Figure 5-4. Tombstone Type Parts

The part is not treated like other parts that have forces applied
perpendicular to the PWB, because the stresses are not related to PWB bending.
The first step in calculating the stresses on these parts is to determine the
motion that they will experience.

Due to its odd shape, calculations must determine the position of the part
in the X and Z axes during its oscillations. Those values will be designated
as X_{T} and Z_{T}, (See Equations 5-1l and 5-12
respectively). Because this is not a purely liner motion, a factor for
Z_{T2} must be calculated using Equation 5-13. The parameters for
these calculations are the weight of the part in pounds (W), the height from
the PWB to the lead bend in inches (l_{2}) the length from the lead
bend to the part edge in inches (l_{1}), the length from the edge of
the part to its center of gravity in inches (a), the moment of inertia (I) for
the part, and (d) the diameter of the lead.