On-Chip Two-Phase Cooling With Refrigerant 85 $\mu{\rm m}$ -Wide Multi-Microchannel Evaporator Under Hot-Spot Conditions

Hot-spots are present in micro-electronics and are challenging to cool effectively. This paper presents highly nonuniform heat flux measurements obtained for a pseudo-CPU with 35 local heaters and temperature sensors cooled by a silicon multi-microchannel evaporator with 85 μm wide and 560 μm high channels separated by 46 μm wide fins. A low pressure dielectric refrigerant, R245fa, was used as evaporating test fluid. The base heat flux was varied from 6 to 160 W/cm² and the junction temperature always remained below 65^°C, while the fluid inlet saturation temperature was 30.5^°C. On-chip two-phase cooling was found to very effectively cool the hot-spots without inducing flow instabilities. Building on analogous uniform heat flux tests made on the same test section, the effects of position, orientation size, and strength of the hot-spots were analyzed.