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.
Summary of Contents for Celeron Dual-Core E1000 Series
Page 10: ...10 Thermal and Mechanical Design Guidelines...
Page 26: ...Processor Thermal Mechanical Information 26 Thermal and Mechanical Design Guidelines...
Page 68: ...ATX Thermal Mechanical Design Information 68 Thermal and Mechanical Design Guidelines...
Page 86: ...Heatsink Clip Load Metrology 86 Thermal and Mechanical Design Guidelines...
Page 88: ...Thermal Interface Management 88 Thermal and Mechanical Design Guidelines...
Page 120: ...Legacy Fan Speed Control 120 Thermal and Mechanical Design Guidelines...
Page 126: ...Fan Performance for Reference Design 126 Thermal and Mechanical Design Guidelines...
Page 127: ...Fan Performance for Reference Design Thermal and Mechanical Design Guidelines 127...
