Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Thermal Design Guidelines

Transcription

1 Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Thermal Design Guidelines Design Guide Supporting the Intel Pentium 4 Processor with Hyper-Threading Technology 1 November 2002 Document Number:

2 INFOMATION IN THIS DOCUMENT IS POVIDED IN CONNECTION WITH INTEL PODUCTS. NO LICENSE, EXPESS O IMPLIED, BY ESTOPPEL O OTHEWISE, TO ANY INTELLECTUAL POPETY IGHTS IS GANTED BY THIS DOCUMENT. EXCEPT AS POVIDED IN INTEL S TEMS AND CONDITIONS OF SALE FO SUCH PODUCTS, INTEL ASSUMES NO LIABILITY WHATSOEVE, AND INTEL DISCLAIMS ANY EXPESS O IMPLIED WAANTY, ELATING TO SALE AND/O USE OF INTEL PODUCTS INCLUDING LIABILITY O WAANTIES ELATING TO FITNESS FO A PATICULA PUPOSE, MECHANTABILITY, O INFINGEMENT OF ANY PATENT, COPYIGHT O OTHE INTELLECTUAL POPETY IGHT. Intel products are not intended for use in medical, life saving, or life sustaining applications. Intel may make changes to specifications and product descriptions at any time, without notice. Designers must not rely on the absence or characteristics of any features or instructions marked "reserved" or "undefined." Intel reserves these for future definition and shall have no responsibility whatsoever for conflicts or incompatibilities arising from future changes to them. The Intel Pentium 4 processor may contain design defects or errors known as errata which may cause the product to deviate from published specifications. Current characterized errata are available on request. Contact your local Intel sales office or your distributor to obtain the latest specifications and before placing your product order. 1 Hyper-Threading Technology requires a computer system with an Intel Pentium 4 processor at 3.06 GHz or higher, a chipset and BIOS that utilize this technology, and an operating system that includes optimizations for this technology. Look for systems with the Intel Pentium 4 Processor with HT Technology logo which your system vendor has verified utilize Hyper-Threading Technology. Performance will vary depending on the specific hardware and software you use. See the following UL for more information: Intel, Pentium and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries. *Other names and brands may be claimed as the property of others. Copyright 2002, Intel Corporation 2 Intel Pentium 4 Processor Thermal Design Guide

3 Contents 1 Introduction Document Goals and Scope Importance of Thermal Management Document Goals Document Scope eferences Definition of Terms Mechanical equirements Processor Package Heatsink Attach Thermal Specifications Processor Case Temperature and Power Dissipation Designing a Cooling Solution for the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Heatsink Design Considerations Thermal Interface Material Summary Looking at the Whole Thermal Solution Chassis Thermal Design Capabilities Improving Chassis Thermal Performance Characterizing Cooling Performance equirements Example of Heatsink Performance Evaluation Thermal Metrology for the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Processor Cooling Solution Performance Assessment Local Ambient Temperature Measurement Guidelines Processor Case Temperature Measurement Guidelines Thermocouple Attachment Heatsink Preparation ectangular (Cartesian) Geometry Heatsink Preparation adial (Cylindrical) Geometry Thermal Measurement Thermal Test Vehicle Information Introduction Thermal Test Die Alternate Method for TTV Connections Thermal Measurements TTV Correction Factor to the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Thermal Management Logic and Thermal Monitor Feature Processor Power Dissipation Thermal Monitor Implementation Bi-Directional POCHOT# Operation and Configuration System Considerations...36 Intel Pentium 4 Processor Thermal Design Guide 3

4 3.4.6 Operating System and Application Software Considerations Legacy Thermal Management Capabilities Thermal Diode THEMTIP# Thermal Measurement Correlation Cooling System Failure Warning Intel Thermal Mechanical eference Design Information Intel Validation Criteria for the eference Design Acoustics Altitude eference Heatsink Thermal Validation Fan Performance for Active Heatsink Thermal Solution Environmental eliability Testing Structural eliability Testing andom Vibration Test Procedure Shock Test Procedure ecommended Test Sequence Post-Test Pass Criteria Long-Term eliability Testing Temperature Cycling ecommended BIOS/CPU/Memory Test Procedures Material and ecycling equirements Safety equirements Geometrical Envelope for Intel eference Thermal Mechanical Design GHz or Higher Intel eference Thermal Solution eference Components Overview Enabled eference Components etention Mechanism Heatsink Attach Clip Information Heatsink Mechanical Design Guidelines Thermal Interface Material Enabled eference Design Test esults Conclusion...57 Appendix A: Thermal Interface Management...59 Appendix B: Mechanical Drawings...61 Appendix C: Intel Enabled eference Thermal Solution...71 Appendix D: Evaluated Third-Party Thermal Solutions Intel Pentium 4 Processor Thermal Design Guide

