Intel Celeron D Thermal Design Manual
Intel® Celeron® D Processor in
the 775-Land LGA Package for
Embedded Applications
Thermal Design Guide
July 2005
Order #303730-002
Contents
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Celeron® D Processor in the 775-Land LGA Package for Embedded Applications may contain design defects or errors known as errata
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Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide
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Contents
Contents
1.0 Introduction....................................................................................................................................6
1.1 Document Goals and Scope.................................................................................................6
1.1.1 Importance of Thermal Management.......................................................................6
1.1.2 Document Goals......................................................................................................6
1.1.3 Document Scope.....................................................................................................6
1.2 References ...........................................................................................................................7
1.3 Terms and Definitions...........................................................................................................7
2.0 Processor Thermal/Mechanical Information...............................................................................9
2.1 Mechanical Requirements ........................................................... .... ... ... ... .... ... .....................9
2.1.1 Processor Package..................................................................................................9
2.1.2 Heatsink Attach......................................................................................................10
2.1.2.1 General Guidelines................................................................................10
2.1.2.2 Heatsink Clip Load Requirement................................. .... ......................11
2.1.2.3 Additional Guidelines.............................................................................11
2.2 Thermal Requirements .......................................................................................................11
2.2.1 Processor Case Temperature and Power Dissipation...........................................12
2.2.2 Thermal Profile ......................................................................................................12
2.2.3 T
2.3 Heatsink Design Considerations.........................................................................................14
2.3.1 Heatsink Size.........................................................................................................15
2.3.2 Heatsink Mass.......................................................................................................15
2.3.3 Package IHS Flatness...........................................................................................15
2.3.4 Thermal Interface Material.............. ... .... ...................................... .... ... ... ... ... .... ... ...16
2.3.5 Summary ...............................................................................................................16
2.4 System Thermal Solution Considerations........... ... ... ... .... ... ... ... ....... ... ... ... .... ... ... ... ... .... ... ...16
2.4.1 Improving Chassis Thermal Performance..............................................................16
CONTROL
...............................................................................................................13
3.0 Thermal Metrology ......................................................................................................................18
3.1 Characterizing Cooling Performance Requirements ..........................................................18
3.1.1 Example.................................................................................................................19
3.2 Processor Thermal Solution Performance Assessment .....................................................20
3.3 Local Ambient Temperature Measurement Guidelines ......................................................20
3.3.1 Measuring Active Heatsinks ............................... ... ... ... ... .... ... ................................20
3.3.2 Measuring Passive Heatsinks................ ................................................................21
3.4 Processor Case Temperature Measurement Guidelines....................................................22
4.0 Thermal Management Logic and Thermal Monitor ..................................................................23
4.1 Processor Power Dissipation..............................................................................................23
4.2 Thermal Monitor Implementation........................................................................................23
4.2.1 PROCHOT# Signal................... ... ... ... .... ... ... ....................................... ... ... ... .... ... ...23
4.2.2 Thermal Control Circuit..........................................................................................24
4.2.3 Operation and Configuration.............. .... ... ... ... .... ... ...................................... .... ... ...25
4.2.4 On-Demand Mode.................................................................................................25
4.2.5 System Considerations.......................................................... ... ... .... ... ... ... .............26
4.2.6 Operating System and Application Software Considerations ................................26
4.2.7 On-Die Thermal Diode........................... ... ... ... .... ...................................... ... .... ... ...26
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4.2.7.1 Reading the On-Die Thermal Diode Interface........................................27
4.2.7.2 Correction Factors for the On-Die Thermal Diode.................................27
4.2.8 THERMTRIP# Signal.............................................................................................28
4.2.8.1 Cooling System Failure Warning...........................................................28
4.2.9 How On-Die Thermal Diode, TCONTROL and Thermal Profile Work Together....29
4.2.9.1 On-Die Thermal Diode Less than TCONTROL......................................29
4.2.9.2 On-Die Thermal Diode Greater than TCONTROL.................................29
4.3 Acoustic Fan Speed Control........... ....................................... ... ... ... .... ... ... ..........................29
5.0 Intel Enabled Thermal Solutions................................................................................................30
5.1 Thermal Solution Requirements.........................................................................................30
5.2 ATX Form Factor................................................................................................................31
5.3 1U Form Factor............................... ... ... .... ...................................... .... ... ... ... .... ... ................31
5.4 2U Form Factor............................... ... ... .... ...................................... .... ... ... ... .... ... ................33
5.5 Reference Thermal Mechanical Solution............................................................................35
