Four dimensional (4D) microstructural evolution of Cu6Sn5 intermetallic and voids under electromigration in bi-crystal pure Sn solder joints

Marion Branch Kelly, Sridhar Niverty, Nikhilesh Chawla

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Electromigration (EM) causes intermetallic and void growth that decreases the reliability and lifetime of solder joints. As a diffusion-controlled process, EM is highly dependent on the fastest diffusion pathways in a structure. In anisotropic β-tetragonal Sn those pathways are along high angle grain boundaries and along the c-axis of the Sn grains. A bicrystal sample with two major grain orientations and two major grain boundary types was EM tested for 100 h. EM was interrupted at intervals for x-ray microtomography to reveal the 3D evolution of intermetallic compounds (IMCs) and voids within the joint. Quantitative IMC growth along high angle grain boundaries and twins was captured for the first time and related to the effective Cu diffusivity of multiple grains. Using a correlative approach that combined scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) mapping, IMC growth and morphology were linked to the evolution of the Sn grain structure. Unusual void shrinkage and void splitting behavior were connected to uneven cathode interface consumption and thermal compression.

Original languageEnglish (US)
Pages (from-to)118-128
Number of pages11
JournalActa Materialia
Volume189
DOIs
StatePublished - May 1 2020
Externally publishedYes

Keywords

  • Electromigration
  • Intermetallics
  • Lead-free solder
  • Void growth
  • X-ray microtomography

ASJC Scopus subject areas

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

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