A metastable phase of tin in 3D integrated circuit solder microbumps

Yingxia Liu, Nobumichi Tamura, Dong Wook Kim, Sam Gu, King-Ning Tu*

*Corresponding author for this work

Research output: Contribution to journalArticle

12 Scopus citations


A metastable phase of Sn has been found to co-exist with β-Sn in Pb-free SnAg microbumps in 3D integrated circuit technology. Synchrotron microbeam X-ray diffraction, high-resolution TEM imaging and selected-area electron diffraction were used to confirm the metastable phase, which has an orthorhombic lattice, with lattice parameter a = 0.635 nm, b = 0.639 nm, and c = 1.147 nm. Its composition is Sn containing a few percent of Ni. A higher rate of nucleation might have enabled its formation.

Original languageEnglish
Pages (from-to)39-42
Number of pages4
JournalScripta Materialia
StatePublished - 1 Jun 2015


  • Electronic packaging Joining
  • Lead-free solder
  • Metastable phases

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