Closed-loop electroosmotic microchannel cooling system for VLSI circuits

Abstract

The increasing heat generation rates in VLSI circuits motivate research on compact cooling technologies with low thermal resistance. This paper develops a closed-loop two-phase microchannel cooling system using electroosmotic pumping for the working fluid. The design, fabrication, and open-loop performance of the heat exchanger and pump are summarized. The silicon heat exchanger, which attaches to the test chip (1 cm 2), achieves junction-fluid resistance near 0.1 K/W using 40 plasma-etched channels with hydraulic diameter of 100 m. The electroosmotic pump, made of an ultrafine porous glass frit with working volume of 1.4 cm 3 , achieves maximum backpressure and flowrate of 160 KPa and 7 ml/min, respectively, using 1 mM buffered de-ionized water as working fluid. The closed-loop system removes 38 W with pump power of 2 W and junction-ambient thermal resistance near 2.5 K/W. Further research is expected to strongly reduce the thermal resistance for a given heating power by optimizing the saturation temperature, increasing the pump flowrate, eliminating the thermal grease, and optimizing the heat exchanger dimensions. Index Terms-Electroosmotic pump, IC cooling technology, microchannel heat exchanger, two-phase heat transfer.

Improved Flow Rate in Electro-Osmotic Micropumps for Combinations of Substrates and Different Liquids With and Without Nanoparticles

“…The microflow meter was connected to a computer, where the flow rate data was obtained. This system is well suited for closed-loop thermal management applications, where the flow is circulated from the heat exchanger to a heat rejection unit [17].…”

Absorption Heat Pump/Refrigeration System Utilizing Ionic Liquid and Hydrofluorocarbon Refrigerants

“…Energy conservation for the condenser and the evaporator yield the respective heat loads, Eqs. (5) and (6):…”

“…Cooling is one of the major factors in total energy consumption in data centers accounting for about 30%-50% of the total power drawn from the grid [2]. A variety of novel alternative thermal solutions for electronics cooling have been reported, including thermosyphon [3], loop heat pipes [4], electroosmotic pumping [5], stacked microchannels [6], impinging jets [7], thermoelectric microcoolers [8], vapor compression refrigeration [9], and absorption based refrigeration systems [10,11]. The cooling systems can be categorized into passive and active; passive cooling systems utilize capillary or gravitational force to circulate the working fluid.…”

A review of micropumps

“…The small fluid volumes in these systems are often pumped, controlled or otherwise manipulated during operation. For example, biological samples must be moved through the components of miniature assay systems [1][2][3][4], and coolant must be forced through micro heat exchangers [5][6][7]. Microfluidic transport requirements such as these can sometimes be met by taking advantage of passive mechanisms, most notably surface tension [8][9][10][11].…”

“…A number of researchers have sought to develop micropumps for use in single-or two-phase cooling of microelectronic devices [5][6][7]. Microelectronics cooling is highly demanding with respect to flow rate.…”