High-performance electrodeposited copper wicks for heat-spreading vapor chambers

Abstract

A capillary wick structure is a key component for producing the capillary pressure that drives two-phase circulation in phase-change heat transfer devices such as heat pipes and vapor chambers. This study examines the capillary performance of a porous Cu wick structure fabricated using a new electrodeposition process. This Cu wick exhibits large channels generated by hydrogen bubbles and small pores in the dendritic Cu deposits resulting from high-current electrodeposition. The capillary wick performance can be effectively enhanced by adjusting the morphology of the dendritic Cu deposits. Dendritic Cu wicks with different porous features are prepared using different electrodeposition current densities and Cu sulfate concentrations in the electrolyte. A capillary rate-of-rise method is used to assess the liquid permeability (K), effective pore radius (Reff), and capillary performance (K/Reff) of dendritic Cu wicks with deionized wateras the working fluid. The Cu wick is then thermally treated at 700 °C in ambient N2 for 90 min to improve its structural integrity. Despite partial welding occurring between the fine Cu dendrites, the Cu wick shows a superior K/Reff of 1.5 ± 0.06 μm and excellent structural stability. The high capillary performance can enhance the mass transport rate and effective transport distance of the working liquid in vapor chambers for high-density and large-area heat dissipation applications. A vapor chamber integrated with an electrodeposited Cu wick demonstrates excellent heat-spreading characteristics, with a vapor thermal conductivity of up to 6500 W/m⋅K.