| Objectives | Background | Approach |
This project will provide software models for the rapid
assessment of solder joint failures in components where the
leaded length of the component is much larger than the other
dimension, e.g. surface mount connectors.
Existing thermo-mechanical fatigue solder joint design models have been developed for components and component styles with a nearly square outline. The dominant parameter in most of these models is the distance to the neutral point, DNP, or centroid of the component. When components dramatically differ from the nearly square shape, such as with surface mount connectors, these models do not accurately predict failures. The basic difficulty is the distance to the neutral point is now much larger. Not only is it larger, but the basic deformation motion imparted onto the critical solder joint is more of a torsional motion than a pure shear. For these types of components, a new solder joint model needs to be developed.
The approach for surface mount connectors will be similar to that taken previously with BGA's and CSP's. First several typical component packages will be selected from manufacturer catalogs that will represent the variations in geometry and material make-up. Available experimental thermal cycling data will be carefully searched for and studied. Finite element models of representative connectors will be developed, analyzed. The results of the available experimental data and the FEM thermal cycling simulations will be compared to proposed models. If necessary, model calibration factors will be developed. These calibration factors will be added to the failure model implementation with the appropriate documentation. As part of the documentation a detailed bibliography will be created on all published papers related to connector solder joint failure.