Abstract:
A heat dissipating apparatus for use on a heat generating electric component inside a computer comprises an interposer mounted on the heat generating electric component and a heat absorbing member including a heat absorber, a bracing member, and a spring biasing said heat absorber toward the bracing member. The heat absorbing member is moveable between a first position in which the interposer is compressed between the heat absorber and the bracing member and a second position in which the interposer is not compressed between the heat absorber and the bracing member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to the cooling of heat-generating components in electronic apparatus and more particularly to the cooling of a heat-generating computer components. Still more particularly, the present invention relates to a spring-loaded heat dissipation apparatus that is particularly suited for use with heat generating components inside a computer. 
     2. Background of the Invention 
     As computer operating speeds and chip capacities keep increasing, it is becoming increasingly difficult to provide adequate cooling for processors and other high heat generating components used in electronic equipment. This is particularly true in the case of computers utilizing multiple processors and hot plug drive arrays. At the same time, as component density and power usage increase, it becomes increasingly important to remove the heat generated during operation so as to avoid overheating and ensure consistent operation of the devices. 
     For example, one trend in the computer industry has been to increase the number of CPUs per rack unit. Because rack space inside a computer is limited, there has been a trend toward packing more components, such as CPUs, memory, disk drives, and I/O, more and more closely together. As the components, each of which generate heat, are packed more closely together, air cooling becomes less feasible. Forced air cooling, which entails blowing air across hot components, or across a heat sink in thermal contact with the hot components, is limited to applications in which the flowing air can maintain a sufficient velocity across the hot components and thus can effectively remove heat from it. When components are packed together, it is no longer possible to achieve sufficient air velocity across the hot components. 
     This is particularly true when chips are disposed within multi-chip modules that generate significant amounts of heat. In addition, because there is a great demand to run these processor modules at higher speeds, the corresponding clock frequencies at which these devices must operate become higher. In this regard, it should be noted that power generation rises in proportion to the clock frequency. Accordingly, that the desire for faster computers generates not only demand for faster components, but also generates thermal demands in terms of energy that must be removed for faster, safer and more reliable circuit operation. 
     Until recently, extruded aluminum heat sinks have been considered sufficient for computer cooling needs. These metal heat sinks depend on air moving through the system to carry away waste heat, However, aluminum heat sinks have a number of well known disadvantages, which include the following: 1) heat sinks often obstruct access and impede processor removal; 2) the to include large heat sinks can force too wide spacing of multiple processors, causing signal propagation delay and package volume concerns; 3) the chassis design must allow sufficient air flow past the heat sink; 4) large heat sinks often obstruct air flow to other components; 5) large heat sink volumes decrease the density of a system design; 6) air heated by the processor heat sink is less effective for cooling other components in the electronic apparatus; 7) supporting the mass of a large heat sink poses mounting and vibration concerns; and 8) fans may be required to provide sufficient air flow across a heat sink. 
     With air cooling becoming less adequate, liquid cooling has begun to be more widely practiced for cooling computer components. In liquid cooling, sometimes also referred to as “cold plate” cooling, a liquid is pumped through a closed loop cooling system and removes heat from heat exchangers that are in thermal contact with each of the processor chips (or other high heat-generating components or assemblies). Provided sufficient heat transfer occurs between the hot components and the liquid coolant, liquid cooling is much more effective than air cooling. On the other hand, liquid cooling requires a suitable heat transfer mechanism between the hot components and the coolant, and requires plumbing to handle the liquid cooling medium in both cooled and heated states. In instances where it is desired to provide hot-add and/or hot-replace access to the components, conventional cold plate installations often require disconnection of the fluid lines from the cold plates so as to allow access to the desired component(s). 
     Known techniques for achieving the required degree of thermal contact between a hot component and its associated cold plate typically involve cams or screws, which can maintain a desired amount of pressure at the interface between the hot component and the cold plate. However, cams may require special linkages to force the surfaces together during installation and to release contact prior to removal. Similarly, screws and/or bolts may be difficult to access and to or remove, particularly when the hot component is buried deep within the chassis or obstructed by other devices. 
