Intel Core 2 Duo E7300 BX80570E7300 User Manual

Thermal and Mechanical Design Guidelines   

 17 

There are no features on the LGA775 socket to directly attach a heatsink: a 

mechanism must be designed to attach the heatsink directly to the motherboard. In 

addition to holding the heatsink in place on top of the IHS, this mechanism plays a 

significant role in the robustness of the system in which it is implemented, in 

particular: 

 

Ensuring thermal performance of the thermal interface material (TIM) applied 

between the IHS and the heatsink. TIMs based on phase change materials are 

very sensitive to applied pressure: the higher the pressure, the better the initial 

performance. TIMs such as thermal greases are not as sensitive to applied 

pressure. Designs should consider a possible decrease in applied pressure over 

time due to potential structural relaxation in retention components. 

 

Ensuring system electrical, thermal, and structural integrity under shock and 

vibration events. The mechanical requirements of the heatsink attach mechanism 

depend on the mass of the heatsink and the level of shock and vibration that the 

system must support. The overall structural design of the motherboard and the 

system have to be considered when designing the heatsink attach mechanism. 

Their design should provide a means for protecting LGA775 socket solder joints. 

One of the strategies for mechanical protection of the socket is to use a preload 

and high stiffness clip. This strategy is implemented by the reference design and 
described in Section 

6.7. 

Note:  Package pull-out during mechanical shock and vibration is constrained by the LGA775 

socket load plate (refer to the LGA775 Socket Mechanical Design Guide for further 
information).  

The attach mechanism for the heatsink developed to support the processor should 

create a static preload on the package between 18 lbf and 70 lbf throughout the life 

of the product for designs compliant with the reference design assumptions: 

 

72 mm x 72 mm mounting hole span for ATX (refer to Figure 

 

TMA preload vs. stiffness for BTX within the limits shown on Figure 

 

And no board stiffening device (backing plate, chassis attach, etc.).  

The minimum load is required to protect against fatigue failure of socket solder joint in 

temperature cycling. 

It is important to take into account potential load degradation from creep over time 

when designing the clip and fastener to the required minimum load. This means that, 

depending on clip stiffness, the initial preload at beginning of life of the product may 

be significantly higher than the minimum preload that must be met throughout the life 

of the product. For additional guidelines on mechanical design, in particular on designs 
departing from the reference design assumptions refer to 

Appendix A. 

For clip load metrology guidelines, refer to 

Appendix B.