6.0 Conclusion...................................................................................................................................36
A LGA775 Socket Heatsink Loading.............................................................................................37
B Heatsink Clip Load Metrology....................................................................................................42
C Thermal Interface Management..................................................................................................46
D Case Temperature Reference Methodology.............................................................................47
E Board Level PWM and Fan Speed Control Requirements.......................................................57
F Mechanical Drawings..................................................................................................................58
G Vendor Information .....................................................................................................................64
Figures
1 Package IHS Load Areas .............................................................................................................9
2 Processor Case Temperature Measurement Location...............................................................12
3 Example Thermal Profile............................................................................................................13
4 Processor Thermal Characterization Parameter Relationships..................................................19
5 Measuring T
6 Measuring T
7 Concept for Clocks under Thermal Monitor Control ...................................................................24
8 Thermal Characterization Parameters for Various Operating Conditions ..................................31
9 1U Copper Heatsink ...................................................................................................................32
10 1U Thermal Solution Z-Height Constraints.................................................................................33
11 2U Copper Heatsink ...................................................................................................................33
12 Case-to-Ambient Thermal Characterization Parameter Ψ
13 2U Height Restrictions................................................................................................................35
14 Board Deflection Definition..................... ... ... .... ... ... ... .... ...................................... .... ... ... ... ..........38
15 Example: Defining Heatsink Preload Meeting Board Deflection Limit........................................40
16 Load Cell Installation in Machined Heatsink Base Pocket – Bottom View .................................43
17 Load Cell Installation in Machined Heatsink Base Pocket – Side View......................................43
18 Preload Test Configuration.........................................................................................................44
— Active Heatsink...............................................................................................21
LA
— Passive Heatsink............................................................................................22
LA
(°C/W)............................. ... ... .... ...34
CA
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Contents
19 FC-LGA4 Package Reference Groove Drawing.........................................................................49
20 IHS Reference Groove on the FC-LGA4 Package .....................................................................50
21 IHS Groove Orientation Relative to the LGA775 Socket............................................................50
22 Bending the Tip of the Thermocouple.........................................................................................51
23 Securing Thermocouple Wires with Kapton* Tape Prior to Attach.............................................51
24 Thermocouple Bead Placement (View 1)...................................................................................52
25 Thermocouple Bead Placement (View 2)...................................................................................52
26 Position Bead on Groove Step ...................................................................................................53
27 Detailed Thermocouple Bead Placement...................................................................................53
28 Using 3D Micromanipulator to Secure Bead Location................................................................54
29 Measuring Resistance between Thermocouple and IHS............................................................54
30 Applying the Adhesive on the Thermocouple Bead....................................................................55
31 Thermocouple Wire Management in the Groove........................................................................55
32 Removing Excess Adhesive from IHS........................................................................................56
33 Filling the Groove with Adhesive ................................................................................................56
34 ATX/µATX Motherboard Keep-Out Footprint Definition and Height Restrictions
for Enabling Components, Sheet 1.............................................................................................59
35 ATX/µATX Motherboard Keep-Out Footprint Definition and Height Restrictions
for Enabling Components, Sheet 2.............................................................................................60
36 ATX/µATX Motherboard Keep-Out Footprint Definition and Height Restrictions
for Enabling Components, Sheet 3.............................................................................................61
37 1U/2U Motherboard Component Keep-In Definition, Primary Side ............................................62
38 1U/2U Motherboard Component Keep-In Definition, Secondary Side........................................63
Tables
1 Reference Documents..................................................................................................................7
2 Terms and Definitions...................................................................................................................7
3 Thermal Diode Interface.............................................................................................................27
4 Thermal Characterization Parameter at Various TLA Levels .....................................................30
5 Enabled Thermal Solutions............................ ... ... ... .... ...................................... .... ... ... ... ... .... ......31
6 Board Deflection Configuration Definitions.................................................................................38
7 Typical Test Equipment..............................................................................................................44
8 Definitions...................................................................................................................................47
9 Supporting Test Equipment........................................................................................................47
10 Mechanical Drawings..................................................................................................................58
11 Intel Reference Component Thermal Solution Provider.......................................................... ...64
Revision History
Date Revision Description
July 2005 002 Updated Table 1 and Table 4.
