Abstract:
A heat sink retention assembly for retaining a heat sink in thermal contact with a CPU while transmitting load away from the CPU. The heat sink retention assembly includes a frame sized to receive the heat sink, the frame including opposing pin capture channels and a wire module. The wire module includes an upper handle section and a lower pivoting section. The wire module is pivotably coupled to the frame at the lower pivoting section. The wire module further includes opposing end pins, wherein each pin is moveably retained within and extends through a corresponding pin capture channel such that when the wire module is rotated with respect to the frame, the pins travel within their respective channels in order to engage the heat sink.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Statement of the Technical Field  
         [0002]     The present invention relates to heat sinks and more particularly to a method and apparatus of securing a heat sink above a central processing unit (CPU) of a computer in order to divert the weight and force of the heat sink to the computer&#39;s chassis or mounting plate rather than toward the CPU while maintaining the requisite thermal interface with the CPU.  
         [0003]     2. Description of the Related Art  
         [0004]     Heat sinks are a vital part of any computer system. The heat generated by continued and extended use of a computer can severely damage the electrical components in the computer. Heat sinks provide a way for the heat to be transferred away from the source and away from critical components. To increase the amount of thermal transfer, heat sinks typically include a large surface area or a large number of thermally conductive fins. However, the problem that arises when large heat sinks or heat sinks with a large number of fins are used is that critical space within the confines of the computer chassis is used up. Also, heavy heat sinks must be secured directly to the computer chassis in order to avoid transmitting the direct weight of the heat sink on the CPU.  
         [0005]     The contact area between the heat sink and the electrical components and the pressure at the point of contact between the heat sink and the heat source are also important considerations in heat sink design. A heat sink with a flat contact area is preferred since a thinner layer of thermal compound may be used. This reduces the thermal resistance between the heat sink and the heat source. The pressure between the heat sink and the heat source must be high in order to maintain the requisite thermal contact and to facilitate thermal flow. Mechanical clips may help maintain the requisite pressure between the surface of the heat sink and the CPU, but such clips are usually difficult to install and are not reliable when the computer is being shipped. Even a slight jarring during shipping may cause the weight of the heat sink to fall directly on the CPU or motherboard causing severe damage. Further, because of the increased thickness in motherboards, the use of an under-the-board spring to dampen the force exhibited by the heat sink on the CPU and other electrical components is no longer feasible.  
         [0006]     The recent proliferation of Land Grid Array (LGA) sockets have created another problem that must be considered during heat sink design and particularly in the manner in which heat sinks or other cooling devices are attached to the socket/CPU assembly. Current LGA socket designs frequently contain heat sinks as part of the assembly. The heat sink base is usually used as one of the loading plates in the assembly and is typically attached to a back-side stiffener using multiple screws or spring-loaded threaded fasteners. Even these simple attachment means can consume a significant portion of the effective heat sink volume, since the screws or spring-loaded fasteners protrude through the heat sink and require removal or partial removal of some of the fin structure, thereby reducing its thermal efficiency. Additionally, deflection that might occur under actuation load can create gaps between the heat sink and the assembly that can compromise the thermal effectiveness of the heat sink and/or cause the weight of the heat sink to fall directly on the CPU.  
         [0007]     It is therefore desirable to have an apparatus and method that allows a heat sink to be mounted above a CPU and to deliver a load commensurate with the required thermal flow characteristics of the heat sink and to provide a mechanism to hold the heat sink firmly in place with the weight of the heat sink being transmitted to the chassis or mounting plate of the computer rather than the CPU, motherboard or other critical components of the computer.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention addresses the deficiencies of the art with respect to heat sink retention assemblies and provides a novel and non-obvious apparatus and method for securing a heat sink to the chassis of a computer while maintaining thermal contact between the heat sink and the CPU. In this regard, a mechanical retention assembly is provided and actuated by the user. The assembly, upon actuation, advantageously prevents the heat sink from separating from the CPU, affixes the heat sink to the chassis of the computer, removes the load from the CPU, and provides mechanical support and stability to the heat sink.  
