Intel Xeon Processor with 800 MHz System Bus Thermal/Mechanical Design Guide

14 Intel® Xeon™ Processor with 800 MHz System Bus Thermal/Mechanical Design Guidelines
Thermal/Mechanical Reference Design
The processor connects to the baseboard through a 604-pin surface mount, zero insertion force
(ZIF) socket. A description of the socket can be found in the mPGA604 Socket Design Guidelines.
The processor package has mechanical load limits that are specified in the processor Intel® Xeon™
Processor with 800 MHz System Bus at 2.80 GHz and 3.60 GHz Datasheet and in Table 2-3. 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 processor EMTS.
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 compressive dynamic load specified in the
Intel® Xeon™ Processor with 800 MHz System Bus at 2.80 GHz and 3.60 GHz Datasheet and in
Table 2-3 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 Intel® Xeon™ Processor with 800 MHz System
BusConsiderations
An attachment mechanism must be designed to support the heatsink since there are no features on
the mPGA604 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 Chapter 2.4.2 for information on trade-offs 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 mPGA604socket solder joints
as well as preventing package pullout from the socket.
Note: The load applied by the attachment mechanism must comply with the package specifications, along
with the dynamic load added by the mechanical shock and vibration requirements, as identified in
Chapter 2.1.1.
A potential mechanical solution for heavy heatsinks is the direct attachment of the heatsink to the
chassis pan. In this case, the strength of the chassis pan can be utilized rather than solely relying on
the baseboard strength. In addition to the general guidelines given above, contact with the
baseboard surfaces should be minimized during installation in order to avoid any damage to the
baseboard.
The Intel reference design for Intel Xeon Processor with 800 MHz System Bus is using such a
heatsink attachment scheme. Refer to Chapter 2.4 for further information regarding the Intel
reference mechanical solution.