Generalized fracture mechanical integral concept JG and its application in microelectronic packaging technology

Abstract

The fracture mechanical J G integral is theoretically generalized for the calculation of the energy release rate during fatigue crack propagation in inelastic solids, which may include material interfaces. An advanced program is developed to calculate the J G integral by a FEM-tool. Some measurement set-ups are manufactured to measure fatigue crack growth of eutectic Sn63Pb37 solder material, as an investigated example. A thermo-mechanical FE-analysis of the measurement set-ups and calculation of the J G integral deliver the dependence of fatigue crack growth on the mean value of the J G integral. The application of the integral concept in microelectronic packaging technology is demonstrated in the FE-analysis of a ball grid array (BGA) packaging, which is loaded by thermal cycling. The outermost balls at the corners, which offer the highest stresses, are simulated, where a tiny crack is set in a zone that contains the highest stress. The possibility and speed of propagation of this crack can be estimated by calculation of the advanced J G integral.