MPC8241EC datasheet(52/58 Pages) FREESCALE

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MPC8241 Integrated Processor Hardware Specifications, Rev. 10

Freescale Semiconductor

Ordering Information

where:

TT = thermocouple temperature atop the package (°C)

JT = thermal characterization parameter (°C/W)

PD = power dissipation in package (W)

The thermal characterization parameter is measured per JESD51-2 specification 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 caused by cooling effects of the

thermocouple wire.

When a heat sink is used, the junction temperature is determined from a thermocouple inserted at the

interface between the case of the package and the interface material. A clearance slot or hole is normally

required in the heat sink. Minimizing the size of the clearance minimizes the change in thermal

performance that is caused by removing part of the thermal interface to the heat sink. Considering the

experimental difficulties with this technique, many engineers measure the heat sink temperature and then

back calculate the case temperature using a separate measurement of the thermal resistance of the

interface. From this case temperature, the junction temperature is determined from the junction-to-case

thermal resistance.

In many cases, it is appropriate to simulate the system environment using a computational fluid dynamics

thermal simulation tool. In such a tool, the simplest thermal model of a package that has demonstrated

reasonable accuracy (about 20%) is a two-resistor model consisting of a junction-to-board and a

junction-to-case thermal resistance. The junction-to-case covers the situation where a heat sink is used or

a substantial amount of heat is dissipated from the top of the package. The junction-to-board thermal

resistance describes the thermal performance when most of the heat is conducted to the printed-circuit

board.

7.8

References

Semiconductor Equipment and Materials International

805 East Middlefield Rd.

Mountain View, CA 94043

(415) 964-5111

MIL-SPEC and EIA/JESD (JEDEC) specifications are available from Global Engineering Documents at

800-854-7179 or 303-397-7956.

JEDEC specifications are available on the web at http://www.jedec.org.

Ordering Information

Ordering information for the parts that this document fully covers is provided in Section 8.1, “Part

Numbers Fully Addressed by This Document.” Section 8.2, “Part Numbers Not Fully Addressed by This

Document,” lists the part numbers which do not fully conform to the specifications of this document.

These special part numbers require an additional document called a hardware specifications addendum.

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