Abstract

It has recently been documented that Pb-free solder alloys doped with trace amounts of rare earth (RE) elements show a very strong propensity to grow Sn whiskers. In this work, we have investigated the effect of the addition of 2 wt.% Ce, La or Y on the whiskering behavior of Sn-3.9Ag-0.7Cu. Hillock-type whiskers around particle peripheries were observed in water-quenched alloys with smaller RESn3 particles, while furnace-cooled alloys with larger RESn3 particles formed needle-like whiskers from within the particle. Phase separation between Sn and RE oxides occurred during oxidation of the RESn3 intermetallics. A focused ion beam serial sectioning approach was used to visualize the Sn whiskers and the oxide structure. We show that the driving force for whisker growth is related to the compressive stresses that develop in these particles during the oxidation of the RE intermetallic phases.

Original languageEnglish (US)
Pages (from-to)4588-4599
Number of pages12
JournalActa Materialia
Volume57
Issue number15
DOIs
StatePublished - Sep 1 2009

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Keywords

  • 3-D materials science
  • Focused ion beam (FIB)
  • Whiskers

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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