Abstract:
A low-cost, fan assisted cooling device is disclosed. The cooling device includes a narrow bottom and broad top shape to optimize a material versus performance ratio. A plurality of vanes surround a central heat mass and an inside surface of the vanes define a chamber that surrounds the heat mass. A portion of each vane is split into a plurality of fins and both the vanes and the fins have a surface area that increase in a radially outward direction from an axis of the heat mass. The heat mass includes a boss that is surrounded by a groove. Both the boss and the grove have arcuate surface profiles. The vanes, the fins, the boss, and the groove efficiently dissipate heat when a fan or the like forces air into the chamber thereby producing air flows in three different directions. In a first direction, the air flows out of the chamber through the vanes. In a second direction, a low pressure region in the chamber induces air from outside the chamber to flow through the fins. In a third direction, the low pressure region induces an airflow over the groove and boss. Openings between the vanes are angled and offset from an orientation of the fans blades to minimize the airflow shock losses thereby reducing fan noise. The vanes and the fins can be homogeneously formed with the heat mass.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a cooling device for removing heat from a component connected with the cooling device. More specifically, the present invention relates to a cooling device for removing heat from an electronic component connected with the cooling device. 
     BACKGROUND OF THE INVENTION 
     It is well known in the electronics art to place a heat sink in contact with an electronic device so that waste heat generated by operation of the electronic device is thermally transferred into the heat sink thereby cooling the electronic device. With the advent of high clock speed electronic devices such as microprocessors (μP), digital signal processors (DSP), and application specific integrated circuits (ASIC), the amount of waste heat generated by those electronic devices and the operating temperature of those electronic devices are directly proportional to clock speed. Therefore, higher clock speeds result in increased waste heat generation which in turn increases the operating temperature of the electronic device. However, efficient operation of the electronic device requires that waste heat be continuously and effectively removed. 
     Heat sink devices came into common use as a preferred means for dissipating waste heat from electronic devices such as the types described above. In a typical application, a component to be cooled is carried by a connector that is mounted on a PC board. A heat sink is mounted on the component by attaching the heat sink to the connector using a clip or fasteners, for example. Alternatively, the heat sink is mounted to a PC board that carries the electronic device and fasteners or the like are used to connect the heat sink to the PC board via holes that are drilled in the PC board. 
     The need to drill holes can be one disadvantage to using fasteners because the fasteners or other mounting hardware used for connecting the heat sink to the PC board are usually electrically conductive and there is a risk of an electrical short due to contact between a PC board trace and the mounting hardware. Moreover, to avoid electrical shorts, the PC board traces can be routed around the hole, but that routing requires keep out zones that can complicate the routing of the traces. 
     Typically, a heat sink used in conjunction with a modem high clock speed electronic device will use an electrical fan mounted on top of the heat sink or within a cavity formed by cooling fins/vanes of the heat sink. The cooling fins increase the surface area of the heat sink and maximize heat transfer from the heat sink to ambient air that surrounds the heat sink. The fan causes air to circulate over and around the cooling fins thereby transferring heat from the cooling fins into the ambient air. 
     As mentioned previously, with continuing increases in clock speed, the amount of waste heat generated by electronic devices has also increased. Accordingly, to adequately cool those electronic devices, larger heat sinks and/or larger fans are required. Increasing the size of the heat sink results in a greater thermal mass and a greater surface area from which the heat can be dissipated. Increases in fan size provide for more air flow through the cooling fins. 
     There are disadvantages to increased fan and heat sink size. First, if the size of the heat sink is increased in a vertical direction (i.e. in a direction transverse to the PC board), then the heat sink is tall and may not fit within a vertical space in many applications, such as the chassis of a desktop computer. Second, if the PC board has a vertical orientation, then a heavy and tall heat sink can mechanically stress the PC board and/or the electronic device resulting in a device or PC board failure. 
     Third, a tall heat sink will require additional vertical clearance between the heat sink and a chassis the heat sink is contained in to allow for adequate air flow into or out of the fan. Fourth, if the heat sinks size is increased in a horizontal direction, then the amount of area available on the PC board for mounting other electronic devices is limited. Fifth, when the heat sink has a cylindrical shape formed by the fins it is often not possible to mount several such heat sinks in close proximity to each other because air flow into and out of the fins is blocked by adjacent heat sinks with a resulting decrease in cooling efficiency. 
     Finally, increases in fan size to increase cooling capacity often result in increased noise generation by the fan. In many applications such as the desktop computer or a portable computer, it is highly desirable to minimize noise generation. In portable applications that depend on a battery to supply power, the increased power drain of a larger fan is not an acceptable solution for removing waste heat. 
     In the above mentioned heat sink with cooling fins there are additional disadvantages to mounting the fan within a cavity formed by the fins. First, a substantial portion of a heat mass of the heat sink is partially blocked by the fan because the fan is mounted directly on the heat mass and therefore blocks a potential path for heat dissipation from the heat mass because air from the fan does not circulate over the blocked portion of the heat mass. 
     Second, without the fan, a depth of the fins could extend all the way to a center of the heat mass; however, the depth and surface area of the fins is reduced by a diameter of the fan because the fan is mounted in a cavity having a diameter that is slightly larger than the fans diameter to provide clearance for the fans blades. Consequently, the heat mass of the heat sink must be made broader to compensate for the reduced surface area of the fins. The broader heat mass increases the size, cost, and weight of the heat sink. 
     Third, the reduced depth of the fins makes it easier for the fins to be bent if damaged. One possible consequence of a bent fin is that it will contact and damage the fan blades and/or cause the fan to stall thereby damaging the fan or causing the fan to fail. Fourth, because the fan is mounted in the cavity formed by the fins, power leads for the fan must be routed through a space between the fins. Sharp edges on the fins can cut the power leads or cause an electrical short. In either case, the result is that the fan will fail. Fifth, glue is typically used to mount the fan to the heat sink and the glue can get into the fan and cause the fan to fail. Any of the above mentioned fan failure modes can lead to a failure of the electronic device the heat sink was designed to cool because air circulation generated by the fan is essential to effectively dissipate waste heat from the electronic device. 
