Guidelines

Reference Thermal Solution 2
38 Intel
®
7500 Chipset Thermal Mechanical Design Guide
7.5.2 Extruded Heatsink Profiles
The reference thermal solution uses an extruded heatsink for cooling the IOH.
Figure 7-6 shows the heatsink profile. Appendix A lists a supplier for this extruded
heatsink. Other heatsinks with similar dimensions and increased thermal performance
may be available. Full mechanical drawing of this heatsink is provided in Appendix B.
7.5.3 Mechanical Interface Material
There is no mechanical interface material associated with this reference solution.
7.5.4 Thermal Interface Material
A thermal interface material (TIM) provides improved conductivity between the die top
surface and heat sink. The reference thermal solution uses Honeywell PCM45 F*,
0.25 mm (0.010 in.) thick, 20 mm x 20 mm (0.79 in. x 0.79 in.) square.
Note: Unflowed or “dry” Honeywell PCM45 F has a material thickness of 0.010 cm. The flowed
or “wet” Honeywell PCM45F has a material thickness of ~0.003 cm after it reaches its
phase change temperature.
7.5.4.1 Effect of Pressure on TIM Performance
As mechanical pressure increases on the TIM, the thermal resistance of the TIM
decreases. This phenomenon is due to the decrease of the bond line thickness (BLT).
BLT is the final settled thickness of the thermal interface material after installation of
heatsink. The effect of pressure on the thermal resistance of the Honeywell PCM45 F
TIM is shown in Table 7-2.
Intel provides both End of Line and End of Life TIM thermal resistance values of
Honeywell PCM45F. End of Line and End of Life TIM thermal resistance values are
obtained through measurement on a Test Vehicle similar to Intel 7500 chipset’s
physical attributes using an extruded aluminum heatsink. The End of Line value
Figure 7-6. Short Torsional Clip Heatsink Extrusion Profile