26

MPC106 PCI Bridge/Memory Controller Hardware Specifications

System Design Information

1.8.5.2 Board and System-Level Modeling

A common figure-of-merit used for comparing the thermal performance of various microelectronic

packaging technologies is the junction-to-ambient thermal resistance. The final chip-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. For example, these factors might include airflow, board

population, heat sink efficiency, heat sink attach, next-level interconnect technology, and system air

temperature rise.

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 this reason, we recommend using conjugate heat transfer models for

the board as well as system-level designs. To expedite system-level thermal analysis, several “compact”

CBGA thermal models are available on request within FLOTHERM®.

The die junction-to-ambient thermal resistance is shown in Table 14. The model results are in accordance

with SEMI specification G38. This standard specifies a single component be placed on a 7.5 cm x 10 cm

single-layer printed-circuit card. Note that this single metric may not adequately describe

three-dimensional heat flow.

Table 14. Die Junction-to-Ambient Thermal Resistance

Airflow Velocity

(Meter/Second)

Airflow Velocity

(Feet/Minute)

Die Junction-to-Ambient Thermal Resistance

(SEMI G38) (°C/W)

1

196.8

22.0

2

393.7

18.5

3

590.0

17.0

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com