     Thus, there exists a need for a cooling device that overcomes the aforementioned disadvantages associated with fan assisted heat sinks. 
     SUMMARY OF THE INVENTION 
     Broadly, the present invention is embodied in a cooling device for dissipating waste heat from a component to be cooled. The cooling device includes a heat mass with an arcuate boss that is surrounded by an arcuate groove. A heat conductive base including a mounting surface for connecting the cooling device with the component to be cooled is connected with the heat mass. Extending from the heat mass are a plurality of vanes that are spaced apart from each other to define a primary slot between adjacent vanes and extending to the heat mass. The vanes have a surface area that increases in a radially outward direction from an axis of the heat mass and a portion of the surface area of the vanes also increase in a direction that is along the axis. The vanes include a top face upon which a fan can be mounted, an aerodynamically profiled inner wall that defines a chamber that surrounds the boss and the groove, and an outer wall including a surface profile that widens from the base to the top face and includes a smooth curved portion, a draft portion, and a smooth radially outward portion. Furthermore, the surface area of the vanes is increased by a plurality of fins formed in each vane by a secondary slot extending through a portion of the vane. 
     An air flow entering the chamber creates a three-dimensional air flow that dissipates heat from the cooling device. First, the air flow exits through the vanes and a portion of the fins in an exhaust flow that dissipates heat from the vanes and the fins. Second, the exhaust flow creates a low pressure region within the chamber that induces an intake flow into the chamber through a major portion of the fins and a top portion of the vanes thereby dissipating heat from the fins and the vanes. Third, the low pressure region induces a surface flow along the inner wall so that the surface flow wets the groove and the boss as it passes over the groove and the boss to dissipate heat from the heat mass. 
     The cooling device of the present invention solves the aforementioned disadvantages of prior heat sinks. The cooling device can be mounted to a component to be cooled by using a clip to connect the cooling device with a connector that carries the component. Therefore, holes need not be drilled in a PC board to mount the cooling device. The cooling device employs vanes that extend deep within the heat mass and the surface area of the vanes increases from a bottom of the cooling device to a top of the cooling device and in a radially outward direction from the heat mass. Furthermore, each vane is split into at least two fins thus further increasing the surface area available for cooling. As a result, the cooling device need not be made taller to increase vane surface area and the cooling device need not be made wider to increase the size of the heat mass. 
     The top of the cooling device is adapted to mount a fan so that the heat mass is not blocked by the fan and air can circulate over the heat mass thus further dissipating heat from the cooling device. The fan can include a shroud that surrounds the blades unlike the fans that are mounted in a cavity formed by fins of prior heat sink devices. However, the cooling device can also mount a fan without a shroud using a clip or space frame to mount the fan to the top of the cooling device. Because the fan is mounted on top of the cooling device, the wires of the power leads for the fan are not routed through the vanes or fins thereby eliminating the risk of the wires being cut or short circuited. 
     The shape of the cooling device (wider at the top than at the bottom) allows for several of the cooling devices to be placed adjacent to each other without blocking air flow into and out of the vanes and fins. 
     The vanes of the cooling device can be tangentially oriented with a circle centered on an axis of the heat mass and the vanes can be inclined at an angle with respect to the axis such that the angle of inclination substantially matches or closely approximates a pitch angle of the blades of a fan. The tangential orientation and the inclination of the vanes reduces fan noise due to air shock losses. 
     Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view along line A—A of FIG. 2 a  of a cooling device according to the present invention. 
     FIGS. 2 a  and  2   b  are top plan views of a cooling device according to the present invention. 
     FIGS. 2 c  is detailed view of a portion of the top plan view of FIG. 2 b.    
     FIG. 3 a  is a cross-sectional view along line A—A of FIG. 3 b  of air flow into and out of a cooling device according to the present invention. 
     FIG. 3 b  is a top plan view of air flow into and out of a cooling device according to the present invention. 
     FIG. 4 is a cross-sectional view of a cooling device with a base with an inset neck portion according to the present invention. 
     FIGS. 5 a  and  5   b  are side views of a cooling device with vanes inclined at an angle according to the present invention. 
     FIG. 6 is a top plan view illustrating a cooling device having vanes with a tangential orientation according to the present invention. 
     FIG. 7 is a profile view of a mounting ring for connecting a fan with a cooling device according to the present invention. 
     FIG. 8 is a side view of a fan mounted to a cooling device according to the present invention. 
     FIG. 9 is a cross-sectional view illustrating various dimensional relationships between a fan and a cooling device according to the present invention. 
     FIG. 10 is a side view of a space frame mounting a fan to a cooling device according to the present invention. 
     FIG. 11 is a side view of a cooling device with a base having projections and a thermal interface material according to the present invention. 
     FIGS. 12 a  through  12   d  are various views of a cooling device with a base having projections and flats according to the present invention. 
     FIG. 13 is a side view of a system for dissipating heat according to the present invention. 
     FIG. 14 is a side view of a system for dissipating waste heat according to the present invention. 
     FIGS. 15 a  through  15   c  illustrate insertion of a cooling device into a spring clip according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     In the following detailed description and in the several figures of the drawings, like elements are identified with like reference numerals. 
     As shown in the drawings for purpose of illustration, the present invention is embodied in a cooling device for dissipating heat from a component that is in thermal communication with the cooling device. The thermal communication can be by direct contact between the cooling device and the component or by an intermediate material positioned between the cooling device and the component as will be described below. The component can be any heat source such as an electrical component, for example. The cooling device includes a heat mass with a boss surrounded by a groove and with the groove and the boss symmetrically positioned about an axis of the heat mass. The boss has a convex arcuate surface profile and the groove has a concave arcuate surface profile. A heat conductive base is in contact with the heat mass and includes a mounting surface adapted to contact the component to be cooled. 
