On the formation mechanism of solid-solution Cu-to-Cu joints in the Cu/Ni/Ga/Ni/Cu system

Shih kang Lin, Che yu Yeh, Mei jun Wang

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Copper (Cu)-to-Cu interconnection is crucial in electronic packaging for applications ranging from three-dimensional integrated circuits to die-attachment in wide band-gap devices. Solid-solution phases are innate with better ductility and electrical and thermal conductivity over intermetallic compounds, which are brittle, electrical resistant, and unstable; yet are commonly seen in electronic joints. The desired solid-solution Cu-to-Cu joints have recently been demonstrated using transient-liquid-phase bonding with gallium (Ga) as the filler material to bond Cu substrates with electroplated nickel (Ni) as under-bump-metallurgy. The Cu/Ni/Ga/Ni/Cu couples can fully transform into the Cu/face-centered cubic (fcc)-(Ni,Cu,Ga)/Cu solid-solution joints. However, why and how the solid-solution joints were formed remains unclear. Here we proposed the formation mechanism of the fcc-(Ni,Cu,Ga) solid-solution joints based on five sets of Cu-Ni-Ga couples, namely the Ni/Ga, Ni/Cu/Ga, Ni/Ni/Ga, (Cu,Ni)/Ga, and Cu/Ni/Ni3Ga7/Ni3Ga7/Ni/Cu reactions. The roles of each element in the Cu-Ga-Ni interactions as well as the reaction progressions are elaborated.

Original languageEnglish
Pages (from-to)14-23
Number of pages10
JournalMaterials Characterization
Publication statusPublished - 2018 Mar

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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