Processor Thermal Solution Performance Assessment; Local Ambient Temperature Measurement Guidelines; Measuring Active Heatsinks - Intel Celeron D Thermal Design Manual

775-land lga package for embedded applications
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Thermal Metrology
3.2
Processor Thermal Solution Performance
Assessment
Thermal performance of a heatsink should be assessed using a thermal test vehicle (TTV) provided
by Intel. The TTV is a well-characterized thermal tool, whereas real processors can introduce
additional factors that can impact test results. In particular, the power level from actual processors
varies significantly, even when running the maximum power application provided by Intel, due to
variances in the manufacturing process. The TTV provides consistent power and power density for
thermal solution characterization and results can be easily translated to real processor performance.
Once the thermal solution is designed and validated with the TTV, it is strongly recommended to
verify functionality of the thermal solution on real processors and on fully integrated
systems.Contact your Intel field sales representative for further information on TTV or regarding
accurate measurement of the power dissipated by an actual processor.
3.3
Local Ambient Temperature Measurement
Guidelines
The local ambient temperature T
processor. For a passive heatsink, T
actively cooled heatsink, it is the temperature of inlet air to the active cooling fan.
It is worthwhile to determine the local ambient temperature in the chassis around the processor to
understand the effect it may have on the case temperature.
T
is best measured by averaging temperature measurements at multiple locations in the heatsink
A
inlet airflow. This method helps reduce error and eliminate minor spatial variations in temperature.
The following guidelines are meant to enable accurate determination of the localized air
temperature around the processor during system thermal testing.
3.3.1

Measuring Active Heatsinks

It is important to avoid taking measurement in the dead flow zone that usually develops above
the fan hub and hub spokes. Measurements should be taken at four different locations
uniformly placed at the center of the annulus formed by the fan hub and the fan housing to
evaluate the uniformity of the air temperature at the fan inlet. The thermocouples should be
placed approximately 3mm to 8 mm [0.1 to 0.3 in] above the fan hub vertically and halfway
between the fan hub and the fan housing horizontally as shown in
spokes).
Using an open bench to characterize an active heatsink can be useful, and usually ensures
more uniform temperatures at the fan inlet. However, additional tests that include a solid
barrier above the test motherboard surface can help evaluate the potential impact of the
chassis. This barrier is typically clear Plexiglas*, extending at least 100 mm [4 in] in all
directions beyond the edge of the thermal solution. Typical distance from the motherboard to
the barrier is 81 mm [3.2 in].
For even more realistic airflow, the motherboard should be populated with significant elements
like memory cards, graphic card, and chipset heatsink. If a barrier is used, the thermocouple
can be taped directly to the barrier with a clear tape at the horizontal location as previously
described, half way between the fan hub and the fan housing.
Intel
20
(or T
A
A
®
®
Celeron
D Processor in the 775-Land LGA Package Thermal Design Guide
) is the temperature of the ambient air surrounding the
LA
is defined as the heatsink approach air temperature; for an
Figure 5
(avoiding the hub
Order #303730

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