Intel QX9770 - Core 2 Extreme Quad-Core Processor, QX68000 Core 2 Extreme Design Manual
Intel® Core™2 Extreme Processor
Δ
QX6800
Extreme Processor QX9770
Thermal and Mechanical Design Guidelines
— For the Intel® Core™2 Extreme Processor QX6800Δ B3
Stepping and the Intel® Core™2 Extreme Processor
QX9770Δ C0 Stepping
March 2008
and Intel® Core™2
Δ
Document Number: 316854-002
LGA775 Socket Heatsink Loading
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Not all specified units of this p rocessor support Thermal Monitor 2 (TM2). See the Processor Spec Finder at
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∆
family, not across differe nt processor families. Over time processor numbers will increment based on changes in clock, speed,
cache, FSB, or other features, and increments are not intended to represent proportional or quantitative increases in any
particular feature. Current roadmap processor number progression is not necessarily representative of future roadmaps. See
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Intel, Pentium, Core, and the Int el logo are trademarks of Intel Corporation in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Copyright © 2007–2008 Intel Corporation
®
Core™2 Extreme Processor QX6800 and Intel® Core™2 Extreme Processor QX9770 may contain design defects or
Intel processor numbers are not a measure of performance. Processor numbers differentiate features within each processor
http://www.intel.com .
2 Thermal and Mechanical Design Guidelines
Contents
1 Introduction.....................................................................................................9
1.1 Document Goals and Scope .....................................................................9
1.1.1 Importance of Thermal Management............................................9
1.1.2 Document Goals........................................................................9
1.1.3 Document Scope.....................................................................10
1.2 References..........................................................................................11
1.3 Definition of Terms...............................................................................11
2 Processor Thermal/Mechanical Information.........................................................13
2.1 Mechanical Requirements ......................................................................13
2.1.1 Processor Package ...................................................................13
2.1.2 Heatsink Attach ......................................................................15
2.1.2.1 General Guidelines....................................................15
2.1.2.2 The Pump Assembly Clip Load Requirement..................15
2.1.2.3 Additional Guidelines.................................................16
2.2 Thermal Requirements..........................................................................16
2.2.1 Processor Case Temperature.....................................................16
2.2.2 Thermal Profile .......................................................................17
2.2.3 T
2.3 Heatsink Design Considerations..............................................................19
2.3.1 Heatsink Size..........................................................................20
2.3.2 Package IHS Flatness...............................................................20
2.3.3 Thermal Interface Material........................................................21
2.4 System Thermal Solution Considerations .................................................21
2.4.1 Chassis Thermal Design Capabilities...........................................21
2.4.2 Improving Chassis Thermal Performance ....................................21
2.4.3 Summary...............................................................................22
2.5 System Integration Considerations..........................................................22
..................................................................................18
CONTROL
3 Thermal Metrology..........................................................................................23
3.1 Characterizing Cooling Performance Requirements....................................23
3.1.1 Example ................................................................................25
3.2 Processor Thermal Solution Performance Assessment................................26
3.3 Local Ambient Temperature Measurement Guidelines.................................26
3.4 Processor Case Temperature Measurement Guidelines...............................29
4 Thermal Management Logic and Thermal Monitor Feature.....................................31
4.1 Processor Power Dissipation ...................................................................31
4.2 Thermal Monitor Implementation............................................................31
4.2.1 PROCHOT# Signal...................................................................32
4.2.2 Thermal Control Circuit ............................................................32
4.2.3 Thermal Monitor 2...................................................................33
4.2.4 Operation and Configuration .....................................................34
4.2.5 On-Demand Mode ...................................................................35
4.2.6 System Considerations.............................................................35
4.2.7 Operating System and Application Software Considerations...........36
Thermal and Mechanical Design Guidelines 3
LGA775 Socket Heatsink Loading
4.2.8 THERMTRIP# Signal.................................................................36
4.2.9 Cooling System Failure Warning ................................................36
4.2.10 Digital Thermal Sensor.............................................................37
4.2.11 Platform Environmental Control Interface (PECI)..........................38
5 Intel Thermal/Mechanical Reference Design Information.......................................39
5.1 Validation Results for the ATX Reference Design .......................................39
5.1.1 Heatsink Performance..............................................................40
5.1.2 Acoustics ...............................................................................40
5.1.3 Altitude..................................................................................41
5.1.4 Reference Heatsink Thermal Validation.......................................41
5.1.5 Fan Motor Performance ............................................................42
5.1.6 Pump Motor Performance .........................................................43
5.2 Environmental Reliability Testing............................................................44
5.2.1 Structural Reliability Testing .....................................................44
5.2.1.1 Random Vibration Test Procedure................................44
5.2.1.2 Shock Test Procedure................................................45
5.2.2 Power Cycling.........................................................................46
5.2.3 Reliability Testing....................................................................46
5.2.3.1 Tubing Material Selection...........................................48
5.2.3.2 Reservoir Sizing .......................................................48
5.2.3.3 Reliability Test Results...............................................50
5.2.4 Recommended BIOS/CPU/Memory Test Procedures......................51
5.3 Material and Recycling Requirements ......................................................52
5.4 Safety Requirements ............................................................................52
5.5 Geometric Envelope for Intel Reference ATX Thermal Mechanical Design......52
5.6 Reference Attach Mechanism..................................................................54
5.7 Socket and Voltage Regulation Cooling Strategy .......................................55
6 Intel® Quiet System Technology (Intel® QST) .....................................................57
6.1 Intel® Quiet System Technology Algorithm...............................................57
6.1.1 Output Weighting Matrix ..........................................................58
6.1.2 Proportional-Integral-Derivative (PID)........................................58
6.2 Board and System Implementation of Intel® Quiet System Technology .......60
6.3 Intel® QST Configuration & Tuning..........................................................62
6.4 Fan Hub Thermistor and Intel® QST ........................................................62
Appendix A LGA775 Socket Heatsink Loading ......................................................................63
A.1 LGA775 Socket Heatsink Considerations..................................................63
A.2 Metric for Heatsink Preload for ATX/uATX Designs Non-Compliant with Intel®
Reference Design .................................................................................
