LGA775 Socket Heatsink Loading
Thermal and Mechanical Design Guidelines
75
Appendix A
LGA775 Socket Heatsink
Loading
A.1
LGA775 Socket Heatsink Considerations
Heatsink clip load is traditionally used for:
•
Mechanical performance in mechanical shock and vibration
⎯
6.7.1 for the information on the structural design strategy for
the reference design
•
Thermal interface performance
⎯
Required preload depends on TIM
⎯
Preload can be low for thermal grease
In addition to mechanical performance in shock and vibration and TIM performance,
LGA775 socket requires a minimum heatsink preload to protect against fatigue failure
of socket solder joints.
Solder ball tensile stress is originally created when, after inserting a processor into the
socket, the LGA775 socket load plate is actuated. In addition, solder joint shear stress
is caused by coefficient of thermal expansion (CTE) mismatch induced shear loading.
The solder joint compressive axial force (F
axial
) induced by the heatsink preload helps
to reduce the combined joint tensile and shear stress.
Overall, the heatsink required preload is the minimum preload needed to meet all of
the above requirements: Mechanical shock and vibration and TIM performance AND
LGA775 socket protection against fatigue failure.
A.2
Metric for Heatsink Preload for ATX/uATX
Designs Non-Compliant with Intel
®
Reference Design
A.2.1
Heatsink Preload Requirement Limitations
Heatsink preload by itself is not an appropriate metric for solder joint force across
various mechanical designs and does not take into account for example (not an
exhaustive list):
•
Heatsink mounting hole span
•
Heatsink clip/fastener assembly stiffness and creep
•
Board stiffness and creep
•
Board stiffness is modified by fixtures like backing plate, chassis attach, etc.
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Страница 26: ...Processor Thermal Mechanical Information 26 Thermal and Mechanical Design Guidelines...
Страница 68: ...ATX Thermal Mechanical Design Information 68 Thermal and Mechanical Design Guidelines...
Страница 86: ...Heatsink Clip Load Metrology 86 Thermal and Mechanical Design Guidelines...
Страница 88: ...Thermal Interface Management 88 Thermal and Mechanical Design Guidelines...
Страница 120: ...Legacy Fan Speed Control 120 Thermal and Mechanical Design Guidelines...
Страница 124: ...Balanced Technology Extended BTX System Thermal Considerations 124 Thermal and Mechanical Design Guidelines...
Страница 126: ...Fan Performance for Reference Design 126 Thermal and Mechanical Design Guidelines...
Страница 127: ...Fan Performance for Reference Design Thermal and Mechanical Design Guidelines 127...
Страница 139: ...Mechanical Drawings Thermal and Mechanical Design Guidelines 139 Figure 7 57 Reference Fastener Sheet 1...
Страница 140: ...Mechanical Drawings 140 Thermal and Mechanical Design Guidelines Figure 7 58 Reference Fastener Sheet 2...
Страница 141: ...Mechanical Drawings Thermal and Mechanical Design Guidelines 141 Figure 7 59 Reference Fastener Sheet 3...
Страница 142: ...Mechanical Drawings 142 Thermal and Mechanical Design Guidelines Figure 7 60 Reference Fastener Sheet 4...