IPC-7095C-2013.pdf - 第14页

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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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IPC-7095C January 2013

xii

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Design and Assembly Process Implementation for BGAs

1 SCOPE

This document describes the design and assembly chal-

lenges for implementing Ball Grid Array (BGA) and Fine

Pitch BGA (FBGA) technology. The effect of BGA and

FBGA on current technology and component types is

addressed, as is the move to lead-free assembly processes.

The focus on the information contained herein is on criti-

cal inspection, repair, and reliability issues associated with

BGAs. Throughout this document the word ‘‘BGA’’ can

mean all types and forms of ball/column/bump/pillar grid

array packages.

1.1 Purpose The target audiences for this document are

managers, design and process engineers, and operators and

technicians who deal with the electronic assembly, inspec-

tion, and repair processes. The purpose is to provide useful

and practical information to those who are using BGAs,

those who are considering BGA implementation and

companies who are in the process of transition from stan-

dard tin/lead reﬂow processes to those that use lead-free

materials.

1.2 Intent This document, although not a complete

recipe, identiﬁes many of the characteristics that inﬂuence

the successful implementation of a robust assembly pro-

cess. In many applications, the variation between assembly

methods and materials is reviewed with the intent to high-

light signiﬁcant differences that relate to the quality and

reliability of the ﬁnal product. The accept/reject criteria for

BGA assemblies, used in contractual agreements, is estab-

lished by J-STD-001 and IPC-A-610.

An additional challenge in implementing BGA assembly

processes, along with other types of components, is the

need to meet the legislative directives that declare certain

materials as hazardous to the environment. The require-

ments to eliminate these materials from electronic assem-

blies have caused component manufacturers to rethink the

materials used for encapsulation, the plating ﬁnishes on the

components and the metal alloys used in the assembly

attachment process.

2 APPLICABLE DOCUMENTS

2.1 IPC

J-STD-001 Requirements for Soldered Electrical and Elec-

tronic Assemblies

J-STD-020 Handling Requirements for Moisture Sensitive

Components

J-STD-033 Standard for Handling, Packing, Shipping and

Use of Moisture/Reﬂow Sensitive Surface Mount Devices

J-STD-609 Marking and Labeling of Components, PCBs

and PCBAs to Identify Lead (Pb), Pb-Free and Other

Attributes

IPC-T-50 Terms and Deﬁnitions for Printed Boards and

Printed Board Assemblies

IPC-D-279 Design Guidelines for Reliable Surface Mount

Technology Printed Board Assemblies

IPC-D-356 Bare Substrate Electrical Test Information in

Digital Form

IPC-A-600 Acceptability of Printed Boards

IPC-A-610 Acceptability of Electronic Assemblies

IPC-SM-785 Guidelines for Accelerated Reliability Testing

of Surface Mount Attachments

IPC-1601 Printed Board Handling and Storage Guidelines

IPC-2221 Generic Standard on Printed Board Design

IPC-2581 Generic Requirements for Printed Board Assem-

bly Products Manufacturing Description Data and Transfer

Methodology

IPC-2611 Generic Requirements for Electronic Product

Documentation

IPC-2614 Sectional Requirements for Board Fabrication

Documentation

IPC-2616 Sectional Requirements for Assembly Docu-

mentation

IPC-4554 Speciﬁcation for Immersion Tin Plating for

Printed Circuit Boards

IPC-4761 Design Guide for Protection of Printed Board

Via Structures

IPC-7093 Design and Assembly Process Implementation

for Bottom Termination Components

IPC-7094 Design and Assembly Process Implementation

for Flip Chip and Die Size Components

IPC-7351 Generic Requirements for Surface Mount

Design and Land Pattern Standard

IPC-7525 Stencil Design Guidelines

1. www.ipc.org

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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