AMD Thermal Mechanical Chassis Cooling Design Guide

Publication # 23794 Rev: AIssue Date: May 2000

AMDThermal, Mechanical,and Chassis Cooling

Design Guide

Trademarks

AMD, the AMD logo, AMD Athlon, and combinations thereof are trademarks of Advanced Micro Devices, Inc.

Other product names used in this publication are for identification purposes only and may be trademarks of their respective companies.

© 2000 Advanced Micro Devices, Inc. All rights reserved.

The contents of this document are provided in connection with AdvancedMicro Devices, Inc. (“AMD”) products. AMD makes no representations orwarranties with respect to the accuracy or completeness of the contents ofthis publication and reserves the right to make changes to specifications andproduct descriptions at any time without notice. No license, whether express,implied, arising by estoppel or otherwise, to any intellectual property rightsis granted by this publication. Except as set forth in AMD’s Standard Termsand Conditions of Sale, AMD assumes no liability whatsoever, and disclaimsany express or implied warranty, relating to its products including, but notlimited to, the implied warranty of merchantability, fitness for a particularpurpose, or infringement of any intellectual property right.

AMD’s products are not designed, intended, authorized or warranted for useas components in systems intended for surgical implant into the body, or inother applications intended to support or sustain life, or in any other applica-tion in which the failure of AMD’s product could create a situation where per-sonal injury, death, or severe property or environmental damage may occur.AMD reserves the right to discontinue or make changes to its products at anytime without notice.

23794A—May 2000 AMD Thermal , Mechanical, and Chassis Cooling Design Guide

Contents

Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .iii

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Summary of Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

PGA Socket A-Based Processor Thermal Requirements . . . . . . . . . . 2

Socket Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Socket A-Based Processor Specifications . . . . . . . . . . . . . . . . . 4

General Socketed Design Targets . . . . . . . . . . . . . . . . . . . . . . . 5

Suggested Interface Materials . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Sample Socket A Heatsink Drawings. . . . . . . . . . . . . . . . . . . . . 7

Socket A Heatsink Design Considerations . . . . . . . . . . . . . . . . 7

Socketed Motherboard Restrictions. . . . . . . . . . . . . . . . . . . . . 10

Slot A-Based Processor Thermal Requirements . . . . . . . . . . . . . . . . 11

Slot A-Based Processor Specifications . . . . . . . . . . . . . . . . . . . 11

General Slot A Design Targets . . . . . . . . . . . . . . . . . . . . . . . . . 11

Sample Slot A Heatsink Drawings . . . . . . . . . . . . . . . . . . . . . . 12

Heatsink Performance Measurements for Slot A-Based Solu-tions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Chassis Cooling Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Chassis Airflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Power Supply as Part of the Cooling Solution . . . . . . . . . . . . 19

Rules for Proper Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Contents iii

AMD Thermal , Mechanical, and Chassis Cooling Design Guide 23794A—May 2000

iv Contents

23794A—May 2000 AMD Thermal, Mechanical, and Chassis Cooling Design Guide

List of Figures

Figure 1. Socket A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Figure 2. Dimensions of Socket A. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Figure 3. Socket A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Figure 4. Dimensions of Socket A. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Figure 5. Sample Drawing of Socket A Heatsink . . . . . . . . . . . . . . . 7Figure 6. Heatsink and Load Pads . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Figure 7. Motherboard Keepout Area for Socketed Heatsinks . . . 10Figure 8. AMD Athlon™ Processor Module Package . . . . . . . . . . . 13Figure 9 Impact Extrusion for Clip Attachment . . . . . . . . . . . . . . 14Figure 10. Module Heat Plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Figure 11 Drill Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Figure 12. Drilled Hole Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Figure 13. Closeup of Drilled Hole Location . . . . . . . . . . . . . . . . . . . 18Figure 14. Airflow through the Chassis . . . . . . . . . . . . . . . . . . . . . . . 19Figure 15. Power Supply Venting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

