Heterogeneous nucleation of βSn on NiSn4, PdSn4 and PtSn4

During Pb-free soldering, βSn often requires a high nucleation undercooling and there is an ongoing effort to develop nucleation catalysts. It is shown here that NiSn4, PdSn4 and PtSn4 are heterogeneous nucleants for βSn, reducing the nucleation undercooling to ∼4K when these intermetallics are pres...

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Bibliographic Details
Published in:Acta materialia 2014-06, Vol.71, p.56-68
Main Authors: Belyakov, S.A., Gourlay, C.M.
Format: Article
Language:English
Subjects:
Applied sciences
Brazing. Soldering
Catalysis
Crystal lattices
Crystal structure
Eutectic
Eutectics
Exact sciences and technology
Heterogeneous nucleation of phase
Intermetallic compounds
Joining, thermal cutting: metallurgical aspects
Metals. Metallurgy
Nucleation
Origins
Soldering
Supercooling
Undercooling
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Summary:During Pb-free soldering, βSn often requires a high nucleation undercooling and there is an ongoing effort to develop nucleation catalysts. It is shown here that NiSn4, PdSn4 and PtSn4 are heterogeneous nucleants for βSn, reducing the nucleation undercooling to ∼4K when these intermetallics are present either in the bulk solder or as the interfacial layer. Nucleation catalysis occurs by βSn nucleating on the (008) facet of XSn4 crystals with an orientation relationship (OR) (100)Sn||(008)XSn4 and [001]Sn||[100]XSn4 where there is a planar lattice match of ∼5%. This OR is also the origin of well-aligned lamellar βSn–XSn4 eutectic morphologies, even though the eutectics contain less than 2vol.% of faceted NiSn4, PdSn4 or PtSn4.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2014.02.044