Study on carbon fiber surface treatment based on surface oxidation method
Surface conditions of carbon fibers severely effect on the bonding strength between the fibers and the matrix, even on the mechanical properties of the composites when carbon fibers were used as reinforcement on the preparation of ceramic matrix composites. Surface treatment of carbon fibers was carried out based on the air oxidation method and the liquid oxidation method with concentrated nitric acid (68%) as the oxidizing solution. It could remove impurities from the surface of carbon fibers and increase the degree of the surface concavoconvex, so the active surface area were increased and then improved the bonding strength between fibers and matrix. The surface topographies of carbon fibers after surface oxidation were characterized by SEM. The results illustrate that, impurities on the surface of carbon fibers are decreased and there are many longitudinal grooves evenly distributed on the surface in favor of increasing the bonding strength between the fibers and matrix.
An investigation into the surface heterogeneity of nitric acid oxidized carbon fiber
Abstract The carbon fiber surface plays a critical role in the performance of carbon fiber composite materials and, thus it is important to have a thorough understanding of the fiber surface. A series of nitric acid treated intermediate modulus carbon fibers with increasing treatment level was prepared and characterized using a range of surface sensitive techniques including Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. The results, which were found to be consistent with increasing treatment levels, were compared to the literature. Raman spectral mapping has been used to investigate the heterogeneity of the carbon fiber surface after nitric acid oxidation. The mapping enabled the effects of surface treatment on carbon fiber to be investigated at a spatial resolution unattainable by XPS and provided chemical structure information not provided by SEM or AFM. The highest level of treatment resulted in the most heterogeneous surface. Raman mapping, while time consuming, can provide valuable information which can lead to an enhanced understanding of the heterogeneity of the carbon fiber surface.
Chip scale packaging using chip-on-flex technology
An increasing number of electronic designers, fabricators and users see Chip Scale Packaging (CSP) as a way to obtain the benefits foreseen in multichip packaging and Chip-on-Board (COB) without the problems and limitations currently associated with each. The Chip-on-Flex (COF) multichip packaging technology has been demonstrated to be applicable to single chip packages that meet chip scale packaging goals. This paper looks at the Chip-on-Flex Chip Scale technology and addresses issues including the process, structure, assembly, yields and reliability.