64
A.2.1 Heatsink Preload Requirement Limitations...................................64
A.2.2 Motherboard Deflection Metric Definition.....................................64
A.2.3 Board Deflection Limits ............................................................66
A.2.4 Board Deflection Metric Implementation Example.........................66
A.2.5 Additional Considerations .........................................................67
A.2.5.1 Motherboard Stiffening Considerations.........................68
A.3 Heatsink Selection Guidelines.................................................................68
Appendix B Heatsink Clip Load Metrology............................................................................69
B.1 Overview ............................................................................................69
B.2 Test Preparation...................................................................................69
4 Thermal and Mechanical Design Guidelines
B.2.1 Heatsink Preparation................................................................69
B.2.2 Typical Test Equipment ............................................................72
B.3 Test Procedure Examples.......................................................................72
B.3.1 Time-Zero, Room Temperature Preload Measurement...................73
B.3.2 Preload Degradation under Bake Conditions ................................73
Appendix C Thermal Interface Management.........................................................................75
C.1 Bond Line Management.........................................................................75
C.2 Interface Material Area..........................................................................75
C.3 Interface Material Performance...............................................................75
Appendix D Case Temperature Reference Metrology..............................................................77
D.1 Objective and Scope .............................................................................77
D.2 Supporting Test Equipment....................................................................78
D.3 Thermal Calibration and Controls............................................................79
D.4 IHS Groove .........................................................................................79
D.5 Thermocouple Attach Procedure .............................................................82
D.5.1 Thermocouple Conditioning and Preparation................................82
D.5.2 Thermocouple Attachment to the IHS.........................................83
D.5.3 Solder Process........................................................................88
D.5.4 Cleaning and Completion of Thermocouple Installation..................91
D.6 Thermocouple Wire Management............................................................95
Appendix E Legacy Fan Speed Control................................................................................97
E.1 Thermal Solution Design .......................................................................97
E.1.1 Determine Thermistor Set Points ...............................................97
E.1.2 Minimum Fan Speed Set Point...................................................98
E.2 Board and System Implementation .........................................................99
E.2.1 Choosing Fan Speed Control Settings .........................................99
E.2.1.1 Temperature to Begin Fan Acceleration......................100
E.2.1.2 Minimum PWM Duty Cycle........................................ 102
E.3 Combining Thermistor and Digital Thermal sensor Control........................103
E.4 Interaction of Thermal Profile and T
CONTROL
.............................................103
Appendix F BTX System Thermal Considerations................................................................ 109
Appendix G Mechanical Drawings .....................................................................................113
Appendix H Intel Enabled Reference Solution Information.................................................... 123
Thermal and Mechanical Design Guidelines 5
Figures
LGA775 Socket Heatsink Loading
Figure 1. Package IHS Load Areas.....................................................................13
Figure 2. Processor Case Temperature Measurement Location ...............................17
Figure 3. Example Thermal Profile.....................................................................18
Figure 4. Processor Thermal Characterization Parameter Relationships....................24
Figure 5. Locations for Measuring Local Ambient Temperature, Active Heatsink........27
Figure 6. Locations for Measuring Local Ambient Temperature, Liquid-Cooling Heat
Exchanger.........................................................................................
28
Figure 7. Locations for Measuring Local Ambient Temperature, Passive Heatsink......28
Figure 8. Concept for Clocks under Thermal Monitor Control..................................33
Figure 9. Thermal Monitor 2 Frequency and Voltage Ordering................................34
Figure 10. T
for Digital Thermometer ........................................................37
CONTROL
Figure 11. Random Vibration PSD......................................................................44
Figure 12. Shock Acceleration Curve..................................................................45
Figure 13. The Assembly Cumulative Mass Loss Data in Continuous Operation
Test at 50 ºC and 1450 RPM..............................................................
49
Figure 14. Thermal Resistance Curve for Liquid Loss of Reservoir...........................49
Figure 15. Reservoir Location............................................................................50
Figure 16. Intel® ALCT Reference Design Major Components.................................53
Figure 17. Heat Exchanger Fan Combination Foot Print View .................................53
Figure 18. Structure to Motherboard Interface.....................................................54
Figure 19. Diagram of Location of Heat Exchanger VR and Socket Airflow Cooling
Feature...........................................................................................
55
Figure 20. CPU Maximum Current Draw for Heat Exchanger Fan Speed...................56
Figure 21. Intel® Quiet System Technology Overview...........................................58
Figure 22. PID Controller Fundamentals .............................................................59
Figure 23. Intel® Quiet System Technology Platform Requirements ........................60
Figure 24. Example Acoustic Fan Speed Control Implementation............................61
Figure 25. Digital Thermal Sensor and Thermistor................................................62
Figure 26. Board Deflection Definition................................................................65
Figure 27. Example: Defining Heatsink Preload Meeting Board Deflection Limit ........67
Figure 28. Load Cell Installation in Machined Heatsink Base Pocket – Bottom View ...70
Figure 29. Load Cell Installation in Machined Heatsink Base Pocket – Side View .......71
Figure 30. Preload Test Configuration.................................................................71
Figure 31. Omega Thermocouple.......................................................................79
Figure 32. 775-LAND LGA Package Reference Groove Drawing...............................80
Figure 33. IHS Groove on the 775-LAND LGA Package..........................................81
Figure 34. IHS Groove Orientation Relative to the LGA775 Socket..........................81
Figure 35. Inspection of Insulation on Thermocouple............................................82
Figure 36. Bending the Tip of the Thermocouple..................................................83
Figure 37. Securing Thermocouple Wires with Kapton* Tape Prior to Attach ............83
Figure 38. Thermocouple Bead Placement...........................................................84
Figure 39. Position Bead on the Groove Step.......................................................85
Figure 44. Detailed Thermocouple Bead Placement ..............................................85
Figure 41. Third Tape Installation......................................................................86
Figure 42. Measuring Resistance between Thermocouple and IHS ..........................86
Figure 43. Applying Flux to the Thermocouple Bead.............................................87
Figure 44. Cutting Solder.................................................................................87
Figure 45. Positioning Solder on IHS..................................................................88
Figure 46. Solder Station Setup ........................................................................89
Figure 47. View Through Lens at Solder Station...................................................90
Figure 48. Moving Solder back onto Thermocouple Bead.......................................90
6 Thermal and Mechanical Design Guidelines
Figure 49. Removing Excess Solder ...................................................................91
Figure 50. Thermocouple placed into groove.......................................................92
Figure 51. Removing Excess Solder ...................................................................92
Figure 52. Filling Groove with Adhesive..............................................................93
Figure 53. Application of Accelerant...................................................................93
Figure 54. Removing Excess Adhesive from IHS ..................................................94
Figure 55. Finished Thermocouple Installation.....................................................94
Figure 56. Thermocouple Wire Management........................................................95
Figure 57. Thermistor Set Points .......................................................................98
Figure 58. Example Fan Speed Control Implementation........................................99
Figure 59. Fan Speed Control..........................................................................100
Figure 60. Temperature Range = 5 °C ............................................................. 101
Figure 61. Temperature Range = 10 °C............................................................ 102
Figure 62. Digital Thermal Sensor and Thermistor..............................................103
Figure 63. FSC Definition Example................................................................... 105
Figure 64. System Airflow Illustration with System Monitor Point Area Identified.... 110
Figure 65. Thermal sensor Location Illustration ................................................. 111
Figure 66. ATX/µATX Motherboard Keep-out Footprint Definition and Height
Restrictions for Enabling Components - Sheet 1..................................
114
Figure 67. ATX/µATX Motherboard Keep-out Footprint Definition and Height
Restrictions for Enabling Components - Sheet 2..................................
115
Figure 68. ATX/µATX Motherboard Keep-out Footprint Definition and Height
Restrictions for Enabling Components - Sheet 3..................................
116
Figure 69. Balanced Technology Extended (BTX) Thermal Module Keep Out
Volumetric – Sheet 1......................................................................
