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Factors Affecting the Bulk Embrittlement of Pb-Free Solder Joints

  • K. Lambrinou
Chapter

Abstract

This chapter mainly addresses the factors affecting the bulk embrittlement of Sn-based Pb-free solder joints, as this type of embrittlement may occur during the life cycle of these solder joints, depending on the requirements of their ‘mission profile’. The term ‘bulk embrittlement’ is used to describe brittle failures occurring in the solder bulk, in contrast to the brittle failures that occur in the intermetallic layers at the solder joint/bond pad interface. The factors affecting the bulk embrittlement of Sn-based Pb-free solder joints may be divided into ‘intrinsic’ and ‘extrinsic’. Examples of ‘intrinsic’ factors include the solder composition, crystal structure, and microstructure, while examples of ‘extrinsic’ factors include the temperature, strain rate, and constraint of the solder during service, as well as the cooling rate from the processing temperature. By understanding the mechanism of bulk solder embrittlement and the factors affecting it, one may try to find the ways to control it, especially when the conditions of the end application favour such type of embrittlement.

Keywords

Fracture Toughness Solder Joint Impact Toughness Stable Crack Growth Notch Toughness 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Abbreviations

ASTM

American Society for Testing and Materials

bcc

Body-centred cubic

bct

Body-centred tetragonal

BSE

Back scattered electron

CAT

Crack-arrest temperature

CMOD

Crack-mouth opening displacement

CTOD

Crack-tip opening displacement

CVN

Charpy V-notch

DBTT

Ductile-to-brittle transition temperature

fcc

Face-centred cubic

FTE

Fracture transition elastic temperature

FTP

Fracture transition plastic temperature

hcp

Hexagonal close-packed

IMC(s)

Intermetallic(s) or intermetallic compound(s)

LLD

Load line displacement

NDT

Nil ductility temperature

Pb-free

Lead-free

SAC

Sn–Ag–Cu

SE

Secondary electron

SEM

Scanning electron microscopy

Sn-based

Tin-based

Special Symbols

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Figure adapted from the reference given in []

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From “The Science and Engineering of Materials”, 5th edition, by Askeland and Phulé. © 2006 by Nelson. Reprinted with permission of Nelson, a division of Thomson Learning: www.tomsonrights.com. Fax: 800 730 2215

[]#

From “The Science and Engineering of Materials”, 1st edition, by Askeland. © 1984 by Wadsworth, Inc. Reprinted with permission of Brooks/Cole, a division of Thomson Learning: www.tomsonrights.com. Fax: 800 730 2215

[]&

From “Deformation and Fracture Mechanics of Engineering Materials”, 4th edition, by Hertzberg. © 1996 by John Wiley & Sons, Inc. Reprinted with permission of John Wiley and Sons, Inc

[]

From “Fracture and Fatigue Control in Structures: Applications of Fracture Mechanics”, 3rd edition, by Barsom and Rolfe. © 1999 by ASTM International. Reprinted with permission of ASTM International

[]

Reproduced with permission of Emerald Group Publishing Ltd. © 2000 by MCB University Press

Notes

Acknowledgments

The author would like to acknowledge certain persons, whose comments improved the quality of this text. These persons are listed in alphabetical order:

Dr. Dag Andersson (IVF, Sweden),

Prof. Ingrid De Wolf (imec, Belgium),

Dr. Paul Michelis (IMMG, Greece),

Prof. Marc Seefeldt (Department MTM, K. U. Leuven, Belgium),

Dr. Geert Willems (imec, Belgium).

The author also wishes to acknowledge the financial support provided by IWT (Flemish Government) in the framework of the ALSHIRA (Aspects of Lead-Free Soldering for High-Reliability Applications) Project. Last but not least, the author would like to thank Dr. B. Vandevelde, Mr. P. Limaye, and Mr. F. Duflos from imec, as well as Prof. B. Verlinden and Mr. W. Maurissen from the Department MTM of the Katholieke Universiteit Leuven (K. U. Leuven), for their collaboration on the research related with the embrittlement of Pb-free solder alloys.

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Copyright information

© Springer-Verlag London Limited 2011

Authors and Affiliations

  1. 1.IMECLeuvenBelgium
  2. 2.SCK-CENMolBelgium

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