mpc8568e Freescale Semiconductor, Inc, mpc8568e Datasheet - Page 128

• Manufacturer Part Number: mpc8568e
• Description: Mpc8568e Powerquicc Iii Processor
• Manufacturer: Freescale Semiconductor, Inc

Thermal
Figure 71
printed-circuit board.
The heat sink removes most of the heat from the device. 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. The junction-to-case thermal resistance is low enough that the heat sink attach
material and heat sink thermal resistance are the dominant terms.
24.2.3
A thermal interface material is required at the package-to-heat sink interface to minimize the thermal
contact resistance. For those applications where the heat sink is attached by spring clip mechanism,
Figure 72
graphite/oil, floroether oil), a bare joint, and a joint with thermal grease as a function of contact pressure.
As shown, the performance of these thermal interface materials improves with increasing contact pressure.
The use of thermal grease significantly reduces the interface thermal resistance. The bare joint results in a
thermal resistance approximately six times greater than the thermal grease joint.
Heat sinks are attached to the package by means of a spring clip to holes in the printed-circuit board (see
Figure
interface pressure.
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69). Therefore, the synthetic grease offers the best thermal performance, especially at the low
The die junction-to-board thermal resistance
depicts the primary heat transfer path for a package with an attached heat sink mounted to a
shows the thermal performance of three thin-sheet thermal-interface materials (silicone,
MPC8568E/MPC8567E PowerQUICC III™ Integrated Processor Hardware Specifications, Rev. 0
Thermal Interface Materials
(Note the internal versus external package resistance)
External Resistance
External Resistance
Internal Resistance
Figure 71. Package with Heat Sink Mounted to a Printed-Circuit Board
Printed-Circuit Board
Heat Sink
Radiation
Radiation
Convection
Convection
Thermal Interface Material
Die/Package
Die Junction
Package/Leads
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