Intel QX9770 Design Guidelines - Page 24

Processor, Heatsink, Processor Thermal Characterization Parameter Relationships

Page 24 highlights

LGA775 Socket Heatsink Loading The case-to-local ambient thermal characterization parameter of the processor, ΨCA, is comprised of ΨCS, the thermal interface material thermal characterization parameter, and of ΨSA, the sink-to-local ambient thermal characterization parameter: ΨCA = ΨCS + ΨSA (Equation 2) Where: ΨCS = Thermal characterization parameter of the thermal interface material (°C/W) ΨSA = Thermal characterization parameter from heatsink-to-local ambient (°C/W) ΨCS is strongly dependent on the thermal conductivity and thickness of the TIM between the heatsink and IHS. ΨSA is a measure of the thermal characterization parameter from the bottom of the heatsink to the local ambient air. ΨSA 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 TA Heatsink TIM IHS Processor ΨCA TS TC LGA775 Socket System Board 24 Thermal and Mechanical Design Guidelines

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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