Two-Electrode Growth and Optimization of Copper Nanocone Structures for Immersion Phase-Change Liquid Cooling

Utilizing superwettability micro/nanostructures to enhance immersion phase-change liquid cooling (IPCLC) performance of metal heat sinks has attracted great interest due to its academic and commercial values. Here, we demonstrate IPCLC performance maximization of copper nanocone array structures via two-electrode growth technique optimization. Through regulating current density, reaction temperature, pH, concentration of electrolytes involving copper sulfate, poly(ethylene glycol), nickel sulfate, sodium hypophosphite, boric acid, and trisodium citrate, and reaction time, we realize the optimization of growth conditions and IPCLC performance of copper nanocone structure. As compared to the flat copper surface, the optimal copper nanocone structure can exhibit maximally 13.4 °C decrease in the surface temperature of the simulated chip heat source. We found that each variable has proper values for creating the optimal IPCLC surface. Among others, the reaction time is the most sensitive variable that can affect the IPCLC performance. Besides, in each group of orthogonal experiments, the IPCLC performance optimization of nanocones has no rules with the variation of their density, bottom radius, and height but is positively associated with their total surface area. The larger the surface area, the better the performance. Based on energy disperse spectroscopy, X-ray diffraction, and transmission electron microscope characterizations, the optimal nanocones are demonstrated to be polycrystalline, consisting of face-centered cubic copper-doped with a tiny amount (3.7 wt %) of nickel. This work establishes a mass-producible two-electrode growth recipe for low-cost and large-area fabrication of copper nanocones, which helps develop high-performance IPCLC devices for chip cooling as well as explore more technological applications.