Crystal structure of Au1−xNixSn4 intermetallic alloys
2002; Elsevier BV; Volume: 334; Issue: 1-2 Linguagem: Inglês
10.1016/s0925-8388(01)01780-7
ISSN1873-4669
AutoresL. Zavalij, A. Zribi, Richard R. Chromik, Susan Pitely, Peter Y. Zavalij, E. J. Cotts,
Tópico(s)Intermetallics and Advanced Alloy Properties
ResumoNi coated with a thin layer of Au is commonly used as a metallization in electronics packaging. Such Ni/Au metallizations are alloyed with Sn at temperatures above the Pb–Sn solder liquidus. Thermal treatment of these joints in the solid state, for instance at 150°C, has been shown to result in the formation of Au1−xNixSn4 compounds at the solder interface. These compounds are found to be deleterious to joint integrity. In this work, synthesis, microstructural analysis and crystal structure determination of Au1−xNixSn4 alloys were performed. The alloys were examined by powder and single crystal X-ray diffraction, metallography, electron microprobe analysis, and thermal analysis. It was found that Ni atoms substitute for Au atoms in the AuSn4 structure giving compounds with general composition Au1−xNixSn4 (with x≤0.5). The structure of the title compounds is considered isotypical with the AuSn4 phase (the PdSn4 structure type), with a symmetry increment from Aba2 to Ccca. Crystal structure refinement from powder data using the Rietveld method was performed for two alloys with x=0.25 and 0.50 yielding Au0.73Ni0.27Sn4 (sp. group Ccca, a=6.448 Å, b=11.606 Å, c=6.441 Å) and Au0.51Ni0.49Sn4 (sp. group Ccca, a=6.424 Å, b=11.522 Å, c=6.384 Å). A single crystal experiment was performed for compound Au0.91Ni0.09Sn4 (sp. group Ccca, a=6.523 Å, b=11.676 Å, c=6.485 Å).
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