Journal Article

The Influence of Cu on Metastable NiSn^sub 4^ in Sn-3.5Ag-xCu/ENIG Joints

Gourlay, C M, Belyakov, S A

2016

Overview

Issue Title: Special Sections: Pb-free Solders and Materials for Emerging Interconnect and Packaging Technologies; Phase Stability, Phase Transformations, and Reactive Phase Formation in Electronic Materials XIII; and Advanced Materials for Power Electronics and Power Conditioning Systems We have investigated the effect of small amounts of Cu on suppression of metastable [beta]Sn-NiSn^sub 4^ eutectic growth in solder joints between Sn-3.5Ag-xCu solders and Ni-based substrates. For Sn-3.5Ag/electroless nickel immersion gold (ENIG) and Sn-3.5Ag/Ni solder joints we showed that the eutectic mixture contains [beta]Sn, Ag^sub 3^Sn, and metastable NiSn^sub 4^. It was found that addition of only 0.005 wt.% Cu to Sn-3.5Ag-xCu/ENIG or Sn-3.5Ag-xCu/Ni joints promoted formation of a stable [beta]Sn-Ni^sub 3^Sn^sub 4^ eutectic and that both Ni^sub 3^Sn^sub 4^ and NiSn^sub 4^ occur in the eutectic at this Cu level. We also showed that for complete prevention of formation of metastable NiSn^sub 4^ during eutectic solidification of the solder joint, addition of at least 0.3 wt.% Cu was required.

• Publisher: Springer Nature B.V
• Subject: Soldering