     A plurality of vanes surround the heat mass and the vane are spaced apart from one another to define a primary slot between adjacent vanes. The primary slot extends to the heat mass so that an exhaust flow of air cools the vanes and the heat mass. The vanes have a surface area that increases in a radially outward direction from the axis and in a direction along the axis. A plurality of fins are formed in each vane by a secondary slot extending through a portion of each vane. 
     The vanes include a top face and an aerodynamically profiled inner wall that includes a first portion extending from the groove and terminating at a second portion that extends to the top face. The inner wall defines a chamber that surrounds the groove. The vanes also include an outer wall having a surface profile that widens from the base to the top face. The surface profile includes a smooth curved portion, a draft portion, and a smooth radially outward portion. 
     An air flow entering the chamber creates a three-dimensional air flow that dissipates heat from the cooling device. First, the air flow exits the primary slots and a bottom portion of the secondary slots in an exhaust flow that dissipates heat from the vanes and the fins. Second, the exhaust flow creates a low pressure region within the chamber that induces an intake flow into the chamber through a major portion of the secondary slots and a top portion of the primary slots thereby dissipating heat from the fins and the vanes. Third, the low pressure region induces a surface flow along the first and second portions of the inner wall so that the surface flow wets the groove and the boss as it passes over the groove and the boss to dissipate heat from the heat mass. 
     In FIGS. 1 and 2 a  through  2   c,  a cooling device  10  for dissipating heat from a component (not shown) includes a heat mass  11 , a boss  13 , and a groove  15  that completely surrounds the boss  13 . The boss  13  and the groove  15  are symmetrically positioned about an axis Z—Z of the heat mass  11 . The boss  13  has a convex arcuate surface profile and the groove  15  has a concave arcuate surface profile. The arcuate profiles of the boss and the groove ( 13 ,  15 ) blend into each other as illustrated by dashed line a. The cooling device  10  further includes a heat conductive base  17  (base  17  hereinafter) that is in contact with the heat mass  11  and the base  17  includes a mounting surface  19  for contacting a surface of the component to be cooled. A plurality of vanes  21  are in contact with the heat mass  11  and the vanes  21  are spaced apart from one another to define a primary slot P (see FIGS. 2 a  and  2   c ) between adjacent vanes  21 . The vanes  21  have a surface area that increases in a radially outward direction from the axis Z—Z as indicated by the dashed arrow. At least a portion of the vanes  21  have a surface area that increases in a direction along the axis Z—Z as shown by dashed arrow y. 
     Preferably, the primary slot P extends to the heat mass  11  and the primary slot P includes a first arcuate surface profile  21   a  along the heat mass  11 . The first arcuate profile  21   a  terminates on a plane H—H (see FIG.  1 ). The plane H—H can be coincident with a bottom surface  11   a  of the heat mass  11 . It is also preferable that the vanes  21  are equidistantly spaced apart from each another. By extending the primary slot P to the heat mass  11 , air flow through the vanes  21  also wets the heat mass  11  to dissipate heat therefrom. The first arcuate surface profile  21   a  can be an arc having a radius from about 38.0 millimeters to about 45.0 millimeters. 
     One advantage of the cooling device  10 , is that a fan (not shown) for generating an air flow is not mounted on the heat mass  11 . Consequently, the vanes  21  can extend deep into the heat mass  11  (as illustrated by arrow e) and the depth of the vanes  21  provides a large surface area for efficient dissipation of waste heat and exposes the heat mass  11  to an air flow (see FIGS. 3 a  and  3   b ) that wets over the boss  13  and the groove  15  so that additional waste heat can be dissipated from the heat mass  11 . 
     The vanes  21  also include a top face  29 , an aerodynamically profiled inner wall  26  including a first portion  25  that extends from the groove  15  and terminates at a second portion  27  that extends to the top face  29 . The first portion  25  blends with the arcuate profile of the groove  15  as illustrated by dashed line b and the first portion  25  blends with the second portion  27  as illustrated by dashed line C. The second portion  27  blends with the top face  29  as illustrated by dashed line d. The inner wall  26  can include additional portions and the present invention is not to be construed as being limited to the first and second portions ( 25 ,  27 ). The inner wall  26  defines a chamber  30  that surrounds the groove  15 . 
     In one embodiment of the present invention, as illustrated in FIGS. 1,  2   c,  and  4 , the first portion  25  of the inner wall  26  is a slope surface and the second portion  27  of the inner wall  26  is a concave arcuate surface. The sloped and concave arcuate surfaces aerodynamically interact with an air flow into the chamber  30  so that the air flows along the first and second portions ( 25 ,  27 ) of the inner wall  26  and wet over the groove and the boss ( 15 ,  13 ) to dissipate heat from the heat mass  11  as will be described below in reference to FIGS. 3 a  and  3   b.    
     The first portion  25  can be inclined at an angle Ψ with respect to the axis Z—Z as illustrated in FIG.  1 . The angle Ψ can be in a range from about 15.0 degrees to about 75.0 degrees. If the vanes  21  have a tangential orientation with a circle about the axis Z—Z as will be discussed below in reference to FIG. 6, then the first portion  25  will have a tangential orientation with the groove  15 . The angle Ψ will vary based primarily on an output of a fan (not shown) in cubic feet per minute (CFM). 
     The vanes  21  further include an outer wall  32  having a surface profile that widens from a bottom  11   a  of the heat mass  11  to the top face  29  and includes a smooth curved portion  33 , a draft portion  35 , and a smooth radially outward portion  37 . The draft portion  35  an be substantially parallel to the axis Z—Z or the draft portion  35  can be inclined at an angle λ as illustrated in FIG.  4 . 
