Transcript Diapositiva 1 - univie.ac.at

Surface properties and wetting
characteristics of
lead-free solder alloys
E. Ricci, D. Giuranno, F. Gnecco, S. Amore, T. Lanata, R. Novakovic
National Research Council (CNR) – Institute for Energetics and Interphases (IENI)
Genoa - Italy
Contribution from IENI Genova to COST 531
Characterization Surface Properties and wetting behaviour of
Selected groups of Lead-free Alloys as Soldering Materials
Surface Tension + modelling:
Binary systems
Wetting behaviour:
Ternary systems:
Binary sub-systems:
Ag-Cu
Cu-Sn
In-Sn
Au-Sn
Au-In
Bi-In
Au-In-Sn/Cu
Bi-In-Sn/Cu
Au-In/Cu
Bi-In /Cu
Au-Sn/(Cu,Ni)
In-Sn /(Cu,Ni)
Cu-Sn/(Cu,Ni)
Final Meeting COST Action 531 Vienna 17-18 May 2007
Experimental
Preparation of the samples
 Preparation of the alloys from the pure elements by melting in a clean atmosphere
 Control of alloys compositions by SEM-EDS
 Mass of alloy sample
3.0 g ST measurements
1.0 g wetting experiments
mechanical and chemical
cleaned
Working Conditions
Surface Tension Measurements
 Sapphire crucible
Wetting Experiments
 Cu, Ni square plate (13x13x1mm)
 Clean Conditions
metallogrhaphically mirror polished
 Flux Ar N60 atmosphere 10-4 < PO2<10-2 Pa;
(Ra<0.05 mm)
Vacuum conditions Ptot ≈ 10 -5 Pa
 Tl+ 50 K <Texp< 1300 K
 Ar N60 atmosphere PO2 ≤ 10-6 Pa
Texp = Tl+ 50 K up to 900K
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Experimental
Temperature
Surface Tension
Oxygen Partial Pressure
Contact Angles
Acquisition of drop profile in real time (2 s)
by ASTRAview® appropriate Software
g SV = g LS + g LV cos q
g LV
Liquid
g SV
q < 90°
wettability
g LS
q > 90°
no wettability
Final Meeting COST Action 531 Vienna 17-18 May 2007
Surface Tension Results
Final Meeting COST Action 531 Vienna 17-18 May 2007
Surface tension
Au-In
1200
Au-Sn
1200
pure Au
1100
pure Au
1100
30.0 In at%
800
36.4 In at%
700
49.5 In at%
54.9 In at%
600
1000
6.1 at %Sn
900
11.8 at% Sn
800
37.8 at% Sn
700
54.1 at% Sn
600
88.7 In at%
500
81.8 at% Sn
500
pure In *
at%Au
900
Surface Tension [mN/m]
1000
at%Au
Surface tension [mN/m]
9.9 In at%
95.3 at% Sn
pure Sn
400
400
1273
1323
1373
1423
Temperature [K]
1473
1523
1273
1323
1373
1423
1473
1523
Temperature [K]
Experimental determination of the surface tension
Experimental data are in good agreement with surface tension values calculated using different theoretical models
Theoretical calculations of the surface tension
Final Meeting COST Action 531 Vienna 17-18 May 2007
Surface tension
Bi-In
In-Sn
560
500
85.0 at% In
79.5 at% In
450
67.5 at% In
51.5 at% In
36.5 at% In
30.0 at% In
400
15.5 at% In
5.0 at% In
pure
Bi Bi
350
573
673
773
Temperature [K]
873
550
In 79.49
In 51.70
540
Sn 100
at%In
In
pure In
95.0 at% In
Surface tension [mN/m]
In 100
at%In
Surface Tension [mN/m]
550
In 50.08
530
In 29.685
In 14.47
520
In 85.36
In 67.62
510
500
600
In 36.63
650
700
750
800
850
900
950
Temperature [K]
Experimental determination of the surface tension
Experimental data are in good agreement with surface tension values calculated using different theoretical models
Theoretical calculations of the surface tension
Final Meeting COST Action 531 Vienna 17-18 May 2007
Surface tension
Cu-Sn
Ag-Cu
1400
1000
800
at%Cu
at%Cu
Surface Tension [mN/m]
1200
600
400
600
800
1000
1200
1400
1600
Temperature [K]
Experimental determination of the surface tension
T=1373K
1 REG. SOL
2 Prasad’smodel
□ Exp Results
Theoretical calculations of the surface tension
Final Meeting COST Action 531 Vienna 17-18 May 2007
Wetting Results
Final Meeting COST Action 531 Vienna 17-18 May 2007
Wetting Results
Composition [at%]
Temperatures [K]
Substrates
710
Ni
qf[°]
20
Cu
qf [°]
41
529
710
30
23
Au – 55 In
768
852
50
Au – 97 In
Au-82Sn
588
582
760
710
23
21
34
Cu-70Sn
813
910
26
<5
Cu-80Sn
743
910
25
<5
Cu – 90 Sn
653
910
10
Cu-95Sn
583
910
<5
Bi – 52 In
Bi – 80 In
Au – 5 In – 81 Sn
Au – 11 In – 84 Sn
383
355
538
493
623
648
645
600
Au – 8 In – 88 Sn
503
602
Bi – 5 In – 81 Sn
483
608
39
Bi – 8 In – 88 Sn
430
608
30
Tl
Tf
In-70Sn
450
In-85Sn
<5
51
44
33
52
23
Final Meeting COST Action 531 Vienna 17-18 May 2007
39
Interface Characterization
Cu substrate
h-Cu6Sn5
based phase
e-Cu3Sn
based phase
 60 mm
In – 70Sn
Similar behaviour:
Ni substrate
•Cu-Sn/Ni
•Au-In-Sn/Cu
Ni3Sn4 based phase
 14 mm
As Pb-Sn solder alloys these systems show :
Formation of a layer (<100 mm) of intermetallic
compounds at the interface between solder alloys and
substrate
These reactions are dominated by the Sn-component,
but the h and the e-phase are exchanged
Final Meeting COST Action 531 Vienna 17-18 May 2007
Interface Characterization
Excessive dissolutive wetting
Cu substrate
Au-55In
Erosion of the substrate and
Increase in the total volume
of liquid phase
Negative influence on
mechanical and
electrical properties
Cu
Similar behaviour:
•Cu-Sn/Cu
Final Meeting COST Action 531 Vienna 17-18 May 2007
Interface Characterization
Bi-52In
Cu substrate
BiIn2
Cu
Interface macroscopically planar
Similar behaviour:
•Au-Sn/(Cu,Ni)
•Bi-In-Sn/Cu
Weakness of solder joint
Final Meeting COST Action 531 Vienna 17-18 May 2007
Conclusions
Complete characterization of the surface properties and
the wetting behaviour of selected groups of lead-free
solder alloys
 In-Sn and Cu-Sn are good candidates as basic systems for new
lead free solders concerning their wettability on Cu and Ni
 The additional elements should be chosen in order to preserve
the wetting properties to exchange the e and h phase formation
at the interface, and inhibit the excessive growth of a reactive
layer keeping good mechanical and electrical properties
Final Meeting COST Action 531 Vienna 17-18 May 2007
Thank for your attention
Final Meeting COST Action 531 Vienna 17-18 May 2007