5 Figures Figure 1. Processor Case Temperature Measurement Location...13 Figure 2. Processor Thermal characterization parameter elationships...18 Figure 3. Guideline Locations for Measuring Local Ambient Temperature for an Active Heatsink (not to scale)...20 Figure 4. Guideline Locations for Measuring Local Ambient Temperature for a Passive Heatsink (not to scale)...21 Figure 5. Desired Thermocouple Location...22 Figure 6. Location of Kapton* Tape for Temporary Bond...23 Figure 7. Thermocouple Bead Covered with Epoxy...23 Figure 8. Grooved Heatsink Bottom...24 Figure 9. Heatsink Bottom Groove Dimensions...25 Figure 10. adial Heatsink Geometry...26 Figure 11. Thermal Test Vehicle Markings...27 Figure 12. Un-populated Mainboard...28 Figure 13. Mainboard Wire Attach Location for TTV Heater Access...29 Figure 14. Measured esistance Between Processor Power and Ground Planes...29 Figure 15. TTV Wiring Diagram...31 Figure 16. Thermal Sensor Circuit...34 Figure 17. Concept for Clocks under Thermal Monitor Control...35 Figure 18. Thermal Diode Sensor Time Delay...38 Figure 19. andom Vibration PSD...44 Figure 20. Shock Acceleration Curve...44 Figure 21. Motherboard Keep-out Footprint Definition and Height estrictions for Enabling Components Figure 22. Motherboard Keep-out Footprint Definition and Height estrictions for Enabling Components Figure 23. Volumetric Keep-in for Enabling Components...51 Figure 24. Exploded eference Design Concept Sketch...53 Figure 25. etention Mechanism 1 of Figure 26. etention Mechanism 2 of Figure 27. Clip...64 Figure 28. Fan Attach...65 Figure 29. Fan Impeller Sketch...66 Figure 30. Heatsink Drawing - 1 of Figure 31: Heatsink Drawing 2 of Figure 32. Fan Heatsink Assembly (with non-validated fan guard) 1 of Figure 33. Fan Heatsink Assembly (with non-validated fan guard) 2 of Tables Table 1. ecommended DC Power Supply atings...30 Table 2. TTV Correction Factors...32 Table 3. eference Heatsink Thermal Performance Targets...41 Table 4. Temperature Cycling Parameters...45 Table 5. eference Design esults Summary...55 Table 6. Intel epresentative Contact for Licensing Information...71 Table 7. Intel eference Component Thermal Solution Provider(s)...71 Table 8. Independently Evaluated Thermal Solutions...73 Intel Pentium 4 Processor Thermal Design Guide 5

6 evision History ev. No. Description Date -001 Public elease November Intel Pentium 4 Processor Thermal Design Guide

7 Introduction 1 Introduction 1.1 Document Goals and Scope 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, and in particular its electrical circuits, 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 cooling solution. All of these parameters are aggravated 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 remain 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 Document Goals The thermal power of the Intel Pentium 4 processor with 512-KB L2 cache on 0.13 micron process is higher, as well as denser, than previous Intel architecture processors. Depending on the type of system and the chassis characteristics, new system designs may be required to provide adequate cooling for the processor. The goal of this document is to provide an understanding of these thermal characteristics and discuss guidelines for meeting the thermal requirements imposed on single processor systems for the entire life of the Pentium 4 processor with 512-KB L2 cache on 0.13 micron process Document Scope Chapters 2 and 3 of this document discusses thermal solution design requirements for the Pentium 4 processor with 512-KB L2 cache on 0.13 micron process. Chapter 3 includes thermal metrology recommendations to validate a processor cooling solution; it also addresses the benefits of the processor integrated thermal management logic on thermal design. Intel Pentium 4 Processor Thermal Design Guide 7

8 Introduction Chapter 4 provides information on the Intel reference cooling solution for the Pentium 4 processor with 512-KB L2 cache on 0.13 micron process that covers the entire life of the processor. This section focuses on the reference solution that has been developed to support the end of life of the processor. The physical dimensions and thermal specifications of the processor that may be used in this document are for illustration only. efer to the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Datasheet for the product dimensions, thermal power dissipation, and maximum case temperature. In case of conflict, the data in the datasheet supercedes any data in this document. 1.2 eferences Material and concepts available in the following documents may be beneficial when reading this document. Document Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Datasheet Intel Pentium 4 Processor in the 478-pin Package Datasheet Intel Pentium 4 Processor in the 478-pin Package / Intel 850 Chipset Platform Family Design Guide Intel Pentium 4 Processor in 478-pin Package and Intel 845 Chipset Platform for SD Platform Design Guide Intel Pentium 4 Processor in the 478-Pin Package Thermal Design Guidelines Intel Pentium 4 Processor 478-Pin Socket (mpga478b) Design Guidelines Mechanical Enabling for the Intel Pentium 4 in the 478-Pin Package Performance ATX Desktop System Thermal Design Suggestions Performance microatx Desktop System Thermal Design Suggestions Document Number/ Location pentium4/datashts/ htm pentium4/datashts/ htm pentium4/guides/ htm chipsets/designex/ htm pentium4/guides/ htm pentium4/guides/ htm pentium4/guides/ htm Intel Pentium 4 Processor Thermal Design Guide

