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A.2.4, Board Deflection Metric Implementation Example

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LGA775 Socket Heatsink Loading R A.2.4 Board Deflection Metric Implementation Example This section is for illustration purposes only, and relies on the following assumptions: • 72 mm x 72 mm hole pattern of the reference design • Board stiffness = 900 lb/in at BOL, with degradation that simulates board creep over time ⎯ Though these values are representative, they may change with selected material and board manufacturing process. Check with your motherboard vendor. • Clip stiffness assumed constant - No creep. Using Figure 23, the heatsink preload at beginning of life is defined to comply with d_EOL - d_ref = 0.15 mm depending on clip stiffness assumption. Note that the BOL and EOL preload and board deflection differ. This is a result of the creep phenomenon. The example accounts for the creep expected to occur in the motherboard. It assumes no creep will occur in the clip. However, there is a small amount of creep accounted for in the plastic fasteners. This situation is somewhat similar to the Intel Reference Design. The impact of the creep to the board deflection is a function of the clip stiffness: • The relatively compliant clips store strain energy in the clip under the BOL preload condition and tend to generate increasing amounts of board deflection as the motherboard creeps under exposure to time and temperature. • In contrast, stiffer clips store very little strain energy, and therefore do not generate substantial additional board deflection through life. NOTES: 1. Board and clip creep modify board deflection over time and depend on board stiffness, clip stiffness, and selected materials. 2. Designers must define the BOL board deflection that will lead to the correct end of life board deflection. Figure 23. Example: Defining Heatsink Preload Meeting Board Deflection Limit 64 Thermal/Mechanical Design Guide

Section	Page
Contents	3
Figures	6
Tables	7
Revision History	8
1 Introduction	9
1.1 Document Goals and Scope	9
1.1.1 Importance of Thermal Management	9
1.1.2 Document Goals	9
1.1.3 Document Scope	10
1.2 References	11
1.3 Definition of Terms	12
2 Processor Thermal/Mechanical Information	15
2.1 Mechanical Requirements	15
2.1.1 Processor Package	15
2.1.2 Heatsink Attach	17
2.1.2.1 General Guidelines	17
2.1.2.2 Heatsink Clip Load Requirement	17
2.1.2.3 Additional Guidelines	18
2.2 Thermal Requirements	18
2.2.1 Processor Case Temperature	18
2.2.2 Thermal Profile	19
2.2.3 TCONTROL	20
2.3 Heatsink Design Considerations	21
2.3.1 Heatsink Size	22
2.3.2 Heatsink Mass	22
2.3.3 Package IHS Flatness	22
2.3.4 Thermal Interface Material	23
2.4 System Thermal Solution Considerations	23
2.4.1 Chassis Thermal Design Capabilities	23
2.4.2 Improving Chassis Thermal Performance	23
2.4.3 Summary	24
2.5 System Integration Considerations	24
3 Thermal Metrology	25
3.1 Characterizing Cooling Performance Requirements	25
3.1.1 Example	26
3.2 Processor Thermal Solution Performance Assessment	27
3.3 Local Ambient Temperature Measurement Guidelines	27
3.4 Processor Case Temperature Measurement Guidelines	30
4 Thermal Management Logic and Thermal Monitor Feature	31
4.1 Processor Power Dissipation	31
4.2 Thermal Monitor Implementation	31
4.2.1 PROCHOT# Signal	32
4.2.2 Thermal Control Circuit	32
4.2.3 Operation and Configuration	33
4.2.4 On-Demand Mode	34
4.2.5 System Considerations	34
4.2.6 Operating System and Application Software Considerations	35
4.2.7 On-Die Thermal Diode	35
4.2.7.1 Reading the On-Die Thermal Diode Interface	35
4.2.7.2 Correction Factors for the On-Die Thermal Diode	36
4.2.8 THERMTRIP# Signal	37
4.2.8.1 Cooling System Failure Warning	37
5 Intel® Thermal/Mechanical Reference Design Information	39
5.1 Intel Validation Criteria for the Reference Design	39
5.1.1 Heatsink Performance Target	39
5.1.2 Acoustics	40
5.1.3 Altitude	40
5.1.4 Reference Heatsink Thermal Validation	41
5.1.5 Fan Performance for Active Heatsink Thermal Solution	41
5.2 Environmental Reliability Testing	42
5.2.1 Structural Reliability Testing	42
5.2.1.1 Random Vibration Test Procedure	42
5.2.1.2 Shock Test Procedure	42
5.2.2 Power Cycling	44
5.2.3 Recommended BIOS/Processor/Memory Test Procedures	44
5.3 Material and Recycling Requirements	44
5.4 Safety Requirements	45
5.5 Geometric Envelope for ATX Intel® Reference Thermal Mechanical Design	45
5.6 ATX Reference Thermal Mechanical Solution for the Intel® Pentium® 4 Processor in the 775–Land LGA Package	46
5.7 Reference Attach Mechanism	48
5.7.1 Structural Design Strategy	48
5.7.2 Mechanical Interface to the Reference Attach Mechanism	49
6 Acoustic Fan Speed Control	53
6.1 Acoustic Fan Speed Control	53
6.2 Thermal Solution Design	53
6.2.1 Compliance to Thermal Profile	53
6.2.2 Determine Thermistor Set Points	53
6.2.3 Minimum Fan Speed Set Point	54
6.3 Board and System Implementation	55
6.3.1 Choosing Fan Speed Control Settings	55
6.3.1.1 Temperature to begin Fan Acceleration	56
6.3.1.2 Minimum PWM Duty Cycle	58
6.4 Combining Thermistor and Thermal Diode Control	59

Match case Limit results 1 per page

LGA775 Socket Heatsink Loading

Thermal/Mechanical Design Guide

A.2.4

Board Deflection Metric Implementation Example

This section is for illustration purposes only, and relies on the following assumptions:

•

72 mm x 72 mm hole pattern of the reference design

•

Board stiffness = 900 lb/in at BOL, with degradation that simulates board creep over time

⎯

Though these values are representative, they may change with selected material and

board manufacturing process. Check with your motherboard vendor.

•

Clip stiffness assumed constant – No creep.

Using Figure 23, the heatsink preload at beginning of life is defined to comply with

d_EOL – d_ref = 0.15 mm depending on clip stiffness assumption.

Note that the BOL and EOL preload and board deflection differ. This is a result of the creep

phenomenon. The example accounts for the creep expected to occur in the motherboard. It

assumes no creep will occur in the clip. However, there is a small amount of creep accounted for

in the plastic fasteners. This situation is somewhat similar to the Intel Reference Design.

The impact of the creep to the board deflection is a function of the clip stiffness:

•

The relatively compliant clips store strain energy in the clip under the BOL preload condition

and tend to generate increasing amounts of board deflection as the motherboard creeps under

exposure to time and temperature.

•

In contrast, stiffer clips store very little strain energy, and therefore do not generate

substantial additional board deflection through life.

NOTES:

Board and clip creep modify board deflection over time and depend on board stiffness, clip stiffness, and

selected materials.

Designers must define the BOL board deflection that will lead to the correct end of life board deflection.

Figure 23. Example: Defining Heatsink Preload Meeting Board Deflection Limit