         [0009]     According to one aspect, the present invention provides a heat sink retention assembly having a frame sized to receive the heat sink, the frame including opposing pin capture channels, and a wire module having an upper handle section and a lower pivoting section. The wire module is pivotally coupled to the frame at the lower pivoting section. The wire module also includes opposing end pins, wherein each pin is moveably retained within and extends through a corresponding pin capture channel such that when the wire module is rotated with respect to the frame, the pins travel within their respective channels in order to engage the heat sink.  
         [0010]     According to another aspect, the present invention provides a heat sink assembly for maintaining contact with an electrical component. The assembly includes a heat sink having an upper and a lower surface. The heat sink includes ramped slots along its lower surface, and a frame sized to receive the heat sink. The frame includes opposing pin capture channels. The heat sink assembly also includes a wire assembly having an upper handle section and a lower pivoting section. The wire assembly is pivotally coupled to the frame and includes opposing pins, where each pin is moveably retained within and extends through a corresponding channel of the frame such that when the wire assembly is rotated with respect to the frame, the pins travel within their respective channels in order to engage one of the ramped slots of the heat sink.  
         [0011]     According to still another aspect, a method of maintaining contact between a heat sink and an electronic component in a computer while transmitting load away from the electronic component is provided. The method includes affixing a heat sink retention assembly to a computer motherboard, where the heat sink retention assembly includes a frame positioned over the electrical component and sized to receive the heat sink, placing the heat sink proximate the electrical component such that the heat sink fits within the frame of the heat sink retention assembly, and activating the heat sink retention assembly such that the heat sink maintains contact with the electrical component while transmitting the load of the heat sink to the heat sink retention assembly.  
         [0012]     In yet another aspect of the invention, a latching mechanism for maintaining an interface between a first object and a second object is provided. The latching mechanism includes a frame positioned over the second object and sized to receive the first object, the frame having opposing pin capture channels, where the first object includes ramped entry slots disposed along its lower surface. The latching mechanism also includes a wire assembly having an upper handle section and a lower pivoting section. The wire assembly is pivotally coupled to the frame at the lower pivoting section, and includes opposing end pins, where each pin is moveably retained within and extends through a corresponding pin capture channel such that when the wire assembly is rotated with respect to the frame, the pins travel within their respective channels in order to engage one of the ramped entry slots of the first object.  
         [0013]     Additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The aspects of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The accompanying drawings, which are incorporated in and constitute part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention. The embodiments illustrated herein are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown, wherein:  
         [0015]      FIG. 1  is an illustration of an exemplary apparatus constructed in accordance with the principles of the present invention;  
         [0016]      FIG. 2  illustrates the retention assembly of the present invention interfacing with a heat sink;  
         [0017]      FIG. 3  illustrates an alternate embodiment of the retention assembly of the present invention;  
         [0018]      FIG. 4  illustrates the dual sloped entry ramps of the heat sink which receive the wire module pin of the retention assembly;  
         [0019]      FIG. 5  shows the retention assembly interfacing with a heat sink after the heat sink has been placed upon the wire assembly pins of the retention assembly in an unlatched position; and  
         [0020]      FIG. 6  shows the retention assembly interfacing with a heat sink in a latched position after activation of the wire module of the retention assembly.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     The present invention advantageously provides a method and apparatus for mounting a heat sink above an electrical component in a computer, such as a CPU, such that the heat sink is in thermal contact with the CPU but the weight of the heat sink is absorbed by the computer chassis or CPU mounting plate and not the CPU. When used with Land Grid Array (LGA) CPU technology, the present invention advantageously provides an apparatus that secures the heat sink to the motherboard or CPU of the computer and prevents unwanted separation between the heat sink and the CPU which might occur due to the solder connection between the CPU and its socket.  
