An increasingly important requirement of microelectronics is the development of thermal management systems for cooling chips.
Chips generate excessive amounts of heat that peak in certain parts and potentially threaten their functioning by destroying their internal circuitry. Current cooling technologies are capable of cooling at the rate of 200 W/cm², but technologies have stagnated at this point for several years.
As more high-performance chips are being developed, the heat generated from them will exceed that of conventional microprocessors, calling for better cooling techniques than heatsinks and fans. In light of this, researchers at Purdue University have developed a hybrid cooling technique based on microjets and microfluidic channels that is capable of cooling high-performance chips.
The microjets are used to inject liquid into miniaturised channels and are said to absorb five times more heat than other techniques being developed for chip-cooling in computers and electronics. The technique is capable of cooling at the rate of 1000 W/cm², which allows for greater advances in performance. The method involves the circulation of cooling liquid or hydrofluorocarbon within the chip. As the coolant is an insulator, it does not conduct electricity or cause short circuits.
The cooling system consists of narrow grooves less than a millimetre wide that form channels on top of a chip and are covered using a metal plate with tiny holes. The microjets inject the coolant through these holes and the liquid then flows along grooves to cool the chip. On getting heated by the chip within the channels, the coolant bubbles and momentarily becomes a vapour in order to aid rapid cooling.
The hydrofluorocarbon coolant is used in airconditioning and refrigeration systems owing to their low global warming effects. The difference is that hydrofluorocarbons used in airconditioning are in their vapour form at room temperature, whereas those used in Purdue’s experimental chip-cooling system are in liquid form.
Prior research applied on the concept of coolant flow through microchannels suffered from the drawback that the coolant flowed from one part of the chip to the other, collecting heat and was already heated by the time it reached the end of the channel. This put a limit on the cooling efficiency. Purdue’s microjets technique overcomes this challenge by enabling uniform cooling as the liquid is supplied simultaneously through the jets everywhere along the length of each channel.
This method also prevents the overheating of any specific part of the chip. The coolant on circulation collects at both ends of the channel and is then re-circulated through the system.
For more information contact Patrick Cairns, Frost & Sullivan, +27 (0)21 680 3274, patrick.cairns@frost.com, www.frost.com
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