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5.6
Preload and TMA Stiffness
5.6.1
Structural Design Strategy
Structural design strategy for the Intel Type II TMA is to minimize upward board
deflection during shock to help protect the LGA775 socket.
BTX thermal solutions use the SRM and TMA that together resists local board
curvature under the socket and minimize, board deflection (Figure 5-5). In addition, a
moderate preload provides initial downward deflection.
Figure 5-5. Upward Board Deflection During Shock
5.6.2
TMA Preload verse Stiffness
The Thermal Module assembly is required to provide a static preload to ensure
protection against fatigue failure of socket solder joint. The allowable preload range
for BTX platforms is provided in Table 5–4, but the specific target value is a function
of the Thermal Module effective stiffness.
The solution space for the Thermal Module effective stiffness and applied preload
combinations is shown by the shaded region of Figure 5-6. This solution space shows
that the Thermal Module assembly must have an effective stiffness that is sufficiently
large such that the minimum preload determined from the relationship requirement in
Figure 5-6 does not exceed the maximum allowed preload shown in Table 5–4.
Furthermore, if the Thermal Module effective stiffness is so large that the minimum
preload determined from Figure 5-6 is below the minimum required value given in
50
Balanced Technology Extended (BTX) Thermal/Mechanical Design Information
Less curvature in region
Shock Load
between SRM and TMA
Thermal and Mechanical Design Guidelines
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