mpc7450 Freescale Semiconductor, Inc, mpc7450 Datasheet - Page 45

• Manufacturer Part Number: mpc7450
• Description: Mpc7450 Risc Microprocessor
• Manufacturer: Freescale Semiconductor, Inc

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.
1.9.9.1
For the exposed-die packaging technology, shown in Table 3, the intrinsic conduction thermal resistance
paths are as follows:
Figure 25 depicts the primary heat transfer path for a package with an attached heat sink mounted to 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.
Because the silicon thermal resistance is quite small, for a first-order analysis, the temperature drop in the
silicon may be neglected. Thus, the thermal interface material and the heat sink conduction/convective
thermal resistances are the dominant terms.
1.9.9.2
A thermal interface material is recommended at the package lid-to-heat sink interface to minimize the
thermal contact resistance. For those applications where the heat sink is attached by spring clip mechanism,
Figure 26 shows the thermal performance of three thin-sheet thermal-interface materials (silicone,
MOTOROLA
Cool Innovations Inc.
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Concord, Ontario L4K 4P9
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Internet: www.coolinnovations.com
•
•
The die junction-to-case (or top-of-die for exposed silicon) thermal resistance
The die junction-to-ball thermal resistance
(Note the internal versus external package resistance)
Internal Package Conduction Resistance
Thermal Interface Materials
External Resistance
External Resistance
Figure 25. C4 Package with Heat Sink Mounted to a Printed-Circuit Board
Internal Resistance
MPC7450 RISC Microprocessor Hardware Specifications
Freescale Semiconductor, Inc.
Printed-Circuit Board
For More Information On This Product,
Heat Sink
Go to: www.freescale.com
Radiation
Radiation
Convection
Convection
905-760-1992
Thermal Interface Material
Package/Leads
Die Junction
Die/Package
System Design Information
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