Papers by Author: Un Chung Cho

Abstract: Spherical silicon balls are applied to photovoltaic energy conversion. Silicon balls are produced by droplet spray method as well as abrasive machining of a single crystalline silicon wafer. A reflective mirror is used to maximize the solar cell efficiency. It is demonstrated the solar cell efficiency depends on the crystalline structure of silicon balls and the mirror in the module.

Abstract: V-grooved quartz substrates are manufactured by glass molding press and the pitch errors of the molded quartz fiber array blocks are statistically investigated. The V-grooved carbon molds of 8 and 16 channels and 250 μm in pitch are machined and then quartz substrates are molded on the V-grooved carbon molds by glass molding press. The pitch errors of X, Y and diagonal axis are measured and then statically analyzed. It is demonstrated that the V-grooved quartz fiber array blocks of 8 and 16 channels and 250 μm in pitch can be manufactured by glass molding technology without significant pitch errors.

Abstract: A new dry cleaning methodology named laser shock cleaning and optical inspection technique has been applied not only to remove the particles from the surfaces of image sensors but also to inspect the surfaces automatically before or after the cleaning. In the packaging of CMOS and CCD image sensing modules, the particles generated during the assembly process should be removed from the surfaces of image sensors in order to ensure clear image as well as to enhance the yield. The different kinds of particles were removed from the surfaces by the laser shock cleaning technique which utilizes the airborne shock wave induced by intense laser pulse. For the quantitative evaluation of cleaning performance, number, shape and size of the particles on the surfaces of image sensors were measured by vision inspection technique before and after cleaning. It was found that most particles on the surfaces were successfully removed after the treatment of laser-induced shock waves. The average removal efficiency of the particles was over 95 %. It is interestingly found that the remaining particles after the cleaning are based on organics, which are probably attached during the bonding process.