Intel Pentium 4 Processor In the 423-pin Package Thermal Design Guidelines

Pentium® 4 Processor in the 423-pin Package Thermal Design Guidelines

Intel has determined through mechanical characterization that the use of phase change thermal interface materials

may lead to motherboard, processor, and /or surface mount component damage in mechanical shock or mechanical

drop testing. Phase change thermal interface materials create a strong adhesive bond between the processor package

and heat sink that can lead to large deflections and high stresses. The damage induced may not be readily

detectable.

5.6 Fans

Fans are needed to move the air through the chassis. The acoustic noise level of a fan is usually related to the speed

of the fan as well as the number and shape of the fan blades.. Maximum acceptable noise levels may limit the fan

output or the number of fans selected for a system. The enabled reference design for the Pentium® 4 processor

incorporates a fan into the heat sink.

5.6.1 Placement

Proper placement of the fans can help ensure that the processor is being properly cooled. Because of the difficulty in

building, measuring and modifying a mechanical assembly, models are typically developed. A well designed model

can be used to simulate a proposed solution for thermal effectiveness to determine the optimum location for fans and

vents within a chassis. Prototype assemblies can also be built and tested to verify that the system components and

processor thermal specifications are met.

An intake air fan ideally is centered vertically and placed along one axis with respect to the processor and passive

heat sink. The fan should also be approximately 2 inches from the leading edge of the heat sink. Figure 5 shows the

typical fan placement for an ATX form factor chassis.

With an active fan heat sink, such as the enabled reference heat sink design, the critical function of the system fan is

to provide sufficient amounts of cool air to the heat sink fan inlet and push the exhaust air away to minimize re-

circulation.

The system fans should be pulling in air from the exterior of the system, which flows directly toward the heat sink.

By reducing the preheating of the air flowing into the heat sink fan, a 1°C for 1°C reduction in processor case

temperature can be achieved with all other parameters remaining constant.

Motherboard

Power Supply

Exhaust Fan

Peripherals

Front

Fan

Power

Supply

Vent

Willamette

Processor

Figure 5. Fan Placement and Layout of an ATX Form Factor Chassis – Top View