MPC852T datasheet(11/80 Pages) FREESCALE

11 / 80 page

MPC852T PowerQUICC™ Hardware Specifications, Rev. 4

Freescale Semiconductor

References

If the board temperature is known and the heat loss from the package case to the air can be ignored,

acceptable predictions of junction temperature can be made. For this method to work, the board and board

mounting must be similar to the test board used to determine the junction-to-board thermal resistance,

namely a 2s2p (board with a power and a ground plane) and vias attaching the thermal balls to the ground

plane.

7.4

Estimation Using Simulation

When the board temperature is not known, a thermal simulation of the application is needed. The simple

two-resistor model can be used with the thermal simulation of the application [2], or a more accurate and

complex model of the package can be used in the thermal simulation.

7.5

Experimental Determination

To determine the junction temperature of the device in the application after prototypes are available, the

thermal characterization parameter (

ΨJT) can be used to determine the junction temperature with a

measurement of the temperature at the top center of the package case using the following equation:

TJ = TT + (ΨJT × PD)

where:

ΨJT = thermal characterization parameter

TT = thermocouple temperature on top of package

PD = power dissipation in package

The thermal characterization parameter is measured per JESD51-2 specification published by JEDEC

using a 40-gauge type T thermocouple epoxied to the top center of the package case. The thermocouple

should be positioned so that the thermocouple junction rests on the package. A small amount of epoxy is

placed over the thermocouple junction and over about 1 mm of wire extending from the junction. The

thermocouple wire is placed flat against the package case to avoid measurement errors that cooling effects

of the thermocouple wire cause.

References

Semiconductor Equipment and Materials International (415) 964-5111

805 East Middlefield Rd

Mountain View, CA 94043

MIL-SPEC and EIA/JESD (JEDEC) specifications

800-854-7179 or

(Available from Global Engineering documents)

303-397-7956

JEDEC Specifications

http://www.jedec.org

1. C.E. Triplett and B. Joiner, “An Experimental Characterization of a 272 PBGA Within an

Automotive Engine Controller Module,” Proceedings of SemiTherm, San Diego, 1998, pp. 47–54.

2. B. Joiner and V. Adams, “Measurement and Simulation of Junction to Board Thermal Resistance

and Its Application in Thermal Modeling,” Proceedings of SemiTherm, San Diego, 1999,

pp. 212–220.

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