Enhancing Precision in Fabricating Micro Monolithic Tungsten Ball Tips Using Magnetic Field-Assisted Arc Discharge

Abstract Micro monolithic tungsten ball tips are widely used for precision measurements related to high-aspect-ratio microdevices, where submicron accuracy is increasingly required. However, conventional fabrication methods do not effectively meet these precision requirements. This study presents a magnetic field-assisted arc discharge technique to achieve enhanced precision in the fabrication of tungsten styli. By introducing a uniform axial magnetic field generated by a Helmholtz coil, the technique suppresses the asymmetric electromagnetic force that induces center offset and simultaneously enhances the roundness and surface finish. A mathematical model was developed to describe the relationship between eccentricity and electromagnetic force, and was verified through experiments. Under the optimized magnetic field of 25 mT, the roundness error, center offset, and surface roughness were reduced by 43%, 53%, and 51.6%, respectively, achieving submicron precisions of 0.86 μm, 0.70 μm, and R a 1.05 μm, respectively. These results confirm the effectiveness of magnetic field assistance in improving the morphological uniformity and providing a promising route for the high-precision fabrication of tungsten microprobes.