researchers at purdue university (west lafayette, ind.) have created a novel cooling system for radars and supercomputers that circulates liquid coolant through microchannels and directly onto electronic chip stacks that is capable of dissipating as much as 1,000 watts per square centimeter.
a new electronics-cooling technique relies on microchannels, just a few microns wide, embedded within the chip itself. the device was built at purdue university’s birck nanotechnology center. (purdue university/kevin p. drummond)
according to a report from the university, the research was funded by a grant from the u.s. defense advanced research projects agency (darpa) and the new threshold for dissipating heat is 10 times greater than that of current high-performance computers.
“the system uses a commercial refrigerant called hfe-7100, a dielectric, or electrically insulating fluid, meaning it won’t cause short circuits in the electronics,” the article explained. “as the fluid circulates over the heat source, it boils inside the microchannels.”
boiling exponentially increases the amount of heat is removed by the fluid. also, using this cooling method removes the effect of interfacial thermal resistance found in conventional heat sinks.
the new cooling system uses channels that are only 10-15 microns in width and was designed with short, parallel channels instead of long channels across the entire chip. this channel pattern overcomes the challenge of pumping the fluid across the entire chip stack. the article added, “a special ‘hierarchical’ manifold distributes the flow of coolant through these channels.”
channels were etched in silicon and were 300 microns deep.
the research was published this fall in the international journal of heat and mass transfer. the abstract read:
“high-heat-flux removal is necessary for next-generation microelectronic systems to operate more reliably and efficiently. extremely high heat removal rates are achieved in this work using a hierarchical manifold microchannel heat sink array.
“the microchannels are imbedded directly into the heated substrate to reduce the parasitic thermal resistances due to contact and conduction resistances. discretizing the chip footprint area into multiple smaller heat sink elements with high-aspect-ratio microchannels ensures shortened effective fluid flow lengths.
“phase change of high fluid mass fluxes can thus be accommodated in micron-scale channels while keeping pressure drops low compared to traditional, microchannel heat sinks. a thermal test vehicle, with all flow distribution components heterogeneously integrated, is fabricated to demonstrate this enhanced thermal and hydraulic performance.
“the 5 mm × 5 mm silicon chip area, with resistive heaters and local temperature sensors fabricated directly on the opposite face, is cooled by a 3 × 3 array of microchannel heat sinks that are fed with coolant using a hierarchical manifold distributor. using the engineered dielectric liquid hfe-7100 as the working fluid, experimental results are presented for channel mass fluxes of 1300, 2100, and 2900 kg/m2 s and channel cross sections with nominal widths of 15 μm and nominal depths of 35 μm, 150 μm, and 300 μm.
“maximum heat flux dissipation is shown to increase with mass flux and channel depth and the heat sink with 15 μm × 300 μm channels is shown to dissipate base heat fluxes up to 910 w/cm2 at pressure drops of less than 162 kpa and chip temperature rise under 47 °c relative to the fluid inlet temperature.”