Design and analysis of solder connections using accelerated approximate procedure with disturbed state concept

Abstract

The accelerated approximate procedure developed and used herein for analysis, design and parametric optimization in electronic packaging is based on the disturbed state concept (DSC) and the hierarchical single surface (HISS) constitutive models. Over the past many years the benefits of the DSC/HISS model, compared to those of available plasticity models, have been demonstrated and validated for a wide range of materials and solder connections. When the DSC/HISS model is implemented in a two-dimensional finite element code, it is well suited for failure analyses of lead/tin solder connections under cyclic thermal and mechanical loading that are typically occur in electronic packages. Unfortunately, an analysis of a single solder connection, for approximately 4000 or more cycles, can require much effort and computer time, which may be too long to be of practical use. The accelerated approximate procedure significantly reduces the effort and the analysis time to approximately 10 to 15 minutes on a Pentium 4, 3.2 GHz personal computer. The main emphasis of this dissertation is the use of the unified DSC model with the finite element procedure to predict the behavior of chip-substrate solder connections. The DSC code is used to validate the performance of a number of packages (144 BPGA, 313 PBGA) tested in the laboratory under thermomechanical loading. Using the accelerated approximate procedure, the effect of the variable thickness solder connection in a plane stress idealization is compared with that of the constant thickness assumption, and a three-dimensional analysis. It shows that the analysis with variable thickness (in plane stress idealization) yields improved results. The accelerated approximate procedure is then used to perform parametric design analyses of a solder connection by varying a number of important factors such as connection size, shape and misalignment. The effects of varying the DSC/HISS parameters on cycle life are also analyzed. The results of this research can be used for design, analysis and failure life prediction of solder connections in electronic packages. The accelerated approximate procedure is considered to yield improved results compared to other available modeling methods.