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CBGA Surface Mount Assembly and Rework
User’s Guide
May 23, 2002
®
Copyright International Business Machines Corporation 2002.
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Printed in the United States of America May 23, 2002.
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CBGA Surface Mount Assembly and Rework User’s Guide
May 23, 2002
.
CBGA Surface Mount Assembly and Rework User’s Guide
Contents
Figures .......................................................................................................................................... 7
1. Introduction .............................................................................................................................. 9
2. Assembly ................................................................................................................................ 11
2.1 Package Description .......................................................................................................................
2.2 Card Considerations .......................................................................................................................
2.2.1 Card Pad Design ...................................................................................................................
2.2.2 Card Warping ........................................................................................................................
2.2.3 Other Card Considerations ....................................................................................................
2.2.3.1 Component Compatibility ...............................................................................................
2.2.3.2 Tented Vias ....................................................................................................................
2.2.3.3 Card Quality ...................................................................................................................
2.3 General SMT Process .....................................................................................................................
2.4 Solder-Paste Screening ..................................................................................................................
2.4.1 Paste .....................................................................................................................................
2.4.2 Print Requirements ................................................................................................................
2.4.2.1 1.27 mm Pitch CBGA .....................................................................................................
2.4.2.2 1.00 mm Pitch CBGA .....................................................................................................
2.4.3 Process Controls ...................................................................................................................
2.4.4 Stencils ..................................................................................................................................
2.5 Print Inspection ...............................................................................................................................
2.6 Placement .......................................................................................................................................
2.6.1 Accuracy ................................................................................................................................
2.6.2 Placement Force ...................................................................................................................
2.6.3 Placement Techniques ..........................................................................................................
2.6.3.1 Body Recognition ...........................................................................................................
2.6.3.2 Mechanical Alignment ....................................................................................................
2.6.3.3 Visual Recognition ..........................................................................................................
2.6.3.4 Placement Accuracy .......................................................................................................
2.7 Solder Reflow ..................................................................................................................................
2.7.1 Reflow Requirements ............................................................................................................
2.7.2 Thermal Profiling ...................................................................................................................
2.7.3 Reflow Techniques ................................................................................................................
2.8 Cleaning ..........................................................................................................................................
2.9 Wave Solder ....................................................................................................................................
2.9.1 Secondary Reflow .................................................................................................................
2.9.2 Card Warping ........................................................................................................................
2.10 Fixtures .........................................................................................................................................
2.11 Assembly Inspection .....................................................................................................................
2.12 Joint Reliability ..............................................................................................................................
2.12.1 Solder Fatigue .....................................................................................................................
2.12.2 Design Variations ................................................................................................................
2.12.2.1 Finite Element Model ....................................................................................................
2.12.2.2 Joint Standoff ...............................................................................................................
2.12.2.3 1.27 mm Pitch CBGA ...................................................................................................
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Contents
May 23, 2002
Page 3
CBGA Surface Mount Assembly and Rework User’s Guide
2.12.2.4 High-Performance Glass Ceramic ................................................................................
2.12.2.5 1.00 mm Pitch CBGA ...................................................................................................
2.12.2.6 Double-Side CBGA .......................................................................................................
2.12.2.7 Stress Database (DLA, 25 mm CBGA, 1.0 mm Pitch) .................................................
2.13 Voids .............................................................................................................................................
2.14 Assembly Summary ......................................................................................................................
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3. Rework .................................................................................................................................... 51
3.1 Process Flow ...................................................................................................................................
3.2 Material Sets ...................................................................................................................................
3.3 Tooling Requirements .....................................................................................................................
3.3.1 PCB Preheater .......................................................................................................................
3.3.2 Nozzle Design ........................................................................................................................
3.3.3 Thermal Profiling ....................................................................................................................
3.3.3.1 Method One ....................................................................................................................
3.3.3.2 Method Two ....................................................................................................................
3.3.3.3 Method Three .................................................................................................................
3.3.4 Module Removal ....................................................................................................................
3.3.5 Site Dress ..............................................................................................................................
3.3.6 Solder Vacuum ......................................................................................................................
3.3.7 Clean ......................................................................................................................................
3.3.8 Solder Application ..................................................................................................................
3.3.8.1 Module Screening ...........................................................................................................
3.3.8.2 Site Screening ................................................................................................................
3.3.8.3 Solder Preforms ..............................................................................................................
3.3.8.4 Solder Paste Dispense ...................................................................................................
3.3.9 Module Placement .................................................................................................................
3.4 Module Reflow .................................................................................................................................
3.5 Rework Inspection ...........................................................................................................................
3.6 1.00 mm Pitch CBGA Rework .........................................................................................................
3.7 Forced Rework ................................................................................................................................
3.7.1 NiAu Card Rework .................................................................................................................
3.7.2 Double-Side Module Rework .................................................................................................
3.7.3 Close-Proximity Module Rework ............................................................................................
3.8 Summary .........................................................................................................................................
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4. Revision Log .......................................................................................................................... 67
Appendix A. References ........................................................................................................... 69
Appendix B. Glossary ............................................................................................................... 71
Appendix C. Test Vehicles ........................................................................................................ 73
Appendix D. Coffin-Manson Acceleration Factor ................................................................... 75
Contents
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May 23, 2002
CBGA Surface Mount Assembly and Rework User’s Guide
Appendix E. Solder Reflow ....................................................................................................... 77
E.1 Alpha 1208 Paste ........................................................................................................................... 77
E.2 Kester R244 No-Clean Reflow Profile ............................................................................................ 77
Contents
May 23, 2002
Page 5

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