Lead-Free Soldering: Phase Relationships and Thermochemistry of Ag-Cu-Ni-Sn

1. COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 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

2. COST 531 Final Meeting Vienna, Austria May 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

3. COST 531 Final Meeting Vienna, Austria May 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!

4. COST 531 Final Meeting Vienna, Austria May 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: • p1 = 489 °C (480 °C) • p2 = 729 °C (725 °C)

5. COST 531 Final Meeting Vienna, Austria May 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!

6. COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 MixH of Ag-Ni, Ag-Sn and Ni-Sn • Ag-Ni • No MixH 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

7. COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 MixH 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

8. COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 MixH 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

9. COST 531 Final Meeting Vienna, Austria May 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)

10. COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 Experiments and achievements • 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

11. 1 cm 20 µm COST 531 Final Meeting Vienna, Austria May 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-, Ni3Sn and Ag3Sn powders. They were annealed at the respective temperatures, re-powdered and annealed again up to three times.

12. 1050 °C 200 °C COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 Isothermal sections

13. 240 °C COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 Comparison with a literature diagram this work H.-F. Hsu and S.-W. Chen

14. 35 at.% Sn 60 at.% Sn COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 Isopleths

15. COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 Liquidus projection

16. 1000 °C COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 Enthalpy of mixing

17. COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 Phase limits from calorimetry

18. COST 531 Final Meeting Vienna, Austria May 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.

19. COST 531 Final Meeting Vienna, Austria May 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-16495-N11 • All the co-operation partner of the project and COST-531 Action

20. COST 531 Final Meeting Vienna, Austria May 17 - May 18, 2007 Thank You for Your attention!