1. THERMODYNAMICS OF LEAD FREE Bi-Sn SOLDER ALLOYS WITH Ni and Cu S. Amore, S. Delsante, E. Puzo, G. Borzone Department of Chemistry and Industrial Chemistry (DCCI) University of Genoa (Italy)

2. Introduction Interactions between Pb-free solder alloys and substrates Final Meeting COST Action 531 Vienna 17-18 May 2007 Solder systemBi-Sn Bi-Sn Substrates Ni, Cu Substrates Ni, Cu  Study of the interfacial reaction between Bi-Sn alloy and Ni, Cu substrate  Study of the wetting properties (contact angle and interfacial reaction) of Bi-Sn system on Cu and Ni  Comprensive understanding of the phase equilibria and thermodynamic properties Measurments of partial enthalpy at infinite dilution of solid Ni and Cu in liquid Bi-Sn On going @IENI-CNR Genova Literature works This work

3. Final Meeting COST Action 531 Vienna 17-18 May 2007 Experimental Dissolution Calvet Calorimeter Pure Ar flux (6l/h) Graphite crucible Ta getter Real time acquisition of Heat Flow, calorimeter temperature (S-type thermocouple) and room temperature (K- type thermocouple); scan rate 1s Samples Pure elements mechanically a chemically cleaned Mass of bath about 20g After each experiment thermodynamic equilibrium checked by SEM-EDS analysis Appropriate software in LabView environment

4. Bi-Sn-X (X=Ni,Cu) system Final Meeting COST Action 531 Vienna 17-18 May 2007 Ni-Sn Bi-Sn Bi-Ni Cu-Sn H. Ipser, et al, J Mater Sci: Mater Electron (2007) 18:3–17 TB Massalski Binary Alloy Phase Diagrams vol 1,2

5. Final Meeting COST Action 531 Vienna 17-18 May 2007 Literature Data H. Ipser, H. Flandorfer, Ch. Luef, C. Schmetterer, U. Saeed, J Mater Sci: Mater Electron (2007) 18:3–17 Integral enthalpy of mixing Sn-Ni system Partial Enthalpy of mixing of Ni in liquid Sn at T=773 K approx -60kJ/mol

6. Final Meeting COST Action 531 Vienna 17-18 May 2007 Bi-Sn-Ni experimental results T= 820 K Nominal composition of the bath Bi-57at%Sn Drop of Ni with 0.01g<m Ni <0.03g 0<x(Ni)<0.015 4 different runs in same conditions Partial enthalpy of mixing at infinite dilution for Ni in liquid Bi-57at%Sn alloy

7. Bi-Sn-Ni experimental results Final Meeting COST Action 531 Vienna 17-18 May 2007 Calorimetric sample after measure at T= 820 K Bi36at%-Sn63at%-Ni1at% Change of the composition due to the evaporation of Bi p 0 Bi (T=800K) ≈ 4 10 -8 atm p 0 Sn (T=800K) ≈ 4 10 -10 atm Ni 3 Sn 4 Eutectic at 57at%Sn

8. Bi-Sn/Ni interfacial reaction Final Meeting COST Action 531 Vienna 17-18 May 2007 J. Wang, H.S. Liu, Z.P. Jin, J. Electronic Materials 35 (2006) 10 T=423K Bi-91at%Sn Bi-64at%Sn Bi-43at%Sn

9. Bi/Ni interfacial reaction Final Meeting COST Action 531 Vienna 17-18 May 2007 V.I. Dybkov, K. Barmak, w. Lengauer, P. Gas, Journal of Alloys and Compounds 389 (2005) T=423K Pure liquid Bi in contact with solid Ni Formation of the NiBi 3 phase

10. Final Meeting COST Action 531 Vienna 17-18 May 2007 Bi-Sn-Ni experimental results “Calorimetric” sample after measurement at T= 820 K NiBi 3 Ni 3 Sn 4 Bi36at%-Sn63at%-Ni1at%

11. Final Meeting COST Action 531 Vienna 17-18 May 2007 Bi-Sn-Ni experimental results Sample annealed at 820 K and then quenched in cold water Ni 3 Sn 4 Primary cristals Bi37at%-Sn62at%-Ni1at% Change of the composition due to the evaporation of Bi p 0 Bi (T=800K) ≈ 4 10 -8 atm p 0 Sn (T=800K) ≈ 4 10 -10 atm

12. Final Meeting COST Action 531 Vienna 17-18 May 2007 Bi-Sn-Cu experimental results T= 820 K Bi-57at%Sn + Cu 4 different runs in same conditions 0<x(Cu)<0.018 Partial enthalpy of mixing at infinite dilution for Cu in liquid Bi-57at%Sn alloy

13. Final Meeting COST Action 531 Vienna 17-18 May 2007 Bi-Sn-Cu literature data H. Ipser, H. Flandorfer, Ch. Luef, C. Schmetterer, U. Saeed, J Mater Sci: Mater Electron (2007) 18:3–17 Integral enthalpy of mixing Bi-Sn-Cu system The literature data of the integral enthalpy of mixing confirm the endothermic value of the partial enthalpy of mixing of Cu in liquid Bi-Sn at a composition near to the eutectic

14. Final Meeting COST Action 531 Vienna 17-18 May 2007 Bi-Sn-Cu experimental results “Calorimetric” sample after measurement at T= 820 K  -phase Cu 6 Sn 5 Eutectic at 57at%Sn Bi36at%-Sn62.5at%-Cu1.5at% Primary cristals

15. Final Meeting COST Action 531 Vienna 17-18 May 2007 Bi-Sn-Ni experimental results Partial enthalpy of mixing at infinite dilution for Ni and Cu in liquid Bi-61at%Sn alloy

16. Final Meeting COST Action 531 Vienna 17-18 May 2007 Conclusions Results  Exothermic partial enthalpy of mixing of Ni in liquid Bi-Sn at composition near to the eutectic  Endothermic partial enthalpy of mixing of Cu in liquid Bi-Sn at composition near to the eutecticDifficulties  Change of the composition due to the evaporation of Bi during the experiment Future Work  Measurements of the partial enthalpy of mixing for Bi-Sn-X (X=Cu,Ni) at different temperatures  Study of wetting behaviour of Bi-Sn alloys on Cu and Ni substrates

17. Prof. Gabriella Borzone Prof. Gabriella Borzone – Group leader Dr. Nadia Parodi – Senior Scientis Dr. Simona Delsante – Post Doc Stefano Amore – Ph.D. Enrico Puzo – SEM EDS technician Università di Genova Department of Chemistry and Industrial Chemistry

18. Thank you for your attention