Optimization of gas atomization processes in production of ultra-fine solder powder

Taguchi experiment is utilized to optimize the production of metal powder in the atomization processes. We aim at the development of the atomizer with low cost and high atomization efficiency. The atomizer is designed with internal impingement to enhance the atomization performance. The production of the extra-fine metal powder is optimized using the L₁₈(2 ¹×3⁷) scheme of Taguchi method. This scheme is designed as eight factors including the design parameters and the operational parameters. The droplet size of the metallic spray is measured by Malvern Spraytec and the data are calculated by averaging the results of three test runs. The goal is to produce the metal powder with particle size less than 15μm. Optimization analysis shows that the control parameters are atomization gas, melt inlet diameter, nozzle outlet orifice, melt injection pressure and materials among the eight factors. Results of the eighteen experiments show that the mean quality is 32.86 with standard deviation 2.67 and S/N ratio 29.7. Confirmation test with the optimized conditions indicates that the accumulative volume of the powder within 0∼15μm as high as 56.9% is achieved. The micrographs of the solder powders are quite uniform and are all spherical.