Thermal Metrology
R
26
Thermal/Mechanical Design Guide
Ψ
CS
is strongly dependent on the thermal conductivity and thickness of the TIM between the
heatsink and IHS.
Ψ
SA
is a measure of the thermal characterization parameter from the bottom of the heatsink to the
local ambient air.
Ψ
SA
is dependent on the heatsink material, thermal conductivity, and geometry.
It is also strongly dependent on the air velocity through the fins of the heatsink.
Figure 4 illustrates the combination of the different thermal characterization parameters.
Figure 4. Processor Thermal Characterization Parameter Relationships
TIM
T
S
T
A
Ψ
CA
LGA775 Socket
Processor
IHS
System Board
T
C
Heatsink
TIM
T
S
T
A
Ψ
CA
LGA775 Socket
Processor
IHS
System Board
T
C
Heatsink
3.1.1 Example
The cooling performance,
Ψ
CA,
is then defined using the principle of thermal characterization
parameter described above:
•
The case temperature T
C-MAX
and thermal design power TDP given in the processor
datasheet
.
•
Define a target local ambient temperature at the processor, T
A
.
Since the processor thermal profile applies to all processor frequencies, it is important to identify
the worst case (lowest
Ψ
CA
) for a targeted chassis characterized by T
A
to establish a design
strategy such that a given heatsink can cover a given range of processor frequencies.
The following provides an illustration of how one might determine the appropriate performance
targets. The example power and temperature numbers used here are not related to any Intel
processor thermal specifications, and are for illustrative purposes only.
Assume the TDP, as listed in the processor datasheet, is 100 W and the maximum case
temperature from the thermal profile for 100 W is 67 °C. Assume as well that the system airflow
Summary of Contents for 640 - Pentium 4 640 3.2GHz 800MHz 2MB Socket 775 CPU
Page 14: ...Introduction R 14 Thermal Mechanical Design Guide ...
Page 38: ...Thermal Management Logic and Thermal Monitor Feature R 38 Thermal Mechanical Design Guide ...
Page 52: ...Intel Thermal Mechanical Reference Design Information R 52 Thermal Mechanical Design Guide ...
Page 60: ...Acoustic Fan Speed Control R 60 Thermal Mechanical Design Guide ...
Page 72: ...Heatsink Clip Load Metrology R 72 Thermal Mechanical Design Guide ...
Page 99: ...Mechanical Drawings R Thermal Mechanical Design Guide 99 Figure 50 Reference Fastener Sheet 1 ...
Page 103: ...Mechanical Drawings R Thermal Mechanical Design Guide 103 Figure 54 Clip Heatsink Assembly ...
