Transactions of The Japan Institute of Electronics Packaging
Online ISSN : 1884-8028
Print ISSN : 1883-3365
ISSN-L : 1883-3365
Technical Papers
Effects of Bismuth in Sn-Cu Based Solder Alloys and Interconnects
Kazuhiro NogitaMohd A. A. Mohd SallehSelena SmithYueqin WuStuart D. McDonaldAhmad Ghazie A. RazakShiqian LiuTetsuya AkaiwaTakatoshi Nishimura
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2017 Volume 10 Pages E17-003-1-E17-003-7


Additions of 1.5wt%Bi to Sn-0.7wt%Cu-0.05wt%Ni (SN100C) were investigated for their influence on mechanical properties and the intermetallic (IMC) layer formed between the solder and Cu substrates. Solder balls of Sn-0.7wt%Cu (Sn07Cu), SN100C, Sn-0.7wt%Cu-0.05wt%Ni-1.5wt%Bi (SN100CV) and Sn-3wt%Ag-0.5wt%Cu (SAC) were reflowed onto Cu ball grid arrays (BGAs). They were examined in the as reflowed condition and after a heat treatment of annealing at 150°C up to 1,500 hours. The mechanical properties of SN100C, SN100CV and SAC solder balls were investigated by nano-indentation, and cross-sections of the interfacial IMC layer were observed by SEM to determine the morphology and average interfacial IMC layer thickness. It was found that the effect of Bi additions was to increase the lattice parameters and alter the mechanical properties. The near-eutectic microstructure and suppression of Cu3Sn at the IMC layer that are associated with Ni additions are not altered by the presence of 1.5wt%Bi.

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