List of Tables

Table 1. Socketed Processor Specifications . . . . . . . . . . . . . . . . . . . 4

Table 2. General Socketed Thermal Solution Design Targets . . . . 5

Table 3. Suggested Thermal Interface Materials. . . . . . . . . . . . . . . 6

Table 4. Slot A Processor Specifications . . . . . . . . . . . . . . . . . . . . 11

Table 5. General Slot A Thermal Solution Design Targets . . . . . . 12

List of Figures and Tables v

AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794A—May 2000

vi List of Figures and Tables


Revision History

Date Rev Description

May 2000 A Initial release based on AMD Athlon™ Processor Family Thermal Cooling Requirements Version 2.1.

Revision History vii


viii Revision History


AMD Thermal, Mechanical, and Chassis Cooling Design Guide

This document specifies performance requirements for thedesign of thermal, mechanical, and chassis cooling solutions forthe AMD Athlon™ processor. In addition to providing designtargets, drawings are provided from an AMD-designed solutionmeeting the requirements of the AMD Athlon processor.

Summary of Requirements

To ensure optimal reliability for AMD Athlon processor-basedsystems, the thermal design solution should dissipate heat froma theoretical processor running at a given maximum thermalpower. The following sections specify recommended values forthese optimal thermal parameters. By setting a high-powertarget, the engineer avoids redesigning a point solutionheatsink/fansink, thus increasing the life of the particularthermal solution.

Summary of Requirements 1


PGA Socket A-Based Processor Thermal Requirements

Socket Description

Socket A is a new PGA socket designed for socketedAMD Athlon processors. Figure 1 shows the new socket.

Note: The figure socket is labeled SOCKET 462, which issynonymous with the Socket A.

Figure 1. Socket A

Socket A is very similar in form factor to previous sockets, suchas Socket 7. Socket A incorporates additional pins in the innerportion of the socket. Thus, a thermal solution for Socket A canleverage preexisting design efforts.

2 PGA Socket A-Based Processor Thermal Requirements


Figure 2 details the physical dimensions of Socket A.

Figure 2. Dimensions of Socket A

PGA Socket A-Based Processor Thermal Requirements 3


Socket A-Based Processor Specifications

Table 1 lists the thermal specifications of the socketedprocessor.

Table 1. Socketed Processor Specifications

Symbol Description Max Value Notes

TdieMaximum die temperature 90ºC

Total die size Die size 117mm2 Includes L2 cache

Acore Core area 100mm2 Die size not including L2 cache

Form factor Heatsink form factor PGA PGA Socket A form factor

PthermalMax processor thermal power

48W Required minimum supported power55W Recommended minimum supported power

70W Targeted theoretical maximum supported power



General Socketed Design Targets

To maintain the die temperature of the processor below themaximum Tdie value, certain heatsink design points must beconsidered. Table 2 details additional specifications that mustbe met to ensure reliable operation of the AMD Athlonprocessor system.

Table 2. General Socketed Thermal Solution Design Targets

Symbol Description Min Max NotesL Length of heatsink 60mm Measurements are for the entire

assembly, including attached fan.W Width of heatsink 60mm 80mmH Height of heatsink 60mm

θSA Sink-to-ambient thermal resistance:For 48W processor 0.55º C/WFor 55W processor 0.41º C/WFor 70W processor 0.32º C/W

θJS Interface material thermal resistance:

Based on core area

For 48W processor 0.39º C/WFor 55W processor 0.41º C/WFor 70W processor 0.32º C/W

CFM Fan airflow 16 cfm Minimum 16-cfm airflowmHS Mass of heatsink 300 g

Fclip Clip force 12 lbs 24 lbs Typical F: 14 lbs≤ F ≤18 lbs

Nominal F = 16 lbs.TA Inside the box local

ambient temperature45º C



Suggested Interface Materials

AMD validates thermal interface materials for socketeddesigns. A list of suggested materials tested by AMD isprovided in Table 3 .