     In FIGS. 2 a  through  2   c,  the vanes  21  include at least one secondary slot S that extends through a portion of each vane  21  to define a plurality of fins  23  (two are shown) in each vane  21 . By splitting at least a portion of each vane  21  into a plurality of fins  23 , the available surface area for dissipating waste heat is increased and the secondary slot S provides an additional air flow path between the fins  23  that further increases waste heat dissipation. 
     In another embodiment of the present invention, the secondary slot S extends to the heat mass  11  and the secondary slot S includes a second arcuate profile  23   a  (see dashed line in FIG. 1) along the heat mass  11 . The second arcuate profile  23   a  terminates on the plane H—H. By extending the secondary slot S to the heat mass  11 , air flow through the fins  23  also wets the heat mass  11  to dissipate heat therefrom. The second arcuate profile  23   a  can be an arc having a radius from about 31.0 millimeters to about 38.0 millimeters. 
     Reference points for a center of the above mentioned radiuses (i.e. for  21   a  and  23   a ) will be positioned outside the cooling device  10  and the actual location of the center will depend on the arcs radius. However, the position of the center of the radius will be at least about 5.0 millimeters out side of the cooling device  10  to accommodate a cutting tool used in a machining process for making the cooling device  10 . The position of the center of the radius is a limitation imposed by a machining process that uses cutting wheels to form the vanes  21  and the fins  23 . If the vanes  21  and the fins  23  can be diecasted or impact forged, then the arc radius could be reduced and the position of the center of the radius could come inside the cooling device  10 . The cooling device  10  can be made amendable to a diecasted or impact forged process by reducing the number of vanes  21 . 
     In FIGS. 3 a  and  3   b,  heat dissipation by an air flow F entering the chamber  30  is illustrated. A portion of the air flow F exits the chamber  30  through the primary slots P and a bottom portion of the secondary slots S (not shown) in an exhaust flow E. The exhaust flow E passes over the vanes  21  and the fins  23  and dissipates heat therefrom. A low pressure region ΔP is created within the chamber  30  by the exhaust flow E. Consequently, the low pressure region ΔP induces an intake flow I into the chamber  30  through a major portion of the secondary slots S and a top portion of the primary slots P (not shown) thereby dissipating heat from the fins  23  and the vanes  21 . The low pressure region ΔP also induces a surface flow B along the aerodynamically shaped first and second portions ( 25 ,  27 ) of the inner wall  26 . The surface flow B passes over the arcuate profiles of the groove and boss ( 15 ,  13 ) thereby dissipating heat from the heat mass  11  as the surface flow B circulates back towards (i.e. it is a balancing air flow) the low pressure region ΔP. Therefore, another advantage of the cooling device  10  is that waste heat is efficiently dissipated by a three-dimensional air flow (comprising E, I, and B) through the vanes  21  and the fins  23 , and passing over the groove and boss ( 15 ,  13 ). 
     In one embodiment of the present invention, the arcuate surface profile of the boss  13  includes but is not limited to a profile of a sphere, a frustum of a sphere, a cone, and a frustum of a cone. In FIG. 1, the boss  13  has a conical surface profile. On the other hand, the surface profile could also be spherical. In FIG. 4, the boss  13  has a surface profile that is a frustum  13   a  of a cone. The boss  13  could also have a surface profile that is a frustum  13   a  of a sphere. 
     In another embodiment of the present invention, the arcuate surface profile of the groove  15  includes but is not limited to a semi-circular profile as illustrated in FIGS. 1 and 4. Preferably, the boss  13  has a diameter d B  (see FIG. 1) that is less than a diameter of a hub  79  of a fan  70  (see FIG.  9 ). The groove  15  should have a radius r G  (see FIG. 9) that provides a smooth change in air flow direction for the surface flow B as it transitions from the first portion  25  to the groove  15  so that the surface flow B flows over the groove  15  and onto the boss  13  (see FIG. 3 a ). As mentioned previously, the boss  13 , the groove  15 , and the inner wall  26  (i.e.  25  and  27 ) can be formed by forging, machining, or diecasting. 
     In FIGS. 5 a  and  5   b,  the vanes  21  can be inclined at angle with respect to the axis Z—Z. In FIG. 5 a,  the vanes  21  are inclined at an angle β measured between a line  21   c  and the axis Z—Z. The line  21   c  is measured along the primary slot P of the fins  23 . The inclination of the angle β includes but is not limited to a range from about 0 (zero) degrees to about 25.0 degrees. In another embodiment of the present invention as illustrated in FIG. 5 b,  the angle at which the vanes  21  are inclined with respect to the axis Z—Z includes a first angle δ 1  measured between a line  21   d  and the axis Z—Z and a second angle  62  measured between a line  21   e  and the axis Z—Z. The first angle δ 1  is measured along the smooth radially outward portion  37  of the fins  23 . The inclination of the first angle δ 1  includes but is not limited to a range from about 0 (zero) degrees to about 25.0 degrees. The second angle δ 2  is measured along the the smooth curved portion  33  of the fins  23 . The inclination of the second angle δ 2  includes but is not limited to a range from about 5.0 degrees to about 18.0 degrees. Because the fins  23  are defined by the vanes  21 , the fins  23  and the vanes  21  are inclined at the angles (β, δ 1 , and δ 2 ) as described above. 
     In one embodiment of the present invention as illustrated in FIG. 6, the vanes  21  have a tangential orientation with respect to a circle C t  (shown in dashed line) centered about the axis Z—Z (shown as a “+”) and having a predetermined diameter. In FIG. 6, an example of the. tangential orientation of the vanes  21  is illustrated by a plurality of the vanes  21  having tangent lines t drawn through their primary slots P and tangentially crossing a perimeter of the circle C t . A line M through the axis Z—Z and a parallel line N that also is tangential to the circle C t  define a radius R therebetween and the predetermined diameter of the circle C t  is two times the radius R (that is: C t= 2* R). The predetermined diameter includes but is not limited to a range from about 3.0 millimeters to about 12.0 millimeters. 
