This paper compares the application of different constitutive material and fatigue models for lead-free (SnAg4.0CuO.5) solder proposed by Schubert, Wiese, Dudek and Syed. The application of these models is demonstrated and results are compared with the experimental findings for different type of Ball Grid Array packages, which are subjected to a controlled temperature cycling condition. In addition, a semi-empirical approach was used to fit the finite element modeling results with experimental temperature cycling test data for 2nd level solder joint fatigue failures.

We report a case study for the optimization of a flip chip based stacked die array test package. We demonstrate the importance of package substrate design and substrate thickness on the processibility and package warpage control. We found that for thin substrates copper balancing of the top and bottom die is crucial. We show the impact of flip chip die thickness and substrate thickness on the die attach of the top die(s) in the stack. Investigations on different top die attach alternatives show that tape die attach can have advantages. We demonstrate the importance of the vertical stack structure (i.e. flip chip thickness) and material selection (i.e. mold compound) on the overall warpage control of the package. The results show that even small changes in the package structure can have large impact on the warpage characteristics of the stacked die package.