RF thermal plasma treatment for size reduction and spheroidization of glass powders used in ceramic electronic devices

Abstract

Summary form only given. Very fine spherical glass powders are key ingredients in the sintering or package processes to achieve high performance of ceramic electronic devices, such as MLCC (multi layer ceramic capacitor), LTCC (low temperature co-fired ceramics) and PDP (plasma display panel). To provide much finer glass powders with nano-sized spherical shape, a RF (radio-frequency) thermal plasma is employed in our work as a clean heat source for a size-reducing and spheroidizing process of coarse glass powders. As reported earlier by other researchers, very hot flame from thermal plasma generators can easily evaporate refractive materials, and then reduce their size by condensing the droplets rapidly. In our thermal plasma treatment, SEM images and particle size analyzer indicate that most of coarse glass powders with average diameter of 2 mm are reformed into spherical ones with the size of below 300 nm by a high powered 4 MHz RF plasma of 20 kW. The compositions of glass powders before and after the plasma treatment are also compared by an ICP analysis, and they show negligible changes of less than 2% during the RF thermal plasma process, which demonstrates a successful preparation of nano-sized glass powders for the advanced ceramic electronic applications. Further experiments with different operating values of RF power, size of precursor and powder feed rate, are made and operating variable effects on the glass powder characteristics are discussed