Table 3. Suggested Thermal Interface Materials

Vendor Interface Material Material Type

ChomericsT725 Phase changeT443 Phase change

Bergquist200U Phase change300U Phase change

Shin-EtsuG749 Thermal greaseG750 Thermal grease

FerroTG5125 Thermal grease

TG051-17 Thermal grease

Furon1055 Phase change1060 Phase change



Sample Socket A Heatsink Drawings

Figure 3 provides a reference drawing of a heatsink AMD hasdesigned to work with Socket A processors.

Figure 3. Sample Drawing of Socket A Heatsink

Socket A Heatsink Design Considerations

Heatsink Considerations

Flat Base to Contact Support Pads. The PGA processor is housed in a50 x 50mm ceramic package. The heatsink makes direct contactwith the f l ip -chip die. While the die dimensions areconsiderably less than the 50 x 50mm package footprint, theheatsink base must maintain a minimum flat surface of 46 x46mm centered on the package and 48 x 48mm at a maximum.This positioning is required for the heatsink to make contactwith compliant load support pads. The pads protect the diefrom mechanical damage during heatsink installation, as wellfrom shock and vibration. Figure 4 on page 8 details theceramic package and compliant load support pads.

Measurements are in millimeters



Figure 4. Heatsink and Load Pads



Maximum Base Footprint of 60 X 80mm. The maximum base footprintfor socket heatsinks is 60 x 80mm (as detailed in Figure 2 onpage 5). Not all processor speeds require the full 60 x 80mmfootprint. Heatsinks with approximately 60 x 60mm footprintshave proven to be adequate for low to moderate clockfrequencies.

Clearance in Heatsink Base for Socket Cam Box. The heats ink basemust have enough clearance so that it does not contact the cambox on the socket. The clearance zone is defined in the exampleshown in the Figure 3 on page 7 and Figure 4 on page 8.

Clip Considerations

Load Target Of 16 lb with Range of 12–24 lbs. The clip load is greaterthan that allowed for previous processors with similarmechanical form factors. Table 2 on page 5 details the clip forcerequirements.

Load Applied Directly over Center of Die (Asymmetric Design). To ensureadequate thermal interface performance between the flip-chipdie and the heatsink, the clip must apply its load to the heatsinkalong a single contact axis. The load should be applied 26.8 mmfrom the front (non-cam side) socket tab load point (seeFigure 4 on page 8). The acceptable tolerance for off-center clipload is +/– 1.5 mm.

Feature to Lock Relative Position of Heatsink, Clip, and Socket. A lockingfeature is needed to avoid incorrect placement of the heatsinkon the package. Such a lock can be constructed with small tabsthat project from the sides of the clip and fit into a heatsinkchannel.

Installation Features Designed to Minimize Operator Fatigue. With theincreased clip load requirements of the socketed processor,emphasis should be focused on providing a clip design that iseasily installed. While clips that do not require tools forinstallation offer some advantages, designs that accept aflat-head screwdriver (or nutdriver) near the clip hook havecertain advantages. Such advantages include the ability to prythe clip hook over the socket tab during installation and theability to install the clips onto the tabs in areas that are tightlyconfined by motherboard components surrounding the socket.



Interface Considerations

Pre-applied Pad Size and Location. Many customers have indicated apreference for pre-applied thermal interface materials. Aheatsink vendor that chooses to offer pre-applied interfacematerials should apply a 25 x 25 mm pad centered 25 mm fromthe front edge of the heatsink.

Socketed Motherboard Restrictions

The motherboard design and layout must meet certainrestrictions to ensure that the socketed thermal solution doesnot impede the performance of components on themotherboard. To maintain adequate airflow around themicroprocessor, certain areas on the motherboard must be freeof projecting components. Figure 5 shows these ‘keepout’ areason the motherboard.

Figure 5. Motherboard Keepout Area for Socketed Heatsinks



Slot A-Based Processor Thermal Requirements

Slot A-Based Processor Specifications

Table 4 contains a list of the thermal specifications of theslotted processor. These values and additional information canbe found in the AMD Athlon™ Processor Module Data Sheet,order# 21016.

