Intel FCPGA2 - Processor - 1 x Pentium 4 2.66 GHz Instruction Manual

Intel®Pentium®III Processor in the
FC-PGA2 Package
Thermal Design Guidelines
June 2001
Order Number: 249660-001
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* Other names and brands may be claimed as the property of others.
Copyright © 2001, Intel Corporation

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Contents
1. Introduction .................................................................................................................................. 7
1.1. Document Scope............................................................................................................. 7
1.2. References......................................................................................................................7
1.3. Definition of Terms.......................................................................................................... 8
2. Importance of Thermal Management........................................................................................... 9
3. FC-PGA2 Processor Packaging Technology............................................................................. 11
4. Thermal Specifications............................................................................................................... 13
4.1. Processor Case Temperature....................................................................................... 13
5. Designing for Thermal Performance.......................................................................................... 15
5.1. Airflow Management...................................................................................................... 15
5.2. Recommended Fan Performance and Limitations........................................................ 16
5.3. Bypass........................................................................................................................... 16
5.4. Heatsink Solutions and Keep-in Areas.......................................................................... 16
5.5. Thermal Interface Management.................................................................................... 16
5.5.1. Bond Line Thickness................................................................................... 17
5.5.2. Interface Material Area................................................................................ 17
5.5.3. Interface Material Performance................................................................... 17
5.6. Fans............................................................................................................................... 17
5.6.1. Placement ................................................................................................... 18
5.6.2. Fan Direction............................................................................................... 18
5.6.3. Size and Quantity........................................................................................ 18
5.6.4. Venting ........................................................................................................ 18
5.6.4.1. Placement....................................................................................... 18
5.6.4.2. Area and Size................................................................................. 18
5.6.4.3. Vent Shape..................................................................................... 19
6. Alternative Cooling Solutions ..................................................................................................... 21
6.1. Ducting .......................................................................................................................... 21
6.1.1. Ducting Placement...................................................................................... 21
6.2. System Components..................................................................................................... 21
6.2.1. Placement ................................................................................................... 21
6.2.2. Power ........................................................................................................ 21
7. Thermal Metrology for FC-PGA2 Packaged Processors........................................................... 23
7.1. Thermal Resistance ...................................................................................................... 23
7.2. Thermal Solution Performance ..................................................................................... 24
7.3. Local-ambient Temperature Measurement Guidelines................................................. 25
7.3.1. Local-ambient Temperature Measurement for a Passive Heatsink............ 25
7.3.2. Local-ambient Temperature Measurement for an Active Heatsink............. 26
7.4. Processor Measurements for Thermal Specifications ..................................................26
7.4.1. Processor Case Temperature Measurements............................................ 27
7.4.1.1. Heatsink Preparation...................................................................... 30
7.4.2. About the High Power Application............................................................... 31
7.4.3. Executing the High Power Application Software ......................................... 31

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8. Conclusion..................................................................................................................................33
Figures
Figure 3-1. FC-PGA2 Mechanical Specifications.....................................................................11
Figure 5-1. Example of Air Exchange Through a µATX PC Chassis.......................................15
Figure 7-1. Processor-Heatsink Thermal Resistance Relationships........................................23
Figure 7-2. Local-ambient Thermocouple Measurement Locations (Passive Heatsink)..........25
Figure 7-3. Local-ambient Thermocouple Measurement Locations (Active Heatsink).............26
Figure 7-4. Locating Geometric Center of Processor...............................................................28
Figure 7-5. Thermocouple Preparation.....................................................................................28
Figure 7-6. Thermocouple Adhesive Placement......................................................................29
Figure 7-7. Example of Machined Heatsink with Thermocouple Groove.................................30
Figure 7-8. Example of Dimensioning for Thermocouple Groove............................................31
Tables
Table 3-1. FC-PGA2 Processor Package Dimensions.............................................................12
Table 7-1. List of Items for Thermocouple Attach....................................................................27
Equations
Equation 1. Case to Ambient Thermal Resistance...................................................................23
Equation 2. Case to Ambient Thermal Resistance...................................................................24

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Revision History
Rev. Description Date
-001 • Initial Release June 2001

