Thermal Metrology
30 Thermal and Mechanical Design Guidelines
The case-to-local ambient thermal characterization parameter of the processor,
CA
, is
comprised of
CS
, the thermal interface material thermal characterization parameter,
and of
SA
, the sink-to-local ambient thermal characterization parameter:
CA
=
CS
+
SA
(Equation 2)
Where:
CS
= Thermal characterization parameter of the thermal interface material
(°C/W)
SA
= Thermal characterization parameter from heatsink-to-local ambient
(°C/W)
CS
is strongly dependent on the thermal conductivity and thickness of the TIM
between the heatsink and IHS.
SA
is a measure of the thermal characterization parameter from the bottom of the
heatsink to the local ambient air.
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
CA
LGA775 Socket
Processor
IHS
System Board
T
C
Heatsink
TIM
T
S
T
A
CA
LGA775 Socket
Processor
IHS
System Board
T
C
Heatsink
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