Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L23/00—Details of semiconductor or other solid state devices
  • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
  • H01L23/46—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids
  • H01L23/467—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids by flowing gases, e.g. air
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L23/00—Details of semiconductor or other solid state devices
  • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
  • H01L23/46—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids
  • H01L23/473—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids by flowing liquids
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L23/00—Details of semiconductor or other solid state devices
  • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
  • H01L23/46—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids
  • H01L23/473—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids by flowing liquids
  • H01L23/4735—Jet impingement
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/0001—Technical content checked by a classifier
  • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/30—Technical effects
  • H01L2924/301—Electrical effects
  • H01L2924/3011—Impedance

Definitions

• the present invention relates to a pulsating cooling system, i.e. a cooling system where a transducer induces an oscillation creating a pulsating fluid stream that can be directed towards an object that is to be cooled. It may be advantageous to drive the system at, or at least close to, its resonance frequency, in order to obtain a high fluid velocity.
• the cavity and the tube form a Helmholtz resonator, i.e. a second order system where the air in the cavity acts as a spring, while the air in the tube acts as the mass.
• a synthetic jet is disclosed having two diaphragms each communicating with the same orifice.
• a pulsating fluid stream typically air stream
• the resonance cooling systems further require less space, and generates less noise.
• a cooling device comprising two cavities, the transducer being arranged between the two cavities, such that the membrane forms a fluid tight seal between the cavities, each cavity having at least one opening adapted to emit a pulsating net output fluid flow, wherein the cavities and openings are formed such that, at the working frequency, a first harmonic fluid flow emitted by the opening(s) of a first one of the cavities is in anti-phase with a second harmonic fluid flow emitted by the opening(s) of a second one of the cavities, so that a sum of harmonic fluid flow from the openings is essentially zero.
• the transducer arranged between two cavities will act as a dipole, i.e. two acoustical sources in anti-phase.
• the invention is based on the idea that the harmonic parts of the sound from these two sources will cancel out.
• the non- harmonic parts which represent the dominating part of the cooling effect, will not add coherently, and will thus not cancel out.
• the cooling device according to the present invention may be used for cooling a large variety of objects through directed outflow of various liquid or gaseous fluids, not only air. It is, however, particularly useful for air-cooling of such objects as electronic circuitry.
• Each cavity may have only one opening, or have more than one opening. It is important however that the sum of harmonic contributions from all openings is essentially zero.
• More than one transducer may be arranged between the cavities. For example, two, oppositely positioned transducers operating in counter phase will result in a larger air flow. By “oppositely positioned” is intended a situation where pressure waves from one transducer are directed into one cavity, while pressure waves of the other transducer are directed into the other cavity.
• a “transducer” is here a device capable of converting an input signal to a corresponding pressure wave output. The input signal may be electric, magnetic or mechanical. Examples of suitable transducers include various types of membranes, pistons, piezoelectric structures and so on. In particular, a suitably dimensioned electrodynamic loudspeaker may be used as a transducer.
• the distance between the openings should be short compared to the wavelength at the working frequency.
• the pressure p at distance r from these sources will be
• the distance d is less than
• the working frequency is preferably chosen such that the air velocities and air displacement through the openings have a local maximum, and typically this occurs in a neighborhood of a resonance frequency of the device, i.e. a frequency corresponding to a local maximum of the electric input impedance of the device (the transducer in combination with the cavities and openings). Typically the lowest such frequency is chosen.
