lead-free soldering: phase relationships and thermochemistry of ag-cu-ni-sn h. flandorfer, c....

Lead-Free Soldering:Lead-Free Soldering:

Phase Relationships and Phase Relationships and

Thermochemistry of Ag-Cu-Ni-SnThermochemistry 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 Meeting Vienna, Austria May 17 - May 18, 2007

OutlineOutline

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


The binary systems Ag-Ni, Ag-Sn and Ni-SnThe binary systems Ag-Ni, Ag-Sn and Ni-Sn

Ag-NiPhase diagram version from Massalski‘s compilation

• 3 samples prepared byarc-melting

• XRD• DTA

No significant deviations!No significant deviations!

A ssessed N i-A g phase diagram .



Ag-SnPhase diagram version from Massalski‘s compilation


• XRD• SEM-EDX• DTA

Good agreement except:Good agreement except:p1 = 489 °C (480 °C)p2 = 729 °C (725 °C)



Ni-SnPhase diagram version from Massalski‘s compilation


• XRD• SEM-EDX• DTA

A ssessed N i-Sn phase diagram.

Significant deviations of transition temperatures, compositionsSignificant deviations of transition temperatures, compositionsand crystal structure of IMC’s!and crystal structure of IMC’s!


MixMixH of Ag-Ni, Ag-Sn and Ni-SnH of Ag-Ni, Ag-Sn and Ni-Sn

xAg

0,0 0,2 0,4 0,6 0,8 1,0

M

ixH

J

/mo

l

0

2000

4000

6000

8000

10000

12000

14000

Ni Ag

Ag-NiNo 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



Ag-SnSeveral 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 regionxAg

0,0 0,2 0,4 0,6 0,8 1,0

MixH

in k

J/m

ol

-4

-3

-2

-1

0

1

2

500 °C; two runs700 °C900 °C1000 °C

1250 °C

fitted curve at 500 °C

1100 °C

fitted curve at 1250 °C

977 °C [73Hul]



Ni-SnA 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 regionxNi

0,0 0,2 0,4 0,6 0,8 1,0

MixH

in

kJ/

mo

l

-25

-20

-15

-10

-5

0

5

1100°C; two runs1250 °C; two runs1500 °C1500 °C; Sn dropped

Haddad et al.Hultgren

fitted curve at 1500 °Cfitted curve at 1250 °Cfitted curve at 1100 °C


Literature data for Ag-Ni-SnLiterature 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)


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 achievementsExperiments and achievements


Sample preparation in Ag-Ni-SnSample 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.

1 cm 20 µm


1050 °C

Isothermal sectionsIsothermal sections

200 °C


240 °C

Comparison with a literature diagramComparison with a literature diagram

this work H.-F. Hsu and S.-W. Chen


IsoplethsIsopleths

35 at.% Sn

60 at.% Sn


Liquidus projectionLiquidus projection


Enthalpy of mixingEnthalpy of mixing

0.00

0.25

0.50

0.75

1.00Sn

0.00

0.25

0.50

0.75

1.00

Ag

0.00 0.25 0.50 0.75 1.00

Ni

-4

-2

-2

26 12108

4

0

0

-12-20

-18

-16

-14

-10-8

-6

1000 °C


Phase limits from calorimetryPhase limits from calorimetry

0 10 20 30 40 50 60 70 80 90 1000

10

20

30

40

50

60

70

80

90

1000

10

20

30

40

50

60

70

80

90

100

NiAg

Sn

1220°C

1400°C

1000°C

Exp. points from kinks in enthalpy curvesIsothermExtension of liquid miscibility gap at 1220 and 1400°C.Maximum extension of the miscibility gap [07Sch]


ConclusionsConclusions

• 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.


AcknowledgementsAcknowledgements

Thanks to:Thanks to:

• All my colleagues of the Materials Chemistry Departmentfor 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


Thank You for Your attention!Thank You for Your attention!


lead-free soldering: phase relationships and thermochemistry of ag-cu-ni-sn h. flandorfer, c....

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