117
Figure 70. Balanced Technology Extended (BTX) Thermal Module Keep Out
Volumetric – Sheet 2......................................................................
118
Figure 71. Balanced Technology Extended (BTX) Thermal Module Keep Out
Volumetric – Sheet 3......................................................................
119
Figure 72. Balanced Technology Extended (BTX) Thermal Module Keep Out
Volumetric – Sheet 4......................................................................
120
Figure 73. Balanced Technology Extended (BTX) Thermal Module Keep Out
Volumetric – Sheet 5......................................................................
121
Figure 74. Intel Advanced Liquid Cooling Technology Assembly............................122
Tables
Table 1. Heatsink Inlet Temperature of Intel Reference Thermal Solutions..............21
Table 2. Intel Liquid Cooled Reference Design Performance (ALCT).........................40
Table 3. Acoustic Results.................................................................................. 40
Table 4. Fan Electrical Performance Requirements ...............................................42
Table 5. Pump Electrical Performance Requirements.............................................43
Table 6. The Reliability Test Matrix ....................................................................47
Table 7. The Weekly Loss Rate of Different Tubing Materials..................................48
Table 8. Reliability Test Results.........................................................................51
Table 9. Maximum Estimated Processor Current Capability at 35 ºC External
Ambient.............................................................................................
Table 10. Board Deflection Configuration Definitions ............................................65
Table 11. Typical Test Equipment......................................................................72
Table 12. FSC Definitions...............................................................................104
Table 13. ATX FSC Settings............................................................................106
Table 14. BTX Fan Speed Control Settings........................................................106
Table 15. Intel Representative Contact for Licensing Information ......................... 123
Table 16. Intel Reference Component ATX Thermal Solution Providers.................. 123
Thermal and Mechanical Design Guidelines 7
56
LGA775 Socket Heatsink Loading
Revision History
Revision
Number
-001 • Initial release April 2007
-002 • Added Intel® Core™2 Extreme processor QX9770 C0 Stepping
• Edits throughout
Description Revision Date
March 2008
§
8 Thermal and Mechanical Design Guidelines
Introduction
1 Introduction
1.1 Document Goals and Scope
1.1.1 Importance of Thermal Management
The objective of thermal management is to ensure that the temperatures of all
components in a system are maintained within their functional temperature range.
Within this temperature range, a component is expected to meet its specified
performance. Operation outside the functional temperature range can degrade
system performance, cause logic errors or cause component and/or system damage.
Temperatures exceeding the maximum operating limit of a component may result in
irreversible changes in the operating characteristics of this component.
In a system environment, the processor temperature is a function of both system and
component thermal characteristics. The system level thermal constraints consist of
the local ambient air temperature and airflow over the processor as well as the
physical constraints at and above the processor. The processor temperature depends
in particular on the component power dissipation, the processor package thermal
characteristics, and the processor thermal solution.
All of these parameters are affected by the continued push of technology to increase
processor performance levels and packaging density (more transistors). As operating
frequencies increase and packaging size decreases, the power density increases while
the thermal solution space and airflow typically become more constrained or remains
the same within the system. The result is an increased importance on system design
to ensure that thermal design requirements are met for each component, including
the processor, in the system.
1.1.2 Document Goals
Depending on the type of system and the chassis characteristics, new system and
component designs may be required to provide adequate cooling for the processor.
The goal of this document is to provide an understanding of these thermal
characteristics and discuss guidelines for meeting the thermal requirements imposed
on single processor systems using the Intel
Stepping and Intel
The concepts given in this document are applicable to any system form factor.
Specific examples used will be the Intel enabled reference solution for ATX/uATX
systems. See the applicable BTX form factor reference documents to design a thermal
solution for that form factor.
®
Core™2 Extreme processor QX9770 C0 Stepping.
®
Core™2 Extreme processor QX6800 B3
Thermal and Mechanical Design Guidelines 9
1.1.3 Document Scope
This design guide supports the following processor:
• Intel® Core™2 Extreme processor QX6800 B3 Stepping
• Intel® Core™2 Extreme processor QX9770 C0 Stepping
In this document when a reference is made to “the processor” it is intended that this
includes all the processors supported by this document. If needed for clarity, the
specific processor will be listed.
LGA775 Socket Heatsink Loading
In this document, when a reference is made to “the datasheet”, the reader should
refer to the Intel
Processor Q9000 Series Datasheet and Intel
QX6000
Δ
Sequence and Intel® Core™2 Quad Processor Q6000Δ Sequence Datasheet,
®
Core™2 Extreme Processor QX9000 Series and Intel® Core™2 Quad
®
Core™2 Extreme Quad-Core Processor
as appropriate. If needed for clarity the specific processor datasheet will be
referenced.
Chapter
2 of this document discusses package thermal mechanical requirements to
design a thermal solution for the processor in the context of personal computer
applications. Chapter
3 discusses the thermal solution considerations and metrology
recommendations to validate a processor thermal solution.
Chapter
4 addresses the benefits of the processor’s integrated thermal management
logic for thermal design.
Chapter
Advanced Liquid Cooling Technology) for the processor. Chapter 6 discusses the
implementation of Intel
5 gives information on the Intel reference thermal solution called ALCT (Intel
®
Quiet System Technology.
The physical dimensions and thermal specifications of the processor that are used in
this document are for illustration only. Refer to the datasheet for the product
dimensions, thermal power dissipation and maximum case temperature. In case of
conflict, the data in the datasheet supersedes any data in this document.
10 Thermal and Mechanical Design Guidelines
Introduction
1.2 References
Material and concepts available in the following documents may be beneficial when
reading this document.
Document Location
Intel® Core™2 Extreme Processor QX9000 Series and Intel®
Core™2 Quad Processor Q9000 Series Datasheet
Intel® Core™2 Extreme Quad-Core Processor QX6000Δ
Sequence and Intel
Datasheet
LGA775 Socket Mechanical Design Guide
Fan Specification for 4-wire PWM Controlled Fans http://www.formfactors.org/
ATX Thermal Design Suggestions http://www.formfactors.org/
microATX Thermal Design Suggestions http://www.formfactors.org/
Balanced Technology Extended (BTX) System Design Guide http://www.formfactors.org/
®
Core™2 Quad Processor Q6000Δ Sequence
1.3 Definition of Terms
Term Description
The measured ambient temperature locally surrounding the processor. The ambient
T
T
Ψ
Ψ
Ψ
T
A
TC
T
E
T
S
C-MAX
LIQUID
CA
CS
SA
temperature should be measured just upstream of a passive heatsink or at the fan
inlet for an active heatsink.
The case temperature of the processor, measured at the geometric center of the
topside of the IHS.
The ambient air temperature external to a system chassis. This temperature is usually
measured at the chassis air inlets.
Heatsink temperature measured on the underside of the heatsink base, at a location
corresponding to
The maximum case temperature as specified in a component specification.
Working fluid temperature as it leaves the pump (or enters the heat exchanger).
Case-to-ambient thermal characterization parameter (psi). A measure of thermal
solution performance using total package power. Defined as (T
Power.
