Three-dimensional real-space images of the carbon fiber (CF)/polymer composites were obtained by a high-contrast X-ray computerized tomography (CT). Since both CF and polymers do not include heavy atoms, CF has not been supposed to be suitable to X-ray CT observation. In this study, we used the X-ray CT apparatus which is designed to enhance the contrast of the materials consisting only of lightweight atoms. Besides the usage of the appropriate apparatus, the experimental conditions were found to be important : cutting the sample into a thin rod, and obtaining sufficient number of projections. In our case, we used 1mm × 1mm × 4mm sample, and 720 projections with 0.25 degree intervals in order to obtain the 3μm voxel resolution in the reconstructed three-dimensional images. Eventually, each CF in polystyrene was clearly visualized in three dimensions.
In this study, the peeling process of UV-curable pressure sensitive adhesive tape from bump wafer is investigated through the use of finite element analysis, observation of high speed video, and actual wafer back-grinding process testing. In our experiment, a large deformation of adhesive is observed at the edge of bottom of bump, appearing on the side of the bump opposite tape-peeling direction when observed with high speed microscope video. The largely deformed adhesive creates a string shaped elongation. The adhesive residue is caused by the fracture of the adhesive string. We investigated how to generate the adhesive string in the tape-peeling process through the use of finite element analysis. In this analysis, a cohesive element is introduced into the adhesive layer. The analytical result shows the adhesive string at the same position of experiment and the stress distribution is different between the string part and the other area of adhesive. The influence of peeling angle and bump size is also investigated by the same finite element model. As a result, higher peeling angle and smaller bump sizes shows a shorter adhesive string, which lowers the risk of adhesive residue.
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