9 Introduction 1.3 Definition of Terms Term T A T E T C T S T C-MAX Ψ CA Ψ CS Ψ SA Θ CA Θ CS Θ SA TIM P MAX Description 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. The ambient air temperature external to a system chassis. This temperature is usually measured at the chassis air inlets. The case temperature of the processor, measured at the geometric center of the topside of the IHS. The heatsink temperature generally measured at the geometric center of the bottom surface of a heatsink base. 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 C T A) / Total Package Power. Heat source should always be specified for Ψ measurements. Case-to-sink thermal characterization parameter. A measure of thermal interface material performance using total package power. Defined as (T C T S) / Total Package Power. Sink-to-ambient thermal characterization parameter. A measure of heatsink thermal performance using total package power. Defined as (T S T A) / Total Package Power. Case-to-ambient thermal resistance (theta). Defined as (T C T A) / Power dissipated from case to ambient. Case-to-sink thermal resistance. Defined as (T C T S) / Power dissipated from case to sink. Sink-to-ambient thermal resistance. Defined as (T S T A) / Power dissipated from sink to ambient. 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. TDP IHS mpga478 Socket ACPI Bypass Thermal Monitor TCC 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, Zero Insertion Force (ZIF) socket designed to accept the Intel Pentium 4 processor with 512-KB L2 cache on 0.13 micron process. Advanced Configuration and Power Interface. Bypass is the area between a passive heatsink and any object that can act to form a duct. For this example, it can be expressed as a dimension away from the outside dimension of the fins to the nearest surface. A feature on the Pentium 4 processor with 512-KB L2 cache on 0.13 micron process that can keep the processor s die temperature within factory specifications under nearly all conditions. 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. Intel Pentium 4 Processor Thermal Design Guide 9

10 Introduction This page is intentionally left blank. 10 Intel Pentium 4 Processor Thermal Design Guide

11 Mechanical equirements 2 Mechanical equirements Processor Package The Pentium 4 processor with 512-KB L2 cache on 0.13 micron process is packaged in a Flip- Chip Pin Grid Array 2 (FC-PGA2) package technology and often referred as the 478-pin package. efer to the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Datasheet for detailed mechanical specifications. The package includes an integrated heat spreader (IHS). The IHS spreads the non-uniform heat from the die to the top of the IHS, increasing heat uniformity and reducing the power density due to the larger surface area. This allows more efficient heat transfer from the package to an attached cooling device. The IHS is designed to be the interface for mounting a heatsink. Details can be found in the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Datasheet. The processor connects to the motherboard through a 478-pin surface mount, zero insertion force (ZIF) socket. A description of the socket can be found in the Intel Pentium 4 Processor 478-Pin Socket (mpga478) Design Guidelines. The processor package has mechanical load limits that are specified in the datasheet. These load limits should not be exceeded during heatsink installation, removal, mechanical stress testing, or standard shipping conditions. For example, when a compressive static load is necessary to ensure thermal performance of the thermal interface material between the heatsink base and the IHS (see Appendix A for more information regarding bond line management), this compressive static load should not exceed the compressive static load 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 have to 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 1lbm heatsink, an acceleration of 50 g during a 11ms shock results approximately in a 100 lbf dynamic load on the processor package. If a 100 lbf static load is also applied on the heatsink for thermal performance of the thermal interface material and/or for mechanical reasons, the processor package sees 200 lbf. The calculation for the thermal solution of interest should be compared to the processor datasheet specification. It is not recommended to use any portion of the substrate as a mechanical reference or loadbearing surface in either static or dynamic compressive load conditions. Intel Pentium 4 Processor Thermal Design Guide 11