         [0022]     Referring now to the drawing figures in which like reference designators refer to like elements there is shown in  FIG. 1  an apparatus constructed in accordance with the principles of the present invention and designated generally as “ 100 ”. Apparatus  100  includes a retention module assembly  10 , which is adapted for placement on top of a motherboard or Central Processing Unit (CPU) and socket assembly of a personal computer. Assembly  10  includes a frame  12 , which provides a border around a central, open area  14 , to allow for placement of a heat sink therethrough. It is contemplated that frame  12  of assembly  10  is sized to allow a heat sink of a specified size to fit through opening  14  in order to contact a CPU without the heat sink resting on frame  12 . A plurality of standoffs  16  extend from the bottom surface of frame  12 . Each standoff  16  is received by a corresponding mounting hole in the motherboard placed on top of the computer&#39;s chassis. Affixing devices such as screws or bolts may be inserted at affixing point  17  to firmly affix frame  12  to the motherboard or other surface of the computer.  
         [0023]     Assembly  10  includes a wire module  18 , which includes a handle section  20 , and opposing side sections  22 , which each terminate in a wire module pin  24 . The lower potion of each side section  22  is bent in such a fashion as to pass under and through a pin capture bracket  26 . A pair of brackets  26  are affixed to opposing sides of frame  12  as shown in  FIG. 1 . Each bracket  26  includes a pin capture track  28  through which a corresponding wire module pin  26  extends. Track  28  is slightly curved in order to facilitate movement of pin  24  therein when handle  20  is rotated.  
         [0024]     Initially, handle  20  is an unlatched position where it is positioned substantially upright with respect to frame  12 . In this position, a heat sink may be placed above the wire module pins  24  thus securing the heat sink (discussed below). When handle  20  is pulled back in the direction of the arrow shown in  FIG. 1 , the upper portion of each side section  22  of wire module  18  is locked in place by wire module retention column  32 . This secures wire module  18  in a latched position. The retention columns  32  shown in  FIG. 1  are merely illustrative of an exemplary embodiment. Other types of wire retention methods commonly known in the art may be used.  
         [0025]     When handle  20  of wire module  18  is rotated from an unlatched to a latched position in the direction of the arrow, each pin  24  moves within track  28 , in the same direction as handle  20 . Due to the arcuate shape of track  28 , each pin  24  travels in a slight arc within its corresponding track  28 . The arcuate shape of track  28  advantageously allows wire module  18  to pivot freely. The movement of pins  24  within their respective tracks assist in retaining the heat sink to assembly  10  (discussed below).  
         [0026]     A pivot point  30  is created where the lower portion of side section  22  is captured within a lower slot in bracket  26 . When handle  20  is rotated, load is transmitted to each pin  24  via the captured wire portion at pivot point  30 . The rotation of pin  24  is constrained by the arcuate dimensions of the capture track  28  in which it travels. While in track  28 , tip  24  cannot move up or down, but is forced to move along track  28  as handle  20  of wire module  18  is rotated.  
         [0027]     In  FIG. 2 , a heat sink  34  is placed within frame  12  of the retention module assembly  10 . Heat sink  34  is typically made of a solid metal base  46  such as aluminum or copper, with heat dissipation fins  50  mounted on and above the base  46 . As described above, frame  12  is sized to receive heat sink  34 . Heat sink  34  fits within the opening  14  of frame  12  but does not rest on any portion of the frame  12 . In  FIG. 2 , handle  20  can be seen in the latched or “loaded” position. Although not shown, the tip of each pin  24  extends beneath heat sink  34 . Pin  24  can be seen within track  28 . As handle  20  is rotated, a torsion load is applied to wire module pins  24  as the lower portions of side sections  22  remain captured within bracket  26  at pivot point  30 . Again, after rotation, side sections  22  may be secured within their respective capture columns  32 .  
