Figure 4. Processor Thermal Characterization Parameter Relationships - Intel Q9450 - Core 2 Quad Quad-Core Processor Design Manual

The case-to-local ambient thermal characterization parameter of the processor, 
comprised of 
and of 
 = 
CA
Where:

CS
(°C/W)

SA
(°C/W)
 is strongly dependent on the thermal conductivity and thickness of the TIM
CS
between the heatsink and IHS.
 is a measure of the thermal characterization parameter from the bottom of the
SA
heatsink to the local ambient air. 
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

Heatsink Heatsink
Processor Processor
30
, the thermal interface material thermal characterization parameter,
CS
, the sink-to-local ambient thermal characterization parameter:
SA
+  (Equation 2)
CS SA
= Thermal characterization parameter of the thermal interface material
= Thermal characterization parameter from heatsink-to-local ambient
TIM TIM
IHS IHS
is dependent on the heatsink material, thermal
SA
T T
A A
T T
S S
T T
C C
Thermal and Mechanical Design Guidelines
Thermal Metrology
, is
CA
 
CA CA
LGA775 Socket LGA775 Socket
System Board System Board