12 Mechanical equirements Heatsink Attach There are no features on the mpga478 socket to directly attach a heatsink. Therefore, a mechanism must be designed to support the heatsink. In addition to holding the heatsink into place on top of the IHS, this mechanism plays a significant role in the robustness of the system in which it is implemented. In particular: Ensuring thermal performance of the thermal interface material used between the IHS and the heatsink. Some of these materials are very sensitive to pressure applied to them; the higher the pressure, the better the performance up to a point of diminishing return. Ensuring system electrical, thermal and structural integrity under shock and vibration events. The mechanical requirements of the attach mechanism depend on the mass of the heatsink and the level of shock and vibration that the system has to support. The overall structural design of the motherboard and the system has to be considered as well when designing the heatsink attach mechanism, in particular their impact on motherboard stiffening needed to protect mpga478 socket solder joint, and prevent package pull-out from the socket. A popular solution for heatsink attach mechanism is to use a retention mechanism and attach clips. In that case, the clips should be designed to the general guidelines given above. More particularly: To hold the heatsink in place under shock and vibration events and apply force to the heatsink base to maintain desired pressure on the thermal interface material. The load applied by the clip also plays a role in ensuring that the package does not disengage from the socket during mechanical shock testing. Lastly, the load applied by the clip should provide protection to surface mount components during mechanical shock. Note that the load applied by the clips must comply with the package specifications described Section 2.1.1, along with the dynamic load added by the shock and vibration requirements. To engage easily with the retention mechanism tabs, if possible without the use of special tools. This should also take into account that, in general, heatsink and clip are installed once the motherboard has been installed into the chassis. To minimize contact with the motherboard surface during clip attach to the retention mechanism tab features; the clip should not scratch or otherwise damage the motherboard. The Intel eference design is using such a retention mechanism and clip assembly. efer to Chapter 4 and the document Mechanical Enabling for the Intel Pentium 4 in the 478-Pin Package for further information regarding the Intel eference mechanical solution. 12 Intel Pentium 4 Processor Thermal Design Guide

13 Thermal Specifications 3 Thermal Specifications 3.1 Processor Case Temperature and Power Dissipation efer to the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Datasheet for processor thermal specifications. Thermal specifications for the Pentium 4 processor with 512-KB L2 cache on 0.13 micron process are given in terms of maximum case temperature specification and thermal design power (TDP). These values may depend on the processor frequencies and also include manufacturing variations. Designing to these values allows optimizing thermal design for processor performance (refer to Section 3.4). Processor power is dissipated through the IHS. There is no additional component (i.e., BSAMs, which generates heat on this package). The case temperature is defined as the temperature measured at the center of the top surface of the IHS. For illustration, the measurement location for a 35-mm x 35-mm FC-PGA2 package is shown in Figure 1. Techniques for measuring the case temperature are detailed in Section Figure 1. Processor Case Temperature Measurement Location Intel Pentium 4 Processor Thermal Design Guide 13

14 Thermal Specifications 3.2 Designing a Cooling Solution for the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Heatsink Design Considerations To remove the heat from the processor, three basic parameters have to be considered: The extension of the surface on which the heat exchange takes place. Without any additional enhancements, this is the surface of the processor package IHS. One method used to improve thermal performance is to increase the surface area of the IHS by attaching a heatsink to it. Heatsinks extend the heat exchange surface through the use of fins that can be of various shapes and are attached to a heatsink base which is then in contact with the IHS. 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 improve 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 higher impact on the overall cooling solution performance as processor cooling requirements become stricter. Thermal interface material (TIM) can be used to fill any gaps between the IHS and the bottom surface of the heatsink, thereby improving the overall performance of the stack-up (IHS-TIM-Heatsink). Although, 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 load applied to it. efer to Appendix A for further information regarding managing the bond line 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 A, and the local air velocity over the surface. The higher the air velocity and turbulence over the surface, and the cooler the air, the more efficient is the resulting cooling. In the case of a heatsink, the surface exposed to the flow includes the fin faces and the heatsink base. 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. In addition, they may see lower air speeds. These heatsinks are therefore typically larger (and heavier) than active heatsinks due to the increase in fin surface area required to match thermal 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 will travel around the heatsink instead of through it, unless air bypass is carefully managed. Using air-ducting techniques to manage bypass are an effective method for controlling airflow through the heatsink. 14 Intel Pentium 4 Processor Thermal Design Guide

