Numerical modeling of interfacial delamination propagation in a novel peripheral array package

Interfacial delamination, due to the presence of dissimilar material systems, is one of the primary concerns in electronic package designs. The mismatch in the coefficient of thermal expansion between the different layers in the package can generate high interfacial stresses upon heating or cooling of the structure during fabrication, assembly, or in field use. These stresses, if sufficiently large, can compromise the adhesive integrity of the interface. The propagation of the resulting delamination along an interface can degrade or completely destroy the functionality of the system. The focus of this study is to examine the potential for interfacial delamination propagation in current and future versions of a novel peripheral array package. Two-dimensional (2-D) and three-dimensional (3-D) numerical models were constructed of this package with cracks embedded along a critical interface. The energy release rate associated with interfacial fracture was determined by employing the global energy balance and the crack closure technique. The fracture mode mixity was determined using the crack surface displacement method. These critical fracture parameters were compared with experimentally determined interfacial fracture toughness data to determine the possibility of delamination growth. A material parametric study was also completed using the numerical models with pre-existing delaminations to identify material property trends that would lower the potential for failure. Also, the effect of plastic behavior on interfacial crack growth was studied through J-integral calculations.