Microelectronic packages can be considered as composite structures fabricated from highly dissimilar materials. Interface delamination related failure often occurs when the packaged devices are subjected to thermo-mechanical loading. The analysis of delamination of a laminate structure with a crack along the interface is central to the characterization of interfacial toughness. Due to the mismatch in thermal mechanical properties of the materials adjacent to the interface and also possible asymmetry of loading and geometry, usually the crack propagates under mixed mode conditions. In this paper, the interface toughness of epoxy molding compound - copper interface in IC packages is characterized. The test specimen is directly obtained from a production process line. A small-size multi-functional mixed mode bending (MMB) tool was designed and fabricated. For measurements under various temperatures and moisture conditions, a special climate chamber is designed. The ¿current crack length¿ is required for the interpretation of measurement results through FEM-fracture mechanics simulations. Therefore, during testing the ¿current crack length¿ is captured using a CCD camera. The critical fracture properties are obtained by interpreting the experimental results through finite element modeling. As input parameters, the material properties are both experimentally and numerically characterized as functions of temperature and moisture. In order to get more accurate interfacial toughness, the influence of residual stresses in the sample is considered.@en

We proposed a molecular modeling methodology to study the protonic acid doping of emeraldine base polyaniline which can be used in gas detection. The commerical forcefield COMPASS was used for the polymer and protonic acid molecules. The molecular model, which is capable of representing the polyaniline doping with the aqueous hydrochloric acid, was built by Monte Carlo method. The initial entire systems were equilibrated using a new protocol, which aims at creating a final structure with realistic density and low-potential energy characteristics. The doping process is modeled by a combined molecular mechanics and molecular dynamics simulation technique. The radial distribution functions of doped emeraldine salt and the relationships including pKa/pH and doping percentage/pH, were computed and compared with the experimental data. This method contributes a novel molecular modeling approach to select and evaluate the conducting polymers in chemical sensor applications.@en

Delamination between copper and epoxy molding compound (EMC) is one of the common failure modes in packages due to relatively weak adhesion at the interface. Delamination is difficult to predict because a package is often with a complex structure design constructed with different materials and under combined normal and shear loading. Development of cohesive zone elements applied in FEM has emerged into the application of cohesive zones as an effective tool for crack propagation simulation. In this study, a methodology to obtain useful parameters for cohesive zone modeling from experimental measurements is proposed. The approach is demonstrated with the adhesive joint between epoxy molding compound and copper that was under residual stresses and applied mixed-mode loading. The proposed approach to determine the traction-separation function does not rely on the uncertainties of crack tip stresses. The predicted load-displacement result is matched with experimental measurement results at the crack propagation region. Package delamination can be predicted by implementing the proposed testing and modeling scheme within the cohesive zone model.@en