Thermal/Mechanical Reference Design
Figure 2-22. Isometric View of the 2U+ CEK Heatsink
Note: Refer to Appendix B for more detailed mechanical drawings of the heatsink.
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Figure 2-23. Isometric View of the 1U CEK Heatsink
Note: Refer to Appendix B for more detailed mechanical drawings of the heatsink.
The function of the standoffs is to provide a bridge between the chassis and the heatsink for attaching and load carrying. When assembled, the heatsink is rigid against the top of the standoff, and the standoff is rigid to a chassis standoff with the CEK spring firmly sandwiched between the two. In dynamic loading situations the standoff carries much of the heatsink load, especially in lateral conditions, when compared to the amount of load transmitted to the processor package. As such, it is comprised of steel. The distance from the bottom of the heatsink to the bottom of the standoff is
8.79mm [0.346 in.] for a board thickness of 1.57 mm [0.062 in]. The standoff will need to be modified for use in applications with a different board thickness, as defined in Section 2.5.4.2.
The function of the screw is to provide a rigid attach method to sandwich the entire CEK assembly together, activating the CEK spring under the baseboard, and thus providing the TIM preload. A screw is an inexpensive, low profile solution that does not negatively impact the thermal performance of the heatsink due to air blockage. Any fastener (i.e. head configuration) can be used as long as it is of steel construction; the head does not interfere with the heatsink fins, and is of the correct length of 20.64 mm [0.8125 in.].
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