Note: Heat source must be specified for
Case-to-sink thermal characterization parameter. A measure of thermal interface
material performance using total package power. Defined as (T
Power.
Note: Heat source must be specified for
Sink-to-ambient thermal characterization parameter. A measure of heatsink thermal
performance using total package power. Defined as (T
Note: Heat source must be specified for
T
http://w.ww.intel.com/design/pro
cessor/datashts/318726.htm
http://developer.intel.com/design
/processor/datashts/315592.htm
http://intel.com/design/
Pentium4/guides/ 302666.htm
.
C
– TA) / Total Package
C
Ψ measurements.
– TS) / Total Package
C
Ψ measurements.
– TA) / Total Package Power.
S
Ψ measurements.
Thermal and Mechanical Design Guidelines 11
LGA775 Socket Heatsink Loading
Term Description
Thermal Interface Material: The thermally conductive compound between the heatsink
TIM
and the processor case. This material fills the air gaps and voids, and enhances the
transfer of the heat from the processor case to the heatsink.
P
MAX
TDP
IHS
LGA775 Socket
The maximum power dissipated by a semiconductor component.
Thermal Design Power: a power dissipation target based on worst-case applications.
Thermal solutions should be designed to dissipate the thermal design power.
Integrated Heat Spreader: a thermally conductive lid integrated into a processor
package to improve heat transfer to a thermal solution through heat spreading.
The surface mount socket designed to accept the processors in the 775–Land LGA
package.
ACPI
Bypass
Thermal
Monitor
TCC
DTS
T
DIODE
FSC
T
CONTROL_BASE
T
CONTROL_OFFSET
T
CONTROL
PWM
Health Monitor
Component
BTX
TMA
T
Advanced Configuration and Power Interface.
Bypass is the area between a passive heatsink and any object that can act to form a
duct. For this example, it can be expressed as a dimension away from the outside
dimension of the fins to the nearest surface.
A feature on the processor that attempts to keep the processor die temperature within
factory specifications.
Thermal Control Circuit: Thermal Monitor uses the TCC to reduce die temperature by
lowering effective processor frequency when the die temperature has exceeded its
operating limits.
Digital Thermal Sensor: Processor die sensor temperature defined as an offset from
the onset of PROCHOT#.
Temperature reported from the on-die thermal diode.
Fan Speed Control: Thermal solution that includes a variable fan speed which is
driven by a PWM signal and uses the digital thermal sensor as a reference to change
the duty cycle of the PWM signal.
Constant from the processor datasheet that is added to the T
results in the value for
T
CONTROL
CONTROL_OFFSET
Value read by the BIOS from a processor MSR and added to the T
results in the value for
is the specification limit for use with the digital thermal sensor.
CONTROL
T
CONTROL
CONTROL_BASE
that
that
Pulse width modulation is a method of controlling a variable speed fan. The enabled
4 wire fans use the PWM duty cycle % from the fan speed controller to modulate the
fan speed.
Any standalone or integrated component that is capable of reading the processor
temperature and providing the PWM signal to the 4 pin fan header.
Balanced Technology Extended
Thermal Module Assembly. The heatsink, fan and duct assembly for the BTX thermal
solution
§
12 Thermal and Mechanical Design Guidelines
Processor Thermal/Mechanical Information
2 Processor Thermal/Mechanical
Information
2.1 Mechanical Requirements
2.1.1 Processor Package
The processors covered in the document are packaged in a 775-Land LGA package
that interfaces with the motherboard via a LGA775 socket. Refer to the datasheet for
detailed mechanical specifications.
The processor connects to the motherboard through a land grid array (LGA) surface
mount socket. The socket contains 775 contacts arrayed about a cavity in the center
of the socket with solder balls for surface mounting to the motherboard. The socket is
named LGA775 socket. A description of the socket can be found in the LGA775 Socket
Mechanical Design Guide.
The package includes an integrated heat spreader (IHS) that is shown in
illustration only. Refer to the processor datasheet for further information. In case of
conflict, the package dimensions in the processor datasheet supersedes dimensions
provided in this document.
Figure 1. Package IHS Load Areas
Top Surface of IHS
Substrate
Substrate
Top Surface of IHS
to install a heatsink
to install a heatsink
Figure 1 for
IHS Step
IHS Step
to interface with LGA775
to interface with LGA775
Socket Load Plate
Socket Load Plate
Thermal and Mechanical Design Guidelines 13
LGA775 Socket Heatsink Loading
The primary function of the IHS is to transfer the non-uniform heat distribution from
the die to the top of the IHS, out of which the heat flux is more uniform and spread
over a larger surface area (not the entire IHS area). This allows more efficient heat
transfer out of the package to an attached cooling device. The top surface of the IHS
is designed to be the interface for contacting a heatsink.
The IHS also features a step that interfaces with the LGA775 socket load plate, as
described in LGA775 Socket Mechanical Design Guide. The load from the load plate is
distributed across two sides of the package onto a step on each side of the IHS. It is
then distributed by the package across all of the contacts. When correctly actuated,
the top surface of the IHS is above the load plate allowing proper installation of a
heatsink on the top surface of the IHS. After actuation of the socket load plate, the
seating plane of the package is flush with the seating plane of the socket. Package
movement during socket actuation is along the Z direction (perpendicular to
substrate) only. Refer to the LGA775 Socket Mechanical Design Guide for further
information about the LGA775 socket.
The processor package has mechanical load limits that are specified in the processor
datasheet. The specified maximum static and dynamic load limits should not be
exceeded during their respective stress conditions. These include heatsink
installation, removal, mechanical stress testing, and standard shipping conditions.
• When a compressive static load is necessary to ensure thermal performance of the
thermal interface material between the heatsink base and the IHS, it should not
exceed the corresponding specification given in the processor datasheet.
• When a compressive static load is necessary to ensure mechanical performance, it
should remain in the minimum/maximum range specified in the processor
datasheet
• The heatsink mass can also generate additional dynamic compressive load to the
package during a mechanical shock event. Amplification factors due to the impact
force during shock must be taken into account in dynamic load calculations. The
total combination of dynamic and static compressive load should not exceed the
processor datasheet compressive dynamic load specification during a vertical
shock. For example, with a 0.550 kg [1.2 lb] heatsink, an acceleration of 50G
during an 11 ms trapezoidal shock with an amplification factor of 2 results in
approximately a 539 N [117 lbf] dynamic load on the processor package. If a
178 N [40 lbf] static load is also applied on the heatsink for thermal performance
of the thermal interface material the processor package could see up to a
717 N [156 lbf]. The calculation for the thermal solution of interest should be
compared to the processor datasheet specification.
No portion of the substrate should be used as a load- bearing surface.
Finally, the processor datasheet provides package handling guidelines in terms of
maximum recommended shear, tensile and torque loads for the processor IHS relative
to a fixed substrate. These recommendations should be followed in particular for
heatsink removal operations.
