Appendix B Heatsink Clip Load Metrology; Overview; Test Preparation; Heatsink Preparation - Intel EM64T - Celeron D 336 Boxed Ena User Manual

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Appendix B Heatsink Clip Load
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 LGA775 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 24 and
Figure 25. 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 (Refer to Figure 25).
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 additional load by artificially raising the heatsink base. The measurement offset
depends on the whole assembly stiffness (i.e. motherboard, clip, fastener, etc.). For example, the
Intel RCBFH-3 Reference Heatsink Design clip and fasteners assembly has a stiffness of around
380 N/mm [2180 lb/in]. In that case, a protrusion of 0.038 mm [0.0015"] will create an extra load
of 15 N [3.3 lb]. Figure 26 shows an example using the Intel RCBFH-3 Reference Heatsink
designed for the Pentium 4 processor in the 775–land LGA package.
Thermal/Mechanical Design Guide
Metrology
Heatsink Clip Load Metrology
67