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Preliminary Information
26633 Rev. 3.03 September 2003
AMD Athlon™ 64 and AMD Opteron™ Processors
Thermal Design Guide
2.6 Thermal Solution Design Considerations
The two thermal reference design solutions shown in Figure 5 on page 20 and Figure 8 on page 23
contain several components that have specific functions. A complete set of drawings is shown in
Appendix A.4 beginning on page 68. Because the µPGA processors have features that are
significantly different from the previous generation of processors, some background is given in the
following sections on the various aspects of the mechanical requirements for the thermal solution.
Also, additional design considerations and requirements are given for improved thermal and
acoustic performance.
2.6.1 Backplate Assembly
The backplate assembly is designed to prevent excessive motherboard warpage in the area near the
processor. Without using a backplate, the warpage could cause serious damage to electrical
connections of the processor socket and integrated circuit packages surrounding the processor.
The reference backplate is made from cold rolled steel and incorporates three stiffening ribs to
meet stiffness requirements. The center rib is partially cut away by a square hole located in the
center of the backplate. This region is for decoupling the capacitors on the backside of the
motherboard. It is important to not cut entirely through the center rib, as that action would
compromise the stiffness of the reference backplate. The size of the square hole differs according
to the type of processor. The AMD Athlon 64 processor version has a 20 mm square hole while
the AMD Opteron processor version has a 26 mm square hole. Using a 26-mm hole on both AMD
Athlon 64 and AMD Opteron processors is being investigated, and the results will be included in
an update of this document.
There are two PEM standoffs used in the plate. The standoffs serve multiple purposes, mainly as
attachment points for the retention frame screws and for aligning the backplate easily and properly
to the motherboard. The retention frame is made to slide over the standoffs and allow the screws to
be installed with a minimum chance of cross threading.
The insulator also serves multiple purposes. The primary function of the insulator is to prevent the
backplate from shorting to the motherboard. Additionally, a pressure-sensitive adhesive in the
insulator keeps the backplate in place against the motherboard during assembly. The insulator is
thick enough to prevent any significant capacitive coupling between the motherboard and
backplate.
2.6.2 Spring Clip
The spring clips used for both thermal reference design solutions were designed to apply 75 lbs of
force to the heatsink. This force is necessary to prevent a large-mass heatsink from lifting off the
package during a shock or vibration-induced event. Any lifting of the heatsink away from the
processor could result in damage to the processor pins, the socket contacts, or the socket solder
ball joints. This spring force is greater than required in previous generations of AMD processors.
Maintaining the spring force is important for the life of the processor and for repeated installations
and upgrades of the processor.
Chapter 2
AMD Athlon™ 64 and AMD Opteron™ Processors Thermal Requirements
25
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