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1. Introduction
In a system environment, the processor's temperature is a function of both the system and component
thermal characteristics. The system level thermal constraints consist of the local-ambient temperature at
the processor and the airflow over the processor, as well as the physical constraints at and above the
processor. The processor’s temperature depends on the component power dissipation, size and material
(effective thermal conductivity) of the integrated heat spreader, and the presence of a thermal cooling
solution.
All of these parameters are aggravated by the continued push of technology to increase performance
levels (higher operating speeds, GHz) and packaging size and density (more transistors). As operating
frequencies increase and packaging size decreases, the power density increases and the thermal cooling
solution space and airflow become more constrained. The result is an increased importance on system
design to ensure that thermal design requirements are met for each component in the system.
1.1. Document Scope
This document discusses thermal management techniques for Intel®Pentium®III processors in the FC-
PGA2 package with an integrated heat spreader, which is primarily intended for the desktop and server
segments. The physical dimensions and power numbers used in this document are for reference only.
Please refer to the respective datasheets for the product dimensions, thermal power dissipation, and
maximum case temperature. In case of conflict, the specifications in the processor datasheets supercede
any data in this document.
1.2. References
Document Title Order Number
Pentium®III Processor for the PGA370 Socket Datasheet 245264
Intel®Pentium®III Processor with 512Kb L2 Cache Datasheet 249657
370-Pin Socket (PGA370) Design Guidelines 244410
AP-905 Pentium®III Processor Thermal Design Guidelines 245087
FC-PGA2 Package Thermal / Mechanical Solution Functional Specifications Contact your Intel Field
Sales Representative
Performance ATX Desktop System Thermal Design Suggestions v1.0 http://www.formfactors.org
ATX Thermal Design Suggestions v1.0 http://www.formfactors.org
Performance MicroATX Desktop System Thermal Design Suggestions v1.0 http://www.formfactors.org
MicroATX Thermal Design Suggestions v1.0 http://www.formfactors.org
FlexATX Thermal Design Suggestions v1.0 http://www.formfactors.org
Evaluation Board for Microprocessor System Temperature Monitor or EVAL-
ADM1021 http://www.analog.com
Analog Devices EVAL-ADM1021 kit datasheet http://www.analog.com
Maxim Integrated Products MAX1617EV Kit datasheet http://www.maxim-ic.com

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1.3. Definition of Terms
• TLA - 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. (See Section 7.3: Local-ambient Temperature Measurement Guidelines)
• TAMBIENT-OEM - the target worst-case ambient temperature at a given external system location as
defined by the system designer (OEM).
• TAMBIENT-EXTERNAL - the measured ambient temperature at the OEM defined external system location.
• TAMBIENT-MAX - the target worst-case local-ambient temperature. It is determined by placing the
system in maximum external temperature conditions and measuring the ambient temperature locally
surrounding the processor. Under these conditions, TLA = TAMBIENT-MAX.
• TCASE-MAX - the maximum allowed case temperature of the processor, as specified in the processor
datasheet.
• TCASE - the measured case temperature of the processor.
• TIM - 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 spreading of the heat
from the case to the heatsink.
• θTIM - the thermal resistance of the thermal interface material. Also referred to as θCS (case to sink
thermal resistance).
• θCA - the thermal resistance between the processor’s case and the ambient air. This is defined and
controlled by the system thermal solution.
• PMAX - the maximum processor power, as specified in the processor’s datasheet.
• PGA370 Socket - a through-hole mount Zero Insertion Force (ZIF) socket designed to accept the
Intel®Pentium®III processor in the FC-PGA2 package.
• FC-PGA2 package - the Flip Chip Pin Grid Array processor package with an integrated heat
spreader (IHS).
• ACPI - Advanced Configuration and Power Interface (See http://www.teleport.com/~acpi/ )
• Bypass - the area between a passive heatsink or air pass-through 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.
• TDP - Thermal Design Power. The processor thermal power specification in the processor
datasheet. OEMs must design their processor thermal solutions to meet the TDP as listed in the
respective datasheets. (Also known as Thermal Design Point.)
• Intel®Pentium®III processor in the FC-PGA2 package - any Pentium®III processor with CPUID
06Bxh, as well as the higher frequencies of Intel®Pentium®III processors with CPUID 068xh (see
the Pentium®III Processor for the PGA370 Socket Datasheet for further details).

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2. Importance of Thermal Management
The objective of thermal management is to ensure that the temperature of all components in a system is
maintained within functional limits. The functional temperature limit is the range within which the
electrical circuits can be expected to meet their specified performance requirements. Operation outside
the functional limit can degrade system performance, cause logic errors or cause component and/or
system damage. Temperatures exceeding the maximum operating limits may result in irreversible
changes in the operating characteristics of the component.