         [0028]      FIG. 3  illustrates an alternate embodiment of the retention module assembly  10  described above and shown in  FIG. 1 . In this embodiment, a heat sink  34  has been placed upon frame  12 . However, the wire module pin configuration of assembly  10  is slightly different than what is shown in  FIG. 1 . Instead of each pin  24  being formed to extend past bracket  26  within the perimeter of frame  12 , in this embodiment, each pin  24  extends through bracket  26  but outside the perimeter of frame  12 . Thus, the present invention is not limited by the design, shape or orientation of pin  24 . Depending upon the size and shape of heat sink  34 , the CPU and the socket in which the CPU resides (in an LGA configuration), pins  24  can be configured in any number of ways in order to allow heat sink  34  to be placed securely upon the pins  24  and within frame  12 . In the alternate embodiment of  FIG. 3 , a pair of shorter brackets  36  retain side sections  22  of wire module  18  when in the latched, or “loaded” position.  
         [0029]     Because heat sinks may be large and heavy, the present invention advantageously provides a method and apparatus divert the direct weight of the heat sink  34  away from critical electrical components in a computer such as the CPU. Pins  24  receive the weight of heat sink  34  instead of the CPU. Frame  12 , which is bolted to the frame of the computer (either the motherboard or the chassis) receives the load from the heat sink  34  and transmits it down to the computer chassis, thus protecting the CPU and the motherboard from unwanted weight from the heat sink  34 . However, because heat sink  34  fits within frame  12  and frame  12  has been placed directly above the CPU, the required thermal contact between heat sink  34  and the CPU is still maintained.  
         [0030]     The latching mechanism that allows heat sink  34  to maintain the requisite pressure against the CPU in order to achieve sufficient thermal transfer will now be discussed.  FIG. 4  illustrates the inside of a personal computer that is to receive heat sink  34 . Metal chassis  38  is partially covered by a motherboard  40 , upon which assembly  10  is placed. Motherboard  40  rests on a plurality of standoffs (not shown) that protrude upward from chassis  38 . Motherboard  40  is situated between the top of the standoffs and the bottom of frame  12  and secured with screws, bolts or other affixing means through affixation points  17  of the frame  12 .  
         [0031]     CPU  42  is situated within a socket  44 , which is common in Land Grid Array (LGA) designs. Assembly  10  is placed over CPU  42  and its socket  44  and is affixed to chassis  38 . Heat sink  34  clears frame  12  and extends through the interior space  14  formed by frame  12 . Frame  12  includes its own standoffs  16  (shown in  FIG. 1 ), which fit into mounting holes (not shown) in board  40 . Thus, assembly  10  is secured within board  40  and is ready to receive heat sink  34 .  
         [0032]     From  FIG. 4 , it is evident that heat sink  34  has been modified to receive wire module pins  24  of wire module  18 . Specifically, heat sink  34  includes a lower frame  46 , which has a central longitudinal groove  48 , the end of which can be seen in  FIG. 4 . Groove  48  is formed by opposing sloped ramps  52 . Each ramp  52  increases in thickness as it gets further away from groove  48 , i.e., the center of heat sink  34 . Groove  48  runs the substantial length of the bottom of heat sink  34  and is sized to receive pins  24  of wire module  18  when heat sink  34  is placed over frame  12 . The width of groove  48  and dimensions of ramps  52  may vary depending upon the size and orientation of pins  24 .  
         [0033]     In order to load heat sink  34  upon assembly  10 , handle  20  must be positioned such that each wire module pin  24  is in the relative center of its respective track  28 . In this fashion, when heat sink  34  is lowered over CPU  42  and within frame  12 , each pin  24  fits within groove  48  of heat sink  34 . This is the unloaded or “unlatched” position. At this time, heat sink  34  is in not yet in contact with CPU  42 , and is not secured to assembly  10 . Thus, assembly  10  must be “actuated” in order to “lock” heat sink  34  to assembly  10  and “press” heat sink  34  against CPU  42  in order to initiate thermal contact. Upon loading, the weight of heat sink  34  is supported by pins  24  of assembly  10  and chassis  38 , and not by CPU  42 . However, the required contact between heat sink  34  and the top of CPU  42  in order to allow for thermal transition, is maintained.  
