Thermal/Mechanical Reference Design
2.5.2Thermal Interface Material
TIM application between the processor IHS and the heatsink base is generally required to improve thermal conduction from the IHS to the heatsink. Many thermal interface materials can be
All thermal interface materials should be sized and positioned on the heatsink base in a way that ensures the entire processor IHS area is covered. It is important to compensate for
When
The TIM performance is susceptible to degradation (i.e. grease breakdown) during the useful life of the processor due to the temperature cycling phenomena. For this reason, the measured TCASE value of a given processor can decrease over time depending on the type of TIM material.
Refer to Section 2.5.7.2 for information on the TIM used in the Intel reference heatsink solution.
2.5.3Summary
In summary, considerations in heatsink design include:
•The local ambient temperature TLA at the heatsink, airflow (CFM), the power being dissipated by the processor, and the corresponding maximum TCASE temperature. These parameters are usually combined in a single lump cooling performance
parameter, ΨCA (case to air thermal characterization parameter). More information on the definition and the use of ΨCA is given in Section 2.5 and Section 2.4.2.
•Heatsink interface (to IHS) surface characteristics, including flatness and roughness.
•The performance of the TIM used between the heatsink and the IHS.
•Surface area of the heatsink.
•Heatsink material and technology.
•Development of airflow entering and within the heatsink area.
•Physical volumetric constraints placed by the system.
•Integrated package/socket stackup height information is provided in the LGA771 Socket Mechanical Design Guide.
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