14 Thermal and Mechanical Design Guidelines
Processor Thermal/Mechanical Information
2.1.2 Heatsink Attach
2.1.2.1 General Guidelines
There are no features on the LGA775 socket to directly attach a heatsink: a
mechanism must be designed to attach the heatsink directly to the motherboard. In
addition to holding the heatsink in place on top of the IHS, this mechanism plays a
significant role in the robustness of the system in which it is implemented, in
particular:
• Ensuring thermal performance of the thermal interface material (TIM) applied
between the IHS and the heatsink. TIMs based on phase change materials are
very sensitive to applied pressure: the higher the pressure, the better the initial
performance. TIMs, such as thermal greases, are not as sensitive to applied
pressure. Designs should consider a possible decrease in applied pressure over
time due to potential structural relaxation in retention components.
• Ensuring system electrical, thermal, and structural integrity under shock and
vibration events. The mechanical requirements of the heatsink attach mechanism
depend on the mass of the heatsink and the level of shock and vibration that the
system must support. The overall structural design of the motherboard and the
system have to be considered when designing the heatsink attach mechanism.
Their design should provide a means for protecting LGA775 socket solder joints.
The Intel ALCT reference design attach mechanism described in Section.
5.6
Note: Package pull-out during mechanical shock and vibration i s constrained by the LGA775
socket load plate (refer to the LGA775 Socket Mechanical Design Guide for further
information).
2.1.2.2 The Pump Assembly Clip Load Requirement
The attach mechanism for the pump assembly developed to support the processor
should create a static preload on the package between 18 lbf and 70 lbf throughout
the life of the product for designs compliant with the Intel reference design
assumptions:
• 72 mm x 72 mm mounting hole span (refer to
The minimum load is required to protect against fatigue failure of socket solder joint in
temperature cycling.
It is important to take into account potential load degradation from creep over time
when designing the pump assembly clip to the required minimum load. This means
the initial preload at beginning of life of the product may be significantly higher than
the minimum preload that must be met throughout the life of the product. For
additional guidelines on mechanical design, in particular on designs departing from the
reference design assumptions, refer to
For clip load metrology guidelines, refer to
Appendix A.
Appendix B.
Figure 66)
Thermal and Mechanical Design Guidelines 15
2.1.2.3 Additional Guidelines
In addition to the general guidelines given above, the heatsink attach mechanism for
the processor should be designed to the following guidelines:
• Holds the heatsink in place under mechanical shock and vibration events and
applies force to the heatsink base to maintain desired pressure on the thermal
interface material. Note that the load applied by the heatsink attach mechanism
must comply with the package specifications described in the processor datasheet.
One of the key design parameters is the height of the top surface of the processor
IHS above the motherboard. The IHS height from the top of board is expected to
vary from 7.517 mm to 8.167 mm. This data is provided for information only, and
should be derived from:
⎯ The height of the socket seating plane above the motherboard after reflow,
given in the LGA775 Socket Mechanical Design Guide with its tolerances
⎯ The height of the package, from the package seating plane to the top of the
IHS, and accounting for its nominal variation and tolerances that are given in
the corresponding processor datasheet.
• Engages easily, and if possible, without the use of special tools. In general, the
heatsink is assumed to be installed after the motherboard has been installed into
the chassis.
• Minimizes contact with the motherboard surface during installation and actuation
to avoid scratching the motherboard.
LGA775 Socket Heatsink Loading
2.2 Thermal Requirements
Refer to the datasheet for the processor thermal specifications. The majority of
processor power is dissipated through the IHS. There are no additional components,
e.g., BSRAMs, which generate heat on this package. The amount of power that can
be dissipated as heat through the processor package substrate and into the socket is
usually minimal.
The thermal limits for the processor are the Thermal Profile and T
Profile defines the maximum case temperature as a function of power being
dissipated. T
CONTROL
reported by the digital thermal sensor and a fan speed control method. Designing to
these specifications allows optimization of thermal designs for processor performance
and acoustic noise reduction.
2.2.1 Processor Case Temperature
For the processor, the case temperature is defined as the temperature measured at
the geometric center of the package on the surface of the IHS. For illustration,
Figure 2 shows the measurement location for a 37.5 mm x 37.5 mm [1.474 in x 1.474
in] 775-Land LGA processor package with a 28.7 mm x 28.7 mm [1.13 in x 1.13 in]
IHS top surface. Techniques for measuring the case temperature are detailed in
Section
Note: In case of conflict, the package dimensions in the processor datasheet supersedes
dimensions provided in this document.
3.4.
is a specification used in conjunction with the temperature
. The Thermal
CONTROL
16 Thermal and Mechanical Design Guidelines
Processor Thermal/Mechanical Information
Figure 2. Processor Case Temperature Measurement Location
37.5 mm
37.5 mm
2.2.2 Thermal Profile
The Thermal Profile defines the maximum case temperature as a function of processor
power dissipation. Refer to the datasheet for the further information.
While the thermal profile provides flexibility for ATX /BTX thermal design based on its
intended target thermal environment, thermal solutions that are intended to function
in a multitude of systems and environments need to be designed for the worst-case
thermal environment. The majority of ATX /BTX platforms are targeted to function in
an environment that will have up to a 35 °C ambient temperature external to the
system.
For ATX platforms using the Intel
and QX9770 C0 stepping, an active liquid-cooled design should be designed to
manage the heat exchanger inlet temperature of 35 ºC + 3 ºC = 38 ºC (see
Chapter
5).
Measure TCat this point
Measure TCat this point
(geo metric center of the package)
(geo metric center of the package)
37.5 mm
37.5 mm
®
Core™2 Extreme processor QX6800 B3 stepping
For BTX platforms, the similar BTX liquid cooling design should be designed to manage
the heat exchanger inlet temperature of 35 ºC + 0.5 ºC = 35.5 ºC.
The slope of the thermal profile was established to be the same as the Intel liquid
cooling solution thermal solution performance. This performance is expressed as the
slope on the thermal profile and can be thought of as the thermal resistance of the
heatsink attached to the processor, Ψ
(Refer to Section 3.1). The intercept on the
CA
thermal profile assumes a maximum ambient operating condition that is consistent
with the available chassis solutions.
The thermal profiles for the processor are defined such that a single thermal solution
(e.g., ALCT reference design) can be used for Intel
QX6800 B3 Stepping and QX9770 C0 Stepping processors. See Chapter
®
Core™2 Extreme processor
5 for a
discussion of the ALCT reference design. To determine compliance to the thermal
profile, a measurement of the actual processor power dissipation is required. The
measured power is plotted on the Thermal Profile to determine the maximum case
Thermal and Mechanical Design Guidelines 17
temperature. Using the example in Figure 3 for a processor dissipating 110W the
maximum case temperature is 52.2°C. See the datasheet for the thermal profile.
Figure 3. Example Thermal Profile
LGA775 Socket Heatsink Loading
2.2.3 T
T
when the thermal solution fan speed is being controlled by the digital thermal sensor.
The T
speed can be reduced. This allows the system integrator a method to reduce the
acoustic noise of the processor cooling solution, while maintaining compliance to the
processor thermal specification.
