Can whiskers grow on bulk lead-free solder?

John A. Nychka, Yan Li, Fuqian Yang, Rong Chen

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Many possible mechanisms for whisker growth exist, each possible in various scenarios investigated in the literature. This contribution addresses the importance of residual mechanical stress in a solder alloy for providing some of the energy necessary to drive possible whisker growth. We investigate the indentations made on bulk lead-free solder (Sn3.5Ag) to introduce various levels of residual energy associated with localized residual stresses. We confirm that localized residual stresses, in the absence of a thin-film geometry, significant oxide thickness, and interdiffusional stresses from intermetallic Cu-Sn compounds, do not result in the formation of whiskers in bulk Sn3.5Ag. Thus, the combination of stresses associated with thin films (either thermal misfit, plating, or chemical) and the oxidation of Sn at the surface is likely required for continuous whisker growth.

Original languageEnglish
Pages (from-to)90-95
Number of pages6
JournalJournal of Electronic Materials
Issue number1
StatePublished - Jan 2008

Bibliographical note

Funding Information:
The authors, JAN and FY, are grateful to the Kentucky Science and Engineering Foundation for financial support of this work through Grant Agreement KSEF-148-502-06-180.


  • Lead-free solder
  • Mechanical properties
  • Micro-indentation
  • Residual stress and strain
  • Whisker growth

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Materials Chemistry
  • Electrical and Electronic Engineering


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