September 2004 001 Changes to branding. First public release.
Intel® Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide 5
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Introduction
1.0 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 (higher operating speeds, GHz) 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 chassis characteristics, new system and component designs
may be required to provide adequate cooling for the processor. The goal of this Thermal Design
Guide is to provide an understanding of these thermal characteristics and discuss guidelines for
meeting the thermal requirements imposed on single processor systems for the Intel
Processor in the 775-Land LGA Package for Embedded Applications. The specifications for this
processor (also referred to herein as the Intel Celeron D Processor in the 775-Land LGA Package)
are delineated in the Intel
1.1.3 Document Scope
This document discusses the thermal management techniques for the Intel Celeron D Processor in
the 775-Land Package.
The processor physical dimensions and thermal specifications used in this document are for
illustration only. Refer to the Intel Celeron D Processor in the 775-Land Package Datasheet for
product dimensions, thermal power dissipation and maximum case temperature. In case of conflict,
the datasheet supersedes this document.
®
Celeron® D
®
Celeron® D Processor in the 775-Land LGA Package Datasheet.
6 Intel
®
Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide
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1.2 References
Material and concepts available in the following documents may be beneficial when reading this
document.
Table 1. Reference Documents
Fan Specification for 4 Wire PWM Controlled Fans
®
Intel
Celeron® D Processors 3xx Sequence Datasheet on 90nm Process
in 775-Land Package
Intel® Pentium® 4 Processor 570/571, 560/561, 550/551, 540/541, 530/531
and 520/521 Supporting Hyper-Threading Technology Datasheet
®
Intel
Pentium® 4 Processor on 90 nm Process in the 775-Land LGA
Package Thermal Design Guide
LGA775 Socket Mechanical Design Guide Intel document #302666
Performance ATX Desktop System Thermal Design Suggestions http://www.formfactors.org/
Performance microATX Desktop System Thermal Design Suggestions http://www.formfactors.org/
Server System Infrastructure Thin Electronics Bay Specifications http://www.ssiforum.org/
Introduction
Document Comment
http://www.formfactors.org/dev
eloper%5Cspecs%5CREV1_2_
Public.pdf
Intel document #304092
Intel document # 302351
Intel document #302553
1.3 Terms and Definitions
Table 2. Terms and Definitions (Sheet 1 of 2)
Term Description
T
A
T
C
T
E
T
S
T
C-MAX
Ψ
CA
Ψ
CS
Ψ
SA
The measured ambient temperature locally surrounding the processor. The ambient
temperature should be measured just upstream of a passive heatsink or at the fan inlet
for an active heatsink. Also referred to as T
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.
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
C.
LA
Ψ measurements.
Ψ measurements.
– TA) / Total Package Power.
Ψ measurements.
S
– TA) / Total Package
C
– TS) / Total Package
C
Intel® Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide7
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Introduction
Table 2. Terms and Definitions (Sheet 2 of 2)
TIM
P
MAX
TDP
IHS
LGA775 Socket
ACPI Advanced Configuration and Power Interface.
