MPC755CPX400LE datasheet(49/56 Pages) MOTOROLA

49 / 56 page

MPC755 RISC Microprocessor Hardware Specifications, Rev. 6.1

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.

00.5

11.5

22.5

33.5

Thermalloy #2328B Pin-Fin Heat Sink

Approach Air Velocity (m/s)

(25 × 28 × 15 mm)

MPC755CPX400LE Datasheet(PDF) 49 Page - Motorola, Inc