Influence of open area ratio on microstructure shape in Cu–Ni alloy electrodeposition

Abstract

This research experimentally analyzed the influence of the open area ratio (OAR) on the formation and growth of the microstructure in Cu–Ni alloy electrodeposition. The OAR was controlled by changing the pitch of circular patterns with a diameter of 20 µm. For an OAR higher than 20 %, the electrodeposited structures grew vertically in pillar-like formations. As the OAR was decreased from 100 to 20 %, the density, height, and width of the structures increased. In addition, in this OAR range, the structures formed along the edge area of the circular patterns. In contrast, for an OAR lower than 10 %, dendrite structures were generated. The electrodeposited structures were coated with a hydrophobic plasma-polymerized fluorocarbon (PPFC) layer. In the electrodeposited sample without circular patterns (OAR = 100 %) with an OAR smaller than 1.25 %, the measured contact angles were almost the same as the contact angle (107°) measured from the flat surface without electrodeposition. In contrast, the samples with an OAR range of 2.5–50 % were modified to be superhydrophobic, and they demonstrated an excellent self-cleaning ability.