Bypass
FMB
Thermal Monitor
TCC
T
DIODE
FSC
T
CONTROL_BASE
T
CONTROL_OFFSET
T
CONTROL
PWM
Health Monitor
Component
U
Thermal Interface Material: The thermally conductive compound between the heatsink
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.
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 Intel Celeron D Processor in the
775-Land LGA Package.
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.
Flexible Motherboard Guideline: an estimate of the maximum value of a processor
specification over certain time periods. System designers should meet the FMB values
to ensure their systems are compatible with future processor releases. FMB1 and FMB2
are sequential estimates of processor specifications over time.
A feature on the Intel Celeron D Processor in the 775-Land LGA Package that attempts
to keep the processor’s 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 is very near its
operating limits.
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 on-die thermal diode as a reference to change the duty
cycle of the PWM signal.
Constant from the processor EMTS that is added to the T
in the value for
Value read by the BIOS from a processor MSR and added to the T
results in the value for
T
CONTROL
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.
A unit of measure used to define server rack spacing height. 1U is equal to 1.75 inches,
2U equals 3.50 inches, etc.
is the specification limit for use with the on-die thermal diode.
T
CONTROL
T
CONTROL
CONTROL_OFFSET
CONTROL_BASE
that results
that
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Processor Thermal/Mechanical Information
2.0 Processor Thermal/Mechanical Information
2.1 Mechanical Requirements
2.1.1 Processor Package
The Celeron D Processor in the 775-Land LGA Package is packaged in a Flip-Chip Land Grid
Array (FC-LGA4) package that interfaces with the motherboard via a LGA775 socket. Please refer
to the processor 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 Figure 1 for illustration
only. Refer to the processor datasheet for further information. In case of conflict, the package
dimensions in the processor datasheet supercede dimensions provided in this document.
Figure 1. Package IHS Load Areas
Top Surface of IHS
Substrate
Substrate
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.
Top Surface of IHS
to install a heatsink
to install a heatsink
IH S Step
IH S Step
to in te rface wi th LGA775
to in te rface wi th LGA775
Socket Load P late
Socket Load P late
Intel® Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide9
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Processor Thermal/Mechanical Information
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. The post-actuated 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 datasheet gives details on the IHS geometry and tolerances, and IHS material.
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 (TIM) 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 not
exceed the corresponding specification given in the processor datasheet.
• The heatsink mass can also add 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 0.454 kg [1 lbm] heatsink, an
acceleration of 50G during an 11 ms trapezoidal shock with an amplification factor of 2 results
in approximately a 445 N [100 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 TIM the processor
package could see up to a 623 N [140 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.
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 support the heatsink. 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 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.
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• Ensuring system electrical, thermal, and structural integrity under shock and vibration events.
The mechanical requirements of the heatsink attach mechanism depend on the weight 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.
Note: Package pull-out during mechanical shock and vibration is constrained by the LGA775 socket load
plate (refer to the LGA775 Socket Mechanical Design Guide for further information).
2.1.2.2 Heatsink Clip Load Requirement
The attach mechanism for the heatsink developed to support the Celeron D processor in the
775-land LGA package should create a static load on the package between 18 lbf and 70 lbf
throughout the life of the product.
This load is required to ensure protect against fatigue failure of socket solder joint for a platform
seven year life.
2.1.2.3 Additional Guidelines
Processor Thermal/Mechanical Information
In addition to the general guidelines given above, the heatsink attach mechanism for the Celeron D
processor in the 775-land LGA package 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.
2.2 Thermal Requirements
Refer to the processor datasheet for the processor thermal specifications. The majori ty of proces sor
power is dissipated through the IHS. There are no additional components (e.g., BSRAMs) that
generate heat in this package. The amount of power that can be dissipated as heat through the
processor package substrate and into the socket is usually minimal.
Intel® Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide11
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Processor Thermal/Mechanical Information
Intel has introduced a new method for specifying the thermal limits for the Celeron D Processor in
the 775-Land LGA Package. The new parameters are the Thermal Profile and T
Thermal Profile defines the maximum case temper ature as a function of power being dissipated.
