Bi-Sn-Zn & Pd-Sn-Zn Systems: Summary of the Results Jiri Vizdal 1 and Ales Kroupa 2 Phase Equilibria in Lead-free solders 2 Structure of Phases Group Department of Structure Institute of Physics of Materials, AS CR Brno, Czech Republic 1 Department of Inorganic Chemistry / Materials Chemistry Faculty of Chemistry University of Vienna Vienna, Austria Pb

Presentation outline  Aims + used methodology  Experimental methods summary  Results… Bi-Sn, Bi-Zn, Bi-Sn-Zn Pd-Zn, Pd-Sn-Zn  Conclusions

Our goals and how to achieve them... Aims & methodology  Our work was aimed at thermodynamic and experimental description of phase equilibria in the Bi-Sn-Zn, Pd-Sn-Zn (Pd – Pd/Ni substrate coatings) systems and relevant subsystems >>> contribution to new Pb-free solders design  Analysis + literature survey: optimal thermodynamic assessments selection (if exist!) 1. version of the thermodynamic database  Theoretical study („CALPHAD“ -> Thermo-Calc): predictions calculations  Experimental study (SEM + EDS/WDS, DTA/DSC, etc.)  Theoretical study: modelling -> „COST531“ thermodynamic database expansion

Exp. methods summary Experimental details Materials, treatment  Bi, Sn, Zn, Pd ≥ 99,95 %  Samples were sealed under vacuum into quartz capsules.  Homogeneity {SEM (BSE) + EDS}.  Heat treatment – annealing (different T, t).  Coolant: H 2 O.  Phase identification and composition measurement. >>>  Phase transformations temperatures measurement. >>> Exp. methods  SEM + EDS/WDS (JEOL JSM-6460; BSE; 20 keV / INCA + standards + ZAF)  TEM + EDS (TEM/STEM Philips CM 12 / EDAX Phoenix CM 12)  DTA/DSC (Netzsch DTA/DSC 404; Dept. of Inorganic Chemistry / Material s Chemistry, University of Vienna ): standards: Au/Ag v heating/cooling ~ 2 °C/min. accuracy: ±2 °C atmosphere: vacuum/Ar

Experimental & Theoretical Results

Bi-Sn: Final assessment Bi-Sn: optimization results Enthalpy of mixing in comparison to experimental data from [ASR 2004] and [SHARKEY 1972] Calculated activity of Sn in Liq. in comparison to exp. data from Asryan & Mikula [ASR 2004] Newly modified Bi-Sn system description, that was originally published by [OHT 1994] T E ~ °C [COST 2006]

Bi-Zn: Final assessment Bi-Zn: assessment correction SEM/WDS Overall compos. Bi-76.2Zn Bi in HCP_Zn (Zn) 0.3  0.2 Zn in (Bi) 0.3  0.1 Values in wt. % Annealed 864 h/200 °C Liq. Liq. + (Zn) (Bi) + (Zn) Malakhov [MAL 2000] After change Malakhov [MAL 2000] : J/mol Optimization: J/mol

Bi-Sn-Zn: New assessment Bi-Sn-Zn: selected isopleths Isothermal section (120 °C) together with selected vertical sections compared to available experimental data… BC D E A (Bi) + (Sn) + (Zn) T = 120 °C (Bi) + (Sn) + (Zn) Liq. + (Bi) + (Zn) Liq. + (Sn) + (Zn) x(Zn) = 5 at. % Liq. + (Sn) + (Zn) Liq. + (Zn) (Bi) + (Sn) + (Zn) w(Sn) = 59 hm. % (Sn) + (Zn) (Bi) + (Sn) + (Zn) Liq. + (Zn) (Bi) + (Zn) w(Zn) = 12 hm. % Liq. + (Zn) T T 2 (Bi) + (Sn) + (Zn) (Sn) + (Zn) AB Bi/Zn = 1/2 [This work] [BRA 2007] [LUEF 2006] At. % [COST 2006]

Bi-Sn-Zn: New assessment Bi-Sn-Zn: therm. properties Activities in comparison to exp. data from [OLE 1959] Enthalpies of mixing compared to exp. data from [LUEF 2006] [COST 2006]

Pd-Zn: The reason of study Pd-Zn: overview Massalski’s experimental phase diagram [MASS 1990]Phase diagram by Hansen and Anderko [HAN 1958] Thermodynamic activities of Zn in ordered β 1 Pd-Zn alloys at 1000 °C were measured by Kou and Chang [KOU 1975]. Partial molar and integral properties were determined from vapour pressure measurements by Chiang [CHI 1977] (477 – 1030 °C / 0 – 83 at. % Zn). ?? [E-MRS 2005]

Pd-Zn: New assessment Pd-Zn: phase diagram The detail of the phase diagram showing new exp. information – marked invariant reactions (DTA) and phase‘s composition (SEM + EDS). Pd-Zn phase diagram, calculated on the basis of newly optimized thermodynamic parameters in comparison with available exp. data. [E-MRS 2005]

Pd-Zn: New assessment Pd-Zn: therm. properties Comparison of exp. measured [CHI 1977] and calculated values of: 1.Zn activities in (Pd); 2.integral molar Gibbs energy for the Pd-Zn system at 1000 °C in different concentration ranges. [E-MRS 2005]

Binary prediction + proposed exp. alloys Pd-Sn-Zn: prediction + exp. Calculated isothermal sections in the Pd-Sn-Zn system at 500 and 900 °C based only on binary data together with marked exp. alloys. 500 °C900 °C

Experimental phase diagram Pd-Sn-Zn: SEM/TEM + EDS Preliminary experimental phase diagrams design – isothermal sections constructed according to SEM/TEM + EDS marked experimental results. 500 °C900 °C

Conclusions

Conclusions…  Bi-Sn-Zn system and relevant subsystems: Exp. determined max. solubility of Bi in (Sn) at T E ~ 10 wt. % -> created new assessment of the Bi-Sn system. Exp. determined solubilities of Bi in (Zn) and Zn in (Bi) at T = 200 °C -> correction of the present Bi-Zn assessment. Exp. study of the Bi-Sn-Zn system (SEM + EDS/WDS, DTA) -> own results + results from literature were used for the new assessment (interact. param. for Liq. and (Bi)).  Pd-Zn and Pd-Sn-Zn systems: Exp. study of Zn-rich part of the Pd-Zn phase diagram verified presence of the η-phase at T = 400 °C. Eutectic reaction was established in this part of the Pd-Zn diagram: Liq.  η + (Zn). First thermodynamic description of the Pd-Zn system has been created. First predictions within the Pd-Sn-Zn system were calculated and relevant exp. results at 500 a 900 °C were obtained. These were used for the preliminary exp. phase diagram construction.  Presented finished thermodyn. descriptions of the Bi-Sn, Bi-Zn, Pd-Zn and Bi-Sn-Zn systems are in very good agreement with available data and sets of thermodynamic parameters were included in the „COST531“ database.

Acknowledgements This work was supported by following projects: COST No. OC (Ministry of Education of the Czech Republic) No. 106/05/H008 (Czech Science Foundation) AV0Z (Research project) Cooperation: Dr. Milan Svoboda (IPM AS CR) Prof. Klaus W. Richter (University of Vienna) Dr. Christoph Luef (University of Vienna) Prof. Aloke Paul (Indian Institute of Science) Prof. M. H. Braga (Universidade do Porto) Prof. L. F. Malheiros (Universidade do Porto) Prof. D. Soares (Universidade do Minho) <<< Publications

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