Evaporative intrachip hotspot cooling with a hierarchical manifold microchannel heat sink array

A hierarchical manifold microchannel heat sink is used to dissipate heat from a small hotspot region superposed on a larger region of uniform background heat flux. A 5 mm × 5 mm overall chip footprint area is cooled using a 3 × 3 array of intrachip silicon microchannel heat sinks fed in parallel using a manifold distributor. Each heat sink consists of a bank of 25 high-aspect-ratio microchannels that are nominally 30 μm wide and 300 μm deep. The uniform background heat flux is generated with a 3 × 3 array of thin-film heaters fabricated on the chip; temperature sensors placed in each of these nine heating zones provide spatially resolved chip surface temperature measurements. An individually powered 200 μm × 200 μm hotspot heater is centered on the chip. The heat sink thermal and hydraulic performance is evaluated using HFE-7100 as the working fluid and for mass fluxes ranging from 600 kg/m ² s to 2070 kg/m ² s at a constant inlet temperature of 60°C and outlet pressure of 122 kPa. Background heat fluxes up to 450 W/cm ² and hotspot fluxes of greater than 2500 W/cm ² are simultaneously dissipated. The chip temperature uniformity and maximum temperature rise during hotspot heating are assessed. For the case with the highest simultaneous background and hotspot heat fluxes, the measured heat sink pressure drop is ~75 kPa and the average chip temperature is ~30°C above the fluid inlet temperature.