Generic Thermal Solution
R
Intel
®
845GE / 845PE Chipset (G)MCH Thermal Design Guide
19
3
Generic Thermal Solution
3.1
Generic Thermal Solution Performance
If the thermal designer is able to provide greater than 50 lfm at the air inlet side (upstream) of
the heatsink, the case temperature of the (G)MCH will decrease. Since the thermal resistance of
the package and thermal interface material (TIM) remain constant for all upstream airflow
speeds, the case temperature behavior is due to the decreased thermal resistance (
°
C/W) of the
82845GE GMCH / 82845PE MCH generic thermal solution’s heatsink. Hence, if a thermal
designer can provide greater than 50 lfm upstream of the heatsink, the junction temperature will
be reduced. This reduction in junction temperature leads to greater component reliability.
3.2
Generic Thermal Solution TIM Description
A thermal interface material is used to provide improved conductivity between the die and
heatsink. The reference thermal solution uses Chomerics* T-710, 0.127 mm (0.005 inches)
thick, 12.7 mm x 12.7 mm (0.5 inches x 0.5 inches).
3.2.1
The 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). The effect of pressure on
the thermal resistance of the Chomerics T710 TIM is shown in Table 7. The heatsink clip (see
Figure 1) provides enough pressure for the TIM to achieve a thermal conductivity of 0.9 W/m
⋅
K.
Table 7. Chomerics T710 TIM Performance (at 50 °C as a Function of Attach Pressure)
Pressure (psi)
Thermal Resistance
(°C*In2)/W
5 0.37
10 0.3
20 0.21
50 0.17