Note: The T
activation set point which will be seen as 0 via the digital thermometer. As a result the
T
the thermal management logic and features and Chapter 6 on Intel® Quiet System
Technology (Intel
The value of T
of these is the processor idle power. As a result a processor with a high (closer to 0)
T
more negative number) of T
The value of T
T
some parts is offset by a higher value of T
behave similarly in the acoustic performance.
CONTROL
CONTROL
CONTROL
CONTROL
CONTROL
CONTROL
CONTROL
defines the maximum operating temperature for the digital thermal sensor
parameter defines a very specific processor operating region where fan
value for the processor is relative to the Thermal Control Circuit (TCC)
value will always be a negative number. See Chapter 4 for the discussion
®
QST).
CONTROL
will dissipate more power than a part with lower value (farther from 0, e.g.
CONTROL
value the thermal solution should perform similarly. The higher power of
is driven by a number of factors. One of the most significant
CONTROL
when running the same application.
is calculated such that regardless of the individual processor’s
CONTROL
in such a way that they should
18 Thermal and Mechanical Design Guidelines
Processor Thermal/Mechanical Information
This is achieved in part by using the ΨCA vs. RPM and RPM vs. Acoustics (dBA)
performance curves from the Intel enabled thermal solution. A thermal solution
designed to meet the thermal profile would be expected to provide similar acoustic
performance of different parts with potentially different T
The value for T
CONTROL
is calculated by the system BIOS based on values read from a
factory configured processor register. The result can be used to program a fan speed
control component. See the processor datasheet for further details on reading the
register and calculating T
See Chapter
6 Intel
CONTROL
®
Quiet System Technology (Intel® QST) for details on
implementing a design using T
.
and the Thermal Profile.
CONTROL
2.3 Heatsink Design Considerations
To remove the heat from the processor, three basic parameters should be considered:
The area of the surface on which the heat transfer takes place. Without
•
any enhancements, this is the surface of the processor package IHS. One method
used to improve thermal performance is by attaching a heatsink to the IHS. A
heatsink can increase the effective heat transfer surface area by conducting heat
out of the IHS and into the surrounding air through fins attached to the heatsink
base.
The conduction path from the heat source to the heatsink fins. Providing a
•
direct conduction path from the heat source to the heatsink fins and selecting
materials with higher thermal conductivity typically improves heatsi nk
performance. The length, thickness, and conductivity of the conduction path from
the heat source to the fins directly impact the thermal performance of the
heatsink. In particular, the quality of the contact between the package IHS and
the heatsink base has a higher impact on the overall thermal solution performance
as processor cooling requirements become stricter. Thermal interface material
(TIM) is used to fill in the gap between the IHS and the bottom surface of the
heatsink, and thereby improve the overall performance of the stack-up (IHS-TIMHeatsink). With extremely poor heatsink interface flatness or roughness, TIM may
not adequately fill the gap. The TIM thermal performance depends on its thermal
conductivity as well as the pressure applied to it. Refer to Section
Appendix C for further information on TIM and on bond line management between
the IHS and the heatsink base.
The heat transfer conditions on the surface on which heat transfer takes
•
place. Convective heat transfer occurs between the airflow and the surface
exposed to the flow. It is characterized by the local ambient temperature of the
, and the local air velocity over the surface. The higher the air velocity over
air, T
A
the surface, and the cooler the air, the more efficient is the resulting cooling. The
nature of the airflow can also enhance heat transfer via convection. Turbulent
flow can provide improvement over laminar flow. In the case of a heatsink, the
surface exposed to the flow includes in particular the fin faces and the heatsink
base.
CONTROL
values.
2.3.3 and
Liquid Cooling Technology typically incorporates a fan, an integrated pump with
cold plate and an air radiator type heat exchanger. The design takes advantage of a
pump to provide a uniform liquid-flow across the cold plate taking away the heat then
go to the exchanger. Finally, a fan manages the airflow through the exchanger.
Active heatsinks typically incorporate a fan that helps manage the airflow through
the heatsink.
Thermal and Mechanical Design Guidelines 19
Passive heatsink solutions require in-depth knowledge of the airflow in the chassis.
Typically, passive heatsinks see lower air speed. These heatsinks are therefore
typically larger (and heavier) than active heatsinks due to the increase in fin surface
required to meet a required performance. As the heatsink fin density (the number of
fins in a given cross-section) increases, the resistance to the airflow increases: it is
more likely that the air travels around the heatsink instead of through it, unless air
bypass is carefully managed. Using air-ducting techniques to manage bypass area
can be an effective method for controlling airflow through the heatsink.
2.3.1 Heatsink Size
The size of the heatsink is dictated by height restrictions for installation in a system
and by the real estate available on the motherboard and other considerations for
component height and placement in the area potentially impacted by the processor
heatsink. The height of the heatsink must comply with the requirements and
recommendations published for the motherboard form factor of interest. Designing a
heatsink to the recommendations may preclude using it in system adhering strictly to
the form factor requirements, while still in compliance with the form factor
documentation.
For the ATX/microATX form factor, it is recommended to use:
The ATX motherboard keep-out footprint definition and height restrictions for
•
enabling components, defined for the platforms designed with the LGA775 socket
in Appendix G of this design guide.
LGA775 Socket Heatsink Loading
The motherboard primary side height constraints defined in the ATX Specification
•
V2.2 and the microATX Motherboard Interface Specification V1.2 found at
http://www.formfactors.org/.
The resulting space available above the motherboard is generally not entirely available
for the heatsink. The target height of the heatsink must take into account airflow
considerations (for fan performance for example) as well as other design
considerations (air duct, etc.).
For BTX form factor, it is recommended to use:
The BTX motherboard keep-out footprint definitions and height restrictions for
•
enabling components for platforms designed with the LGA77 socket in
of this design guide.
•
An overview of other BTX system considerations for thermal solutions can be
obtained in the Balanced Technology Extended (BTX) System Design Guide v1.0
found at
http://www.formfactors.org/.
2.3.2 Package IHS Flatness
The package IHS flatness for the product is specified in the datasheet and can be used
as a baseline to predict heatsink performance during the design phase.
Intel recommends testing and validating heatsink performance in full mechanical
enabling configuration to capture any impact of IHS flatness change due to combined
socket and heatsink loading. While socket loading alone may increase the IHS
warpage, the heatsink preload redistributes the load on the package and improves the
resulting IHS flatness in the enabled state.
Appendix G
20 Thermal and Mechanical Design Guidelines
Processor Thermal/Mechanical Information
2.3.3 Thermal Interface Material
Thermal interface material application between the processor IHS and the heatsink
base is generally required to improve thermal conduction from the IHS to the
heatsink. Many thermal interface materials can be pre-applied to the heatsink base
prior to shipment from the heatsink supplier and allow direct heatsink attach, without
the need for a separate thermal interface material dispense or attach process in the
final assembly factory.
All thermal interface materials should be sized and positioned on the heatsink base in
a way that ensures the entire processor IHS area is covered. It is important to
compensate for heatsink-to-processor attach positional alignment when selecting the
proper thermal interface material size.
