In situ heating transmission electron microscopy observation of nanoeutectic lamellar structure in sn-ag-cu alloy on au under-bump metallization

Jong Hyun Seo, Sang Won Yoon, Kyou Hyun Kim, Hye Jung Chang, Kon Bae Lee, Tae Yeon Seong, Eric Fleury, Jae Pyoung Ahn

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

We investigated the microstructural evolution of Sn96.4Ag 2.8Cu0.8 solder through in situ heating transmission electron microscopy observations. As-soldered bump consisted of seven layers, containing the nanoeutectic lamella structure of AuSn and Au5Sn phases, and the polygonal grains of AuSn2 and AuSn4, on Au-plated Cu bond pads. Here, we found that there are two nanoeutectic lamellar layers with lamella spacing of 40 and 250 nm. By in situ heating above 140°C, the nanoeutectic lamella of AuSn and Au5Sn was decomposed with structural degradation by sphering and coarsening processes of the lamellar interface. At the third layer neighboring to the lamella layer, on the other hand, Au5Sn particles with a zig-zag shape in AuSn matrix became spherical and were finally dissipated in order to minimize the interface energy between two phases. In the other layers except both lamella layers, polycrystal grains of AuSn2 and AuSn4 grew by normal grain growth during in situ heating. The high interface energy of nanoeutectic lamella and polygonal nanograins, which are formed by rapid solidification, acted as a principal driving force on the microstructural change during the in situ heating.

Original languageEnglish
Pages (from-to)49-53
Number of pages5
JournalMicroscopy and Microanalysis
Volume19
Issue numberSUPPL. 5
DOIs
Publication statusPublished - 2013 Aug 1

Fingerprint

Lamellar structures
lamella
Metallizing
Transmission electron microscopy
Heating
transmission electron microscopy
heating
Rapid solidification
Microstructural evolution
Polycrystals
Coarsening
Grain growth
Soldering alloys
rapid solidification
polycrystals
solders
Degradation
spacing
degradation
energy

Keywords

  • in situ heating
  • microstructure
  • Sn-Ag-Cu solder
  • STEM
  • TEM
  • UBM

ASJC Scopus subject areas

  • Instrumentation

Cite this

In situ heating transmission electron microscopy observation of nanoeutectic lamellar structure in sn-ag-cu alloy on au under-bump metallization. / Seo, Jong Hyun; Yoon, Sang Won; Kim, Kyou Hyun; Chang, Hye Jung; Lee, Kon Bae; Seong, Tae Yeon; Fleury, Eric; Ahn, Jae Pyoung.

In: Microscopy and Microanalysis, Vol. 19, No. SUPPL. 5, 01.08.2013, p. 49-53.

Research output: Contribution to journalArticle

Seo, Jong Hyun ; Yoon, Sang Won ; Kim, Kyou Hyun ; Chang, Hye Jung ; Lee, Kon Bae ; Seong, Tae Yeon ; Fleury, Eric ; Ahn, Jae Pyoung. / In situ heating transmission electron microscopy observation of nanoeutectic lamellar structure in sn-ag-cu alloy on au under-bump metallization. In: Microscopy and Microanalysis. 2013 ; Vol. 19, No. SUPPL. 5. pp. 49-53.
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abstract = "We investigated the microstructural evolution of Sn96.4Ag 2.8Cu0.8 solder through in situ heating transmission electron microscopy observations. As-soldered bump consisted of seven layers, containing the nanoeutectic lamella structure of AuSn and Au5Sn phases, and the polygonal grains of AuSn2 and AuSn4, on Au-plated Cu bond pads. Here, we found that there are two nanoeutectic lamellar layers with lamella spacing of 40 and 250 nm. By in situ heating above 140°C, the nanoeutectic lamella of AuSn and Au5Sn was decomposed with structural degradation by sphering and coarsening processes of the lamellar interface. At the third layer neighboring to the lamella layer, on the other hand, Au5Sn particles with a zig-zag shape in AuSn matrix became spherical and were finally dissipated in order to minimize the interface energy between two phases. In the other layers except both lamella layers, polycrystal grains of AuSn2 and AuSn4 grew by normal grain growth during in situ heating. The high interface energy of nanoeutectic lamella and polygonal nanograins, which are formed by rapid solidification, acted as a principal driving force on the microstructural change during the in situ heating.",
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