
Introduction 11
aluminum nitride, having a coefcient of thermal expansion different from
the die. As the magnitude of temperature cycle increases during tempera-
ture and power cycling, tensile stresses are developed in the center portion
of the die and shear stresses are developed at the edge of the die. Ultimate
TABLE 1.1
Coefficients of Thermal Expansion for Typical Packaging Materials
Material
Coefficient of Thermal Expansion
(ppm/°C)
Case Materials
Alumina
Copper
Molding compound
4.3–7.4
16
10–30
Die
Silicon
Germanium
Gallium arsenide
2.3–4.7
5.7–6.1
5.4–5.7
Die attach
Silver lled glass
Polyimide
Silicon-based epoxy
8
40–50
60–80
Lead and lead frame
CDA 194
OLIN 7025 ...