T
CONTROL
is a specification used in conjunction with the temperature reported by the on-die
thermal diode. Designing to these specifications allows optimization of thermal designs for
processor performance and acoustic noise reduction.
2.2.1 Processor Case Temperature and Power Dissipation
For the Celeron D processor in the 775-land LGA package, 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] FCLGA4 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 3.4.
Figure 2. Processor Case Temperature Measurement Location
CONTROL
. The
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. The TDP and Maximum Case Temperature are defined as the maximum values of the
thermal profile. By design the thermal solutions must meet the therma l profi le for all system
operating conditions and processor power levels.
37.5 mm
37.5 mm
Measure TCat this point
Measure TCat this point
(g eometric center of the package)
(g eometric center of the package)
The slope of the thermal profile was established assuming a generational improvement in th ermal
solution performance of about 10 % based on previous Intel reference design. This performance is
expressed as the slope on the thermal profile and can be thought of as the
thermal profile assumes a maximum ambient operating condition that is consistent with the
available chassis solutions.
12 Intel
Ψ
. The intercept on the
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T o determine compliance to the thermal profile, a measurement of the actual processor power
dissipated is required. The measured power is plotted on the Thermal Profile to determine the
maximum case temperature. Using the example in Figure 3, a power dissipation of 70 W has a case
temperature of 61 °C. Contact your Intel sales representative for assistance in processor power
measurement.
For the Intel Celeron D Processor in the 775-Land LGA Package, there are two thermal profiles to
consider. The Platform Requirement Bit (PRB) indicates which thermal profile is appropriate for a
specific processor. This document will focus on the development of thermal solutions to meet the
thermal profile for PRB=1. See the processor datasheet for the thermal profile and additional
discussion on the PRB.
Figure 3. Example Thermal Profile
75
70
65
60
Processor Thermal/Mechanical Information
Heatsink
Design Poin t
2.2.3 T
55
50
45
Case Temperature (C)
40
35
30
30 40 50 60 70 80 90 100 110
Watts
CONTROL
T
CONTROL
.
defines the maximum operating temperature for the on-die thermal diode when the
thermal solution fan speed is being controlled by the on-die thermal diode. The T
defines a very specific processor operating region where the T
is not specified. This parameter
C
Thermal Prof ile
FMB2
parameter
CONTROL
allows the system integrator a method to reduce the acoustic noise of the processor cooling
solution, while maintaining compliance to the processor thermal specification.
The value of T
CONTROL
processor idle power . As a result a processor with a high T
part with lower value of T
The value of T
CONTROL
is driven by a number of factors. One of the most significant of these is the
when running the same application.
CONTROL
CONTROL
is calculated such that regardless of the individual processor’s T
will dissipate more power than a
CONTROL
value the thermal solution should perform similarly. The higher leakage of some parts is offset by a
higher value of T
CONTROL
in such a way that they will behave virtually the same acoustically
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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 should perform virtually the same for any value of T
Fan Speed Control” on page 29, for details on implementing a design using Tcontrol and the
Thermal Profile.
CONTROL
. See Section 4.3, “Acoustic
The value for T
CONTROL
is calculated by the system BIOS based on values read from a factory
configured processor register. Th e 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
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 increases 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 heatsink 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-TIM-Heatsink). 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 2.3.4 and 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 air, T
surface. The higher the air velocity over the surface and the cooler the air, the more ef ficient 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
, and the local air velocity over the
A
.
Active heatsinks typically incorporate a fan that helps manage the airflow through the heatsink.
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.
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2.3.1 Heatsink Size
The size of the heatsink is dictated by height restrictions for installation in a system and by the
space 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.
For the ATX/microATX form factor, it is recommended to use:
• The ATX motherboard keep-out footprint definition and heigh t restrictio ns for enabling
components, defined for the platforms designed with the LGA775 socket in Appendix F of this
design guide.
