There are different shape factor methods that you can use for an Underfill Encapsulation analysis, depending on whether the region is modeled away from the solders or near the solders in the model.
Using shape factors
To model the region away from the solders, use a shape factor of 1. To model the region near the solders, you can calculate a shape factor by using the following equation:
Shape factor = (actual area of solid wall in thickness or planar direction) / (area of solid wall used in the simulation)
For example, consider the following case shown below, where one cell is taken around a solder from the array of solders to consider the surface area around that solder:
There are three areas related to this cell:
-
-area around the solder in the upper region (not including the solder region). -
-area around the solder in the lower region (not including the solder region). -
-surface area of the solder.
For this case, the shape factor is = 
If the length of the cell (assuming square cell) is 
and the diameter of the solder is 
and the cavity thickness (which is the same as the solder height) is 
, then:
