Fracture mechanics based crack and delamination risk evaluation and RSM/DOE concepts for advanced microelectronics applications

Fatigue and failure of advanced electronic packages and related systems is often caused by their increasing use under harsh environmental conditions - extreme temperatures, in particular. As a result, its thermomechanical reliability becomes more and more one of the most important preconditions for adopting it in industrial applications. Residual stresses from several steps of the manufacturing process, thermal and static and dynamic mechanical loading conditions along with the fact that microelectronic packages are basically compounds of materials with quite different Young's modules and thermal expansion coefficients contribute to interface delamination, chip cracking and fatigue of interconnects. Consequently, numerical investigations by means of nonlinear parameterized FEA, fracture mechanics concepts are frequently used for design optimizations using sensitivity analyses (Auersperg et al., 2001). So, numerical design studies can help to optimize designs of electronics applications at the earlier phase of the product development processes. Unfortunately, this methodology typically accounts for classical stress/strain evaluation or life-time estimations of solder interconnects using modified Coffin-Manson approaches. Delamination or bulk fracture mechanisms usually remain unconsidered. This contribution intends to figure out and discuss ways of using fracture mechanics numerical approaches in connection with parameterized FEA based DOE/RSM. For improving such methods, the evaluation of mixed mode interface delamination phenomena of several ceramics/encapsulant-specimens under bending has been combined with experimental deformation measurements. Measured force vs. deflection curves, deformation fields as results of optical inspection and deformation analysis as well as crack tip vs. deflection curves determined using constitute the input for the delamination modeling by means of FEM. Major goal of the study is to make such a way determined interface toughness parameters applicable within DOE/RSM-approaches.