• The motherboard primary side height constraints defined in the ATX Specification V2.1 and
the microATX Motherboard Interface Specification V1.1 found at
http://www.formfactors.org/.
For the 1U and 2U server form factor, it is recommended to use:
• The 1U and 2U motherboard keep-out footprint definition and height restrictions for enabling
components, defined for the platforms designed with the LGA775 socket in Appendix E of
this design guide. Note that this keep-out footprint is similar to the ATX motherboard
keep-out, with minor differences in the areas surrounding the processor package.
• The 1U and 2U primary side constraints defined in the Thin Electronics Bay specification
found at http://www.ssiforum.org/.
Processor Thermal/Mechanical Information
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.).
2.3.2 Heatsink Mass
With the need for pushing air cooling to better performance, heatsink solutions tend to grow larger
(increase in fin surface) resulting in increased weight. The insertion of highly thermally conductive
materials like copper to increase heatsink thermal conduction performance results in even heavier
solutions. As mentioned in Section 2.1, “Mechanical Requirements” on page 9, the heatsink weight
must take into consideration the package and socket load limits, the heatsink attach mechanical
capabilities, and the mechanical shock and vibration profile targets. Beyond a certain heatsink
weight, the cost of developing and implementing a heatsink attach mechanism that can ensure the
system integrity under the mechanical shock and vibration profile targets may become prohibitive.
The recommended maximum heatsink weight for the Celeron D processor in the 775-land LGA
package is 450g for the ATX form factor. This weight includes the fan and the heatsink only. The
attach mechanism (clip, fasteners, etc.) is not included.
The weight of the heatsinks for server form factors tends to be heavier than desktop form factors
and therefore there isn't a recommended maximum weight. These solutions are sometimes fastened
to the motherboard with the use of a backplate on the secondary side or in some cases are directly
mounted to the server chassis. In all cases, system integrators must ensure that the load
specifications for the package are met during shock and vibration testing.
2.3.3 Package IHS Flatness
The package IHS flatness for the product is specified in t he pr ocesso r datasheet and can be us ed as
a baseline to predict heatsink performance during the design phase.
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Processor Thermal/Mechanical Information
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.
2.3.4 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 th erm a l
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-toprocessor attach positional alignment when selecting the proper thermal interface material size.
When pre-applied material is used, it is recommended to have a protective cover over it. This cover
must be removed prior to heatsink installation.
2.3.5 Summary
In summary, considerations in heatsink design include:
• The local ambient temperature T
and the corresponding maximum T
performance parameter, Ψ
information on the definition and the use of Ψ
at the heatsink, the power being dissipated by the processor,
A
. These parameters are usually combined in a cooling
C
(case to air thermal characterization parameter). More
CA
is given in Section 2.4 below.
CA
• Heatsink interface (to IHS) surface characteristics, including flatness and roughness.
• The performance of the thermal interface material used between the heatsink and the IHS.
• The required heatsink clip static load, between 18 lbf to 70 lbf throughout the life of the
product (Refer to Section 2.1.2.2, “Heatsink Clip Load Requirement” on page 11 for further
information).
• Surface area of the heatsink.
• Heatsink material and technology.
• Volumetric airflow rate over the heatsink surface area.
• Development of airflow entering and within the heatsink area.
• Physical volumetric constraints placed by the system.
2.4 System Thermal Solution Considerations
2.4.1 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 compo nents. 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
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Processor Thermal/Mechanical Information
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 Performance ATX Desktop System Thermal Design Suggestions or
Performance microATX Desktop System Thermal Design Suggestions documents available on the
http://www.formfactors.org/ web site. For more information on 1U and 2U server refer to the Thin
Electronics Bay Specifications at http://www.ssiforum.org.
