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Thermal/Mechanical Reference Design
18 Quad-Core Intel® Xeon® Processor 5400 Series TMDG
The package includes an integrated heat spreader (IHS). The IHS transfers the non-
uniform heat from the die to the top of the IHS, out of which the heat flux is more
uniform and spreads over a larger surface area (not the entire IHS area). This allows
more efficient heat transfer out of the package to an attached cooling device. The IHS
is designed to be the interface for contacting a heatsink. Details can be found in the
Quad-Core Intel® Xeon® Processor 5400 Series Datasheet.
The processor connects to the baseboard through a 771-land surface mount socket. A
description of the socket can be found in the LGA771 Socket Mechanical Design Guide.
The processor package and socket have mechanical load limits that are specified in the
Quad-Core Intel® Xeon® Processor 5400 Series Datasheet and the LGA771 Socket
Mechanical Design Guide. These load limits should not be exceeded during heatsink
installation, removal, mechanical stress testing, or standard shipping conditions. For
example, when a compressive static load is necessary to ensure thermal performance
of the Thermal Interface Material (TIM) between the heatsink base and the IHS, it
should not exceed the corresponding specification given in the LGA771 Socket
Mechanical Design Guide.
The heatsink mass can also add additional dynamic compressive load to the package
during a mechanical shock event. Amplification factors due to the impact force during
shock must be taken into account in dynamic load calculations. The total combination
of dynamic and static compressive load should not then exceed the processor/socket
compressive dynamic load specified in the LGA771 Socket Mechanical Design Guide
during a vertical shock. It is not recommended to use any portion of the processor
substrate as a mechanical reference or load-bearing surface in either static or dynamic
compressive load conditions.
2.1.3 Quad-Core Intel® Xeon® Processor 5400 Series
Considerations
An attachment mechanism must be designed to support the heatsink since there are no
features on the LGA771 socket to directly attach a heatsink. In addition to holding the
heatsink in place on top of the IHS, this mechanism plays a significant role in the
robustness of the system in which it is implemented, in particular:
• Ensuring thermal performance of the TIM applied between the IHS and the
heatsink. TIMs, especially ones based on phase change materials, are very
sensitive to applied pressure: the higher the pressure, the better the initial
performance. TIMs such as thermal greases are not as sensitive to applied
pressure. Refer to Section 2.5.2 and Section 2.5.7.2 for information on tradeoffs
made with TIM selection. Designs should consider possible decrease in applied
pressure over time due to potential structural relaxation in enabled components.
• Ensuring system electrical, thermal, and structural integrity under shock and
vibration events. The mechanical requirements of the attach mechanism depend on
the weight of the heatsink and the level of shock and vibration that the system
must support. The overall structural design of the baseboard and system must be
considered when designing the heatsink attach mechanism. Their design should
provide a means for protecting LGA771 socket solder joints as well as preventing
package pullout from the socket.
Note: The load applied by the attachment mechanism must comply with the package and
socket specifications, along with the dynamic load added by the mechanical shock and
vibration requirements, as identified in Section 2.1.1.