96

Table 7-6 Void Classiﬁcation ........................................... 103

Table 7-7 Ball-to-Void Size Image -

Comparison for Various Ball Diameters .......... 105

Table 7-8 C=0 Sampling Plan (Sample Size for

Speciﬁc Index Value*) ..................................... 106

Table 7-9 Repair Process Temperature Proﬁles for

Tin Lead Assembly .......................................... 116

Table 7-10 Repair Process Temperature Proﬁles for

Lead-Free Assemblies ..................................... 116

Table 8-1 Tin/Lead Component Compatibility with

Lead-Free Reﬂow Soldering ........................... 121

Table 8-2 Typical Stand-Off

Heights for Tin/Lead Balls (in mm) ................. 128

Table 8-3 Common Solders, Their Melting Points,

Advantages and Drawbacks ........................... 130

Table 8-4 Comparison of Lead-Free Solder Alloy

Compositions in The Sn-Ag-Cu Family

Selection by Various Consortia ....................... 131

Table 8-5

Types of Lead-Free Assemblies Possible ....... 133

Table 8-6 Accelerated Testing for End Use

Environments .................................................. 137

Table A-1 Corrective Action Indicator for Lands used

with 1.5, 1.27 or 1.0 mm Pitch ........................ 152

Table A-2 Corrective Action Indicator for Lands used

with 0.8, 0.65 or 0.5 mm Pitch ........................ 153

Table A-3 Corrective Action Indicator for Microvia

in Pad Lands used with 0.5, 0.4 or

0.3 mm Pitch ................................................... 154

January 2013 IPC-7095C

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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