     In FIGS. 5 a,    5   b,  and  6 , at least a portion of the top face  29  of the vanes  21  includes a substantially planar portion  29   a  (shown as a dashed line). Preferably the substantially planar portion  29   a  covers the entirety of the top face  29  as illustrated in FIG.  6 . One advantage of the substantially planar portion  29   a  of the top face  29  is that a fan can be mounted on the substantially planar portion  29   a.    
     In FIG. 7, a fan  70  is positioned to be mounted on the substantially planar portion  29   a  of the top face  29 . The fan  70  generates an air flow (see reference letter F in FIG. 3 a ) into the chamber  30  of the cooling device  10  in a direction indicated by dashed arrow af. A shroud  73  houses a rotor hub  79  having a plurality of fan blades  77 . The rotor hub  79  is rotatably mounted on a stator  71  and the fan blades  77  rotate in a direction indicated by arrow af. Several holes  75  through the shroud  77  are adapted to receive a fastener  89 . 
     A mounting ring  80  including a frame  81  and several mounting fixtures  83  is abutted against a surface  37   a  of the smooth radially outward portion  37 . The diameter of the smooth radially outward portion  37  at the surface  37   a  is greater than an inside diameter of the frame  81  of the mounting ring  80  so that the frame  81  can be urged into snug contact with the smooth radially outward portion  37  without sliding off of the vanes and fins ( 21 ,  23 ). The only way to slide the mounting ring  80  off of the vanes and fins ( 21 ,  23 ) is in the direction of the base  17  because the diameter of the vanes and fins ( 21 ,  23 ) narrows in that direction. The mounting fixtures  83  receive the fastener  89  and optionally an additional fastener  87  such that the fan  70  is firmly connected with the top face  29  as illustrated in FIG.  8 . The fasteners ( 87 ,  89 ) can be a nut and bolt as shown or another type of fastener. Preferably, a rotational axis B—B of the fan  70  is colinear with the axis Z—Z of the cooling device  10  when the fan  70  is connected with the mounting ring  80 . Examples of suitable materials for the mounting ring  80  include but are not limited to metals, plastics, or ceramics. The mounting ring  80  can be produced by machining, casting, molding, and pressure diecasting. 
     Although the previous discussion has focused on fasteners as one means of connecting the mounting ring  80  with the fan  70 , the present invention is not to be construed as being limited to fasteners only. For instance, a latch on the fan could mate with a complementary latching profile on the mounting ring  80 . Because the mounting ring  80  can be formed by an injection molding process, many possibilities exist for effectuating the mounting of the fan  70  to the mounting ring  80  and fasteners are an example of one of those many possibilities. 
     In FIG. 8, the fan  70  is shown mounted on the substantially planar portion  29   a  of the top face  29 . For purposes of illustration, only one set of fasteners ( 87 ,  89 ) are shown installed through the holes  75  and the mounting fixtures  83 . A power lead  72  of the fan  70  is positioned so that it is not necessary for the power lead  72  to be routed through or to come into contact with the vanes or fins ( 21 ,  23 ). Although shown with only two wires (+ and −) the power lead  72  can include additional wires such as one or more additional wires for communicating with a circuit that controls the fan  70  (e.g turning fan  70  on or off, or controlling fan speed) or for determining if the fan  70  is operating properly. 
     Although only one fan  70  is shown in FIGS. 7 and 8, two or more fans  70  can be stacked one upon the other with the holes  75  aligned so that a longer fastener  89  can be inserted through the holes  75  an into the mounting fixtures  83  of th e mounting ring  80 . Therefore, another advantage of the cooling device  10  of the present invention is that a plurality of fans can be used to generate the air flow F into the chamber  30 . The use of more than one fan  70  allows for redundant cooling if one or more fans should fail. In contrast, prior fan assisted heat sinks in which the fan is mounted in a cavity formed by the fins, it is very difficult to mount more than one fan in the cavity. Moreover, because the fan  70  is not mounted in the chamber  30 , the risk s associated w ith routing the power lead  72  through th e vanes  21  is eliminated because the fan  70  is mounted on the top face  29 . An additional advantage to mounting the fan  70  on the top face is that if one or more of the vanes and fins ( 21 ,  23 ) are damaged, the blades  77  will not come into contact with a damaged vane or fin ( 21 ,  23 ); therefore, potential damage to the blades  77  or the fan  70  is eliminated. In FIG. 3 b,  a notch  41  can be formed in the fins  23 . The notch  41  can have a shape the complements an indexing tab (not shown) on the shroud  73  so that when the fan  70  is mounted on the top face  29  the indexing tab mates with the notch  41 . The notch  41  can be used to ensure proper orientation of the fan  70  with respect to the cooling device  10  and/or to prevent relative movement between the shroud  73  and the cooling device  10 . 
     In FIG. 9, the tangential orientation of the vanes  21  can be determined by two factors (note: the base  17  has been omitted for purposes of illustration) A first factor is a height h 1  from the top of the boss  13  to the top face  29 . For example, when the height h 2  is about 7.5 millimeters, the vanes  21  can be tangential to the circle C t  having a diameter of about 6.5 millimeters. On the other hand, a second factor is a height h 2  from the top of the boss  13  to a bottom  76  of the fan blades  77 . For instance, the diameter of the circle C t  can be from about 3.0 millimeters to about 12.0 millimeters when the height h 2  varies from about 2.0 millimeters to about 8.5 millimeters. The above are examples only and the heights (h 1 , h 2 ) are not to be construed as being limited to the ranges set forth above. 
