Intel Pentium 4 Processor on 90 nm Process Thermal and Mechanical Design Guidelines

Thermal Requirements
R
Intel
®
Pentium
®
4 on 90 nm Process Thermal Design Guide 17
3.2.1.2 Thermal Interface Material
Thermal interface material application between the processor IHS and the heatsink base is
generally required to improve thermal conduction from the IHS to the heatsink. Many thermal
interface materials can be pre-applied to the heatsink base prior to shipment from the heatsink
supplier and allow direct heatsink attach, without the need for a separate thermal interface
material dispense or attach process in the final assembly factory.
All thermal interface materials should be sized and positioned on the heatsink base in a way that
ensures the entire processor IHS area is covered. It is important to compensate for heatsink-to-
processor attach positional alignment when selecting the proper thermal interface material size.
When pre-applied material is used, it is recommended to have a protective application tape over
it. This tape must be removed prior to heatsink installation.
3.2.2 System Thermal Solution Considerations
3.2.2.1 Chassis Thermal Design Capabilities
For the Pentium 4 processor on 90 nm process at frequencies published in the Intel
®
Pentium
®
4
Processor on 90 nm Process Datasheet, the Intel reference thermal solution assumes that the
chassis delivers a maximum T
A
of 38 °C at the inlet of the processor fan heatsink.
3.2.2.2 Improving Chassis Thermal Performance
The heat generated by components within the chassis must be removed to provide an adequate
operating environment for both the processor and other system components. Moving air through
the chassis brings in air from the external ambient environment and transports the heat generated
by the processor and other system components out of the system. The number, size, and relative
position of fans and vents determine the chassis thermal performance, and the resulting ambient
temperature around the processor. The size and type (passive or active) of the thermal solution
and the amount of system airflow can be traded off against each other to meet specific system
design constraints. Additional constraints are board layout, spacing, component placement, and
structural considerations that limit the thermal solution size. For more information, refer to the
Performance ATX Desktop System Thermal Design Suggestions or Performance microATX
Desktop System Thermal Design Suggestions documents available on the
http://www.formfactors.org/
web site.
In addition to passive heatsinks, fan heatsinks, and system fans, other solutions exist for cooling
integrated circuit devices. For example, ducted blowers, heat pipes, and liquid cooling are all
capable of dissipating additional heat. Due to their varying attributes, each of these solutions may
be appropriate for a particular system implementation.
To develop a reliable, cost-effective thermal solution, thermal characterization and simulation
should be carried out at the entire system level, accounting for the thermal requirements of each
component. In addition, acoustic noise constraints may limit the size, number, placement, and
types of fans that can be used in a particular design.
To ease the burden on thermal solutions, the Thermal Monitor feature and associated logic have
been integrated into the silicon of the Pentium 4 processor on 90 nm process. By taking advantage
of the Thermal Monitor feature, system designers may reduce thermal solution cost by designing