Intel LGA 771 3

LGA 771 Socket Mechanical Design Guide 11

Mechanical Requirements

3Mechanical Requirements

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 l oad needed to mee t 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.

The socket is made of four main components: socket body, load plate, load lever, and

socket body stiffener. Refer to AppendixA for detailed drawings.

The socket will be delivered as a single integral assembly.

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