15 Thermal Specifications Thermal Interface Material Summary Thermal interface material application between the processor IHS and the heatsink base is generally required to improve thermal conduction from the IHS to the heatsink. Many thermal interface materials can be pre-applied to the heatsink base prior to shipment from the heatsink supplier and allow direct heatsink attach, without the need for a separate thermal interface material dispense or attach process in the final assembly factory. All thermal interface materials should be sized and positioned on the heatsink base in a way that ensures the entire processor IHS area is covered. It is important to compensate for heatsink-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 application tape or enclosure over it. This protective element must be removed prior to heatsink installation. In summary, considerations in heatsink design include: The local ambient temperature T A at the heatsink, the power being dissipated by the processor, and the corresponding maximum T C at the processor frequency considered. These parameters are usually combined in a single lump cooling performance parameter, Ψ CA (case to air thermal characterization parameter). More information on the definition and the use of Ψ CA is given Sections and Heatsink interface (to IHS) surface characteristics, including flatness and roughness. The performance of the thermal interface material used between the heatsink and the IHS. Surface area of the heatsink. Heatsink material and technology. Volume of airflow over the heatsink surface area. Development of airflow entering and within the heatsink area. Physical volumetric constraints placed by the system. Intel Pentium 4 Processor Thermal Design Guide 15

16 Thermal Specifications Looking at the Whole Thermal Solution Chassis Thermal Design Capabilities Only chassis capable of T A equal or lower than 45 C can be used for the Pentium 4 Processor with 512-KB L2 Cache on 0.13 micron process to support frequencies between 1.20 GHz thru 2.80 GHz. Chassis that do not meet this recommendation may require more sophisticated, and thus more expensive, cooling solution on the processor to compensate the lack of performance of the chassis. It is expected that chassis thermal capabilities are improved and can deliver T A no greater than 42 C for processor frequencies at 3.06 GHz or higher. efer to Section below for further information Improving Chassis Thermal Performance The heat generated by components within the chassis must be removed to provide an adequate operating environment for both the processor and other system components. Moving air through the chassis brings in air from the external ambient environment and transports the heat generated by the processor and other system components out of the system. The number, size and relative position of fans and vents have a decisive impact on the chassis thermal performance, and therefore on the ambient temperature around the processor. The size and type (passive or active) of the thermal cooling device and the amount of system airflow are related and can be traded off against each other to meet specific system design constraints. Additional constraints are board layout, spacing, component placement, 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 web site. 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 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 cooling solutions, the Thermal Monitor feature and associated logic have been integrated into the silicon of the Pentium 4 processor with 512-KB L2 cache on 0.13 micron process. By taking advantage of the Thermal Monitor feature, system designers may reduce the cooling system cost while maintaining the processor reliability and performance goals. Implementation options and recommendations are described in Section Intel Pentium 4 Processor Thermal Design Guide

17 Thermal Specifications Characterizing Cooling Performance equirements The notion of a thermal characterization parameter is convenient to characterize the performance needed for the cooling solution and to compare cooling solutions in identical situations. Be aware, however, of its limitation when it comes to a real design. Heat transfer is a three-dimensional phenomenon that can rarely be accurately and easily modeled by lump values. The thermal characterization parameter value from case-to-local ambient (Ψ CA ) is used as a measure of the thermal performance of the overall cooling solution that is attached to the processor package. It is defined by the following equation, and measured in units of C/W: Equation 1 Ψ CA = (T C - T A ) / TPD Where: Ψ CA = Thermal characterization parameter from case-to-local ambient ( C/W) T C = Processor case temperature ( C) T A = Local ambient temperature in chassis around processor ( C) TPD = Thermal design power (W) (assume all power goes through the IHS) The thermal characterization parameter of the processor case-to-local ambient, Ψ CA, is comprised of Ψ CS, the thermal interface material thermal characterization parameter, and of Ψ SA, the sink-tolocal ambient thermal characterization parameter: Equation 2 Ψ CA = Ψ CS + Ψ SA Where: Ψ CS = Thermal characterization parameter of the thermal interface material ( C/W) Ψ SA = Thermal characterization parameter from heatsink-to-local ambient ( C/W) Ψ CS is strongly dependent on the thermal conductivity and thickness of the TIM between the heatsink and IHS. Ψ SA is a measure of the thermal characterization parameter from the bottom of the heatsink to the local ambient air. Ψ SA is dependent on the heat sink s material, thermal conductivity, and geometry. It is also strongly dependent on the air velocity through the fins of the heatsink. Intel Pentium 4 Processor Thermal Design Guide 17

