Motherboard Deflection Metric Definition; Table 8. Board Deflection Configuration Definitions - Intel Q9450 - Core 2 Quad Quad-Core Processor Design Manual

Simulation shows that the solder joint force (F
deflection measured along the socket diagonal. The matching of F
protect the LGA775 socket solder joint in temperature cycling is equivalent to
matching a target MB deflection.
Therefore, the heatsink preload for LGA775 socket solder joint protection against
fatigue failure can be more generally defined as the load required to create a target
board downward deflection throughout the life of the product
This board deflection metric provides guidance for mechanical designs that differ from
the reference design for ATX//µATX form factor.
A.2.2

Motherboard Deflection Metric Definition

Motherboard deflection is measured along either diagonal (refer to Figure 24):
d = dmax – (d1 + d2)/2
d' = dmax – (d'1 + d'2)/2
Configurations in which the deflection is measured are defined in the Table 8.
To measure board deflection, follow industry standard procedures (such as IPC) for
board deflection measurement. Height gauges and possibly dial gauges may also be
used.

Table 8. Board Deflection Configuration Definitions

Configuration
Parameter
d_ref
d_BOL
d_EOL
BOL: Beginning of Life
EOL: End of Life
64
axial
Processor +
Socket load plate
yes
yes
yes
LGA775 Socket Heatsink Loading
) is proportional to the board
required to
axial
Heatsink Parameter Name
no BOL deflection, no
preload
yes BOL deflection with
preload
yes EOL deflection
Thermal and Mechanical Design Guidelines