• the working frequency can be chosen such that the cone excursion of said transducer has a local minimum at this working frequency. Typically, this occurs at an anti-resonance frequency of the device, i.e. a frequency corresponding to a local minimum of the electric input impedance of the device.
• the cavities can be formed to have equal volume, and the openings can be formed to have equal cross section area. However, this is not a requirement, and canceling air streams may be achieved also with different sized cavities and/or openings.
• the openings are connected to respective cavity via a channel (or pipe).
• a channel or pipe
• the channels can be formed to have equal length and cross section area.
• such channels are sufficiently long to act more as tube resonators.
• the length of the channels is instead sufficiently short to allow the cavities to act as conventional Helmholtz resonators.
• a channel connecting at least one opening of the first cavity can extend through the second cavity, so that this opening is located on the same side of said device as the openings of the second cavity.
• the cavities have essentially planar extension and are arranged on top of each other (i.e. like two discs on top of each other), such a design will enable locating all the openings on the top or bottom side of the device.
• Two or more devices according to the present invention may be combined, to form a cooling arrangement with a multiple of two openings.
• the average distance between the openings of a first device and the openings of a second device is then subject to the same requirements as the distance between the two openings of each device, and should thus preferably be less than 0.2 ⁇ , and even more preferably less than 0.1 ⁇ .
• FIG. 1 shows a cooling system according to a first embodiment of the present invention.
• Fig 2 shows an example of the frequency responses of respectively the electric input impedance, the air velocities, the air displacement, and the cone displacement.
• Fig. 3 shows a cooling system according to a second embodiment of the present invention.
• Fig. 4 shows a cooling system according to a third embodiment of the present invention.
• Fig. 5 shows a cooling system according to a variant of the third embodiment of the present invention.
• Fig. 6 shows a cooling system according to another variant of the third embodiment of the present invention.
• Fig. 7 shows a cooling system according to a fourth embodiment of the present invention.
• Fig. 8 shows a cooling system according to a fifth embodiment of the present invention.
• the cooling system in figure 1 comprises a transducer 1 arranged in an enclosure 2.
• the transducer 1 is arranged to divide the enclosure into two cavities 3, 4 having volumes Vl and V2 respectively.
• Each cavity is connected to the ambient atmosphere respectively via two passages, here pipes 5, 6 having lengths LpI and Lp2, and cross section areas SpI and Sp2.
• the pipes 5, 6 have outlets 7 and 8 positioned on a distance d from each other.
• the openings are illustrated as having round shape, but the invention is not limited to this shape. On the contrary, the openings may have any shape, and may also be tapered to influence the airflow in a desired manner.
• the volumes Vl and V2 and the form of the pipes 5, 6 are chosen such that in use, the transducer will act as a pressure wave dipole, cause a pulsating flows of fluid present in the cavities through the outlets which are essential equal and in counter phase. When driving the transducer at a working frequency, the two fluid flows will thus counteract each other, thereby suppressing any pressure waves escaping from the dipole (i.e. disturbing sound).
• the principle is not limited any particular fluid, but the present description will be based on a device operated in air, i.e. a device that generates oscillating air streams.
• the air pressure radiating from the dipole is kept very small.
• the volumes Vi and V 2 and the form of the pipes 5, 6 can be chosen such that there is a specific frequency for which the air velocities V 1 and V 2 through each outlet 7, 8 have coinciding local maximums and are in counter phase.
• the working frequency can then be chosen to coincide with this frequency, to ensure a maximum air velocity and thereby cooling effect. Often, these local maxima coincide with the most left electric input impedance peak on the frequency scale. This corresponds to a resonance frequency of the device.
• a device may have the following properties:
• fig. 2a) to 2d) show the frequency responses of respectively the electric input impedance, the air velocities v; and V2, the displacement of the air particles in the outlets 7 and 8, and the transducer cone displacement. It is clear that in this illustrated case, the maxima of the V 1 and V 2 curves coincide with the first resonance frequency of the system (first local maximum of the input impedance). Note that, for reasons of clarity, the volumes Vi and V 2 have been chosen slightly different, so that the curves in figure 2 do not coincide completely.
