For high temperature interconnection sintered silver can be used, however, it induces new demands on the thermo-mechanical design. That issue requires knowledge on the thermo-mechanical reliability of silver sintered devices, the subject of this paper. Material characteristics of the sinter layers are needed for simulation, which are addressed in the first part of the paper. Based on material properties of pure silver, for sintered silver with different porosities effective material characteristics have been derived by use of a micromechanical cell model. Shear loadings with in-situ deformation analyses have also been made to investigate sintered silver behavior. A complicated dependence on processing, temperature, and deformation rate is seen. Based on different effective constitutive models for the sintered interconnects, stress loadings are studied for a power module, an IGBT on DCB substrate, for passive and active thermal cycling. For the passive cycle complex interactions of the different layers of the stack are observed, which are not seen in a module with soft solder bonding. This result can be attributed to the missing decoupling by the soft soldering layer. Failure risks are evaluated by both conventional FEA and cohesive zone modeling. A quite different stress situation is depicted for active power cycling. The situation is even more complex and it is obvious from the simulations, that active power cycling can induce failure modes different from passive cycling

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Simple adhesion tests like the pull-out test or the button shear tests have been used in industry for decades. They offer a great potential for comparison of different molding compounds, encapsulants, or adhesives on different types of sub-strates with or without surface treatment. However, for theoretical prediction purposes, interface fracture mechanics parameters are needed. Quantitative evaluations of the test applied to molding compound (MC)-button on Cu-leadframe by different fracture- and damage mechanical approaches are the subjects of the paper. Defect tolerant methodologies like the "virtual crack closure technique" (VCCT), which consider the interface initially delaminated, are compared to the damage methodology "cohesive zone modelling (CZM)", which needs no initial crack and can track the delamination progress. Calculated fracture parameters, in particular the energy release rates and mode mixity are compared. Effects on these parameters are discussed for d ifferent button shapes. In-situ tracking of delamination progress for a cubic button is shown using the optical correlation technique microDAC

The liquid crystal display (LCD) technology is confronted with the task to substitute rigid glass plates enclosing the electro-optically active liquid crystal (LC) material by plastic substrates. In particular, the commercialization of flexible displays requires a sufficient stabilization against external mechanical distortions. To achieve LC layer stabilization, several procedures have been suggested. In this work, the thermal-induced phase separation (TIPS) technique has been applied to generate composite films consisting of LC compartments which are encased by coherent polymer walls after binodal phase separation. Composite films were prepared from a series of poly(methacrylates) and various commercial nematic LC mixtures. Furthermore, the use of copolymers as well as binary blends from ''hard'' and ''soft'' poly(methacrylates) broadens the possibilities to control the film morphology. To compare different polymer/LC composite films regarding their stability under compression load, the samples were investigated by indentation tests using an inverse reflected-light microscope combined with a digital image acquisition technique. The deformation of the composite layers was evaluated by the uniDAC image analysis which relies on the more general method of Digital Image Correlation (DIC). Some of the fabricated composites show a remarkably high indentation resistance, especially such prepared from poly(1-tetralyl methacrylate) and poly(4-tert-butylcyclohexyl methacrylate). The results facilitate the selection of suitable composite systems for the fabrication of mechanically stabilized flexible LC displays.