Microstructural Evolution and Mechanical Properties in (AuSn)eut-Cu Interconnections

Hongqun Dong*, Vesa Vuorinen, Tomi Laurila, Mervi Paulasto-Kröckel

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

9 Citations (Scopus)


The interfacial reactions between the widely employed solder Au-20wt.%Sn and the common contact metallizations (e.g. Ni, Cu and Pt) are normally complex and not well determined. In order to identify the proper contactor for Au-20wt.%Sn solder, the present study focuses on (1) rationalizing the interfacial reaction mechanisms of Au-20wt.%Sn|Cu as well as (2) measuring the mechanical properties of individual intermetallics formed at the interface. The evolution of interfacial reaction products were rationalized by using the experimental results in combination with the calculated Au-Cu-Sn phase diagram information. It was found that the growth of the AuCu interfacial intermetallic layer was diffusion-controlled. The diffusion path of Au-20wt.%Sn|Cu at 150°C was proposed. The hardness and indentation modulus of the interfacial reaction products were measured using nanoindentation tests. The results revealed a significant influence of the Cu solubility on the mechanical properties of (Au,Cu)Sn and (Au,Cu)5Sn, i.e. their hardness and contact modulus increased with the increase in the amount of Cu. Furthermore, results obtained here for the Au-20wt.%Sn|Cu joints were compared to those from Au-20wt.%Sn|Ni in order to assess the similarities and differences between these widely used interconnection metallization systems.

Original languageEnglish
Pages (from-to)5478–5486
Number of pages9
JournalJournal of Electronic Materials
Issue number10
Publication statusPublished - Oct 2016
MoE publication typeA1 Journal article-refereed


  • Au-20wt.%Sn|Cu
  • diffusion path
  • hardness
  • indentation modulus
  • microstructure
  • nanoindentation test
  • phase diagram


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