     An example of such a linkage structure can be found in U.S. Pat. No. 5,886,872. The linkage structure allows the heat absorbing member to shift between first and second positions in which the heat absorbing member is alternately connected and disconnected from thermal contact with the heat generating electronic component. While such a linkage structure has clear advantages in ease of use, it is still desirable to provide a means by which a heat absorbing member can be effectively and quickly attached to a heat generating component. 
     In view of the foregoing problems, limitations and disadvantages associated with the above-mentioned cooling systems, it can seen that a need exists for an alternative type of cooling system that eliminates or at least substantially reduces such problems, limitations and disadvantages. In particular, it is desirable to provide a mechanism for applying a desired amount of pressure at the interface between the hot component and the cold plate. It is further desirable to provide a cooling device that is easy to install, and to eliminate the need for tools and/or special linkages for achieving thermal contact. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention includes a cooling system that substantially reduces the problems, limitations and disadvantages described above. In particular, the present invention provides a mechanism for applying a desired amount of pressure at the interface between the hot component and the cold plate. The present invention further provides a cooling device that is easy to install and makes it possible to achieve and maintain the desired thermal contact without tools and/or special linkages. 
     In one preferred embodiment of the present invention, an electronic device such as a computer comprises a housing and a heat generating electronic component, such as a processor, disposed in the housing. To dissipate operating heat from the heat generating component, a heat dissipation apparatus is provided within the housing and comprises at least one heat absorbing member, a bracing member, and a holding structure connecting the heat absorbing member to the bracing member and supporting the heat absorbing member in a heat transfer relationship with the heat generating electronic component. 
     According to a feature of the invention, the holding structure is manually operable, without tools, to releasably clamp the heat absorbing member against the heat generating electronic component. 
     According to another feature of the invention, the heat generating electric component has at least one heat transfer surface that is provided with a tapered heat sink interposer. In one preferred embodiment, the heat generating electric component has two opposing heat transfer surfaces, each of which is provided with a tapered heat sink interposer. The heat absorbing member is provided with a corresponding pair of opposed heat absorbers supported on a spring-loaded holding device. The combination of the two tapered interposers forms a wedge-shaped body that easily slides between the two opposed heat absorbers, wedging them apart against the closing force applied by the spring-loaded holding device. In another embodiment, the heat generating electric component has only one heat transfer surface and the heat absorbing member is provided with one heat absorber, which contacts the heat transfer surface, and one bracing member, which contacts the opposite surface of the heat generating electric component. 
     According to another feature of the invention, at least one, and preferably both, of the heat absorbers comprises a liquid cooled cold plate. If both heat absorbers are not cold plates, the second heat absorbing member may comprise a finned metal heat sink member adapted for air cooling or some other suitable heat absorbing device. 
     The incorporation of the present heat dissipating apparatus in a computer allows sufficient cooling to be applied to even crowded, high-output systems and allows tool-less installation and removal access to the processor and near by equipment. The present system allows the disconnection of the heat absorbing member from thermal contact without necessitating disconnection of fluid flow lines. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which: 
     FIG. 1 is a schematic top view of a beat dissipation system constructed in accordance with a preferred embodiment of the present invention, shown in its decoupled state; 
     FIG. 2 is a perspective view of the heat dissipation system of FIG. 1; 
     FIG. 3 is a schematic top view of the heat dissipation system of FIG. 1, shown in its coupled state; 
     FIG. 4 is a schematic top view of a heat dissipation system constructed in accordance with a first alternative embodiment of the present invention, shown in its decoupled state; 
     FIG. 5 is a schematic top view of the heat dissipation system of FIG. 4, shown in its coupled state; 
     FIG. 6 is a schematic top view of a heat dissipation system constructed in accordance with an alternative embodiment of the present invention, shown in its decoupled state; 
     FIG. 7 is a perspective view of the heat dissipation system of FIG. 7; and 
     FIG. 8 is a schematic top view of the heat dissipation system of FIG. 6, shown in its coupled state. 