     The angle (β, δ 1 , and δ 2 ) at which the vanes  21  are inclined relative to the axis Z—Z as described above can be set to substantially match or closely approximate a pitch angle θ of the fan blades  77  as illustrated in FIG.  9 . On the other hand, the angles (β, δ 1 , and δ 2 ) can be set so that they are within a predetermined range of the pitch angle θ. For example, the pitch angle θ can be about 15.0 degrees and the angle β can be about 17.0 degrees or the pitch angle θ can be about 12.0 degrees and the angle δ 1  can be about 10.0 degrees and the angle δ 2  can be about 8.0 degrees. 
     Another advantage of the cooling device  10  of the present invention is that the aforementioned tangential orientation and inclination of the vanes  21  and the aerodynamically profiled first and second portions ( 25 ,  27 ) of the inner wall  26  provide a low resistance path to the air flow F thereby reducing airflow shock noise. Additionally, because of the low resistance path, the fan  70  can be a lower RPM fan which produces lower noise levels and can be operated on less power than a higher RPM fan. 
     The cross-sectional view of the cooling device  10  in FIG. 9 (sans the base  17 ) also depicts radiuses for the arcuate shapes of the boss  13 , the groove  15 , the second portion  27 , the first arcuate surface profile  21   a,  and the second arcuate surface profile  23   a.    
     The arcuate profile of the boss  13  can have a radius r B  that is dependent in part on a desired thermal mass for the boss  13 . For instance, for a thermal mass of about 50.0 grams, the radius r B  for the boss  13  is about 15.0 millimeters. Similarly, the arcuate profile of the groove  15  has a radius r G  of about 2.5 millimeters. The actual values for r B  and r G  will be application dependent and the above values are examples only. The present invention is not to be construed as being limited to the values set forth above. 
     Furthermore, the arcuate surface profiles for the first and second arcuate surface profiles ( 21   a,    23   a ) have a radius of r V  and r F  respectively. For example, the radius r V  can be from about 38.0 millimeters to about 45.0 millimeters and the radius r F  can be from about 31.0 millimeters to about 38.0 millimeters. The second portion  27  of the inner wall  26  has a radius r C . The radius r C  can be about 20.0 millimeters, for example. The actual values for r V,  r F  and r G  will be application dependent and the above values are examples only. The present invention is not to be construed as being limited to the values set forth above. 
     The above mentioned radiuses can be determined by a machining process used to form the cooling device  10 . Reference points for the radiuses need not be relative to a point on the cooling device  10 . The radiuses r B , r G  and r C  can be formed by a forging process. They can also be machined or produced using a diecasting process. The radiuses r V  and r F  can be formed by machining after forging the cooling device  10  from a blank or material. 
     In one embodiment of the present invention as illustrated in FIG. 10, a fan  74  without a shroud (i.e. it lacks the shroud  73  of FIGS. 7 and 8) is positioned over the top face  29  of the cooling device  10  by a space frame  90 . A stator  71  of the fan  74  is connected with the space frame  90  and a plurality of arms  91  span the width of the top face  29  and fingers  93  at the ends of the arms  91  clamp the space frame  90  to the cooling device  10  approximately at the surface  37   a  of the smooth radially outward portion  37 . Consequently, a hub  79  and blades  77  of the fan  74  are positioned over the chamber  30  so that an air flow from the fan  74  can enter the chamber  30  as was described above. Moreover, power leads  72  from the fan  74  can be routed away from the fins and vanes ( 21 ,  23 ) of the cooling device  10  and away from the fan blades  77 . 
     The space frame  90  can be integrally formed with the stator  71  or the space frame  90  can be made from a metal or plastic material, preferably plastic because it is electrically non-conductive. 
     In another embodiment of the present invention as illustrated in FIGS. 1,  4 , and  11 , the base  17  of the cooling device  10  includes at least two projections  22  that extend outward of the mounting surface  19 . A thermal interface material  24  is positioned between the projections  22  and is in contact with the mounting surface  19 . The projections  22  protect the thermal interface material  25  from damage when the base  17  is in contact with a component  50  or from damage during manufacturing, transit, and handling. The thermal interface material  24  is in contact with a component face  51  of the component  50  and the thermal interface material  24  provides a thermally conductive path for waste heat from the component face  51  to be communicated through the base  17  and into the heat mass  11 . The projections  22  prevent the thermal interface material  24  from being crushed, deformed, or otherwise damaged by mounting the cooling device  10  on the component  50  and/or during manufacturing, transit, and handling. The projections  22  can extend outward of the mounting surface  19  by a distance d p  (see FIG. 1) from about 0.2 millimeters to about 1.0 millimeters. Preferably, the mounting surface  19  is a substantially planar surface (i.e. it is substantially flat) and the mounting surface  19  is substantially perpendicular to the axis Z—Z (i.e. about 90.0 degrees, see angle α in FIG.  10 ). 
     Additionally, the thermal interface material  24  seals micro voids (i.e. gaps) between the mounting surface  19  and the component face  51  thereby enhancing thermal transfer from the component  50  to the cooling device  10 . Suitable materials for the thermal interface material  24  include but are not limited to a thermally conductive paste, a thermally conductive grease, silicone, paraffin, a phase transition material, graphite, a coated aluminum foil, and carbon fiber. The thermal interface material  24  can be screen printed or pasted to the mounting surface  19 , for example. 
     In FIGS. 4 and 12 a  through  12   d,  the base  17  can include a cylindrical neck  18  that is inset (see reference numeral  18   a ) from the base  17  to define an attachment groove  18   g  between the base  17  and the heat mass  11 . The base  17  can also include a pair of flats  28  that are positioned substantially perpendicular to the mounting surface  19  and positioned in parallel opposition to each other. In FIGS. 12 a  and  12   b,  the base  17  can have a cylindrical or elliptical shape  55  with the flats  28  formed on opposing sides of the base  17  (see FIG. 12 b ). The aforementioned projections  22  can have an arcuate shape that complements the cylindrical shape  55 ; however, the projections  22  can have any shape including a linear shape. The flats  28  can be formed using conventional machining processes such as milling, for example. The projections  22  can be positioned proximate the edges of the base  17  as shown in FIGS. 12 b  and  12   d,  or the projections  22  can be inset (see dashed arrows i) from the edges as illustrated in FIG. 12 b  and FIG.  1 . 
