MPC745 Motorola Semiconductor Products, MPC745 Datasheet - Page 46

• Manufacturer Part Number: MPC745
• Description: Host Processor
• Manufacturer: Motorola Semiconductor Products

System Design Information
Though the die junction-to-ambient and the heat sink-to-ambient thermal resistances are a common
figure-of-merit used for comparing the thermal performance of various microelectronic packaging
technologies, one should exercise caution when only using this metric in determining thermal management
because no single parameter can adequately describe three-dimensional heat flow. The final die-junction
operating temperature, is not only a function of the component-level thermal resistance, but the system-level
design and its operating conditions. In addition to the component's power consumption, a number of factors
affect the final operating die-junction temperature—airflow, board population (local heat flux of adjacent
components), heat sink efficiency, heat sink attach, heat sink placement, next-level interconnect technology,
system air temperature rise, altitude, etc.
Due to the complexity and the many variations of system-level boundary conditions for today's
microelectronic equipment, the combined effects of the heat transfer mechanisms (radiation, convection,
and conduction) may vary widely. For these reasons, we recommend using conjugate heat transfer models
for the board, as well as, system-level designs.
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Figure 28. Thermalloy #2328B Heat Sink-to-Ambient Thermal Resistance Versus Airflow Velocity
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MPC755 RISC Microprocessor Hardware Specifications
0
Freescale Semiconductor, Inc.
For More Information On This Product,
0.5
Go to: www.freescale.com
1
Approach Air Velocity (m/s)
1.5
Thermalloy #2328B Pin-Fin Heat Sink
(25
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2
15 mm)
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3.5
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