Specifications

E PENTIUM® PRO PROCESSOR AT 150, 166, 180, and 200 MHz
61
2.46”
2.66”
1.23”
0.80”
CPU Die L2 Cache Die
A
Figure 38. Location of Case Temperature Measurement (Top-side View)
Heat Spreader
Ceramic Package
A
Heat Sink
Thermal Interface
Material
Ceramic Package
Probe
Figure 39. Thermocouple Placement
6.1.3. THERMAL RESISTANCE
The thermal resistance value for the case-to-
ambient, Θ
CA
, is used as a measure of the cooling
solution’s thermal performance. Θ
CA
is comprised of
the case-to-sink thermal resistance, Θ
CS
, and the
sink-to-ambient thermal resistance, Θ
SA
. Θ
CS
is a
measure of the thermal resistance along the heat
flow path from the top of the IC package to the
bottom of the thermal cooling solution. This value is
strongly dependent on the material, conductivity, and
thickness of the thermal interface used. Θ
SA
is a
measure of the thermal resistance from the top of the
cooling solution to the local ambient air. Θ
SA
values
depend on the material, thermal conductivity, and
geometry of the thermal cooling solution as well as
on the airflow rates.