In addition to passive heatsinks, fan heatsinks and system fans, other solutions exist for cooling
integrated circuit devices. For example, ducted blowers, heat 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 Celeron D Processor in the 775-land LGA package. 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 in rare excursions of workload above TDP. Implementat ion op tions and
recommendations are described in Section 4.0, “Thermal Management Logic and Thermal
Monitor” on page 23 and Section 4.2.2, “Thermal Control Circuit” on page 24.
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Thermal Metrology
3.0 Thermal Metrology
This chapter 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 (psi), will be used.
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
situations (heat source, local ambient conditions). The thermal characterization parameter is
calculated using total package power. Note that 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 (
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:
Equation 1.
Where:
Ψ
T
T
P
The case-to-local ambient thermal characterization parameter of the processor,
of
sink-to-local ambient thermal characterization parameter:
Equation 2.
Where:
Ψ
) is used as a measure of
CA
Ψ
= (TC - TA) / P
CA
= Case-to-local ambient thermal characterization parameter (°C/W)
CA
= Processor case temperature (°C)
C
= Local ambient temperature in chassis at processor (°C)
A
= Processor total power dissi pation (W) (assumes all power dissipates through the IHS)
D
Ψ
, the thermal interface material thermal characterization parameter, and of ΨSA, the
CS
Ψ
= ΨCS + Ψ
CA
SA
D
Ψ
, is composed
CA
Ψ
= Thermal characterization parameter of the thermal interface material (°C/W)
CS
Ψ
= Thermal characterization parameter from heatsink-to-local ambient (°C/W)
SA
Ψ
is strongly dependent on the thermal conductivity and thickness of the TIM between the
CS
heatsink and IHS.
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Ψ
is a measure of the thermal characterization parameter from the bottom of the heatsink to the
SA
local ambient air.
Ψ
is dependent on the heatsink material, thermal conductivity, and geometry. It
SA
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
T
T
A
A
Heatsink
Heatsink
T
T
S
TIM
TIM
Processor
Processor
IHS
IHS
S
T
T
C
C
Thermal Metrology
Ψ
Ψ
CA
CA
LGA775 Socket
LGA775 Socket
3.1.1 Example
The cooling performance, Ψ
in the previous section:
• The case temperature T
datasheet.
• Define a target local ambient temperature at the processor, T
Since the processor thermal profile applies to all processor frequencies, it is important to identify
the worst case (lowest Ψ
strategy such that a given heatsink can cover a given range of processor frequencie s.
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 Intel
processor thermal specifications, and are for illustrative purposes only.
Assume the datasheet TDP is 100 W 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:
T o determine the required heatsink performance, a heatsink solution provider would need to
determine Ψ
heatsink solution were designed to work with a TIM material performing at Ψ
solving for Equation 2 from above, the performance of the heatsink would be:
System Board
System Board
is defined using the thermal characterization parameter described
CA,
and thermal design power TDP given in the processor
C-MAX
.
A
) for a targeted chassis (characterized by TA) to establish a design
CA
Ψ
= (TC – TA) / TDP = (67 – 38) / 100 = 0.29 °C/W
CA
performance for the selected TIM and mechanical load configuration. If the
CS
0.10 °C/W,
CS
Ψ
= ΨCA – ΨCS = 0.29 – 0.10 = 0.19 °C/W
SA
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Thermal Metrology
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 well-characterized thermal tool, whereas real 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.
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.Contact your Intel field sales representative for further information on TTV or regarding
accurate measurement of the power dissipated by an actual processor.
3.3 Local Ambient Temperature Measurement Guidelines
The local ambient temperature TA (or TLA) is the temperature of the ambient air surrounding the
processor. For a pas sive heatsink, T
actively cooled heatsink, it is the temperature of inlet air to the active cooling fan.
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.
T
is best measured by averaging temperature measurements at multiple locations in the heatsink
A
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.
is defined as the heatsink approach air temperature; for an
A
3.3.1 Measuring Active Heatsinks
• 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 3mm 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 5 (avoiding the hub
spokes).
• Using an open bench to characterize an 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 in] 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 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.
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