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LGA 771 Socket Mechanical Design Guide 11
Mechanical Requirements
3 Mechanical Requirements
3.1 Attachment
The socket will be tested against the mechanical shock and vibration requirements
listed in Section 5 under the expected use conditions with a heatsink and retention
mechanism attached under the loading conditions outlined in Section 3.6, and the
processor datasheet. The socket will only be attached by the 771 contact solder balls to
the motherboard. There are no additional external methods (i.e. screw, extra solder,
adhesive, etc.) to attach the socket.
Note: Heatsink Static Compressive Loading
Heatsink static compressive loading is traditionally used for:
• Mechanical performance in mechanical shock and vibration.
• Thermal interface material (TIM) performance
— Required preload depends on selected TIM
In addition to mechanical performance in shock and vibration and TIM performance,
LGA771 socket requires a minimum heatsink static compressive load to protect against
fatigue failure of socket solder joints.
Solder ball tensile stress is created by inserting a processor into the socket and
actuating the LGA771 socket load plate. In addition, solder joint shear stress is caused
by coefficient of thermal expansion (CTE) mismatch induced shear loading. The solder
joint compressive axial force induced by the heatsink static compressive load helps to
reduce the combined joint tensile and shear stress.
Overall, the heatsink required static compressive load is the minimum static
compressive load needed to meet all of the above requirements: Mechanical shock and
vibration, TIM performance, and LGA771 socket protection against fatigue failure.
Refer to Section 3.6 for detailed information for heatsink static compressive load for
the LGA771 socket to ensure socket solder joint protection against fatigue in
temperature cycling.
3.2 Socket Components
The socket is made of four main components: socket body, load plate, load lever, and
socket body stiffener. Refer to Appendix A for detailed drawings.
The socket will be delivered as a single integral assembly.
3.2.1 Socket Body
3.2.1.1 Housing
The housing material will be a thermoplastic or equivalent, UL 94 V-0 flame rating,
temperature rating and design capable of maintaining structural integrity following a
temperature of 260°C for 40 seconds which is typical of a reflow/rework profile for
solder material used on the socket. The material must have a thermal coefficient of
expansion in the XY plane capable of passing reliability tests rated for an expected high