Interfacial microstructure and the kinetics of interfacial reaction in diffusion couples between Sn-Pb solder and Cu/Ni/Pd metallization

G. Ghosh*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

117 Scopus citations

Abstract

The interfacial microstructure and the kinetics of interfacial reaction between eutectic Sn-Pb solder and electroplated Ni/Pd on a Cu substrate have been studied by scanning, transmission and analytical electron microscopies. Besides PdSn4 and Ni3Sn4, small grains of Ni3Sn2 with a hexagonal structure are also observed after long-time aging of the diffusion couples at 125 °C. The presence of intermetallic phases is correlated with the diffusion paths in the calculated Pd-Pb-Sn and Ni-Pb-Sn isothermal sections. The growth kinetics of the Ni3Sn4 scallops in the submicrometer length scale was analyzed with an Arrhenius type of equation. The thickening kinetics yields a time exponent n = 3.1 and an apparent activation energy (Qh) of 25,750 J/mol, while the radial growth kinetics data yield a time exponent m≈6.6 and an apparent activation energy (Qd) of 15,300 J/mol. The radial size distributions (RSDs) of Ni3Sn4 scallops were also quantified. The parameters describing RSDs are consistent with the theories of coarsening in two-phase systems containing a very high volume fraction of the second phase. Selective etching of solder revealed the three-dimensional morphology of PdSn4 and Ni3Sn4, and also the dynamical phenomena, such as faceting, competitive growth and coalescence of Ni3Sn4 scallops during interfacial reaction. Non-parabolic growth kinetics is discussed in terms of the existing theories and characteristics of the evolving microstructure.

Original languageEnglish (US)
Pages (from-to)3719-3738
Number of pages20
JournalActa Materialia
Volume48
Issue number14
DOIs
StatePublished - Sep 4 2000

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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