US 20060090474A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2006/0090474 A1 Sauciuc et al. (43) Pub. Date: May 4, 2006 (54) METHOD AND APPARATUS FOR Publication Classification REMOVING HEAT (51) Int. Cl. F2SB 2L/02 (2006.01) (76) Inventors: Ioan Sauciuc, Phoeniz, AZ (US); Jim F28D 5/00 (2006.01) D. Williams, Banks, OR (US) F25D 23/12 (2006.01) (52) U.S. Cl. ....................... 62/3.2: 62/259.2; 165/104.22 Correspondence Address: BLAKELY SOKOLOFFTAYLOR & ZAFMAN (57) ABSTRACT 124OO WILSHIRE BOULEVARD SEVENTH FLOOR A device includes a liquid metal and a ferrofluid contained LOS ANGELES, CA 90025-1030 (US) in a closed tube. Many electrode groups are connected to the closed tube. A feedback device is connected to the electrode (21) Appl. No.: 10/976,406 groups. The feedback device switches power to each elec trode group in series to circulate the liquid metal and move (22) Filed: Oct. 29, 2004 the ferrofluid in the closed tube. 200 210 -4220 Automatic feedback system and StartUp Circuit (2) (25 260 250 Patent Application Publication May 4, 2006 Sheet 1 of 7 US 2006/0090474 A1 20 FIG. 1A F.G. 1B (Prior Art) (Pr O Art) Patent Application Publication May 4, 2006 Sheet 2 of 7 US 2006/0090474 A1 200 - Automatic feedback system and StartUp Circuit 25 (25 240 E.iSE S3 ES 230 250 FIG. 2 Patent Application Publication May 4, 2006 Sheet 3 of 7 US 2006/0090474 A1 FIG. 3 Patent Application Publication May 4, 2006 Sheet 4 of 7 US 2006/0090474 A1 400 Determine Temperature Alternate power to electrode groups to move ferrofluid 420 Circulate liquid metal Dissipate heat within the liquid metal FIG. 4 Patent Application Publication May 4, 2006 Sheet 5 of 7 US 2006/0090474 A1 Feedback Controller 270 720 S.S. 2 Azzzzzzzz)1" 2777272/ Patent Application Publication May 4, 2006 Sheet 6 of 7 US 2006/0090474 A1 800 210 Automatic feedback system and StartUp Circuit 25 25 FIG. 8 Patent Application Publication May 4, 2006 Sheet 7 of 7 US 2006/0090474 A1 FIG.9 US 2006/0090474 A1 May 4, 2006 METHOD AND APPARATUS FOR REMOVING against the negatively charged glass and push the fluid HEAT through the disk. Because it uses no moving parts, the pump should be reliable and is almost completely silent. BACKGROUND 0008 Besides microchannel cooling using a silent pump, 0001) 1. Field an optional fan can be attached to a radiator. The radiator in the active microchannel cooling system doesn’t need to have 0002 The embodiments relate to cooling by removing a fan attached, and the system is completely silent unless the heat, and more particularly to removing heat of a device user opts to have maximum cooling. A Small, yet important using forced convection liquid metal combined with ther factor in cooling is the size of any cooling system. While moelectric and a ferrofluid. air-cooling requires large fans, active microchannel cooling 0003 2. Description of the Related Art uses a thin silicon block and a small radiator. Compared to 0004 Cooling is one of the main concerns for computer water-cooling systems, the size of the active microchannel and processor manufacturers and developers. The industry cooling is very Small. depends on functional cooling techniques to help cool their 0009. One drawback to active microchannel cooling is rapidly advancing chips, which tend to run hotter and hotter. the installation process. As compared to adding an air Without proper cooling, design engineers will end up sac cooling system to a computer, which is as simple as screw rificing performance and power for lower temperatures and ing a heat sink to the motherboard and attaching a fan, active stability. microchannel cooling can require installing brackets for the 0005. Initially, passive cooling was enough to keep cen pump and radiator, and installing tubing in a computer tral processing units (CPUs) in a stable state. As chips system. evolved, however, so did cooling due to necessity. A tran 0010 Another type of cooling technique is the use of a sition from aluminum and copper to graphite heat sinks, and heat pipe. A heat pipe is self-powered and transfers heat to from passive to active cooling (i.e., using a fan to force out a side edge of a computer or notebook computer, where air the heat that dissipates into the CPUs surrounding airflow) fins or a tiny fan can be used to dissipate the unwanted heat has kept pace with the advances in processing power. Some into air. A heat pipe uses tiny liquid-filled pipes to shuttle computer designers have used water-cooling, which uses heat to pre-chosen locations for dispersal. In the heat pipe water to transfer the heat directly from a chip’s surface more loop, heat from a processor changes liquid, for example efficiently and effectively. Water-cooling, however, is