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Chapter 5 Thermal Design of Custom 2U-4P Systems 35
Thermal Design Guide for Socket F (1207) Processors
32800 Rev. 3.02 August 2006
on flow simulations of an AMD reference 2U system, the flow-through of the heat sink is
approximately 18 CFM. Figure 11 shows that this flow rate corresponds to a case-to-ambient thermal
resistance of 0.22°C/W. This case-to-ambient thermal resistance exceeds requirements (see Table 7
on page 30).
Figure 11. Thermal Performance Chart of Heat Sink When Used with a Dual-Core Processor
in 90 nm Process
5.3.5 Fans
AMD has conducted simulations of the heat sink described in Section 5.3.4 on page 33 with two 60
mm x 60 mm x 38 mm fans (Delta Part number FFB0812EHE-HS2) in series, that is, back to back.
The fans have a maximum flow rate of 80.2 CFM and a maximum pressure drop of 0.8 inches of
water. The heat sinks are ducted so the flow from the two fans enters the processor heat sinks with
some bypass. The bypass is designed to cool the core VRM.
5.3.6 Thermal Interface Material
The heat sink makes contact with the top surface of the processor package utilizing the thermal
interface material between the processor lid and the heat sink. AMD recommends using a high
performance grease such as Shin-Etsu 7783D or Dow Corning TC-5022. AMD does not recommend
using phase change materials between the heat sink and the processor. Phase-change materials
develop high adhesion forces between the heat sink and processor when the material is in the solid
phase. This strong adhesive force may cause the processor to stick to the heat sink, making heat sink
removal difficult and damaging the socket solder balls.