Intel QX9770 - Core 2 Extreme Quad-Core Processor - Figure 4. Processor Thermal Characterization Parameter Relationships

LGA775 Socket Heatsink Loading
24 Thermal and Mechanical Design Guidelines
The case-to-local ambient thermal characterization parameter of the processor, Ψ
CA
, is
comprised of Ψ
CS
, the thermal interface material thermal characterization parameter,
and of Ψ
SA
, the sink-to-local ambient thermal characterization parameter:
Ψ
CA
= Ψ
CS
+ Ψ
SA
(Equation 2)
Where:
Ψ
CS
= Thermal characterization parameter of the thermal interface material
(°C/W)
Ψ
SA
= Thermal characterization parameter from heatsink-to-local ambient
(°C/W)
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