MPC755 datasheet(49/56 Pages) NXP

49 / 56 page

MPC755 RISC Microprocessor Hardware Specifications, Rev. 8

Freescale Semiconductor

System Design Information

Figure 28. Thermalloy #2328B Heat Sink-to-Ambient Thermal Resistance Versus Airflow Velocity

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.

00.511.522.533.5

Thermalloy #2328B Pin-Fin Heat Sink

Approach Air Velocity (m/s)

(25

× 28 × 15 mm)

MPC755 Datasheet(PDF) 49 Page - NXP Semiconductors