Effect of electrodeposition conditions on replication accuracy of electroforming

摘要

Electroforming is an accurate replication technique which provides an inverse shape of a master. In this study, the electrodeposition process using nickel sulfamate solution under room temperature condition, which is usually conducted at 40°C to 60°C, is developed to achieve nanometer-level accurate figure replication. Under ideal electrodeposition conditions, both maintaining the electrolyte composition and eliminating non-uniform deformation caused by the internal stress in the nickel layer have to be realized. First, anodic conditions were investigated by potentiostatic analysis while changing the anodic material. Just as well as conventional processes, a sulfur containing nickel anode dissolved without passivation at room temperature. Second, internal stress in the electrodeposited layer was measured to optimize cathodic conditions. The stress was monitored by a Shack-Hartmann wave-front sensor through measuring the curvature of a test plate in the electrolyte directly. Effects of agitation on replication performance were also examined. Replication experiment was conducted under the influence of solution agitation and the figure accuracy was compared to that obtained under a static condition. Finally, applying the optimized conditions, an advanced replication experiment was conducted. An ellipsoidal-shaped mandrel with figure accuracy of less than 100 nm (PV) in both circumferential and longitudinal direction was used as a master. The replicated figure was measured using a roundness measuring instrument and a wave-front measuring method. The results showed the replication accuracy of 100 nm order in the area of several square centimetres.