An apparatus for cooling a heat source

Abstract: The present invention relates to an apparatus for cooling a heat source (12), the apparatus comprising a thermally conductive base (16) in contact with the heat source (12), the base (16) having a plurality of fins (24) which define a plurality of channels (26), generating an initial flow of fluid. A baffle (20,60) is positioned in the path of the initial flow of fluid so as to create a primary flow of fluid and a secondary flow of fluid, directing the primary flow of fluid against the plurality of fins (24) so as to form a quantity of spent fluid which is advanced into the channels (26), directing the secondary flow of fluid into the plurality of channels (26) so as to force the quantity of spent fluid out of the plurality of channels. The baffle (26,60) is repositioned from a first position to a second position to change the magnitude of the primary flow of fluid.

Description: The present invention generally relates to an apparatus for cooling a heat source and more particularly to an apparatus for cooling an integrated circuit. The temperature of an integrated circuit device must be maintained within a certain temperature range to ensure proper function, reliability and useful life. As a result, a variety of devices have been designed to cool integrated circuit devices. For example, one technique for cooling integrated circuit devices is disclosed in U.S. Pat. No. 5,294,830 which describes a thermal conduction module comprising a chip-carrying surface and at least one integrated circuit chip on the substrate. A deformable, liquid-impermeable, thermally conductive film or foil extends over an upper surface of the chip. A piston has a lower surface which urges and conforms the film against the chip upper surface and contains at least one open channel permitting coolant passage and contact with the film without direct contact between the coolant and the chip. Another example is U.S. Pat. No. 5,264,984 which describes a system for cooling electronic circuit components mounted on a substrate. The system includes containers placed on the respective components, and nozzles each having a central through-hole and peripheral through-holes. The outer bottom surface of each container is in thermal contact with a corresponding electronic circuit component. Liquid coolant is supplied into each container via the central through-hole, and discharged through the peripheral through holes to a location outside the container. Another example is U.S. Pat. No. 5,239,443 which describes a blind hole cold plate cooling system having a fluid inlet manifold with at least one jet nozzle and a heat transfer plate with a first and second surface. The first surface has a complimentary cavity for receiving the jet nozzle. The second surface is planar for contact with at least one heat generating device. The cooling system also has an annular gap defined by the center periphery of the jet nozzle and the surface of the complementary cavity. U.S. Pat. 5,239,200 discloses an apparatus including a thermally conductive cooling plate which has a plurality of integral closed end channels. A cover adapted to seal the periphery of the cooling member is provided and is spaced from the channel-containing surface. The cover has a plurality of integral baffles extending toward the cooling member into and along the length of the channels. The baffles and channels are spaced from each other to permit passage of a coolant in a flow direction normal to the channels. An inlet and outlet for coolant are provided on opposite ends of the apparatus. U.S. Pat. No. 5,005,640 teaches a cooler having a plurality of first passages in fluid communication with a plurality of second passages. A coolant flows through the second passages and then through the first passages which are in close proximity to a heating source. The first and second passages are oriented and connected such that the direction of coolant flow in the first passages is opposite to the direction of flow in the second passages. U.S. Pat. No. 4,897,762 discloses a cooling system in which a fluid is sprayed against the cooling surface of an electronic circuit device to cool the device and air is supplied in the opposite direction to the flow of the fluid to form an air curtain, thereby preventing the fluid from depositing on the electric circuitry of the devices. U.S. Pat. No. 4,750,086 teaches an apparatus including a heat spreader having a planar surface urged against a planar surface of a chip by flexible microbellows. The surface area of the heat spreader is greater than the mating surface area of the chip. The heat spreader is attached to the bottom surface of the microbellows. The surface area of the heat spreader which mates with the surface of the chip is highly polished and coated with a highly conductive soft metal. A jet of coolant is forced into the inner surface of the microbellows. Some of the aforementioned designs of cooling devices for integrates circuits are mechanically complex and would be relatively expensive to implement. Other designs would consume a relatively large amount of space which is a critical parameter in many electronic component environments. DE-A-4106437 discloses a cooling arrangement for integrated circuits where the cooling device has a plurality of thin wire