Intel 640 User Guide - Page 65

LGA775 Socket Heatsink Loading

R

Thermal/Mechanical Design Guide

65

A.2.5

Additional Considerations

Intel recommends designing to {d_BOL – d_ref = 0.15mm} at BOL when EOL conditions are not

known or difficult to assess.

The following information is given for illustration purposes only. It is based on the reference

keep-out, assuming there is no fixture that changes board stiffness:

d_ref is expected to be 0.18 mm on average, and be as high as 0.22 mm.

As a result, the board should be able to deflect 0.37 mm minimum at BOL.

Additional deflection, as much as 0.09 mm may be necessary to account for additional creep

effects impacting the board/clip/fastener assembly. As a result, designs could see as much as

0.50 mm total downward board deflection under the socket.

In addition to board deflection, other elements need to be considered to define the space needed

for the downward board total displacement under load, like the potential interference of through-

hole mount component pin tails of the board with a mechanical fixture on the back of the board.

NOTES:

1.

The heatsink preload must remain below the maximum load limit of the package at all times (Refer to

processor datasheet).

2.

Board deflection should not exceed motherboard manufacturer specifications.

A.2.5.1

Motherboard Stiffening Considerations

To protect LGA775 socket solder joint, designers need to drive their mechanical design to:

•

Allow downward board deflection to put the socket balls in a desirable force state to protect

against fatigue failure of socket solder joint (refer to Sections A.2.1, A.2.2, and A.2.3).

•

Prevent board upward bending during mechanical shock event.

•

Define load paths that keep the dynamic load applied to the package within specifications

published in the processor datasheet.

Limiting board deflection may be appropriate in some situations like:

•

Board bending during shock.

•

Board creep with high heatsink preload.

However, the load required to meet the board deflection recommendation (refer to Section A.2.3)

with a very stiff board may lead to heatsink preloads exceeding package maximum load

specification. For example, such a situation may occur when using a backing plate that is flush

with the board in the socket area, and prevents the board from bending underneath the socket.

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

Intel 640 User Guide - Page 65

A.2.5, Additional Considerations

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