13
0832F–HIREL–02/07
e2v semiconductors SAS 2007
PC7410
7.1.2
Package Thermal Characteristics for CI-CGA
7.2
Internal Package Conduction Resistance
Figure 7-1 depicts the primary heat transfer path for a package with an attached heat sink mounted on a
printed circuit board.
Heat generated on the active side of the chip is conducted through the silicon, then through the heat sink
attach material (or thermal interface material) and finally to the heat sink where it is removed by forced-
air convection.
Since the silicon thermal resistance is quite small, for a first-order analysis the temperature drop in the
silicon may be neglected. Thus, the heat sink attach material and the heat sink conduction/convective
thermal resistances are the dominant terms.
Figure 7-1.
C4 Package with Heat Sink Mounted on a Printed Circuit Board
7.3
Thermal Management Information
This section provides thermal management information for the ceramic ball grid array (CBGA) package
for air-cooled applications. Proper thermal control design is primarily dependent upon the system-level
design – the heat sink, airflow and thermal interface material. To reduce the die-junction temperature,
heat sinks may be attached to the package by several methods: adhesive, spring clip to holes in the
printed-circuit board or package and mounting clip and screw assembly; see Figure 7-2 on page 14. This
spring force should not exceed 5.5 pounds of force. Ultimately, the final selection of an appropriate heat
sink depends on many factors such as thermal performance at a given air velocity, spatial volume, mass,
attachment method, assembly and cost.
Table 7-3.
Package Thermal Characteristics for CI-CGA
Characteristic
Symbol
Value
Unit
PC7410 CI-CGA
Junction to board thermal resistance
R
θ
JB
8.42
° C/W
External Resistance
External Resistance
Internal Resistance
Radiation
Convection
Heat Sink
Thermal Interface Material
Die/Package
Die Junction
Package/Leads
Printed Circuit Board
Radiation
Convection
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