Tailoring Substrate Topography to Enhance Wicking Performance of Electrodeposited Cu Porous Films

Abstract

Porous metallic films have received emerging interests in the fields of catalysts, fuel cells, lithium batteries, and phase-change heat transfer devices. Substrate topography is known to have a strong impact on adhesion and morphology of porous coating layers prepared by electrodeposition. In this study, we have tailored the topography of a Cu substrate by wet etching in a sodium persulfate/sulfuric acid (SPS) solution prior to electrodeposition of porous Cu films. An analytic approach is proposed to quantitatively analyze nucleation and growth of dendritic Cu deposits on the SPS-treated Cu substrates. Such a dendritic porous Cu film can serve as a capillary wick to complete recirculation of condensed liquid in the phase-change heat transfer devices. The maximum heat transfer rate of a heat pipe or vapor chamber indeed is proportional to the capillary performance (K/Reff ) of the wick structure, where K and Reff stand for liquid permeability and effective pore radius of the wick, respectively. A large K/Reff value of 0.975 µm has been attained for the electrodeposited dendritic Cu film on a Cu substrate with an optimal SPS etching treatment. The influence of dendritic deposits on the wicking performance of the electrodeposited Cu film is investigated. Figure 1