17 Interconnect Quality and Reliability of 3D Packaging
529
Table 17.2
Properties of materials constituents of microbumps used in 3D IC technology [32]
Materials
parameters
Cu
6 Sn
5
Cu
3 Sn
Ni
3 Sn
4
Sn
Cu
Ni
Young’s modulus
(GPa)
116.89
± 2.04 [33]
133.49
± 4.44 [33]
141.12
± 3.85 [33]
50
120
186 [34]
Indentation
hardness (GPa)
6.35
± 0.20 [33]
6.32
± 0.15 [33]
6.31
± 0.16 [33]
0.11
± 0.05
[83]
1.7
± 0.2 [83]
2.8 [84]
Yield strength
(MPa)
2009
± 63 [85]
1787
± 108 [85]
35
± 0.4
180
± 9
950 [84]
Indentation
fracture toughness
(MPa
√
m)
2.73
± 0.63
√
m
[29] 5.72
± 0.86
√
m
[29]
3.88
± 0.53
√
m
[29] 35–55
√
m
[86] 100–107
√
m
[86]
122
√
m
[87]
Poison’s ratio
0.31
0.30
0.33
0.36
0.33
0.31
Coefficient of
thermal expansion
(ppm/K)
16.3 [88]
19.0 [88]
13.7 [88]
22.5 [34]
16.4 [88]
12.5 [34]
Electrical
resistivity (μ cm)
17.5
8.8
28.5
11.5
1.71
6.99
Thermal
conductivity
(W/cm K)
0.341
0.704
0.196
0.668
4
0.91
Melting point (°C) 415C
676
795
232
1085
1455
Volume shrinkage
(%)
5.0
6Cu+5Sn=Cu
6 Sn
5 [6]
4.3
Cu
6 Sn
5 +9Cu=5Cu
3 Sn
[6]
11.3
3Ni+4Sn=Ni
3 Sn
4 [6]
Crystal structure
Hexagonal (η) above
186 °C
Orthorhombic (ε)
Monoclinic
Body-centered
tetragonal
Face-centered cubic Face-centered cubic
(continued)