Thermodynamic assessment of Au-Sn-X (X=Co, La, Er) Ternary systems

1. Thermodynamic assessment of Au-Sn-X (X=Co, La, Er) Ternary systems Hongqun Dong

2. Thermodynamic Description of Au-Sn-Co Ternary systems

3. Experimental Information— Au-Co Experimental data of phase boundary are adequate, phase diagram has been assessed by Okamoto et al (in 1985) and Korb (in 2004).

4. Au-Co-Sn Au-Sn Co-Sn H.S. Liu, C.L. Liu, K. Ishida, and Z.P. Jin, J. Electr. Mater. 32(2003)1290 M. Jiang, J. Sato, I. Ohnuma, R. Kainuma, and K. Ishida, Comp. Coup. Phase Dia. Thermoch. 28 (2004) 213–220

5. Au-Co-Sn Isothermal section of Au-Sn-Co system at 380℃ A. Neumann, A. Kjekshus, C. Rø mming, and E. Rø st, J. Alloy. Compound. 240(1996)42-50

6. Thermodynamic Model • All of the solution phases are described as substitutional solution model; • Ternary compound t1 and binary phases without third component solubility are treated as line compound. Their Gibbs energy can be described by Neumann-Kopp rule.

7. Binary compounds with third component solubility • AuSn phase has a maximum Co content up to 12 at%, but the homogeneity range for Sn is unaffected by Co content. So a two-sublattice model (Au, Co): Sn is addopted, the Gibbs energy is formulated as: is the Gibbs energy of assumed compound CoSn. is directly cited from the report of H.S. Liu et al.

8. aCo3Sn2phase has an extended ternary range of homogeneity (up to 23 at. % Au), and almost parallels the Au-Co boundary. Which means that the Co site in the lattice will be partially taken up by Au atoms. So, combining with the work of Jiang et al, a four-sublattice model is employed, i.e. (Au, Co)1: (Sn)1: (Co, Va)0.5: (Co, Va)0.5. The Gibbs energy is expressed as : are the data reported by Jiang et al. and , ,

9. Au-Co-Sn Results and Discussions reference states：Au(fcc), Sn(bct) and Co(hcp)

10. Au-Co-Sn Au-Sn binary system--improved

11. Au-Co-Sn Co-Sn binary system--modified

12. Au-Co-Sn Au-Co binary system--reassessed

13. Au-Co-Sn The thermodynamic quantities of Au-Co binary system Reference states: Au(liquid), Co(fcc) Reference states: Au(liquid), Co(liquid) Reference states: Au(liquid), Co(fcc) at 1573K and 1623K, Au(fcc), Co(fcc) at 1150K

14. Au-Co-Sn isothermal section 380℃ isothermal section at 396℃

15. Au-Co-Sn partial liquidus projection of Au-Sn-Co ternary system liquidus projection of Au-Sn-Co ternary system

16. Au-Co-Sn

17. Au-Co-Sn vertical section across the E2 point of Au-Sn-Co ternary system

18. Au-Co-Sn Section Summary • The complete phase diagram of Au-Sn-Co ternary system is built by TC, Pandat and VASP software; • The optimized parameters can reproduced most of the experimental results; • The present outcomes can provide theory instruction for predicting the formation of IMCs and designing a new-type of 10Au-Sn solder.

19. Thermodynamic Description of Au-Er and Au-La binary systems

20. Experimental information Au-La Au-Er • Canneri partial phase relation √ -- • Rider et. al solubility in Au √ √ • McMasters crystal structure √ √ • Saccone et. al entire phase relation -- √ • Fitzner et. al mixing enthalpy of liquid 1473K -- • Meschel et. al standard formation enthalpy Au51La14 AuEr、Au2Er、 Au3Er • Alqsmmi formation enthalpy of IMCs -- 1073K • Wu et.al formation enthalpy of IMCs -- √ • Gschneidner et. al assessment √ √

21. Au-La Binary Alloy Phase Diagrams

22. Au-La Temperature of invariant reactions involving Au6La phase are 1173K and 1063K, respectively

23. Au-Er • Saccone, D. Maccio, Intemetallics, • 10(2002)903 Binary Alloy Phase Diagrams

24. Au-RE Thermodynamic model • Solution phases were described as substitutional solution model; • All of the IMCs were treated as line compound, their gibbs energy can be describe as Neumann–Kopp rule.

25. Results and discussion The comparison between calculated formation enthalpies of IMCs and experimental outcomes, reference states: Au(fcc), La(dhcp), Er(fcc)

26. Au-Er Calculated phase diagram compared to experimental results

27. Au-Er Reference states：Au(fcc), Er(hcp) Reference states：Au(fcc), Er(hcp)

28. Au-La Calculated phase diagram compared with outcomes of Gshneidner

29. Au-La Reference states:Au(fcc), La(dhcp) Reference states: Au(Liquid), La(Liquid)

30. Au-Sn-La extrapolated Liquidus projection of the Au-Sn-La ternary system E1: L↔Au6La + AuSn +β T=555.5K E3: L↔LaSn3 + AuSn4 +βSn T=483K

31. Au-Sn-La Vertical section across the E1 eutectic point of the Au-Sn-La ternary system

32. Au-RE Section Summary • With the calculated formation enthalpies of IMCs using ab initio approach, the Au-Er and Au-La binary systems were thermodynamic optimized by CALPHAD technique; • the calculated outcomes fit well with the experimental data; • the present work can theoretically guide the designing of new Au-based solder.

33. outlooks • The experimental information of Au-RE and Sn-RE systems should be further investigated; • On the basis of measured phase diagram and thermodynamic quantities, by applying CALPHAD approach to build a more compatible database of Au-Sn-RE systems, and then guide to find the proper candidates of solder alloying elements

34. Thanks and comments

36. isothermal section at 394℃