QFN solder joint reliability simulation (ANSYS)

[mclee]

Hi, I am currently working on solder joint reliability simulation for QFN packages using ANSYS. Yet, after countless attempts, I still couldn't get the correct results in which the stress and strain energy density should be located at the corner solder joint. What I've got is the stress located on the lead frame instead of the solder joint (Figure 1 and 2), and the strain energy density located on the central solder (Figure 3).

Figure 1

Figure 2

Figure 3

Does anyone knows how to solve this problem? Or does anyone knows the correct way to conduct the simulation? Your help is very much appreciated.