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M: Metallphysik

M 20: Intermetallische Phasen I

M 20.5: Vortrag

Samstag, 5. März 2005, 10:15–10:30, TU H2038

Characterization of Cu/Sn and Cu/SnPb solder reaction — •Jens Görlich and Guido Schmitz — Institut für Materialphysik, Wilhelm-Klemm-Straße 10, 48149 Münster

Development of leadfree solders and a further size reduction in electronic devices require a better understanding of physical mechanisms during soldering. Diffusion paths, kinetic processes and - especially for microdevices - the unfavorable fast growth of the non planar intermetallic Cu₆Sn₅ layer during the interreaction between solid Cu and liquid tin-lead or pure liquid tin solder have been investigated. SEM analyses revealed a time dependence of the scallop-like Cu₆Sn₅ intermetllic layer of R∼t^1/3. The interfaces between Cu and the solder were analysed by HREM and EELS and the wetting angles for pure tin and tin-lead solder were determined. The growth of the scallop like structure is controlled by grain boundary diffusion across the existing Cu₆Sn₅ layer. Nevertheless, the observed process may be still described by a recent model [1], which assumes the transport through channel of liquid solder. Furthermore, the influence of a sputter-deposited Cu₆Sn₅ base metallization was investigated. The results will be discussed in view of the technologically desired limitation of the fast growth of Cu₆Sn₅.

[1] A.M. Gusak, Phys. Rev. B 66, 115403 (2002)