The amount of force needed to provide adequate pressure needs to be evaluated in terms of board reliability, particularly for larger devices where more force needs to be delivered and is spaced across greater distance potentially causing board deflection. In some cases, it can require additional board bracing or provision of a heatsink backing plate or brace to ensure the reliability of the Xilinx device and neighboring components is not compromised. This should be considered early because such bracing often requires board keep out areas, as well as modification of component placement like decoupling capacitors or memory components. The following figure is an example board back brace to be used to better distribute the force to a larger board area to prevent board deflection.
Figure 1. Example Board Back Brace