Pool boiling heat transfer performance analysis of DI water on copper chips coated with nano thin layered zinc oxides

Boiling is an efficient heat transfer process that enables significant heat transfer at low driving temperatures. A key indicator of reduced boiling efficiency is the adhesion of nano-thin-film-coated interfaces to the base substrate. However, the mechanics underlying boiling on nano-thin-film surfaces remain insufficiently understood. This study presents an effective spin-coating and annealing method for fabricating zinc oxide (ZnO) nano-thin-film layers on bare copper substrates. ZnO, a conductive material with high surface energy, is commonly used in thin-film conductors. The fabricated substrates are evaluated through pool boiling experiments to determine their heat transfer performance. Before testing, surface characteristics, including roughness, porosity, pore diameter, contact angle, and coating thickness, are assessed. The ZnO coating layer with a thickness of 423 nm is engineered to enhance surface performance. Owing to the robust adhesion among the metal substrate and the ZnO nano film, the 423 nm coated surface demonstrates superior boiling behavior. All fabricated surfaces exhibit increased heat transfer coefficient (HTC) and critical heat flux (CHF) compared to bare copper. Notably, the ZnO-TF-423 surface achieves a 112.5% improvement in CHF and a 310% enhancement in HTC relative to the uncoated (bare) surface. The enhanced surface properties of the fabricated ZnO thin film suggest its potential application in microelectronics cooling devices.