Table 4. Slot A Processor Specifications

General Slot A Design Targets

To maintain the processor plate temperature below themaximum Tplate value, a heatsink must dissipate the heatproduced by the processor. Table 5 on page 12 detailsadditional information that should be met in order to ensurereliable operation of the system.

Symbol Description Max Value NotesTplate Maximum plate temperature 70ºC

Form Factor Heatsink form factor SECC1 SECC1 form factor

Pthermal Max processor thermal power50W Required minimum supported power

65W Targeted theoretical maximum supported power

Slot A-Based Processor Thermal Requirements 11


Table 5. General Slot A Thermal Solution Design Targets

Sample Slot A Heatsink Drawings

Figure 7 on page 14 shows a heatsink that AMD designed andtested to work with the AMD Athlon processor. This designprovides the heat dissipation necessary for optimal processorperformance. Figure 6 on page 13 is a drawing of themechanical module of the AMD Athlon processor.

Symbol Description Min Max Notes

θSASink-to-ambient thermal resistance 0.35ºC/W

θPSInterface material thermal resistance 0.15ºC/W

CFM Fan airflow 16cfm Minimum 16-cfm airflowPfan Fan pressure 0.25in H2O Inches of water

PmaxMaximum theoretical thermal power 64W Power target for future

processorsmHS Mass of heatsink 250g

TAInside the box local ambient temperature 45ºC

12 Slot A-Based Processor Thermal Requirements


Figure 6. AMD Athlon™ Processor Module Package



Figure 7. Impact Extrusion for Clip Attachment

Heatsink Performance Measurements for Slot A-Based Solutions

AMD gauges the performance of thermal design solutions byperforming thermal measurements on heatsinks. Temperaturemeasurements are taken at the module heat plate, at theheatsink base, and in the open air near the fan inlet. Tofacilitate quicker turnaround on thermal measurements, AMDrequires that a 0.0595 inch diameter hole be drilled into thebase of heatsinks that are submitted for thermal testing. Thehole depth is determined by the size of the heatsink and itsposition relative to the AMD Athlon processor module. Testedhole depths have ranged from 25mm to 35mm. The typicaldepth has been around 30mm. A long #53 drill bit should beused to drill the hole.

Figure 8 on page 15 shows an AMD Athlon processor modulefrom the heat plate side. The holes and slots for the heatsinkalignment pins are indicated in the figure. Whether the



heatsink base thermocouple hole is drilled from the top orbottom of the heatsink, the hole depth must be to the edge ofthe alignment hole.

Figure 8. Module Heat Plate



Figure 9 displays a heatsink with the lower alignment pin usedas the reference for the thermocouple hole depth.

Figure 9. Drill Location

Figure 10 on page 17 and Figure 11 on page 18 show the holefrom the top edge of the heatsink. The hole is centered alongthe length of the heatsink. The center of the hole isapproximately 2mm from the edge of the heatsink that is incontact with the module.



Figure 10. Drilled Hole Location



Figure 11. Closeup of Drilled Hole Location

Chassis Cooling Guidelines

As high-performing systems continue to evolve, the powerconsumption of system components such as the processor, harddisks, and video cards continues to increase. The associated risein power consumption can cause the system operatingtemperature specifications to be exceeded. The correctoperating temperature of each system device can be controlledby providing proper airflow through the overall system.

Chassis Airflow

System cooling is dependent on several essential and relatedfactors. Figure 12 shows a typical mid-tower chassis with theinternal physical characteristics and recommended airflow.

