THERMODYNAMICS OF LEAD FREE THERMODYNAMICS OF LEAD FREE Bi-Sn SOLDER ALLOYS WITH Ni and Bi-Sn SOLDER ALLOYS WITH Ni and

CuCu

S. Amore, S. Delsante, E. Puzo, G. Borzone

Department of Chemistry and Industrial Chemistry (DCCI)

University of Genoa (Italy)

IntroductionIntroduction

• Interactions between Pb-free solder alloys and substrates

Final Meeting COST Action 531 Vienna 17-18 May 2007

Solder system

Bi-SnBi-Sn

Solder system

Bi-SnBi-Sn

Substrates

Ni, CuNi, Cu

Substrates

Ni, CuNi, 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 Measurments of partial enthalpy at infinite dilution of enthalpy at infinite dilution of solid Ni and Cu in liquid Bi-Snsolid Ni and Cu in liquid Bi-Sn

On going On going

@IENI-CNR @IENI-CNR GenovaGenova

Literature Literature worksworks

This workThis work

Final Meeting COST Action 531 Vienna 17-18 May 2007

ExperimentalExperimental

Dissolution Calvet CalorimeterDissolution 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

SamplesSamples

•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

Bi-Sn-X (X=Ni,Cu) systemBi-Sn-X (X=Ni,Cu) system

Final Meeting COST Action 531 Vienna 17-18 May 2007

Ni-SnBi-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

Final Meeting COST Action 531 Vienna 17-18 May 2007

Literature DataLiterature 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 systemIntegral enthalpy of mixing Sn-Ni system

Partial Enthalpy of mixing of Ni in liquid Sn at T=773

K approx -60kJ/mol

Final Meeting COST Action 531 Vienna 17-18 May 2007

Bi-Sn-Ni experimental resultsBi-Sn-Ni experimental results

T= 820 K

x(Ni)

0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020

solH

° [k

J/m

ol]

-40

-20

0

20

40

x(Ni)

0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020

solH

° [k

J/m

ol]

-40

-20

0

20

40

Nominal composition of the bath Bi-57at%Sn

Drop of Ni with 0.01g<mNi<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 alloyPartial enthalpy of mixing at infinite dilution for Ni in liquid Bi-57at%Sn alloy

( 20.4 1.0) /solH kJ mol

Bi-Sn-Ni experimental resultsBi-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 Bip0

Bi (T=800K) ≈ 4 10-8 atmp0

Sn (T=800K) ≈ 4 10-10 atm

NiNi33SnSn44

Eutectic at 57at%SnEutectic at 57at%Sn

Bi-Sn/Ni interfacial reactionBi-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

Bi/Ni interfacial reactionBi/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 NiBi3 phase

Final Meeting COST Action 531 Vienna 17-18 May 2007

Bi-Sn-Ni experimental resultsBi-Sn-Ni experimental results

“Calorimetric” sample after measurement at T= 820 K

NiBiNiBi33

NiNi33SnSn44

Bi36at%-Sn63at%-Ni1at%

Final Meeting COST Action 531 Vienna 17-18 May 2007

Bi-Sn-Ni experimental resultsBi-Sn-Ni experimental resultsSample annealed at 820 K and then quenched in cold water

NiNi33SnSn44

Primary cristalsPrimary cristals

Bi37at%-Sn62at%-Ni1at%

Change of the composition due to the

evaporation of Bip0

Bi (T=800K) ≈ 4 10-8 atmp0

Sn (T=800K) ≈ 4 10-10 atm

x(Cu)

0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020

solH

[kJ/

mol

]

-40

-20

0

20

40

Final Meeting COST Action 531 Vienna 17-18 May 2007

Bi-Sn-Cu experimental resultsBi-Sn-Cu experimental results

x(Cu)

0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020

solH

[kJ/

mol

]

-40

-20

0

20

40

T= 820 K

•Bi-57at%Sn + Cu

•4 different runs in same conditions

•0<x(Cu)<0.018

(8.9 1.0) /solH kJ mol

Partial enthalpy of mixing at infinite dilution for Cu in liquid Bi-57at%Sn alloyPartial enthalpy of mixing at infinite dilution for Cu in liquid Bi-57at%Sn alloy

Final Meeting COST Action 531 Vienna 17-18 May 2007

Bi-Sn-Cu literature dataBi-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 systemIntegral 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

8000

6000

4000

2000

0

so

lH°[

kJ/m

ol]

1.00.80.60.40.20.0x(Cu)

Final Meeting COST Action 531 Vienna 17-18 May 2007

Bi-Sn-Cu experimental resultsBi-Sn-Cu experimental results

“Calorimetric” sample after measurement at T= 820 K

-phase Cu-phase Cu66SnSn55

Eutectic at 57at%SnEutectic at 57at%Sn

Bi36at%-Sn62.5at%-Cu1.5at%

Primary cristalsPrimary cristals

Final Meeting COST Action 531 Vienna 17-18 May 2007

Bi-Sn-Ni experimental resultsBi-Sn-Ni experimental resultsPartial enthalpy of mixing at infinite dilution for Ni and Cu in liquid Bi-61at%Sn alloyPartial enthalpy of mixing at infinite dilution for Ni and Cu in liquid Bi-61at%Sn alloy

x(Ni,Cu)

0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020

solH

[kJ/

mol

]

-40

-20

0

20

40

Cu

Ni

(8.9 1.0) /solH kJ mol

( 20.4 1.0) /solH kJ mol

Final Meeting COST Action 531 Vienna 17-18 May 2007

ConclusionsConclusions

ResultsResults 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 eutectic

DifficultiesDifficultiesChange of the composition due to the evaporation of Bi during the experiment

Future WorkFuture 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

Prof. Gabriella BorzoneProf. 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 GenovaDepartment of Chemistry and Industrial Department of Chemistry and Industrial

ChemistryChemistry

Thank you for your Thank you for your attentionattention