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PowerPC 602 RISC Microprocessor Hardware Specifications

measured above, the junction temperature of the device would be as follows:

Tj = Ta + Rθja * P

Tj = 40 °C + (10 °C/Watt * 2.5 Watts) = 65 °C

which is well within the reliability limits of the device.

Notes:

1. Junction-to-ambient thermal resistance is based on measurements on single-sided printed circuit

boards per SEMI (Semiconductor Equipment and Materials International) G38-87 in natural

convection.

2. Junction-to-case thermal resistance is based on measurements using a cold plate per

SEMI G30-88 with the exception that the cold plate temperature is used for the case temperature.

The vendors who supply heat sinks are Aavid Engineering, IERC, Thermalloy, and Wakefield Engineering.

Any of these vendors can supply heat sinks with sufficient thermal performance.

1.7.6 Thermal Management Information for the IBM Package

This section provides a thermal management example for the 602; this example is based on a typical desktop

configuration using a 144-lead, mm x mm, IBM PQFP package.

1.7.6.1 Thermal Characteristics for the IBM PQFP Package

The thermal characteristics for a PQFP package are as follows:

Thermal resistance (junction to heat sink) = Rθjs or θjs = 2.8°C/Watt (junction to heat sink)

1.7.6.2 Thermal Management Example

The following example is based on a typical desktop configuration using an IBM PQFP package. The heat

sink used for this data is a pinfin heat sink #2338 attached to the PQFP package with 2-stage epoxy.

The junction temperature can be calculated from the junction-to-ambient thermal resistance, as follows:

Junction temperature = Tj = Ta + Rθja * P

or

Tj = Ta + (Rθjs + Rsa) * P

Where:

Ta is the ambient temperature in the vicinity of the device

Rθja is the junction-to-ambient thermal resistance

Rθjs is the junction-to-heat sink thermal resistance

Rsa is the heat sink-to-ambient thermal resistance

P is the power dissipated by the device

Note: Rθjs includes the resistance of a typical layer of thermal compound. If a lower conductivity

material is used, its thermal resistance must be included.

In this environment, it can be assumed that all the heat is dissipated to the ambient through the heat sink, so

the junction-to-ambient thermal resistance is the sum of the resistances from the junction to the heat sink

and from the heat sink to the ambient.

Note that verification of external thermal resistance and case temperature should be performed for each

application. Thermal resistance can vary considerably due to many factors including degree of air

turbulence.

Freescale Semiconductor, Inc.

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Go to: www.freescale.com