     FIG. 12 d  is an enlarged view of a section L—L of FIG. 12 c  illustrating the base  17 , cylindrical neck  18 , and the projections  22 . The projections  22  extend slightly outward of the mounting surface  19 ; however, the distance d p  for the projections  22  will depend on factors including the thickness of the thermal interface material  24 . 
     In FIG. 13, a system for dissipating heat  100  includes the cooling device  10  as described above, a fan  70  connected with the top face  29  as described above, a component  50  to be cooled by the cooling device  10 , and a base mount  300 . A component face  51  of the,component  50  is in contact with the mounting surface  19 , or as described above in reference to FIG. 11, a thermal interface material  24  may be positioned intermediate between the component face  51  and the mounting surface  19 . In either case, waste heat is thermally communicated through the component face  51  into the base  17  either by direct contact between the component face  51  and the mounting surface  19  or via the thermal interface material  24 . The base mount  300  urges the mounting surface  19  and the component face  51  into contact with each other so that heat from the component is thermally communicated into the cooling device  10 . 
     In one embodiment of the present invention, the mounting surface  19  of the cooling device  10  includes the projections  22  that extend outward of the mounting surface  19  and the thermal interface material  24  is positioned intermediate between the projections  22  as described above in reference to FIG.  11 . 
     In another embodiment of the present invention, the base  17  of the cooling device  10  includes the cylindrical neck  18  that is inset  18   a  from the base  17  to define the attachment groove  18   g  and the flats  28  as was previously described in reference to FIGS. 4 and 12 a  through  12   d  above. In yet another embodiment of the present invention, the mounting surface  19  includes the projections  22  and the thermal interface material  24  as described above. 
     In another embodiment of the present invention, the component  50  is carried by a support unit  99 . The support unit includes but is not limited to a socket, a substrate, and a PC board. The socket can be mounted to a PC board in a manner that is well understood in the electronics art. For instance the component can be a micro processor that is inserted into a socket that is solder onto a PC board. The base mount  300  is removably connected with the support unit  99 . On the other hand, the support unit can be a PC board on which the component  50  is soldered or otherwise electrically connected with. Although the present invention has described the cooling device  10  in terms of its usefulness in dissipating waste heat from electronic components, the cooling device  10  and the system  100  are not to be construed as being limited to cooling electronic devices exclusively. Accordingly, the component  50  can be any heat generating device from which it is desirable to remove heat. To that end, the support unit  99  need not be a PC board or a socket. The support unit  99  can be a substrate that carries the component  50 . The component  50  may or may not be in electrical communication with the substrate. 
     In FIG. 13, the base mount  300  is a base plate such as the type used for mounting a heat sink to a PC board. A plurality of holes  300   a  formed in the base mount  300  and a plurality of holes  99   a  formed in the support unit  99  receive fasteners ( 87 ,  89 ) that removably connect the base mount  300  with the support unit  99 . Although a nut and bolt are shown, other fasteners and other fastening methods can be used to removably connect the base mount  300  with the support unit  99 . 
     In FIG. 14, a system  200  includes the cooling device  10 , the component  50 , the fan  70 , and the support unit  99  that carries the component  50 . The base mount  300  is a spring clip including a handle  122  for latching and unlatching the spring clip from the support unit  99  that carries the component  50 . In FIG. 14, the support unit  99  is a socket such as a zero insertion force socket, for example. The spring clip includes a hinge end  116  and a latch  117 . The hinge end  116  includes a hinge  118  that can be removably hinged on a tab  94  connected with the support unit  99  and the latch end  117  includes a latch  131  that can be removably latched onto a tab  92  also connected with the support unit  99 . The support unit  99  can be mounted on a PC board  101 . 
     The spring clip includes a pair of ribs (see reference numerals  114 ,  115  in FIGS. 15 b  and  15   c ) that include latch arms  137  and hinge arms  136  that have a vertex V at a rocking axis Y—Y. The rocking axis Y—Y is colinear with a load axis B—B of the spring clip. The hinge arm  136  has a portion  136   a  that is inclined at an angle relative to a base plane (not shown) through the vertex V and the latch arm  137  has two portions  137   a  and  137   b  that are also inclined at an angle with respect to the vertex. Those angles result in a load L being applied substantially along the load axis B—B when the spring clip is latched as shown in FIG.  14 . The load L is also substantially colinear with the axis Z—Z and with a component axis C—C of the component  50 . Preferably the component axis C—C is at a center of the component  50  so that the load L acts substantially at the center of the component. 
     FIGS. 15 a  through  15   c  illustrate insertion of the cooling device  10  into the spring clip which is denoted as reference numeral  300 . In FIGS. 15 a  and  15   b  the flats  28  of the cooling device  10  are aligned with inside edges  132  of the ribs ( 114 ,  115 ) and then the base  17  is inserted through an opening  133  between the ribs ( 114 ,  115 ) until the attachment groove  18   g  of the cylindrical neck  18  is between the ribs ( 114 ,  115 ). Next, the cooling device  10  is rotated as illustrated by angle Ω in FIG. 15 c.  For example, the angle Ω can be about 90.0 degrees. Now, the flats  28  are substantially perpendicular to the ribs ( 114 ,  115 ) and are positioned below the ribs ( 114 ,  115 ) so that the rocking axis Y—Y rests on an upper surface  18   e  of the base  17 . Next, a locking rib  128  is inserted into a set of notches (not shown) on the ribs ( 114 ,  115 ) of the hinge end  116 . After insertion, the locking rib is substantially parallel to the rocking axis Y—Y and the locking rib  128  rests against one of the flats  28  so that the cooling device  10  cannot be rotated out of the spring clip  300 . 
