Journal of Alloys and Compounds 389 (2005) 61–74 Interfacial interaction of solid nickel with liquid bismuth and Bi–base alloys V.I. Dybkov a,∗ , K. Barmak b , W. Lengauer c , P. Gas d a DepartmentofPhysicalChemistryofInorganicMaterials,InstituteforProblemsofMaterialsScience, 03180Kyiv,Ukraine b DepartmentofMaterialsScienceandEngineering,CarnegieMellonUniversity,Pittsburgh,PA15213,USA c InstituteforChemicalTechnologiesandAnalytics,ViennaUniversityofTechnology,1060Vienna,Austria d L2MP-CNRS,Facult´ edesSciencesStJerome,Case142,13397Marseille,France Received 12 February 2004; accepted 25 February 2004 Abstract The dissolution process of nickel in liquid bismuth and a 51%Bi–42%Sn–5%In–2%Zn alloy was investigated by the rotating-disc technique at 300 and 350 ◦ C. The solubility values of nickel in bismuth and its alloy were found to be very different, while the dissolution rate constants were rather close. Appropriate diffusion coefficients were estimated. With bismuth as a melt material, the NiBi 3 intermetallic layer is formed at the interface of nickel and the saturated or undersaturated melt at holding times up to 3600 s. The NiBi phase is found to be missing. A simple mathematical equation is proposed to evaluate the NiBi 3 layer thickness in the case of undersaturated melts. With a 51%Bi–42%Sn–5%In–2%Zn alloy as a melt material, a very thin intermetallic layer of complicated chemical composition occurs at the Ni–alloy interface. With saturated melts, its growth-rate constant is 5.5 × 10 -16 m 2 s -1 at 350 ◦ C, whereas in undersaturated melts, the intermetallic phase does not form at all, if the liquid agitation is sufficiently strong. The rupture strength of the nickel-to-alloy joints is around 25 MPa. Small additions of Sb, Te and Se (2% in total) to the alloy exert a considerable influence on the intermetallic-layer composition, but have minimal impact on its thickness. © 2004 Elsevier B.V. All rights reserved. Keywords: Dissolution kinetics; Intermetallic compounds; Nickel; Bismuth; 51%Bi–42%Sn–5%In–2%Zn alloy 1. Introduction After wetting the solid nickel surface with molten bismuth or a Bi–base alloy, dissolution of the solid in the liquid phase and formation of intermetallic-compound layers at the inter- face take place simultaneously. Knowledge of the kinetics of both processes is essential when brazing nickel by low- melting Bi–base alloys, in microelectronic devices in partic- ular. Nickel is known to be employed as a material for inter- connects. Because of the toxicity of lead, there is a tendency to use Bi–Sn (or Sn–Bi) alloys, with the addition of small amounts (up to a few per cent) of other low-melting-point ∗ Corresponding author. E-mailaddress: vdybkov@ukr.net (V.I. Dybkov). metals (In, Ga, Zn, Sb, Se, etc.), as brazing agents instead of Sn–Pb alloys. The occurrence of intermetallic compounds considerably deteriorates the mechanical strength of the transition zone be- tween dissimilar metals or alloys. Usually, the intermetallics occur both at the phase interface between nickel and bismuth or Bi–base alloys in the form of a brittle continuous layer and in its vicinity in the melt material as the aggregation of relatively coarse grains. The former occurs in the course of a chemical reaction, while the latter during cooling-down the melt or in some cases as a result of destroying the layer under the influence of the liquid phase. It should be noted, however, that the full absence of the intermetallic compounds between dissimilar metals or alloys must not necessarily be considered as a guarantee of their 0925-8388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2004.02.063