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Intel Thermal/Mechanical Reference Design Information
A list of failure mechanisms that were considered in design reliability testing are:
1.
2.
3.
4.
All of the above mechanisms are expected to be active during the pump operation and
relatively inactive during the off mode and so all reliability testing needs to be
performed with pump on. The fatigue mechanisms (# 1) are additionally excited by
the cycling of temperature caused by on-off cycles. The real use condition is a
combination of continuous operation and on-off cycling and for the purpose of testing
can be separated into a) continuous operation and b) on-off power cycles. The liquid
temperature during continuous operation can be estimated by the heat exchanger
thermal resistance, TDP, and T
Ψ
= 0.05 ºC /W gives T
HX
speed and T
can be assumed to be from ambient condition to T
also controlled similar to a fan for acoustics and expected mean pump RPM was
estimated to be 1450 (range = 600-1700). The pump speed of 1450 was used to
simulate typical condition during with use condition.
Note: The heat exchanger thermal resistance, Ψ
approaching the heat exchanger.
The complete test matrix is summarized in the Table 6. The continuous operation tests
were slightly accelerated to reduce duration for failure. The cracking mechanism #1
was accelerated significantly by running at 75 ºC. The T
applying a film heater to the bottom of the pump assembly alone (tubing and heat
exchanger were not included by a closed loop tube was used to provide impedance
from pump outlet to inlet).
Table 6. The Reliability Test Matrix
Use Condition
Continuous operation
On-off cycles
Thermal and Mechanical Design Guidelines
Pump assembly cracking causing liquid loss
Vapor loss through plastic walls and joints causing liquid loss
Thermal performance degradation due to internal mechanisms affecting
CPU T
temperature
C
Pump motor and printed circuit board performance degradation affecting
the pump RPM
(e.g., at T
A
= 45 ºC). The calculated T
LIQUID
= 26 ºC is expected to be approximately the same. A typical on-off cycle
A
Test Conditions
T
LIQUID
T
LIQUID
T
= 75 ºC for 16
LIQUID
T
LIQUID
7500 cycles
= 38 ºC, TDP = 130 W, and
A
= 45 ºC. The pump speed is
LIQUID
= (T
– T
LIQUID
HX
LIQUID
Pump Speed
= 50 ºC
1450
= 50 ºC
1450
1450
weeks
= 35-60 ºC,
1450
when fan is at its low
LIQUID
)/(CPU power). T
is the air
A
A
value was achieved by
Included Failure
Mechanisms
2
3, 4
1
1,2,3,4
47
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