    
    
     NOTATION AND NOMENCLATURE 
     Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, computer companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Also, unless otherwise noted, the term “contact” or “contacts” is intended to require either indirect or direct thermal conductivity other than through air. Thus, if a first device contacts a second device, that heat can be conducted between the devices through either a direct physical contact, or through indirect physical contact via other devices and components. Similarly, references to vertical, horizontal, above, or below, refer to the illustrations in the Figures only, and are not intended to limit the invention in any way. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to FIGS. 1 and 2, a first embodiment of the present heat dissipation apparatus comprises a heat absorbing member  10  and a wedge-shaped body  70 . Heat absorbing member  10  comprises a pair of liquid cooled cold plates  20 , which are connected together and held in a loosely parallel, spaced, opposing relationship by at least one flexible spring member  30 . Spring member  30  can be a metal piece, such as a metal strip, or any other suitably springy material. Each cold plate  20  preferably comprises a thermally conductive body  26  through which a fluid conduit  27  passes. As is known in the art, fluid conduit  27  (shown in phantom) is preferably U-shaped and is connected at one end to a fluid inlet line  28 , and at its other end to a fluid outlet line  29 . Cold plates  20  are preferably connected by means inlet  28  and outlet  29  to flexible coolant lines (not shown), which in turn may be connected to a conventional refrigeration system, which may include, for example, components such as motors, heat exchanger and pressure relief chamber, together with an expansion device. 
     Body  26  of each cold plate  20  is preferably constructed of a highly thermally conductive material, such as aluminum or the like. Cold plates  20  preferably are configured as substantially rectangular prisms, and are arranged with their largest aspects  23  loosely parallel to one another. If desired, a small chamfer  21  can be provided along one or more of the long corners of each body  26 , particularly along the comer facing the opposite cold plate. 
     Cold plates  20  are each preferably connected to their respective end of spring(s)  30  by a pivotable mount  32 . Mount  32  can be any suitable pivotable mounting device, but preferably allows each cold plate  20  to pivot about at least its vertical (as drawn) longitudinal axis. 
     Still referring to FIGS. 1 and 2, a printed circuit board (PCB)  50  has heat generating electric components  54  mounted on both of its opposed faces  52  in a conventional manner. In a preferred embodiment of the invention, each heat generating electric component  54  has an electrical contact face  56 , which faces the PCB  50 , and a heat transfer face  58 , which is outward. Each heat transfer face  58  supports a thermally conducting interposer  60 . Each interposer  60  has a uniform aspect along its height, but tapers from a first, lesser thickness at one long edge  62  to a second, greater thickness at its opposite long edge  64 . As shown in FIG. 1, interposers  60  are preferably mounted such that their thinner edges  62  are oriented the same way with respect to PCB  50  and define an inner end  66 . Likewise, thicker edges  64  are oriented the same way with respect to PCB  50  and define an outer end  68 . In this manner, the tapered interposers  60 , in combination with heat generating electric components  54 , and PCB  50  form wedge-shaped body  70 . If desired, a chamfer  61  can be provided along one or more of the long comers of each interposer  60 , particularly along the comer facing the opposite interposer. It is preferred that the interface between each interposer  60  and its respective heat generating electric component be a highly thermally conductive interface, so as to maximize the heat dissipating capability of the system. 
     Referring now to FIG. 3, heat absorbing member  10  is shown in thermal contact with wedge-shaped body  70 . Specifically, when it is desired to place cold plates  20  in contact with heat generating electric components  54 , heat absorbing member  10  is advanced over the edge of PCB  50  until interposers  60  fully engage cold plates  20 . 