ribs which are arranged and designed to have a Reynolds number of less than 40. US-A-5361188 describes a cooling apparatus for use with electronic equipment which includes a comb-toothed feed duct fitted to a jet stream cooling device and sets a feed area so that a cooling fluid can be supplied in accordance with the heating value of each of the chips on a substrate. US-A-5077601 discloses a cooling system which includes heat radiation fins attached to the heat generating components and a cooling duct defining a cooling fluid flow passage, the cross sectional area of which progressively decreases towards the downstream end. It is an object of the present invention to provide an apparatus for cooling a heat source such as an integrated circuit device which is relatively inexpensive to implement and would not consume a relatively large amount of space in an electronic component environment. According to the present invention there is provided a heat source cooling apparatus according to claim 1. From another aspect, the present invention resides in a method of cooling a heat source according to claim 4. Embodiments of the present invention will now be described by way of example, with reference to the accompanying drawings, in which:- FIG. 1 is a partial cross-sectional view of an example of a cooling apparatus which incorporates some of the features of the present invention therein; FIG. 2 is an enlarged front elevational view of the cooling apparatus taken along the line 2-2 of FIG 1. FIG. 3 is a top elevational view of a base of the cooling apparatus of FIG. 1. FIG. 4 is a side elevational view of the base taken along the line 4-4 of FIG. 3; FIG. 5 is a top elevational view of a plate of the cooling apparatus of FIG. 1; FIG. 6 is a side elevational view of the plate taken along the line 6-6 of FIG. 5; FIG. 7 is a partial cross-sectional view of an embodiment of a cooling apparatus which incorporates the features of the present invention therein; FIG. 8 shows a base having fins which are shaped in an increasingly tapered manner which is a first alternative to the base shown in FIG. 4; and FIG. 9 shows a base having fins which are shaped in a decreasingly tapered manner which is a second alternative to the base shown in FIG. 4. Referring now to FIGS. 1-2, there is shown an example of a cooling apparatus 10. The cooling apparatus 10 is adapted to cool a heat source 12, such as an integrated circuit device which is mounted on a printed circuit board 11. The cooling apparatus 10 includes housing 13 and a fan 14. The fan 14 is positioned at one end of the housing 13. The fan 14 is not shown in FIG. 2 for clarity of description. The cooling apparatus 10 further includes a base 16, a plate 18 and a stationary baffle 20. The base 14 is shown in more detail in FIGS. 3 and 4, while the plate 18 is shown in more detail in FIGS. 5 and 6. The base 16 is positioned in contact with the heat source 12. The plate 18 is positioned over the base 16. The cooling apparatus 10 further includes a plurality of plate baffles 22 which are secured in contact with the plate 18 as shown in FIG. 1. The base 16 is made of a metal such as aluminum. The base 16 includes a plurality of rectangularly-shaped fins 24 which are oriented in parallel with one another as shown in FIGS. 3 and 4. Alternatively, the fins may be shaped in an increasingly tapered manner as shown in FIG. 8 or a decreasingly tapered manner as shown in FIG. 9. Defined between each pair of adjacent fins 24 is a channel 26. On the side of the base opposite the fins 24 is a mating surface 28. The mating surface 28 is adapted to be positioned in contact with the heat source 12 as shown in FIG. 1. The plate 18 is made of a rigid plastics material and has a plurality of openings 30 defined therein as shown in FIG. 5. The openings 30 are circular and are adapted to allow a fluid, such as air, to be advanced therethrough. During operation of the cooling apparatus 10, the fan 14 generates an initial flow of fluid, indicated by arrows 31, such as air. Thereafter, the initial flow of fluid 31 contacts the stationary baffle 20 thereby splitting it into a primary flow of fluid and a secondary flow of fluid. The primary flow of fluid is indicated by arrows 32, while the secondary flow of fluid is indicated by the arrows 34. Thereafter, the primary flow of fluid 32 advances within the housing 13 and is itself split by the plurality of plate baffles 22. The plate baffles direct the primary flow of fluid 32 so that it advances through the openings 30 of the plate 18. After advancing through the openings 30, the primary flow of air 32 impinges upon a top surface 38 of the fins 24. It should be noted that when the primary flow of fluid 32 contacts the top surface 38 of the fins 24, spent or heated fluid is formed which continues to advance into the channels 26 of the base 14. Concurrently with the advancement of the primary flow of fluid 32, the secondary flow of fluid 34 advances within the housing 13 and is guided to advance into the channels 26 of the base 14. As the secondary flow of fluid 34 advances through the channels 26, the spent fluid becomes entrained in the secondary flow of fluid 34. The spent fluid along with the secondary flow of fluid is exhausted out of the channels 26 as an exhausted flow of fluid 40 as shown in FIG. 1. With