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3. FC-PGA2 Processor Packaging
Technology
The Intel®Pentium®III processor is available in Flip Chip Pin Grid Array 2 (FC-PGA2) packaging. The
FC-PGA2 package consists of the microprocessor silicon core with integrated L2 cache mounted on a
pinned substrate. The silicon core is encased by a heat spreader, which is integrally mounted to the FC-
PGA2 substrate. The Integrated Heat Spreader (IHS) is designed to improve thermal performance and is
the interface for attaching a heatsink. The processor core is mounted with the back of the die facing up,
hence the term “flip chip.” The pin grid array on the backside of the interposer is not fully populated and
there may be small, low power, surface mounted components in the center of the pin field. The processor
package connects to the motherboard by plugging into a 370-pin ZIF socket (PGA370). See Figure
3-1and Table 3-1 (below) for a complete mechanical dimensioning. A description of the socket can be
found in the 370-Pin Socket (PGA370) Design Guidelines. Refer to the processor datasheets for package
mechanical loading specifications.
Figure 3-1. FC-PGA2 Mechanical Specifications

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Table 3-1. FC-PGA2 Processor Package Dimensions
Symbol Millimeters Inches
Minimum Maximum Notes Minimum Maximum Notes
A1 2.266 2.690 0.089 0.106
A2 0.980 1.180 0.038 0.047
B1 30.800 31.200 1.212 1.229
B2 30.800 31.200 1.212 1.229
C1 33.000 max 1.299 max
C2 33.000 max 1.299 max
D 49.428 49.632 1.946 1.954
D1 45.466 45.974 1.790 1.810
G1 0.000 17.780 0.000 0.700
G2 0.000 17.780 0.000 0.700
G3 0.000 0.889 0.000 0.035
H 2.540 Nominal 0.100 Nominal
L 3.048 3.302 0.120 0.130
ΦP 0.431 0.483 0.017 0.019
Pin TP 0.508 Diametric True Position (Pin-to-Pin) 0.020 Diametric True Position (Pin-to-Pin)
NOTES:
1. Capacitors will be placed on the pin-side of the FC-PGA2 package in the area defined by G1, G2, and G3. This
area is a keep-out zone for motherboard designers.
2. In case of conflict, the processor datasheets supercede this document.

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4. Thermal Specifications
For the purposes of this design guideline, the following assumptions have been made about the
requirements for proper operation and reliability of the processor:
• Considering the power dissipation levels and typical system ambient environments (TLA), the
processor's temperature cannot be maintained at or below the specified guidelines without additional
thermal enhancement to dissipate the heat generated by the processor.
• The thermal characterization data described in later sections illustrates that both a thermal-cooling
device and reasonable system airflow are needed. The size and type (passive or active) of thermal
cooling device and the amount of system airflow are related and can be traded against each other to
meet specific system design constraints. In typical systems, board layout, spacing, and component
placement limit the thermal solution size. Airflow is determined by the size and number of fans,
along with their placement in relation to the components and the airflow channels within the system.
In addition, acoustic noise constraints may limit the size, number, and types of fans that can be used
in a particular design.
To develop a reliable, cost-effective thermal solution, all of the above variables must be considered.
Thermal characterization and simulation should be carried out at the entire system level accounting for
the thermal requirements of each component.
4.1. Processor Case Temperature
The Integrated Heat Spreader (IHS) is intended to provide the common interface and attach location for
all thermal solutions for FC-PGA2 packaged processors. The IHS acts to spread the heat from the small
area of the processor die to the larger surface area of the IHS, allowing more efficient heat transfer using
heatsink thermal solutions. These solutions can be active or passive. Active solutions are those where a
fan is directly attached to the heatsink. A passive heatsink uses system airflow forced in some manner to
pass-through the heatsink fins. Considerations in heatsink design include:
• Local-ambient temperature at the heatsink (TLA)
• Surface area of the heatsink
• Property of materials (including thermal resistance or conductivity)
• Volume and velocity of airflow over the heatsink surface area
• Power being dissipated by the processor and its associated power density
• Physical volumetric constraints placed by the system
Techniques for measuring case temperatures are provided in Section 7: Thermal Metrology.

