High-strength and thermal stable Cu-to-Cu joint fabricated with transient molten Ga and Ni under-bump-metallurgy

Shih kang Lin, Mei jun Wang, Che yu Yeh, Hao miao Chang, Yu chen Liu

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Copper (Cu)-to-Cu bonding is an essential process for most advanced electronic devices, such as Cu-pillar joining in flip-chip packaging, through-silicon-via interconnections in three-dimensional integrated circuits, and die attachments in wide band-gap electronics. Here we propose an approach for fabricating face-centered cubic solid-solution joints without formation of intermetallic compounds by using a trace amount of gallium (Ga) and nickel (Ni) under-bump-metallurgy (UBM) for the reactive diffusion bonding at 300 °C. The formation of solid-solution joints involves interactions with the Ni[sbnd]Cu[sbnd]Ga mixture at the bonding interface. A shear-strength of 43.5 MPa was achieved in the as-bonded joint due to the formation of grains across the bonding interface, while it does not degrade after prolonged post-annealing at 300 °C for 200 h. Instead, an even stronger joint with a shear-strength of 48.2 MPa was obtained. We demonstrate the fabrication of strong, thermally stable Cu-to-Cu joints using transient molten Ga and Ni UBM.

Original languageEnglish
Pages (from-to)561-567
Number of pages7
JournalJournal of Alloys and Compounds
Publication statusPublished - 2017

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry


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