18 Thermal Specifications Figure 2 illustrates the combination of the different thermal characterization parameters. Figure 2. Processor Thermal characterization parameter elationships T A HEATSINK Ψ SA Ψ CA TIM POCESSO IHS T S T C Ψ CS SOCKET Example of Heatsink Performance Evaluation The cooling performance Ψ CA is then defined using the notion of thermal characterization parameter described above: Define a target case temperature T C-MAX,F and corresponding thermal design power TDP F at a target frequency given in the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Datasheet. Define a target local ambient temperature around the processor, T A. Since the processor thermal specifications (T C-MAX and TDP) can vary with the processor frequency, it may be important to identify the worse case (smallest Ψ CA ) for a targeted chassis (characterized by T A ) to establish a design strategy such that a given heatsink can meet the thermal requirements of a given range of processor frequencies. The following provides an illustration of how one might determine the appropriate performance targets. The power and temperature numbers used here are not related to any Intel processor thermal specifications, and are given only to carry out the example. Assume the TDP is 90W and the case temperature specification is 70 C. Assume as well that the system airflow has been designed such that the local ambient temperature is 38 C. Then the following could be calculated using equation 1 from above: Ψ CA = (T CMAX,F - T A ) / TDP F = (70 38) / 90 = 0.36 C/W Assuming Ψ CS = 0.08 C/W, solving for equation 2 from above, the performance of the heatsink itself has to be: Ψ SA = Ψ CA Ψ CS = = 0.28 C/W 18 Intel Pentium 4 Processor Thermal Design Guide

19 Thermal Specifications 3.3 Thermal Metrology for the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Processor Cooling Solution Performance Assessment This section discusses guidelines for testing thermal solutions, including measuring processor temperatures. In all cases, power dissipation and temperature measurements must be made to validate a cooling solution. Thermal performance of a processor heatsink in a chassis should be assessed using a thermal test vehicle (TTV) provided by Intel (refer to Section 3.3.4). A TTV is a well-characterized thermal tool; using real parts introduces other factors that can impact test results. In particular, the power level from real processors varies significantly. This is due to part-to-part variances in the manufacturing process. The TTV provides consistent power and power density for thermal solution characterization and results can be easily translated to real processor performance. Accurate measurement of the power dissipated by a real processor is beyond the scope of this document. Once the thermal solution and chassis are designed and validated with the TTV, it is recommended to verify functionality of the thermal solution on real processors and on fully integrated systems (see Section 3.4) Local Ambient Temperature Measurement Guidelines The local ambient temperature T A is the temperature of the ambient air surrounding the processor. For a passive heatsink, T A is defined as the heatsink approach air temperature; for an 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 A is best measured by averaging temperature measurements at multiple locations in the heatsink inlet airflow. This method helps reduce error and eliminate minor spatial variations in temperature. The following guidelines are meant to enable accurate determination of the localized air temperature around the processor during system thermal testing. For active heatsinks, it is important to avoid taking measurement in the dead flow zone that usually develops above the fan hub. 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 2.54 mm to 7.62 mm (0.1 to 0.3 inch) above the fan hub vertically, and halfway between the fan hub and the fan housing horizontally as shown in Figure 3. Testing in an open bench environment to characterize an active heatsink can be useful, and usually ensures more uniform temperatures at the fan inlet. However, additional tests that include a barrier above the test motherboard surface can help evaluate the potential impact of the chassis. This barrier is typically clear Plexiglas*, extending at least 4 inches in all directions beyond the edge of the thermal solution. Typical distance from the motherboard to the barrier is 81mm [3.2in]. For even more realistic airflow, the motherboard should be fully populated with significant elements like Intel Pentium 4 Processor Thermal Design Guide 19

20 Thermal Specifications memory cards, AGP card, chipset heatsink, and hard drive(s). If a barrier is used, the thermocouple can be taped directly to the barrier at the horizontal locations as previously described, half way between the fan hub and the fan housing. If a variable speed fan is used, it may be useful to add a thermocouple taped to the barrier above the location of the temperature sensor used by the fan to check its speed setting against air temperature. When measuring T A directly in a chassis with a live motherboard, add-in cards and the other system components, it is likely that T A shows as highly non-uniform across the inlet fan section. For passive heatsinks, thermocouples should be placed approximately 12.7 mm to 25.4 mm (0.5 to 1.0 inches) away from processor heatsink as shown in Figure 4. The thermocouples should be placed approximately 50.8 mm (2 inches ) above the baseboard. This placement guideline is meant to minimize the effect of localized hot spots from baseboard components. Figure 3. Guideline Locations for Measuring Local Ambient Temperature for an Active Heatsink (not to scale) 20 Intel Pentium 4 Processor Thermal Design Guide

21 Thermal Specifications Figure 4. Guideline Locations for Measuring Local Ambient Temperature for a Passive Heatsink (not to scale) Processor Case Temperature Measurement Guidelines To ensure functionality and reliability, the Pentium 4 processor with 512-KB L2 cache on 0.13 micron process is specified for proper operation when T C is maintained at or below the value listed in the Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Datasheet. The measurement location for T C is the geometric center of the IHS. Figure 1 shows the location for T C measurement. Special care is required when measuring T C to ensure an accurate temperature measurement. When measuring the temperature of a surface, which is at a different temperature from the surrounding local ambient air, errors could be introduced in the measurements. The measurement errors could be caused by poor thermal contact between the thermocouple junction and the surface of the integrated heat spreader, heat loss by radiation or convection, by conduction through thermocouple leads, or by contact between the thermocouple cement and the heatsink base. To minimize these measurement errors, the approach outlined in the next section is recommended. Intel Pentium 4 Processor Thermal Design Guide 21