the spent fluid removed from the channels 26, it is prevented from recirculating in the physical space which is located adjacent to the base 14. Referring now to FIG. 7, there is shown an embodiment of the invented cooling apparatus 50. The cooling apparatus 50 is adapted to cool a heat source 52, such as an integrated circuit device which is mounted on a printed circuit board 51. The cooling apparatus 50 includes housing 53 and a fan 54. The fan 54 is positioned at one end of the housing 53. The cooling apparatus 50 further includes a base 56, a plate 58 and a movable baffle 60. The base 56 is positioned in contact with the heat source 52. The plate 58 is positioned over the base 56. The cooling apparatus 60 further includes a plurality of plate baffles 62 which are secured in contact with the plate 58 as shown in FIG. 7. The components of cooling apparatus 50 are substantially similar to the components of cooling apparatus 10, and thus will not be further described. Moreover, the operation of cooling apparatus 50 with the movable baffle 60 positioned as shown in solid lines in FIG. 7 is substantial similar to the operation of the cooling apparatus 10, and thus will not be further described. The movable baffle 60 may be relocated from its position as shown in the solid lines in FIG. 7 to its position as shown in the phantom lines in FIG. 7. The movable baffle 60 may also be temporarily secured at any position between the above two extremes, if desired. Note that the magnitude of the flow of fluid which is directed upwardly in the housing 53 for ultimate impingement upon the top surface of the fins of the base 56 may be changed by selective positioning of the movable baffle 60. Further note that the flow of fluid which is directed upwardly for impingement on the fins may be substantially cut off by securing the movable baffle at its upper most position as shown in the phantom lines in FIG. 7.

Claims: A heat source cooling apparatus comprising a thermally conductive base (16) having a plurality of fins (24) on one surface thereof which are oriented in parallel with each other and which define a plurality of channels (26) between adjacent fins, the channels (26) being in parallel to a mating surface (28) on the opposite side of the base (16) and the mating surface(28) being positioned in contact with a heat source (12); a fan for generating an initial flow of fluid (31); a baffle (60) positioned in the initial low of fluid (31) to generate a primary fluid flow (32) and a secondary fluid flow (34); means (18, 22, 30) for directing the primary fluid flow (32) against the top surface (38) of the fins (24) opposed to the mating surface (28) to form a heated fluid; means for directing the secondary fluid flow (34) into the channels (26) in a direction parallel to the mating surface (28); characterized in that the means for directing the primary fluid flow comprises a plate (18) having a plurality plate baffles (22) secured thereto and having a plurality of openings (30) defined therein wherein the heated fluid is advanced into the channels (26) of the base (14) and becomes entrained with the secondary fluid flow (34); and wherein the baffle (60) is moveable between a first position and a second position, wherein movement of said baffle (60) between the first position and the second position changes the magnitude of the primary (32) and the secondary flow of fluid (34). The apparatus of any preceding claim wherein the plurality of fins (24) are rectangular in shape. The apparatus of any of claims 1 to 3, wherein the plurality of fins (24) have a tapered profile. A method of cooling a heat source (12) comprising the steps of: providing a thermally conductive base (16) having a plurality of fins (24) on a first side thereof and a mating surface (28) on the opposite side thereof, the plurality of fins (24) being oriented in parallel with each other and defining a plurality of channels (26) between adjacent fins (24), the mating surface(28) being positioned in contact with a heat source (12); generating an initial flow of fluid (31); positioning a baffle (60) in the path of the initial fluid flow (31) so as to create a primary fluid flow (32) and a secondary fluid flow (34); directing the primary fluid flow (32) against the top surface (38) of the fins (24) opposed to the mating surface (28) to form heated fluid and advancing the heated fluid through the plurality of channels (26); directing the secondary fluid flow (34) through the plurality of channels (26) in a direction parallel to the mating surface (28) so as to exhaust the heated fluid from the plurality of channels, characterized in that the step of directing the primary fluid flow (32) comprises providing a plate (18) having a plurality plate baffles (22) secured thereto and having a plurality of openings (30) defined therein, and advancing said primary fluid through said openings (30); wherein the baffle (60) is moveable between a first position and a second position and the movement of said baffle (60) between the first position and the second position changes the magnitude of the primary (32) and the secondary flow of fluid (34).

Inventors: PERDUE DAVID W, PERDUE, DAVID W.
Applicants: NCR INT INC, NCR INTERNATIONAL INC.
Application year: 1996
Main classification: H01L23
IPC codes: F25D1, H05K7, G06F1, H01L23