     It is preferred to construct spring  30  such that it supports cold plates  20  such that the distance between their opposed faces  23  when interposers  60  are disengaged is somewhat less than the thickness of the outer end  68  of body  70 . In this manner, it is ensured that spring  30  will be loaded when the interposers  60  are fully engaged and will urge cold plates  20  toward interposers  60  with sufficient force to ensure good thermal conductivity. If the deformation caused by the engagement of interposers  60  alone is insufficient to cause spring  30  to apply a sufficient load, spring  30  can be pre-loaded. If spring  30  is pre-loaded, it will bias cold plates  20  together even when interposers  60  are disengaged. If pre-loading is desired, it is preferred to include a releasable stop (not shown) between cold plates  20 , so that cold plates  20  are prevented from completely coming together when interposers  60  are disengaged. The combination of pre-loading with the use of a stop makes it possible to maintain cold plates  20  farther apart, such that the distance between them is greater than the thickness of inner end  66 , although it must still be less than the thickness at out end  68  so that the load is transferred from the stop to the interposer. This in turn makes it relatively easy to initiate insertion of wedge  70 . Similarly, chamfers  21 ,  62 , if provided, assist in the initial insertion by aligning the inner end  66  between cold plates  20 . The pivotable mounting of cold plates  20  ensures that cold plates  20  align with the outer surfaces of interposers  60 . 
     It is preferred to include at least one releasable latch (not shown), such as a locking tab, for maintaining heat absorbing member  10  in contact with wedge-shaped body  70 . 
     Referring now to FIGS. 4 and 5, an alternative embodiment of the present heat dissipating system includes a heat absorbing member  110  and a wedge-shaped body  70 . Heat absorbing member  110  includes a single cold plate  20  affixed to one end of a spring  30 , with the other end of the spring  30  preferably supporting a non-conductive roller  120 . Roller  120  is preferably mounted so that it rotates around an axis that is out of the plane of the paper as drawn. As discussed above, spring  30  biases cold plate  20  and roller  120  together to ensure good thermal contact between cold plate  20  and interposer  60 . Whereas in the embodiment shown in FIGS. 1-3 each cold plate  20  acts as a bracing member for the other cold plate, in the embodiment shown in FIGS. 4 and 5 roller  120  acts as a bracing member for cold plate  20 . 
     Referring now to FIGS. 6-8, a second alternative embodiment includes a spring-loaded heat absorbing member  10  as described above, in combination with a wedge-shaped body  270  that is thermally coupled to a heat sink  280 . More particularly, wedge-shaped body  270  includes tapered interposer  260  mounted on a thermal conductor  274 . In one preferred embodiment, thermal conductor  274  comprises a vapor phase heat pipe. Alternatively, conductor  274  can comprise a length of thermally conducting material, such as aluminum, or a liquid phase heat pipe. Conductor  274  extends between interposer  260  and a heat sink device  276  (FIG.  8 ), which in turn contacts a heat generating electric component  254 . The inclusion of conductor  274  makes it possible to use the more effective fluid cooling on heat generating electric components that are difficult to access, without forfeiting the easy connection and disconnection of the fluid cooling system. As above chamfers  21  and  261  can be provided to facilitate engagement of the interposer(s) with the cooling plates. 
     It is important to note that in each embodiment of the invention, the movement of the cold plate(s)  20  into and out of contact with the heat generating electric components can be achieved easily and quickly without the use of any tools whatsoever, and without the need to disconnect the fluid lines from the cold plates. 
     While preferred embodiments of the invention have been disclosed and described, it will be understood that various modifications can be made to the apparatus described herein without departing from the scope of the invention. For example, it is not necessary to use a single spring to bias the cold plates together. Instead, each plate can be provided with its own separate spring, with both springs being mounted on a support device. Similarly, the interposers do not have to be tapered along their entire lengths, so long as they form a body that is wider at one point than the resting distance between the cold plates, so that the compression load of the spring pre-loaded or otherwise) can be transferred to the interposer so as to facilitate heat transfer.