When pre-applied material is used, it is recommended to have a protective application
tape over it. This tape must be removed prior to heatsink installation.
2.4 System Thermal Solution Considerations
2.4.1 Chassis Thermal Design Capabilities
The Intel liquid cooling thermal solution assumes that chassis delivers a maximum TA
at the inlet of the processor heat exchanger (refer to Section
the T
requirements for the ALCT and the similar BTX solutions.
A
Table 1. Heatsink Inlet Temperature of Intel Reference Thermal Solutions
Topic ATX ALCT BTX Liquid Cooling
Heatsink Inlet
Temperature
38 °C 35.5 °C
5.1.1). Table 1 shows
2.4.2 Improving Chassis Thermal Performance
The heat generated by components within the chassis must be removed to provide an
adequate operating environment for both the processor and other system
components. Moving air through the chassis brings in air from the external ambient
environment and transports the heat generated by the processor and other system
components out of the system. The number, size and relative position of fans and
vents determine the chassis thermal performance, and the resulting ambient
temperature around the processor. The size and type (passive or active) of the
thermal solution and the amount of system airflow can be traded off against each
other to meet specific system design constraints. Additional constraints are board
layout, spacing, component placement, acoustic requirements and structural
considerations that limit the thermal solution size. For more information, refer to the
ATX Thermal Design Suggestions or microATX Thermal Design Suggestions or
Balanced Technology Extended (BTX) System Design Guide v1.0 documents available
on the http://www.formfactors.org/
In addition to passive heatsinks, fan heatsinks and system fans are other solutions
that exist for cooling integrated circuit devices. For example, ducted blowers, heat
web site.
Thermal and Mechanical Design Guidelines 21
pipes and liquid cooling are all capable of dissipating additional heat. Due to their
varying attributes, each of these solutions may be appropriate for a particular system
implementation.
To develop a reliable, cost-effective thermal solution, thermal characterization and
simulation should be carried out at the entire system level, accounting for the thermal
requirements of each component. In addition, acoustic noise constraints may limit the
size, number, placement, and types of fans that can be used in a particular design.
To ease the burden on thermal solutions, the Thermal Monitor feature and associated
logic have been integrated into the silicon of the processor. By taking advantage of
the Thermal Monitor feature, system designers may reduce thermal solution cost by
designing to TDP instead of maximum power. Thermal Monitor attempts to protect
the processor during sustained workload above TDP. Implementation options and
recommendations are described in Chapter
2.4.3 Summary
In summary, considerations in heatsink design include:
• The local ambient temperature TA at the heatsink, which is a function of chassis
design.
• The thermal design power (TDP) of the processor, and the corresponding
maximum T
combined in a single lump cooling performance parameter, Ψ
thermal characterization parameter). More information on the definition and the
use of Ψ
• Heatsink i nterface to IHS surface characteristics, including flatness and roughness.
•
The performance of the thermal in terface material used between the heatsink and
the IHS.
• The required heatsi nk clip static load, between 18 lbf to 70 lbf throughout the life
of the product (Refer to Section
• Surface area of the heatsink.
•
Heatsink material and technology.
•
Volume of airflow over the heatsink surface area.
•
Development of airflow entering and within the heatsink area.
•
Physical volumetric constraints placed by the system
CA
LGA775 Socket Heatsink Loading
4.
as calculated from the thermal profile. These parameters are usually
C
(case to air
CA
is given section 3.1
2.1.2.2 for further information).
2.5 System Integration Considerations
Manufacturing with Intel® Components using 775–Land LGA Package and LGA775
Socket documentation provides Best Known Methods for all aspects LGA775 socket
based platforms and systems manufacturing. Of particular interest for package and
heatsink installation and removal is the System Assembly module. A video covering
system integration is also available. Contact your Intel field sales representative for
further information.
22 Thermal and Mechanical Design Guidelines
Thermal Metrology
3 Thermal Metrology
This section discusses guidelines for testing thermal solutions, including measuring
processor temperatures. In all cases, the thermal engineer must measure power
dissipation and temperature to validate a thermal solution. To define the performance
of a thermal solution the “thermal characterization parameter”, Ψ
3.1 Characterizing Cooling Performance Requirements
The idea of a “thermal characterization parameter”, Ψ (“psi”), is a convenient way to
characterize the performance needed for the thermal solution and to compare thermal
solutions in identical si tuations (same heat source and local ambient conditions). The
thermal characterization parameter is calculated using total package power.
(“psi”) will be used.
Note: Heat transfer is a three-dimensional phenomenon that can rarely be accurately and
easily modeled by a single resistance parameter like Ψ.
The case-to-local ambient thermal characterization parameter value (Ψ
measure of the thermal performance of the overall thermal solution that is attached to
the processor package. It is defined by the following equation, and measured in units
of °C/W:
Ψ
= (TC – TA) / PD (Equation 1)
CA
Where:
= Case-to-local ambient thermal characterization parameter (°C/W)
Ψ
CA
T
= Processor case temperature (°C)
C
TA = Local ambient temperature in chassis at processor (°C)
P
= Processor total power dissipation (W) (assumes all power dissipates
D
through the IHS)
) is used as a
CA
Thermal and Mechanical Design Guidelines 23
LGA775 Socket Heatsink Loading
The case-to-local ambient thermal characterization parameter of the processor, ΨCA, is
comprised of Ψ
and of Ψ
Ψ
Where:
is strongly dependent on the thermal conductivity and thickness of the TIM
Ψ
CS
between the heatsink and IHS.
is a measure of the thermal characterization parameter from the bottom of the
Ψ
SA
heatsink to the local ambient air. Ψ
conductivity, and geometry. It is also strongly dependent on the air velocity through
the fins of the heatsink.
, the sink-to-local ambient thermal characterization parameter:
SA
= ΨCS + ΨSA (Equation 2)
CA
= Thermal characterization parameter of the thermal interface material
Ψ
CS
= Thermal characterization parameter from heatsink-to-local ambient
Ψ
SA
, the thermal interface material thermal characterization parameter,
CS
(°C/W)
(°C/W)
is dependent on the heatsink material, thermal
SA
Figure 4 illustrates the combination of the different thermal characterization
parameters.
Figure 4. Processor Thermal Characterization Parameter Relationships
T
T
A
A
Heatsink
Heatsink
T
T
S
T
T
S
C
C
System Board
System Board
TIM
TIM
Processor
Processor
IHS
IHS
Ψ
Ψ
CA
CA
LGA775 Socket
LGA775 Socket
24 Thermal and Mechanical Design Guidelines
Thermal Metrology
3.1.1 Example
The cooling performance, Ψ
is then defined using the principle of thermal
CA,
characterization parameter described above:
•
The case temperature T
and thermal design power TDP given in the processor
C-MAX
datasheet.
Define a target local ambient temperature at the processor, T
•
A
.
Since the processor thermal profile applies to all processor frequencies, it is important
to identify the worst case (lowest Ψ
) for a targeted chassis characterized by TA to
CA
establish a design strategy.
