THERMOMECHANICAL RESPONSE OF MATERIALS AND INTERFACES IN ELECTRONIC PACKAGING - PART-I - UNIFIED CONSTITUTIVE MODEL AND CALIBRATION

The disturbed state concept (DSC) presented here provides a unified an d versatile methodology for constitutive modeling of thermomechanical response of materials and interfaces/joints in electronic chip-substra te systems. It allows for inclusion of such important features as elas tic, plastic and creep strains, microcracking and degradation, strengt hening, and fatigue failure. It provides the flexibility to adopt diff erent hierarchical versions in the range of simple (e.g., elastic) to sophisticated (thermoviscoplastic with microcracking and damage), depe nding on the user's specific need. This paper presents the basic theor y and procedures for finding parameters in the model based on laborato ry test data and their values for typical solder materials. Validation of the models with respect to laboratory test behavior and different criteria for the identification of cyclic fatigue and failure, includi ng a new criterion based on the DSC and design applications, are prese nted in the compendium paper (Part II, Desai et al., 1997). Based on t hese results, the DSC shows excellent potential for unified characteri zation of the stress-strain-strength and failure behavior of engineeri ng materials in electronic packaging problems.