22 Thermal Specifications Thermocouple Attachment Thermocouples are often used to measure T C. Before any temperature measurements are made, the thermocouples must be calibrated. This section describes the procedure for attaching a thermocouple to the IHS for the case temperature (T C ) measurement. 1. Obtain the necessary items needed for the quantity of thermocouple attaches desired: Fine point tweezers Exacto* knife (#11 blade) Thermocouples (Type K, 36 gauge, 36 inch, Teflon* insulation). Ensure that the thermocouple has been properly calibrated 3M* Kapton* tape (or equivalent) cut into strips (1/8 inch X ½ inch) Epoxy (Omegabond* 101 or equivalent) Curing oven or equivalent. 2. Use a scribe to mark at the center of the package (IHS side) where the bead of the thermocouple will be placed. Determine the center of the package by drawing two diagonal lines across the length of the package. The intersection of the two lines is the package center. (See Figure 5). Figure 5. Desired Thermocouple Location 3. After the marks are scribed, clean the desired thermocouple attach location with a mild solvent and a lint-free wipe or cloth. Alcohol or acetone should suffice. Cleanliness of the part is critical for a strong epoxy bond after curing. 4. With thermocouple (T/C) in hand, locate the junction and straighten the wire by hand so that the first 4 6 inches are reasonably straight. Use the fine point tweezers to ensure that the bead and the two protruding wires are straight and untwisted. Ensure the second layer of thermocouple insulation, sometimes clear, is not covering the bead. 5. Place a slight downward bend (~30 ) in the protruding wires approximately 1/16 inch from junction using the tweezers. This aids the user in ensuring the thermocouple junction contacts the heat spreader surface. 6. Place the thermocouple on the surface of the part so the bead is contacting the IHS at the desired location. Hold the T/C with one hand and use a pair of tweezers to apply a cut piece of Kapton* tape across the wire approximately about ¼ inch back from the bead. Apply pressure to the tape to ensure a good bond. Apply additional Kapton tape along the length of the wire to ensure a good temporary bond to the part. (See following Figure 6). Check for electrical continuity between the thermocouple and the IHS using a multimeter. If there is no electrical continuity between the thermocouple and the IHS, remove the thermocouple and repeat Steps Intel Pentium 4 Processor Thermal Design Guide

23 Thermal Specifications Figure 6. Location of Kapton* Tape for Temporary Bond 7. With the thermocouple temporarily held to the part, apply epoxy to the thermocouple bead for a permanent bond. If applying Omegabond 101 epoxy, a small piece of paper works well for mixing. Follow the manufacturer s instructions for mixing. 8. Use the Exacto* knife or similar to apply the epoxy to the thermocouple bead. Dab glue on the bead and the exposed wires. Use only the appropriate amount of epoxy to cement the thermocouple to the IHS. Excess epoxy will prevent the heatsink from mating flush with the IHS. The entire bead should be submerged and it is best to have insulated wires protruding from the epoxy. (See following Figure 7). Figure 7. Thermocouple Bead Covered with Epoxy 9. Add other tack-downs of epoxy along the length of wire to provide strain relief for the thermocouple wire. emove any small epoxy dots or lines that have been accidentally added after the epoxy cures. 10. Follow the epoxy manufacturer s instructions for curing the epoxy. If an oven is used for curing the epoxy, ensure the vibration in the oven is minimal to prevent the thermocouple bead from moving and losing intimate contact with the IHS. 11. Once the epoxy has cured, remove all tape and check for any epoxy residual outside the thermocouple attach area. un the tip of your finger around the IHS surface to find any small epoxy dots. emove the non-necessary epoxy residual completely so it does not impact heatsink to IHS mating surface. Clean the IHS surface after conducting this finger test. 12. Check for electrical continuity between the thermocouple and the IHS again. If there is no electrical continuity between the thermocouple and the IHS, repeat Steps Intel Pentium 4 Processor Thermal Design Guide 23

