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Processor Thermal/Mechanical Information
This is achieved in part by using the
curves from the Intel enabled thermal solution. A thermal solution designed to meet the thermal
profile should perform virtually the same for any value of T
Fan Speed Control" on page
Thermal Profile.
The value for T
configured processor register. The result can be used to program a fan speed control component.
See the processor datasheet for further details on reading the register and calculating T
2.3
Heatsink Design Considerations
To remove the heat from the processor, three basic parameters should be considered:
•
The area of the surface on which the heat transfer takes place. Without any enhancements,
this is the surface of the processor package IHS. One method used to improve thermal
performance is by attaching a heatsink to the IHS. A heatsink increases the effective heat
transfer surface area by conducting heat out of the IHS and into the surrounding air through
fins attached to the heatsink base.
•
The conduction path from the heat source to the heatsink fins. Providing a direct
conduction path from the heat source to the heatsink fins and selecting materials with higher
thermal conductivity typically improves heatsink performance. The length, thickness, and
conductivity of the conduction path from the heat source to the fins directly impact the thermal
performance of the heatsink. In particular, the quality of the contact between the package IHS
and the heatsink base has a higher impact on the overall thermal solution performance as
processor cooling requirements become stricter. Thermal interface material (TIM) is used to
fill in the gap between the IHS and the bottom surface of the heatsink, and thereby improve the
overall performance of the stack-up (IHS-TIM-Heatsink). With extremely poor heatsink
interface flatness or roughness, TIM may not adequately fill the gap. The TIM thermal
performance depends on its thermal conductivity as well as the pressure applied to it. Refer to
Section 2.3.4
between the IHS and the heatsink base.
•
The heat transfer conditions on the surface on which heat transfer takes place.
Convective heat transfer occurs between the airflow and the surface exposed to the flow. It is
characterized by the local ambient temperature of the air, T
surface. The higher the air velocity over the surface and the cooler the air, the more efficient is
the resulting cooling. The nature of the airflow can also enhance heat transfer via convection.
Turbulent flow can provide improvement over laminar flow. In the case of a heatsink, the
surface exposed to the flow includes in particular the fin faces and the heatsink base.
Active heatsinks typically incorporate a fan that helps manage the airflow through the heatsink.
Passive heatsink solutions require in-depth knowledge of the airflow in the chassis. Typically,
passive heatsinks see lower air speed. These heatsinks are therefore typically larger (and heavier)
than active heatsinks due to the increase in fin surface required to meet a required performance. As
the heatsink fin density (the number of fins in a given cross-section) increases, the resistance to the
airflow increases: it is more likely that the air travels around the heatsink instead of through it,
unless air bypass is carefully managed. Using air-ducting techniques to manage bypass area can be
an effective method for controlling airflow through the heatsink.
Intel
14
29, for details on implementing a design using Tcontrol and the
is calculated by the system BIOS based on values read from a factory
CONTROL
and
Appendix C
for further information on TIM and on bond line management
®
®
Celeron
D Processor in the 775-Land LGA Package Thermal Design Guide
Ψ
vs. RPM and RPM vs. Acoustics (dBA) performance
CA
CONTROL
. See
Section 4.3, "Acoustic
CONTROL
, and the local air velocity over the
A
Order #303730
.
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