Parameterized FE-modeling and interfacial fracture toughness investigations towards reliability enhancements of advanced plastic packages

Damage, fatigue and failure of electronic packages for MEMS and related systems are often caused by their use under harsh environmental conditions as well as extreme temperatures. Consequently, their thermomechanical reliability increasingly becomes one of the most important preconditions for adoption in industrial applications. Various kinds of inhomogeneity, residual stresses from several of the manufacturing process steps along with the fact that microelectronic packages are basically compounds of materials with quite different Young's moduli and thermal expansion coefficients contribute to interface delamination, chip cracking and fatigue of solder interconnects. Subsequently, numerical investigations by nonlinear FEA and fracture mechanics concepts are frequently used for design optimizations using sensitivity analyses. Parameters used for such sensitivity analyses are typically materials parameters, geometrical and physical boundary conditions, but in particular, the influence of geometrical design parameters on the thermo-mechanical reliability is increasingly required. This paper demonstrates and discusses the advantages of using fully parameterized finite element modeling techniques for design optimization on the basis of damage evaluation and fracture mechanics approaches. To improve that method, the evaluation of mixed mode interface delamination phenomena (J. Auersperg et al, Proc. TMS Solder Joint Symp., pp. S439-445, 1997) and thermal fatigue of solder joints (J. Auersperg et al, Proc. IEMT/IMC Symp., pp. 290-295, 1998; J. Auersperg et al, Proc. Poly '99, EEP-vol. 27, pp. 19-25, 1999) were combined with experimental investigations using a gray scale correlation method. Some results for different meshing techniques and rules clarify their influence on FEA results. The combination of numerical and experimental investigations give a reliable basis for understanding and evaluating failure mechanisms arising for the thermo- mechanical reliability of microcomponents.