Dual-Core Intel® Xeon® Processor 5100 Series Thermal/Mechanical Design Guide 73
Heatsink Clip Load Methodology
B Heatsink Clip Load
Methodology
B.1 Overview
This section describes a procedure for measuring the load applied by the heatsink/clip/
fastener assembly on a processor package.
This procedure is recommended to verify the preload is within the design target range
for a design, and in different situations. For example:
• Heatsink preload for the LGA771 socket.
• Quantify preload degradation under bake conditions.
Note: This document reflects the current metrology used by Intel. Intel is continuously
exploring new ways to improve metrology. Updates will be provided later as this
document is revised as appropriate.
B.2 Test Preparation
B.2.1 Heatsink Preparation
Three load cells are assembled into the base of the heatsink under test, in the area
interfacing with the processor Integrated Heat Spreader (IHS), using load cells
equivalent to those listed in Section B.2.2.
To install the load cells, machine a pocket in the heatsink base, as shown in Figure B-1
and Figure B-2. The load cells should be distributed evenly, as close as possible to the
pocket walls. Apply wax around the circumference of each load cell and the surface of
the pocket around each cell to maintain the load cells in place during the heatsink
installation on the processor and motherboard.
The depth of the pocket depends on the height of the load cell used for the test. It is
necessary that the load cells protrude out of the heatsink base. However, this
protrusion should be kept minimal, as it will create an additional load offset since the
heatsink base is artificially raised. The measurement load offset depends on the whole
assembly stiffness (that is, motherboard, clip, fastener, and so forth). For example, the
Dual-Core Intel Xeon Processor 5100 Series CEK Reference Heatsink Design clip and
fasteners assembly have a stiffness of around 160 N/mm [915 lb/in]. If the resulting
protrusion is 0.038 mm [0.0015”], then a extra load of 6.08 N [1.37 lb] will be created,
and will need to be subtracted from the measured load. Figure B-3 shows an example
using the Dual-Core Intel Xeon Processor 5100 Series CEK Reference Heatsink
designed for the Dual-Core Intel Xeon Processor 5100 Series in the 771–land grid array
(LGA) package.
Note: When optimizing the heatsink pocket depth, the variation of the load cell height should
also be taken into account to make sure that all load cells protrude equally from the
heatsink base. It may be useful to screen the load cells prior to installation to minimize
variation.
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