Stress concentrations in electronic packaging

The reliability of ceramic and plastic packages used in microelectronics is compromised by interface (delamination) and homogeneous (bulk) cracking that is initiated during processing and stress testing. These crackling failures have certain characteristics in that they begin at locations of geometric stress concentrations and propagate along typical failure paths. Characterization of these stress concentrations is therefore essential to a good design and for defining material response parameters such as bulk and interfacial fracture toughness. In this paper, applications of a general-purpose finite element technique for the characterization of stress concentrations are presented. The technique uses the full two-dimensional elasticity solution for different materials that are bonded together. It is possible to use this technique to extract relevant material parameters, such as stress intensity factors, the J-integral, or energy release rate, and hence to eventually define the conditions necessary for crack initiation and propagation.