Water-Based Microchannel and Galinstan-Based Minichannel Cooling Beyond 1 kW/cm $^{2}$ Heat Flux

Microchannel heat sinks are a relevant thermal management technology because the combination of surface area enhancement and small length scales results in low wall-to-bulk temperature differences. Previously, a thermal resistance of 0.09 °C/W was achieved when a heat flux of 790 W/cm $^{2}$ was imposed on a 1 cm $\times 1$ cm footprint portion of a 400- $\mu \text{m}$ -thick Si substrate utilizing single-phase water-based microchannel cooling and a 214 kPa pressure difference to drive the flow. Galinstan, a gallium, indium, and tin eutectic, may be utilized for single-phase liquid metal cooling of microelectronics due to its subambient melting temperature and high thermal conductivity. This paper describes the fabrication and assembly of water-based microchannel and Galinstan-based minichannel heat sinks and the flow sheets utilized to characterize them under the aforementioned constraints. The prefix mini rather than micro is used to describe Galinstan-based heat sinks because optimal channel widths are hundreds as opposed to tens of micrometers. The aforementioned thermal resistance of 0.09 °C was experimentally reproduced. Unprecedentedly low thermal resistance and high heat flux in single-phase water-based microchannel cooling, i.e., 0.071 °C/W and 1003 W/cm $^{2}$ , respectively, were achieved. The first experimental data on Galinstan-based minichannel heat sinks are also reported. A thermal resistance as low as 0.077 °C/W was achieved at a heat flux of 1214 W/cm $^{2}$ and a maximum heat flux of 1504 W/cm $^{2}$ was reached.