5.4.2.4 Maximum Allowable PSD Input Level For A Part Vibrated Perpendicular
To Its Body And PWB

If a part is vibrated perpendicular to its body, the maximum allowable PSD
input level is calculated using the following steps. First, calculate the
expected deflection of the PWB and the expected deflection of the thermal
plane and use the smaller of the two values from Equation 5-3.
Use the applicable Section (5.4.2.1
through 5.4.2.3) to
calculate the maximum allowable deflection. Once these values have been
calculated, insert them in Equation 5-10. This determines the maximum
allowable PSD level at which this particular part can be vibrated based on its
material properties.

This is the maximum allowable input PSD level for the part being analyzed
in the z axis.