18 Chassis Cooling Guidelines


Figure 12. Airflow through the Chassis

Using thermal couples (type K or T, 36 gauge) in the locationsshown in Figure 12, temperatures T1 and T2 can be measured.T1 represents the external ambient air temperature. T2, whichis located approximately 0.5 inch to 1.0 inch away from theprocessor fan (centered on the hub), represents the internallocal ambient air temperature. It is highly recommended thatT2 not exceed 40°C. The following equation shows how to derivethe proper overall system operating temperature:

∆T = T2 – T1∆T ≤ 7°C to ensure proper cooling

Power Supply as Part of the Cooling Solution

For full-tower or mid-tower cases, it is important for systemdesigners to be aware of the characteristics of the power supplyused. Designers should only use a power supply that is on theAMD Athlon™ Processor Recommended Power Supply list (seewww.amd.com). For best results, use a power supply withventing in the processor region, which means that the primaryair intake is on the bottom of the power supply, not the front ofthe power supply. For the purposes of this chapter, such a power

Power supply with bottom intake

Rear cooling fan, 80mm

Chassis Cooling Guidelines 19


supply is referred to as ‘ATX-style’. Some power supplies have‘NLX-style’ venting (the primary air intake is at the front of thepower supply) and does not pull air from the processor area.Figure 13 on page 21 compares desirable power supply ventingdesigns with designs that are less desirable. The front and reardesigns for the desirable and less desirable versions are verysimilar (the differences depend on the brand). However, thebottoms of the most effective power supply designs incorporatean an air intake. Power supply having bottom air intakes coolthe processor more effectively. Bottom air intakes with fansprovide even more effective cooling.



Figure 13. Power Supply Venting

Less Desirable Version

Front—

Bottom—

Rear—

Desirable Version

For the front air intake, the desirable and less desirable versions are very similar. The differences depend on the brand.

For the rear air intake, the desirable and less desirable versions are very similar.The differences depend on the brand.

On the bottom, the desirable version has an air intake. A bottom air intake cools the processor more effectively. If the bottom air intake has a fan, cooling is enhanced.

Chassis Cooling Guidelines 21


Rules for Proper Cooling

The following basic rules for chassis cooling can provideadequate airflow and system temperatures:

■ Use the proper heatsink size for the processor speed used in the system. Make sure that the heatsink has appropriate sized fan(s). See the AMD Athlon™ Processor Recommended Heatsink page at www.amd.com for more information.

■ Use AMD recommended thermal compound (grease, phase-change or pads). Typically, recommended heatsinks include the thermal compound. See the AMD Athlon™ Pro-cessor Thermal Compound page at www.amd.com for more information.

■ Use an auxiliary exhaust rear chassis fan. The suggested size is 80 millimeters or larger. The fan intake should be near the location of the processor.

■ For best results, use an ATX power supply with air intake venting in the processor region, which means that the pri-mary air intake is on the bottom of the power supply, not at the front of the power supply. Supplies with NLX-style vent-ing (the primary air intake is at the front of the power sup-ply) do not pull air from the processor area.

■ Make sure all the internal wires and cables are routed care-fully so airflow through the case is not blocked or hindered. Tie-wraps can help.

■ Many cards, such as AGP cards, generate a lot of heat. Either leave the slot next to these cards open, or use a shorter card in these slots to allow airflow around heat pro-ducing cards (typically those cards with many electrical components).

■ High-speed hard drives, especially 10,000 RPM SCSI hard drives, produce a great deal of heat. Mount these drives in 5.25 inch frames and install them in the larger drive bays. This allows greater airflow around them for better cooling.

■ A front cooling fan is not essential. In some extreme situa-tions, testing showed that these fans recirculate hot air rather than introducing cool air.

■ Maintain a ∆T ≤ 7ºC.



Conclusion

Thermal, mechanical, and chassis cooling solutions that meetthe criteria described in the previous pages have provensuccessful for applications incorporating AMD processors.AMD encourages vendors to innovate and propose otherdesigns. If different heatsink production technologies, whetherextrusion, folded fin, bonded fin, or cold forged, producesimilar or better results than the solutions suggested in thisguide, then designers are encouraged to incorporate them intonew thermal solution designs. Any design, however, must meetthe overall goal of dissipating the heat produced by theprocessor at a given ambient temperature.

Conclusion 23

Documents

AMD Thermal Mechanical Chassis Cooling Design Guide