     Finally, the hinge  118  is inserted over the tab  94  and the latch  131  is latched onto the tab  92  of the support unit  99  thereby placing the mounting surface  19  in contact with the component face  51 . With the spring clip  300  latched to the support unit  99 , the load L exerted by the spring clip  300  acts along the load axis B—B. Preferably, the load axis B—B, the component axis C—C, and the axis Z—Z of the cooling device  10  are colinear with one another. 
     Ideally, the component face  51  and the mounting surface  19  are substantially planar (i.e they are flat) and the component  50  is mounted substantially level in the support unit  99 ; however, due to manufacturing processes there can be deviations from a substantially planar surface, the component  50  may not be level, and thermally induced dimensional changes in any of the aforementioned elements of the system  200  can cause deviations from the ideal. The ribs ( 114 ,  115 ) at the rocking axis have an arcuate surface shape that allows the cooling device  10  some freedom of movement while exerting the load L along the load axis B—B. Therefor, the aforementioned deviations are compensated for by not rigidly fixing the cooling device  10  within the spring clip  300 . Additionally, the ribs ( 114 ,  115 ) can include one or more embossed features  129  that also allow the cooling device some freedom of movement within the spring clip  300 . The embossed features  129  are urged into contact with the upper surface  18 e when the spring clip  300  is latched to the support unit  99 . 
     Removal of the cooling device  10  is the opposite of insertion. The spring clip  300  is unlatched from the support unit  99  by using the handle  122  to unlatch the latch  131  from the tab  92  and pivoting the spring clip  300  to disconnect the hinge  118  from the tab  94 . Next, the locking rib  128  is removed from the spring clip  300  freeing the base  17  to rotate. The base  17  is then rotated until the flats  28  are substantially parallel to the inside edges  132  and then the base  17  is pulled out of the opening  133 . 
     The spring clip  300  is described in applicants Pending U.S. Utility Patent Application Ser. No. 09/916,477 entitled “SPRING CLIP FOR A COOLING DEVICE”, filed on Friday, Jul. 27, 2001 and assigned to the assignee of the present application. The above mentioned Pending application is incorporated herein by reference as though set forth in its entirety. 
     The systems ( 100 ,  200 ) can include the projections  22  on the mounting surface  19  and the thermal interface material  24  as was described above in reference to FIG.  11 . The thermal interface material  24  can be connected with the mounting surface  19 , the component face  51 , or both prior to latching the spring clip  300  to the support unit  99  or prior to mounting the base plate of FIG. 13 to the support unit  99 . 
     In one embodiment of the present invention, the systems ( 100 ,  200 ) can include a shroudless fan  74  as was described above in reference to FIG.  10 . The fan  74  includes the space frame  90  for supporting the fan  74  and for positioning the fan  74  adjacent to the top face  29  and over the chamber  30  so that the air flow af enters the chamber  30 . As previously mentioned, the space frame  90  includes a plurality of arms  91  that span the width of the top face  29  and fingers  93  on the arms  91  clamp the space frame  90  to the smooth radially outward portion  37  of the outer wall  32 . 
     Preferably, the heat mass  11 , the base  17 , and the vanes  21  are homogeneously formed. An extrusion process can be used to homogeneously form the heat mass  11 , the base  17 , and the vanes  21 . The cooling device  10  can be made from a variety of thermally conductive materials including but not limited to copper, electrolytic copper, aluminum, and alloys of aluminum and copper, ceramics, and silicon (Si) substrates. An exemplary material for the cooling device  10  is aluminum 1060 or aluminum 6063. 
     The cooling device  10  can be manufactured by a variety of processes including but not limited to those listed below. First, the cooling device  10  can completely machining from an extruded bar stock. Second, a diecasting, forging, or pressing process can be used to form either one or both of the internal and external features ( 26 ,  32 ) of the cooling device  10 , followed by a machining process to form the base  17 , the mounting surface  19 , the projections  22 , the cylindrical neck  18 , and the attachment groove  18   g.  Next cutting wheels can be used to form the primary P and secondary S slots for the vanes  21  and the fins  23  respectively, followed by deburring and degreasing. Third, impact forging the complete cooling device  10  including the vanes  21  and fins  23 . Fourth, pressure diecasting the complete cooling device  10  including the vanes  21  and fins  23 . 
     An exemplary model of the cooling device  10  was created with a diameter of 65 mm at the top face  29  and a diameter of 50 mm at the bottom surface  11   a  of the heat mass  11 . The base  17  had a diameter of 40 mm and height of 6.5 mm from the bottom surface  11   a.  The cooling device  10  had a total height from the mounting surface  19  to the top face  29  of about 33 mm. The heat mass  11  had a total height of about 22 mm from the mounting surface  19  to a top of the boss  13 . The smooth curved portion  33  had a radius of about 33 mm and the draft portion  35  had a diameter of about 63 mm. A Delta fan, model number EFB0612HA, and having dimensions of 60 mm×60 mm×10 mm in length, breadth, and height was mounted to the cooling device  10  as illustrated in FIG.  14 . The cooling device  10  was then mounted on a processor carried by a PGA 370 connector that was soldered onto a mother board. The processor had a top surface of approximately 9 mm×11 mm and a thermal output of 36 watts. The cooling device  10  as described in this paragraph was capable of maintaining the case temperature of the processor at 38.0 degrees Celsius at an ambient temperature of 25.0 degrees Celsius. Based on the above temperatures, a temperature difference of 13.0 degrees Celsius for 36 watts of thermal power results in an estimated thermal resistance for the cooling device  10  of 0.3611 degrees Celsius per watt (13.0 degrees Celsius /36 watts =0.3611). 
     Although several embodiments of the present invention have been disclosed and illustrated, the invention is not limited to the specific forms or arrangements of parts so described and illustrated. The invention is only limited by the claims.