The following provides an illustration of how one might determine the appropriate
performance targets. The example power and temperature numbers used here are
not related to any specific Intel processor thermal specifications, and are for
illustrative purposes only.
Assume the TDP, as listed in the datasheet, is 100W and the maximum case
temperature from the thermal profile for 100W is 67 °C. Assume as well that the
system airflow has been designed such that the local ambient temperature is 38°C.
Then the following could be calculated using equation 1 from above:
Ψ
= (TC,– TA) / TDP = (67 – 38) / 100 = 0.29 °C/W
CA
To determine the required heatsink performance, a heatsink solution provider would
need to determine Ψ
performance for the selected TIM and mechanical load
CS
configuration. If the heatsink solution were designed to work with a TIM material
performing at Ψ
≤ 0.10 °C/W, solving for equation 2 from above, the performance of
CS
the heatsink would be:
Ψ
= ΨCA − ΨCS = 0.29 − 0.10 = 0.19 °C/W
SA
Thermal and Mechanical Design Guidelines 25
LGA775 Socket Heatsink Loading
3.2 Processor Thermal Solution Performance Assessment
Thermal performance of a heatsink should be assessed using a thermal test vehicle
(TTV) provided by Intel. The TTV is a stable heat source that the user can make
accurate power measurement, whereas processors can introduce additional factors
that can impact test results. In particular, the power level from actual processors
varies significantly, even when running the maximum power application provided by
Intel, due to variances in the manufacturing process. The TTV provides consistent
power and power density for thermal solution characterization and results can be
easily translated to real processor performance. Accurate measurement of the power
dissipated by an actual processor is beyond the scope of this document.
Once the thermal solution is designed and validated with the TTV, it is strongly
recommended to verify functionality of the thermal solution on real processors and on
fully integrated systems. The Intel maximum power application enables steady power
dissipation on a processor to assist in this testing.
3.3 Local Ambient Temperature Measurement Guidelines
The local ambient temperature TA is the temperature of the ambient air surrounding
the processor. For a passive heatsink, T
temperature; for an actively cooled heatsink, it is the temperature of inlet air to the
active cooling fan; for a liquid cooled solution it is the temperature of the air entering
the heat exchanger.
It is worthwhile to determine the local ambient temperature in the chassis around the
processor to understand the effect it may have on the case temperature.
is best measured by averaging temperature measurements at multiple locations in
T
A
the heatsink or heat exchanger inlet airflow. This method helps reduce error and
eliminate minor spatial variations in temperature. The following guidelines are meant
to enable accurate determination of the localized air temperature around the
processor during system thermal testing.
For active heatsinks and liquid cooled solutions, it is important to avoid taking
measurement in the dead flow zone that usually develops above the fan hub and hub
spokes. Measurements should be taken at four different locations uniformly placed at
the center of the annulus formed by the fan hub and the fan housing to evaluate the
uniformity of the air temperature at the fan inlet. The thermocouples should be
placed approximately 3 mm to 8 mm [0.1 to 0.3 in] above the fan hub vertically and
halfway between the fan hub and the fan housing horizontally as shown in
Figure 6 (avoiding the hub spokes). Using an open bench to characterize an
and
active heatsink can be useful, and usually ensures more uniform temperatures at the
fan inlet. However, additional tests that include a solid barrier above the test
motherboard surface can help evaluate the potential impact of the chassis. This
barrier is typically clear Plexiglas*, extending at least 100 mm [4 i n ] in all directions
beyond the edge of the thermal solution. Typical distance from the motherboard to
the barrier is 81 mm [3.2 in]. For even more realistic airflow, the motherboard should
be populated with significant elements like memory cards, graphic card, and chipset
is defined as the heatsink approach air
A
Figure 5
26 Thermal and Mechanical Design Guidelines
Thermal Metrology
heatsink. If a barrier is used, the thermocouple can be taped directly to the barrier
with a clear tape at the horizontal location as previously described, half way between
the fan hub and the fan housing. If a variable speed fan is used, it may be useful to
add a thermocouple taped to the barrier above the location of the temperature sensor
used by the fan to check its speed setting against air temperature. When measuring
in a chassis with a live motherboard, add-in cards, and other system components,
T
A
it is likely that the T
distribution across the inlet fan section.
For passive heatsinks, thermocouples should be placed approximately 13 mm to
25 mm [0.5 to 1.0 in] away from processor and heatsink as shown in
thermocouples should be placed approximately 51 mm [2.0 in] above the baseboard.
This placement guideline is meant to minimize the effect of localized hot spots from
baseboard components.
Note: Testing an active heatsink with a variable speed fan can be done in a thermal chamber
to capture the worst-case thermal environment scenarios. Otherwise, when doing a
bench top test at room temperature, the fan regulation prevents the heatsink from
operating at its maximum capability. To characterize the heatsink capability in the
worst-case environment in these conditions, it is then necessary to disable the fan
regulation and power the fan directly, based on guidance from the fan supplier.
measurements will reveal a highly non-uniform temperature
A
Figure 7. The
Figure 5. Locations for Measuring Local Ambient Temperature, Active Heatsink
NOTE: Drawing Not to Scale
Thermal and Mechanical Design Guidelines 27
LGA775 Socket Heatsink Loading
+
Figure 6. Locations for Measuring Local Ambient Temperature, Liquid-Cooling Heat
Exchanger
Side View
Fa
n
Airflow
Heat
Exchanger
Front View
+
+
+
I
O
NOTE: Drawing Not to Scale
Figure 7. Locations for Measuring Local Ambient Temperature, Passive Heatsink
VR
Fan Hub Spokes
Measure TA as
indicated between the
hub spokes at mid-
blade length
NOTE: Drawing Not to Scale
28 Thermal and Mechanical Design Guidelines
Thermal Metrology
3.4 Processor Case Temperature Measurement Guidelines
To ensure functionality and reliability, the processor is specified for proper operation
when T
measurement location for T
location for T
Special care is required when measuring TC to ensure an accurate temperature
measurement. Thermocouples are often used to measure T
measurements are made, the thermocouples must be calibrated, and the complete
measurement system must be routinely checked against known standards. When
measuring the temperature of a surface that is at a different temperature from the
surrounding local ambient air, errors could be introduced in the measurements. The
measurement errors could be caused by poor thermal contact between the junction of
the thermocouple and the surface of the integrated heat spreader, heat loss by
radiation, convection, by conduction through thermocouple leads, or by contact
between the thermocouple cement and the heatsink base.
Appendix D defines a reference procedure for attaching a thermocouple to the IHS of
a 775-Land LGA processor package for T
account the specific features of the 775-Land LGA package and of the LGA775 socket
for which it is intended.
is maintained at or below the thermal profile as listed in the datasheet. The
C
measurement.
C
is the geometric center of the IHS. Figure 2 shows the
C
. Before any temperature
C
measurement. This procedure takes into
C
§
Thermal and Mechanical Design Guidelines 29
LGA775 Socket Heatsink Loading
30 Thermal and Mechanical Design Guidelines
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