• FIG. 3 Another embodiment is illustrated in Fig. 3, where the tubes 5 and 6 are curved to minimize the footprint, and to minimize the distance d.
• the unit consists of two spiral like elements 11, sandwiching between them a middle plate 12, and closed on their upper and lower sides by end plates 13.
• the membrane 14 of the transducer 1 is arranged in the center of the middle plate 12.
• the innermost space 15 of each spiral corresponds to the volumes Vi and V 2 in fig 1.
• FIG. 4 Yet another embodiment is depicted in Fig. 4, where two cavities 21, 22 are arranged on top of each other, separated by a middle plate with a membrane 23.
• no pipes connect the cavities with the ambient air, only two holes, or very short tubes 24, 25 in the end plates 26, 27.
• acoustic waves will radiate from the holes 24, 25 in anti phase, resulting in combination in very modest sound level.
• the holes 24, 25 need not be arranged on opposite sides of the cavities. As shown in fig 5, they may also be located on the sides of each cavity.
• the holes 24a-d and 25a-d are located pair-wise on respective cavities. The distribution of holes depends on the desired orientation of the resulting cooling jet, in figure 5 illustrated by arrow A.
• the air from both cavities 21, 22 may be directed through holes in one of the end plates 26. As shown in figure 6, this can be accomplished by providing channels 27 leading from the upper cavity 21 through the lower cavity 22 to holes 28 in the bottom end plate 26. Other holes 29 in the bottom plate 26 lead to the lower cavity 22. In order to provide similar passages from each cavity, the holes 29 are also connected to the lower cavity 22 via channels 30, similar in length and cross section to channels 27.
• the number of channels from each cavity must not be equal.
• Figure 7 shows a further embodiment of the invention.
• two cavities 31, 32 are separated by a wall 33 supporting two oppositely arranged transducers 34, 35, operated in anti-phase.
• An advantage with this design is that any differences in geometry caused by the transducer are compensated for (see e.g. in fig 1, where the transducer consumes more volume in the cavity 4).
• this embodiment also features one pipe 36 divided in two channels 37, 38 leading to the respective cavities.
• two devices according to one of the previously described embodiments are used in combination, here devices 41, 42 according to the embodiment in figure 3.
• the two devices form a cooling system with two transducers land four openings 7a, 7b, 8a, 8b. All four openings should preferably be arranged in close proximity, most preferably within a distance D less than 0.2 ⁇ , as described above. Further, as long as the distance is sufficiently small, the direction of the air streams from the various openings is not important. It should thus be realized that the openings need not be parallel and in the same plane, as in the example in figure 8, but on the contrary may be arranged in many other configurations. It should also be noted that the two devices 41 and 42 need not be identical, as in the present example.
• any two dipole devices may be advantageously combined.
• the person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the number of transducers may be increased further, and the placement and form of openings and channels may be varied depending on the application.
• the transducer may be implemented in micro electro -mechanical system (MEMS) technology, i.e. realized on a very small scale. More specifically, on such a small scale, an entire cooling device, including transducer, cavities, openings and any channels, can be completely embodied in silicon using e.g. etching technology. Such a device can advantageously be integrated with an IC to be cooled, e.g. a micro processor. By providing cooling by means of a cooling device on the same scale as the object to be cooled, the cooling may be made more efficient. Of course, a silicon device can be combined with additional channels connected to the silicon substrate.
• MEMS micro electro -mechanical system

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• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Cooling Or The Like Of Electrical Apparatus (AREA)

Priority Applications (1)

Applications Claiming Priority (3)

Publications (1)

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• 2007
  • 2007-11-27 KR KR1020097013612A patent/KR20090085700A/ko not_active Application Discontinuation
  • 2007-11-27 EP EP07849261A patent/EP2089902A1/de not_active Withdrawn
  • 2007-11-27 WO PCT/IB2007/054796 patent/WO2008065602A1/en active Application Filing
  • 2007-11-27 CN CNA2007800438438A patent/CN101542724A/zh active Pending
  • 2007-11-27 JP JP2009538820A patent/JP2010511142A/ja not_active Withdrawn
  • 2007-11-27 US US12/515,999 patent/US20100018675A1/en not_active Abandoned
  • 2007-11-28 TW TW096145319A patent/TW200839980A/zh unknown

Non-Patent Citations (1)

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