         [0034]     Referring again to  FIG. 4 , the sloped ramps  52  and groove  48  of heat sink  34  can be seen. Further, pin  24  of wire module  18  can also be seen as it extends through track  28  of bracket  26  and is situated directly beneath heat sink  34  and aligned with groove  48 . Although  FIG. 4  illustrates the use of a retention module assembly  10  of the type used in  FIG. 1  where the wire module pins  24  extend within the border of frame  12 , the alternate embodiment shown in  FIG. 3  may also be used, where pins  24  extend outside of frame  12 .  FIG. 5  illustrates use of this alternate embodiment.  
         [0035]     It is envisioned that when heat sink  34  is placed within frame  12  with handle  20  in an unlocked position, pins  24  are in the substantial midpoint of their respective tracks  28  and under groove  48 . In  FIG. 5 , handle  20  is still in an unlatched position as evidenced by the position of pin  24  in the relative center of track  28 . Pins  24  are now positioned within groove  48  and heat sink  34  is positioned above CPU  42 . Heat sink  34  clears the top of frame  12  and does not contact the frame. Instead, it fits entirely within space  14  of frame  12 .  
         [0036]     In  FIG. 6 , a user has rotated handle  20  in order to “lock” heat sink  34  to assembly  10 . By rotating handle  20 , pins  24  are rotated in the same direction due to the fixed portion of the wire module trapped in bracket  26  at pivot point  30 . As pin  24  travels along the arcuate path formed by track  28 , it slides into the space between sloped ramp  52  and the bottom surface of heat sink  34 . This space is clearly seen in the illustration of  FIG. 4 . Because ramp  52  is sloped, i.e., it becomes gradually wider away from groove  48 , and the space between the heat sink  34  and ramp  52  becomes smaller. Thus, when handle  20  is rotated, wire module  18  acts as a torsion spring, forcing heat sink  34  down onto pins  24 . Therefore, pins  24  provide the support for heat sink  34  and essentially “lock” heat sink  34  to assembly  10 . At this time, heat sink  34  is brought down on the top of CPU  42 . When heat sink  34  makes contact with CPU  42  and is no longer in motion, the torque load is applied.  
         [0037]     When in the latched or loaded position, heat sink  34  is prevented from moving up or down during shipping or other events and is “clamped” onto assembly  10  by the interaction of pins  24  within the space above the sloped ramps  52  of heat sink  34 . The entire load of heat sink  34  is transmitted to assembly  10  down through chassis  38  and its standoffs. Advantageously, although the load is transmitted down through assembly  10  and away from motherboard  40  and CPU  42 , the original thermal contact between heat sink  34  and CPU  42  remains.  
         [0038]     To unlatch heat sink  34  from retention assembly  34 , the user simply rotates handle  20  back to its initial position, thereby moving pins  24  to the substantial center of their tracks  28 . This releases pins  24  from their captured orientation above sloped ramps  52  and returns pins  24  to groove  48 . The heat sink  34  is no longer latched onto assembly  10  and may be easily removed. Heat sink  34  is moved vertically off CPU  42  by the rotation of handle  20  to its initial position.  
         [0039]     It should be noted that the present invention is not limited to a latching mechanism between a heat sink and a CPU. Rather, the retention assembly described herein is equally adaptable to situations where there is a need to maintain contact between two objects. Frame  12  of assembly  10  is placed over an object and secured to a support surface. The second object is placed over the first object and within frame  12 . The unique pin construction of the wire module  18  of the present invention allows for the handle  20  to be rotated and the pins to be inserted into a corresponding receiving ramp situated on the bottom surface of the second object. Once the assembly  10  has been actuated, the pins  24  provide a secure clamping mechanism to maintain contact between the two objects.  
         [0040]     It should also be noted that handle  20  need not be rotated completely to activate assembly  10 . Depending upon the specific circumstances, handle  20  may only need to be rotated a small amount thus forcing pins  24  only partway within track  28 . This might be applicable in situations where there needs to be only a limited amount of pressure between the two objects. Assembly  10  therefore provides the user with the ability to achieve a wide range of possible clamping positions.