Factors Affecting the Bulk Embrittlement of Pb-Free Solder Joints

  • K. Lambrinou


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.


Fracture Toughness Solder Joint Impact Toughness Stable Crack Growth Notch Toughness 
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American Society for Testing and Materials


Body-centred cubic


Body-centred tetragonal


Back scattered electron


Crack-arrest temperature


Crack-mouth opening displacement


Crack-tip opening displacement


Charpy V-notch


Ductile-to-brittle transition temperature


Face-centred cubic


Fracture transition elastic temperature


Fracture transition plastic temperature


Hexagonal close-packed


Intermetallic(s) or intermetallic compound(s)


Load line displacement


Nil ductility temperature






Secondary electron


Scanning electron microscopy



Special Symbols


Figure adapted from the reference given in []


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: 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: 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



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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