not methanol, to vapor. The vapor absorbs heat at a pre-selected enough to completely eliminate certain hot areas that form site, changes back to liquid and wicks back to its starting on processors with higher heat output. point to collect more heat. 0006. One newer technique uses active microchannel cooling, which actively cools a processor with micro chan 0011. Thermoelectric modules (TEM) have also been nels. Microchannels are extremely small grooves and ridges used as active cooling devices. By placing a TEM between machined into the silicon block that collect heat from the a device or object to be cooled, such as an integrated circuit, processor. The microchannels are about the width of a and a heat sink and supplying the TEM with a current, the human hair, less than /32 of an inch wide. As compared with TEM transfers heat from the integrated circuit to the heat water-cooling, the microchannels in the active microchannel sink. The phenomenon is called the Peltier effect. The TEM cooling system are much more efficient, since there is a consists of ceramic plates with p-type semiconductor mate larger Surface area for the heat to dissipate. Another advan rial and n-type semiconductor material between the plates. tage of microchannels is that since they are machined using The elements of semiconductor material are connected elec standard silicon machining techniques, the price of manu trically in series. When a direct current (DC) voltage is facturing is low and any defects in the product are minimal. applied to the semiconductor material, electrons pass from One of the benefits of using microchannels for cooling is the the p-type material to the n-type material. The elements are efficient heat removal from CPU hot spots. Typical micro arranged in a manner Such that when a DC voltage is channels are approximately 1.5 mm away from any given applied, heat is transferred from one side of the TEM to the hot area. Therefore, the distance that the heat must travel to other. The rate of transfer is proportional to the current and be dissipated is effectively reduced. An interesting aspect of the number of p-n junctions. active microchannel cooling is that the microchannels are 0012. The problem of cooling computers, notebooks and made from silicon, a material not usually known for its processors will continue as performance increases. heat-dissipation properties. Since silicon is a semiconductor, it shares some characteristics of metals and non-metals. Metals are usually good conductors of heat, but compared to BRIEF DESCRIPTION OF THE DRAWINGS metals, silicon dissipates heat poorly. Advantages of using 0013 Embodiments are illustrated by way of example silicon are, for example, silicon is the second most abundant and not by way of limitation in the figures of the accompa element in the earth's crust. Therefore, cooling via micro nying drawings in which like references indicate similar channels help keep the price of computers/processors down. elements. It should be noted that references to “an embodi 0007 An electro-kinetic pump is a feature of active ment in this disclosure are not necessarily to the same microchannel cooling. The pump uses an electro-kinetic embodiment, and they mean at least one. effect to propel cooling fluid through a porous glass disk without any moving parts. The pump works by positively 0014 FIG. 1A illustrates a ferrofluid in a glass container. charging the cooling fluid, therefore generating positively 0.015 FIG. 1B illustrates the ferrofluid in FIG. 1A being charged hydrogen atoms. The hydrogen atoms then repel moved with a magnet. US 2006/0090474 A1 May 4, 2006 0016 FIG. 2 illustrates an embodiment including a heat the applied magnetic field and when the applied field is removing device. removed, the moments randomize quickly. In a gradient field the whole fluid responds as a homogeneous magnetic liquid 0017 FIG. 3 illustrates a system of an embodiment. that moves to the region of highest flux. This means that 0018 FIG. 4 illustrates a block diagram of a process of ferrofluids can be precisely positioned and controlled by an an embodiment. external magnetic field. The forces holding the magnetic fluid in place are proportional to the gradient of the external 0019 FIG. 5 illustrates rotating device having ferrofluid field and the magnetization value of the fluid. This means for an embodiment including a heat removing device. that the retention force of a ferrofluid can be adjusted by 0020 FIG. 6 illustrates another view of the device of changing either the magnetization of the fluid or the mag FIG. 5 included in an embodiment. netic field in the region. 0021 FIG. 7 illustrates the device of FIG. 5 coupled to 0028.