24 Thermal Specifications Heatsink Preparation ectangular (Cartesian) Geometry To measure the case temperature, a heatsink must be mounted on the processor or TTV to dissipate the heat to the environment. The heatsink base must be grooved to allow a thermocouple to be routed from the center of the heatsink without altering the IHS for heatsink attachment. The groove in the heatsink has two features. The first is a 4.5 mm (0.180 inch) diameter relief for the thermocouple bead and surrounding epoxy. The second feature is a 1.0 mm (0.040 inch) wide groove that allows the thermocouple wire to be routed to the edge of the IHS/heatsink assembly. The relief and wire routing groove should be shallow enough to avoid significant impact on heatsink performance, while minimizing interference between thermocouple and the heatsink base. Groove depth should be 0.6 to 1.0 mm maximum (0.025 to inches). Notice the center of the thermocouple bead relief is located 1.3 mm (0.050 inches) from the centerline of the heatsink. An example of a grooved heatsink base is shown in Figure 8. It must be noted that the center of the circle area needs to be located 1.3 mm (0.05 inches) off center from the location corresponding to the thermocouple bead at the center of the IHS. This offset accommodates the bead of epoxy that covers both the thermocouple and thermocouple wires. Figure 8. Grooved Heatsink Bottom 24 Intel Pentium 4 Processor Thermal Design Guide

25 Thermal Specifications Figure 9. Heatsink Bottom Groove Dimensions NOTES: 1. Applies to rectangular or cylindrical heatsink base 2. The groove depth (including the circle area) is 0.6 to 1.0 mm (0.025 to inches) Heatsink Preparation adial (Cylindrical) Geometry For some heatsinks that have a radial geometry (see Figure 10), it may be necessary to locate the center of the heatsink using features in the fin pattern. For example, the 62-fin radial heatsink of the Intel reference design for the Pentium 4 processor in the 478-pin package described in the note below, requires the following procedure: 1. Identify fin gap (a) as shown in Figure Count ¼ of the total amount of fin gaps in clockwise direction; identify fin gap (b). 3. epeat for fin gap (c) and fin gap (d). 4. Scribe lines (a-c) and (b-d) across the core area of the radial heatsink. 5. Locate heatsink center at the intersection of lines (a-c) and (b-d). 6. Machine a groove 1 mm (0.040 inches) wide, 0.6 mm (0.025 inches) deep along line (o-a). 7. Locate the center for the circle area 1.3 mm (0.050 inches) off the heatsink centerline, along line (o-a). 8. Machine the circle area 4.5 mm (0.180 inches) diameter, 0.6 mm (0.025 inches) deep to accommodate the thermocouple and epoxy bead. Note: This procedure takes into account the fact that the center of the IHS and the center of the heatsink coincide for this particular design. Intel Pentium 4 Processor Thermal Design Guide 25

26 Thermal Specifications Figure 10. adial Heatsink Geometry a d o b c Thermal Measurement 1. Attach a thermocouple at the center of the package (IHS-side) using the proper thermocouple attach procedure (refer to Section ). 2. Connect the thermocouple to a thermocouple meter. 3. Mill groove on heatsink base (refer to Section or to Section ). 4. Apply thermal interface material to either IHS top surface or on the surface of heatsink base. 5. Mount the heatsink to the processor package with the intended heatsink attach clip and all relevant mechanical interface components (e.g., retention mechanism, processor EMI attenuation solutions, etc.). 6. efer to Section to setup the thermocouples used for T A measurement, and connect them to a thermocouple meter. 7. Depending on the overall experimental setup, the time needed to have stable thermal conditions may vary. T A and T C measurements are valid once constant (refer to Section for application to the thermal test vehicle). Note: This methodology requires special care when assembling the grooved heatsink to the top of the IHS with the thermocouple attached. Mismatch between the heatsink groove and the thermocouple wires and bead may lead to inaccurate measurements, and even thermocouple damage, in particular when compressive load is required to get better performance from the thermal interface material. 26 Intel Pentium 4 Processor Thermal Design Guide

27 Thermal Specifications Thermal Test Vehicle Information Introduction The Pentium 4 processor with 512-KB L2 cache on 0.13 micron process Thermal Test Vehicle (TTV) is a FC-PGA2 package assembled with a thermal test die. The TTV is designed for use in platforms targeted for the Pentium 4 processor with 512-KB L2 cache on 0.13 micron process. The Pentium 4 processor TTVs are in limited supply; contact your local Intel field office for eligibility and availability. Cooling solution performance should be defined using the TTV only. Not only does the TTV provide a well-characterized tool suitable for thermal testing, it also allows simulating processor thermal targets before real processors are available. The correction factor of the TTV to real processors, given in Section , Table 2, is then used to define the performance of the solution on real processors. The part number for the TTV is A There were two builds of TTV s. The TTV will either have a, ITVN1 THEM SAMP marking or a handwritten part code QEL0 on the topside of the IHS. Samples of both markings are shown in Figure 11. Figure 11. Thermal Test Vehicle Markings Handwritten QELO - Hand written QELO D217A214 XXXX Intel Pentium 4 Processor Thermal Design Guide 27