Interfacial reactions in the SbeSn/(Cu, Ni) systems: Wetting experiments R. Novakovic a, * , T. Lanata a , S. Delsante b , G. Borzone b a National Research Council (CNR) e Institute for Energetics and Interphases (IENI), Via De Marini, 6-16149 Genoa, (Italy) b DCCI-University of Genoa, Via Dodecaneso, 31 e 16146-Genoa, (Italy) highlights < SbeSn alloys are used as high temperature lead-free solders. < SbeSn alloys have good wetting properties on Cu and Ni substrates. < Interfacial reactions and products are important for joint properties. < Interfacial reactions/products data can be used to study the phase diagrams. article info Article history: Received 27 December 2011 Received in revised form 23 August 2012 Accepted 16 September 2012 Keywords: Alloys Interfaces Metals Solidification Electron microscopy abstract Interfacial reactions in the SbeSn/Cu and SbeSn/Ni systems have been investigated by means of wetting experiments. The wetting behaviour of two lead-free alloys, namely, Sb 2.5 Sn 97.5 and Sb 14.5 Sn 85.5 (at.%), in contact with Cu and Ni-substrates has been studied in view of possible applications as high-temperature solders in the electronics industry. The contact angle measurements on Cu and Ni plates were performed by using a sessile drop apparatus. The solder/substrate interface was characterised by the SEM-EDS analyses. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction The step soldering process includes the formation of consecu- tive joints at sequentially lower temperatures and thus solders of different melting temperatures are needed. High-temperature solder alloys such as AueSn, AueGe, AueSi, SbeSn, AgeBieSn, AgeCueSn, AgeSbeSn, CueSbeSn, with melting temperatures above 500 K are widely used in the electronic industry for advanced packing technologies. The applications of gold alloys in new generation electronic devices such as high-power micro- electromechanical systems (MEMS) tend to be limited due to their high costs. In the framework of the Action COST MP0602 project some Sn-rich alloys of the SbeSn system have been proposed as candidates for high temperature lead-free solders [1,2]. The wetting characteristics of a liquid filler alloy/substrate are often overlooked or ignored by the producers due to a wide use of fluxes in soldering processes [3]. The fluxes are used in electronics manufacturing to promote the wettability required to make a good solder joint, to prevent oxidation and to protect a soldering tip. On the other side, the fluxes can be critical to the brazing and soldering processes because of the formation of corrosive by-products with a consequent deterioration in properties of solder joints [4]. Two strategies can be used to overcome the problem of flux: to design a new generation of fluxes that are compatible with solders or, if possible, to use “fluxless” soldering. Both approaches require a complete characterisation of the soldering process in terms of physicoechemical properties and wetting characteristics of a liquid solder/solid substrate system as well as the environmental condi- tions over which the process is carried out [5]. The wetting behaviour of a solder/substrate system is usually described by the contact angle, q, of the liquid metal drop formed on the solid substrate. The formation of a thin intermetallic compound layer at the interface is desirable to achieve a good metallurgical bond [3,6]. Due to the brittle nature of intermetallic compounds, an excessively thick intermetallic layer can be a source of mechanical weakness in the soldered joints [3,4,7]. The * Corresponding author. Tel.: þ39 010 6475724; fax: þ39 010 6475700. E-mail address: r.novakovic@ge.ieni.cnr.it (R. Novakovic). Contents lists available at SciVerse ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys 0254-0584/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matchemphys.2012.09.028 Materials Chemistry and Physics 137 (2012) 458e465