Lead-Free Soldering: Phase Relationships and Thermochemistry of Ag-Cu-Ni-Sn H. Flandorfer, C. Schmetterer, U. Saeed and H. Ipser Department of Inorganic Chemistry / Materials Chemistry University of Vienna COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Outline  The binary systems Phase diagram Enthalpy of mixing  The ternary system Ag-Ni-Sn Literature Difficulties of sample preparation Isothermal sections Vertical sections and liquidus projection Enthalpy of mixing  Conclusions COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

The binary systems Ag-Ni, Ag-Sn and Ni-Sn Ag-Ni Phase diagram version from Massalski‘s compilation 3 samples prepared by arc-melting XRD DTA No significant deviations! COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

The binary systems Ag-Ni, Ag-Sn and Ni-Sn Ag-Sn Phase diagram version from Massalski‘s compilation 9 samples prepared by arc-melting XRD SEM-EDX DTA Good agreement except: p 1 = 489 °C (480 °C) p 2 = 729 °C (725 °C) COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

The binary systems Ag-Ni, Ag-Sn and Ni-Sn Ni-Sn Phase diagram version from Massalski‘s compilation 4 samples prepared by arc-melting XRD SEM-EDX DTA Significant deviations of transition temperatures, compositions and crystal structure of IMC’s! COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

 Mix H of Ag-Ni, Ag-Sn and Ni-Sn Ag-Ni No  Mix H data available in literature. Drop calorimetry from both sides with 3 runs each at 1500 °C Redlich-Kister polynomial applied to fit the experimental data and for interpolation over the liquid miscibility gap COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

 Mix H of Ag-Ni, Ag-Sn and Ni-Sn Ag-Sn Several experimental results and compilations available. Drop calorimetry from the tin side at various temperatures and from the silver side at 1250 °C Redlich-Kister polynomial applied to fit the experimental data and extrapolate into the metastable liquid region COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

 Mix H of Ag-Ni, Ag-Sn and Ni-Sn Ni-Sn A couple of experimental results and compilations available. Drop calorimetry from the tin side at various temperatures and from the silver side at 1500 °C Redlich-Kister polynomial applied to fit the experimental data and extrapolate into the metastable liquid region COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Literature data for Ag-Ni-Sn  Experimental and calculated isothermal section at 240 °C: Hs.-F. Hsu and S.-W. Chen, Acta Mater. 52(9), 2541 (2004) 33 samples prepared from arc-melting EPMA and XRD  Calculated isothermal section at 230 °C: G. Ghosh, J. Electron. Mater. 29, 1182 (2000)  Experimental liquidus projection: S.-W. Chen, Hs.-F. Hsu and Ch.-W. Lin, J. Mater. Res. 19(8), 2262 (2004)  73 samples prepared from arc-melting  Metallography and EPMA (for primary crystallization investigations)  DTA (for 11 samples only) COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Phase diagram investigations ~ 130 samples, prepared using different methods, annealed at different temperatures, quenched or slowly cooled XRD, LOM, SEM, EPMA, DTA, DSC, Heat-flow DSC 4 isotherms at 200, 450, 700, 1050 °C 9 isopleths, liquidus surface projection, reaction scheme Enthalpy measurements Two Tian-Calvet type drop calorimeter from 200 to 1500 °C Drop calorimetry along 12 ternary sections with 11 – 24 drops each Measurement temperatures were 1000, 1220 and 1400 °C Redlich-Kister-Muggianu polynomial fit with (  ) M for the 3 temperatures Experiments and achievements COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Sample preparation in Ag-Ni-Sn There are two main problems: The miscibility gap which extends from the binary Ag-Ni far into the ternary Evaporation during arc-melting and DTA in the Ni-rich part Solution: Samples up to app. 35 at.% Sn have been prepared from Ni-, Ni 3 Sn and Ag 3 Sn powders. They were annealed at the respective temperatures, re-powdered and annealed again up to three times. 1 cm20 µm COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

1050 °C Isothermal sections 200 °C COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

240 °C Comparison with a literature diagram this workH.-F. Hsu and S.-W. Chen COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Isopleths 35 at.% Sn 60 at.% Sn COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Liquidus projection COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Enthalpy of mixing 1000 °C COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Phase limits from calorimetry COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Conclusions The quality of experimental and calculated higher order phase diagrams is limited by the quality of the constituent binary’s. Also well established and widely used binary phase diagram compilations and assessments can exhibit essential errors. A careful check of original literature data and a few experiments should be done. CALPHAD method is powerful to check the consistency of different experimental data and to present phase diagrams and thermochemical data. The predicting power, however, is very low, specially for binary and ternary systems. Based on all experimental data available now an optimized data set for Ni-Sn and Ag-Ni-Sn can be established. COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Acknowledgements Thanks to: All my colleagues of the Materials Chemistry Department for the excellent collaboration The FWF for financing the project No. P N11 All the co-operation partner of the project and COST-531 Action COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007

Thank You for Your attention! COST 531 Final MeetingVienna, AustriaMay 17 - May 18, 2007