Morphologies of Primary Cu6Sn5 and Ag3Sn Intermetallics in Sn–Ag–Cu Solder Balls

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

Abstract

This article focuses on the morphologies of primary Cu6Sn5 and Ag3Sn intermetallics in small Sn-Ag-Cu (Ø 270 μm) solder balls. The Cu6Sn5 phase showed a large variety of different shapes and sizes, ranging from facetted hexagonal rods, to partly facetted splitting crystals and parallel growing branches, to dendritic crystals without facets. The results of electron backscatter diffraction (EBSD) measurements confirm [0001] as the major growth direction and the {101̅0} planes as facets of the hexagonal rods. The formation of crystals splitting parallel to the {101̅0} planes may be caused by a slight deviation of the major growth direction toward (21̅1̅0). Primary Ag3Sn intermetallics showed less morphology variations and solidified as typical plate structures with a planar and an irregular side. Sixfold starshaped formations of multiple plates arranged around a common center have been investigated by EBSD. All plates appear to have the same hexagonal orientation and possible growth directions are parallel to the {101̅0} planes. However, these pseudohexagonal structures showed color differences between plates of different growth directions, if investigated with polarized light microscopy. Those orientation differences were not detectable by EBSD. Possible interpretations are discussed on the basis of the orthorhombic distorted lattice and by possible twinning mechanisms.

Details

Original languageEnglish
Article number8894079
Pages (from-to)18-29
Number of pages12
JournalIEEE Transactions on Components, Packaging and Manufacturing Technology
Volume10
Issue number1
Early online date7 Nov 2019
Publication statusPublished - 1 Jan 2020
Peer-reviewedYes

External IDs

Scopus 85078339711
ORCID /0000-0001-8576-7611/work/165877187

Keywords

Keywords

  • Crystals, Morphology, Temperature measurement, Intermetallic, Shape, Soldering