Direction-dependent magnetic control of nickel microelectroforming: Deposition uniformity, residual stress and micropillar mold fabrication

Thickness gradients, residual stress and texture-related changes jointly constrain the dimensional reliability of nickel microelectroforming. This study examined how low-intensity magnetic-field magnitude and direction affect thickness uniformity, surface appearance, X-ray diffraction response and residual stress during nickel microelectroforming. Magnetic flux density, field angle, stirring rate and cycle-averaged current were varied, while an exploratory reduced-domain transport model was used to estimate the direct Lorentz-force-related contribution to near-cathode mass transfer, and a separate six-variable screening step supplied a fabrication trial. The response was non-monotonic: the mean residual-stress magnitude was 217.7 ± 16.6 MPa at 0 mT, increased to 317.0 ± 13.6 MPa at 5 mT, and decreased to 191.6 ± 18.9 MPa at 10 mT. Field rotation redistributed rather than eliminated thickness gradients, with the poorest combined surface, diffraction and stress response occurring at 60°. The tested 400 and 500 rpm conditions revealed a trade-off between residual stress and thickness uniformity at 10 mT and 90°. Integrating magnetic control with pulse-reverse current and auxiliary-cathode control produced a nickel micropillar mold with a nine-region mean-height range of 1.40 μm and a nonuniformity of 14.7%. The integrated route gave a mean pull-off stress of 2.07 ± 0.11 MPa (n = 3); cohesive failure within the adhesive indicates that this value represents a lower bound on the Ni/Cu interfacial load-bearing capacity.