Heatsink Preparation; Figure 7-7. Example Of Machined Heatsink With Thermocouple Groove - Intel FCPGA2 - Processor - 1 x Pentium 4 2.66 GHz Design Manuallines

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Intel Pentium III Processor in the FC-PGA2 Package Thermal Design Guidelines
7.4.1.1.

Heatsink Preparation

In order to measure the case temperature as accurately as possibly, the heatsink must be modified to
allow for the thermocouple wires and attach points. Depending on the chosen solution the dimensions
may vary. It is imperative that the modifications made to the heatsink align to the location of the
thermocouple wires and attach point when properly installed. Any discrepancy will cause the heatsink to
not sit properly on the IHS surface and provide erroneous data. Figure 7-7 shows the modification on a
typical heatsink base. Figure 7-8 shows the groove dimensions required to route a thermocouple to the
center of the heatsink without interfering the IHS to heatsink attachment. The depth for the entire groove
including the circle area is 0.025 in (0.63 mm). The groove should be 0.04 in (1.0 mm) wide. It must be
noted that the center of the circle area needs to be located 0.05 in (1.3 mm) off center from the location
corresponding to the thermocouple bead. This is because the epoxy covers both the bead and the
exposed thermocouple wires so that the circle area needs to accommodate the whole epoxy location. It is
left to the designer to perform the appropriate tolerance stack-up and to define the placement
dimensioning for a specific heatsink design.

Figure 7-7. Example of Machined Heatsink with Thermocouple Groove

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