Thermomechanical responseof materials and interfaces in electronic packaging: Part ii- unified constitutive models, validation, and design

The constitutive modeling approach based on the disturbed state concept (DSC) described in Part I, provides a unified basis for the characterization of thermomechanical response of materials and joints in electronic chip-substrate systems. Using the material constants given in Part I, the DSC model predictions, obtained by integrating the incremental constitutive equations, are shown here to provide satisfactory backpredietions of stress-strain, fatigue, and failure responses of typical solder materials. The DSC also provides a simple criterion based on the critical disturbance to identify cyclic fatigue failure. Model predictions show good correlation with those from previous models. It is also shown how the DSC model can be used for design applications. Overall, based on Papers I and 11, it can be stated that the DSC can provide a new and powerful means to characterize the thermomeehanical behavior of materials and joints in a number of problems in electronic packaging.