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5. Designing for Thermal Performance
5.1. Airflow Management
It is important to manage the volume and velocity of air that flows within the system, as well as how it
flows, to maximize the amount of cool air that flows over the processor. Total system airflow can be
increased by adding one or more fans to the system, or by increasing the output (increasing the speed or
size) of an existing system fan(s). Managing the airflow direction using baffles or ducts can also increase
local airflow. An important consideration in airflow management is the temperature of the air flowing
over the processor. Heating effects from chipset, voltage regulators, add-in boards, memory, and disk
drives greatly reduce the cooling efficiency of this air, as does re-circulation of warm interior air through
the system fan. Care must be taken to minimize the heating effects of other system components, and to
eliminate warm air re-circulation.
If no air path exists across the processor heatsink, the warm air from the processor will not be removed
from the system, resulting in localized heating ("hot spots") around the processor(s). Passive heatsink fin
designs should be aligned with the direction of the airflow.
Figure 5-1 shows two examples of air exchange through a µATX style PC chassis. The system on the left
is an example of a center mounted power supply, and the one on the right is an example of a top mounted
power supply. Both are examples of good air exchange incorporating the power supply fan as well as an
additional system fan (additional system fan shown as the three large arrows entering the front bezel).
For further information, reference the system thermal design suggestions for the appropriate form factor
available at http://www.formfactors.org/.
Figure 5-1. Example of Air Exchange Through a µATX PC Chassis
System Fan Intake System Fan Intake

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5.2. Recommended Fan Performance and Limitations
For active thermal solutions, the fan must often demonstrate a functional lifetime of 40,000 hours or
greater. In addition, the fan should demonstrate performance to the reliability criteria outlined in the FC-
PGA2 Package Thermal/Mechanical Solution Functional Specifications.
5.3. Bypass
Bypass is the distance around a passive heatsink where air may travel without passing through the fins of
the heatsink. A heatsink will have infinite bypass if it is sitting in free space, while a heatsink that has a
duct, or other devices surrounding it which are 0.2 in (5.1mm) away from the outer edges of the heatsink,
has a bypass of 0.2 in (5.1mm). A smaller bypass forces more air to pass through the fins of the heatsink,
instead of around the heatsink. This is especially important as the heatsink fin density increases. The
higher the fin density, the more resistance the heatsink poses to the air and the more likely the air will
travel around the heatsink instead of through it unless the bypass is small. Air traveling around the
heatsink will have no affect on cooling the processor.
5.4. Heatsink Solutions and Keep-in Areas
One method used to improve thermal performance is to increase the surface area of the device by
attaching a metallic heatsink. To maximize the heat transfer, the thermal resistance from the heatsink to
the air can be reduced by maximizing the airflow through the heatsink fins as well as by maximizing the
surface area of the heatsink itself. Although there have been many advancements in fin density and
geometries that allow for a better performing heatsink, an active or more advanced thermal solution may
be needed. Intel is enabling reference active and passive heatsinks for FC-PGA2 packaged processors.
Please see the FC-PGA2 Package Thermal/Mechanical Solution Functional Specifications for further
details.
5.5. Thermal Interface Management
To optimize the heatsink design for FC-PGA2 packaged processors, it is important to understand the
impact of factors related to the interface between the processor and the heatsink base. Specifically, the
interface material bond line thickness, area, and bulk thermal conductivity should be managed to realize
the most effective thermal solution.
Thermal interface material must be applied between the processor IHS and the heatsink to improve
thermal conduction from the IHS to the heatsink. Thermal interface material also serves as a mechanical
load element during mechanical stress testing (i.e. mechanical shock). 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 must be sized and positioned on the heatsink base in a way that ensures
the entire processor IHS area is covered. It will be important to compensate for heatsink-to-processor
attach positional alignment when selecting the proper thermal interface material size.
If a pre-applied thermal interface material is specified, it may have a protective application tape. This
tape must be removed prior to heatsink attach.

