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Intel
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6700PXH 64-bit PCI Hub Thermal/Mechanical Design Guidelines 21
6.5.4 Thermal Interface Material
A thermal interface material provides improved conductivity between the die and heatsink. The
reference thermal solution uses Chomerics* T-710, 0.127 mm (0.005 in.) thick, 8 mm x 8 mm
square.
Note: Unflowed or “dry” Chomerics* T710 has a material thickness of 0.005 inch. The flowed or “wet”
Chromerics T710 has a material thickness of ~0.0025 inch after it reaches its phase change
temperature.
6.5.4.1 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 Chomerics T710 TIM is shown in Table 6-1Table 6-1Table 6-1. The
heatsink clip provides enough pressure for the TIM to achieve a thermal conductivity of 0.17°C
inch
2
/W.
Table 6-1. Chomerics* T710 TIM Performance as a Function of Attach Pressure
Pressure (psi) Thermal Resistance (°C × in
2
)/W
5 0.37
10 0.30
20 0.21
30 0.17
NOTE: All measured at 50°C.
6.5.5 Heatsink Clip
The reference solution uses a wire clip with hooked ends. The hooks attach to wire anchors to fasten
the clip to the board. See Appendix B for a mechanical drawing of the clip.