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5.5.1. Bond Line Thickness
Any gap between the processor’s heat spreader and the heatsink base will impact thermal solution
performance. The larger the gap between the two surfaces, the greater the thermal resistance. The
thickness of the gap is determined by the flatness of both the heatsink base and the integrated heat
spreader, the thickness of the thermal interface material (i.e. thermal grease) used between these two
surfaces, and the clamping force applied by the heatsink retention clip(s). In comparison with FC-PGA
packaged processors, the addition of the IHS will distribute the vertical force created by the attach
clip(s). For the same applied force (e.g. the same heatsink attach clip configuration), this will result in
lower pressure applied to the thermal interface material. This will lead to an increase in thermal interface
bond line thickness and thermal resistance.
5.5.2. Interface Material Area
The size of the contact area between the integrated heat spreader and the heatsink base will impact the
thermal resistance; increasing contact area typically decreases thermal resistance. It is recommended that
the thermal interface material should cover the entire surface of the integrated heat spreader area (31mm
x 31mm) to optimize the thermal interface performance on FC-PGA2 packaged processors.
5.5.3. Interface Material Performance
Two factors impact the performance of the interface material between the processor and the heatsink
base:
1. Thermal resistance of the material
2. Wetting/filling characteristics of the material
Thermal resistance is a description of the ability of the thermal interface material to transfer heat from
one surface to another. The higher the thermal resistance, the less efficient the interface is at transferring
heat. The thermal resistance of the interface material has a significant impact on the thermal performance
of the overall thermal solution. The higher the thermal resistance, the larger the temperature drop is
across the interface and the more efficient the thermal solution must be to achieve the desired cooling.
The wetting or filling characteristic of the thermal interface material is its ability, under the load applied
by the heatsink retention mechanism, to spread and fill the gap between the processor and the heatsink.
Since air is an extremely poor thermal conductor, the more completely the interface material fills the
gaps, the lower the temperature drop across the interface. Thermal interface material area-size also
becomes significant, as the larger the desired area-size, the higher the force required to spread the
thermal interface material.
5.6. Fans
Fans are needed to move the air through the chassis and/or directly through the processor heatsink. The
airflow rate of a fan is usually directly related to the acoustic noise level of the fan and system.
Maximum acceptable noise levels may limit the fan output or the number of fans selected for a system.
The maximum noise levels may differ from country to country. Fan/heatsink assemblies are one type of
advanced solution that can be used to cool the processor. Intel has worked with fan/heatsink vendors and
computer manufacturers to make fan/heatsink cooling solutions available in the industry. Please consult
such a vendor to acquire the proper solution for your needs.

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5.6.1. Placement
Proper placement of the fans can ensure that the processor is being properly cooled. Because of the
difficulty in building, measuring, and modifying a mechanical assembly for thermal evaluation, models
are typically developed and used to simulate a proposed design for thermal effectiveness, and to
determine the optimum location for fans and vents within a chassis. Investments for prototype
assemblies can then be made to verify that the system components and processor thermal specifications
are met.
5.6.2. Fan Direction
If the fan(s) are not moving air across the processor heatsink, cooling will not occur. This may cause the
processor to operate well above the recommended specification values. Two possibilities exist for
blowing air across a passive heatsink. Air can be blown down vertically or horizontally across the
heatsink. This may depend on the layout of other components on the board and/or within the chassis.
The intake fan should blow through a passive heatsink parallel to the fins if possible. Both of these
factors are considerations when laying out components on the board and in the chassis.
The direction of the airflow can be modified with baffles or ducts to direct the airflow over the processor.
This will increase the local flow over the processor and may eliminate the need for a second fan, a larger
fan, or a higher speed fan. For an actively cooled heatsink, the system airflow direction may not be as
critical for proper thermal performance, but it will be important to manage warm air re-circulation.
5.6.3. Size and Quantity
It does not necessarily hold true that the larger the fan the more air it blows. A small blower using
ducting might direct more air over the heatsink than a large fan blowing non-directed air over the
heatsink.
5.6.4. Venting
Intake venting should be placed at the front (user side) of the system. They should be located to optimize
cooling of processor and peripherals (drives and add-in cards). A good starting point would be the lower
50% of the front panel (bezel). Intake vents directly in front of the intake fan, is the optimal location.
The ideal design will provide airflow directly over the processor heatsink.
5.6.4.1. Placement
In most cases, an exhaust fan and vent located at the power supply is sufficient. However, depending on
the number, location, and types of add-in cards, exhaust venting may be necessary near the cards. This
should be modeled or prototyped for the optimum thermal potential. A system should be modeled for the
worst case, i.e., all expansion slots should be occupied with typical add-in options.
5.6.4.2. Area and Size
The area and size of the intake vents should be designed with the size and shape of the fan(s) in mind.
Adequate air volume requires appropriately sized vents. Intake vents should be located in front of the
intake fan(s) and adjacent to the drive bays. Vents should be approximately 50% to 60% open in the

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EMI containment area due to EMI constraints. Outside the EMI containment area, the open percentage
can be greater if needed for aesthetic appeal (i.e., bezel/cosmetics).
5.6.4.3. Vent Shape
Round, staggered pattern openings are best for EMI containment, acoustics, and airflow balance.

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