Abstract:
A heat sink assembly for removing heat from an electronic component includes a retention clip having a central body and a securing member extending from the central member. The central member has an opening there through, and the securing member is configured to secure the retention clip relative to the electronic component. A heat sink has a base member received through the opening when the heat sink is mounted to the retention clip, and the base member has an engagement surface configured to engage a heat generating surface of the electronic component. A locking mechanism secures the heat sink to the retention clip. The locking mechanism includes a ramp member and a ramp engaging member, wherein the ramp member has a positive stop provided therein. The positive stop provides a tactual indication when the heat sink is fully secured to the retention clip.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to and the benefit of the filing date of U.S. Provisional Application No. 60/708,640, filed on Aug. 16, 2005 and which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates generally to heat sinks, and more particularly to heat sink fastening systems operable without the use of a tool.  
         [0003]     It is well known to use a heat sink to cool a heat generating component or package. Typically, a heat sink is arranged in close contact with heat generating components of the package. Heat generated by the component is transferred to the heat sink and then dissipated from the heat sink to the surrounding air.  
         [0004]     Conventional heat sinks are attached to the electronic component or package with a spring clip. The spring clip provides a fastening force between the heat sink and the component. The heat sink is connected to the spring clip in a conventional manner, such as by a threaded coupling. The amount of torque applied to the heat sink produces a corresponding engagement force between the heat sink and the component.  
         [0005]     However, over-tightening of the heat sink and the spring clip may result in damage to the electronic component as too much force may be applied to the component, and the component may crack or break. Under-tightening of the heat sink and the spring clip may result in improper thermal engagement between the heat sink and the component. As a result, conventional coupling techniques for the heat sink and spring clips utilize a torque wrench to limit the amount of torque applied to the heat sink. However, the use of a torque wrench increases assembly time. Additionally, the torque wrench typically requires calibration which also increases assembly time and the possibility of operator error.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0006]     In one aspect, a heat sink assembly is provided for removing heat from an electronic component. The heat sink assembly includes a retention clip having a central body and a securing member extending from the central member. The central member has an opening there through, and the securing member is configured to secure the retention clip relative to the electronic component. A heat sink has a base member received through the opening when the heat sink is mounted to the retention clip, and the base member has an engagement surface configured to engage a heat generating surface of the electronic component. A locking mechanism secures the heat sink to the retention clip. The locking mechanism includes a ramp member and a ramp engaging member, wherein the ramp member has a positive stop provided therein. The positive stop provides a tactual indication when the heat sink is fully secured to the retention clip.  
         [0007]     One embodiment of the heat sink assembly may include one of the heat sink and retention clip having the ramp member, while the other of the heat sink and retention clip having the ramp engaging member. Optionally, the ramp engaging member includes a protrusion extending from the base member, and the protrusion rides along the ramp member to the positive stop during assembly of the heat sink assembly. The central body of the retention clip may include a slot positioned adjacent and open to the opening, wherein the slot is sized to allow the protrusion to pass therethrough. The ramp member may be located proximate the opening, and the ramp member may have a detent therein, wherein the detent constitutes the positive stop. Optionally, the ramp member may extend from a first end to a second end, wherein the ramp member is oblique with respect to the central member between the first and second ends. In one embodiment, the retention clip is flexed as the ramp engaging member engages the ramp member when the heat sink is secured to the retention clip, such that the flexing of the retention clip provides an increase in a tension force between the base member and the electronic component.  
         [0008]     In another aspect, a heat sink fastening clip is provided for thermally securing a heat sink to an electronic component. The electronic component has a heat generating surface and the heat sink has a base member having an engagement surface configured to engage a heat generating surface of the electronic component. The heat sink fastening clip includes a central member having an opening extending therethrough, wherein the base member of the heat sink is received within the opening such that the base member engages the heat generating surface of the electronic component. A securing member extends from the central member, and the securing member is configured to secure the central member relative to the electronic component. A ramp member is connected to the central member proximate the opening. The ramp member has a positive stop therein, wherein the base member is configured to engage the positive stop during assembly of the heat sink and the fastening clip. The positive stop provides a tactual indication when the heat sink is fully secured to the retention clip. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is an exploded perspective view of a heat sink assembly formed in accordance with an exemplary embodiment of the present invention.  
         [0010]      FIG. 2  is a bottom perspective view of the heat sink assembly shown in  FIG. 1  in an assembled state illustrating a heat sink fastening clip used with the heat sink assembly.  
         [0011]      FIG. 3  is a side perspective view of the heat sink assembly and fastening clip shown in  FIG. 2 .  
         [0012]      FIG. 4  is a side view of the heat sink assembly having an alternative fastening clip.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]      FIG. 1  is an exploded perspective view of a heat sink assembly  10  formed in accordance with an exemplary embodiment of the present invention. The heat sink assembly  10  includes a heat sink  12  capable of cooling at least one electronic component or package  14 . The electronic component  14  has a first or upper side  16  defining a heat generating surface  18 . The electronic component  14  may be a circuit board, a central processing unit (CPU), a connector, or the like. In one embodiment, the electronic component  14  may include an integrated heat sink (not shown) defining the heat generating surface  18 .  
         [0014]     As better shown in  FIG. 2 , the heat sink  12  includes a base member  20  for engaging the electronic component  14 . The base member  20  is preferably fabricated from a thermally conductive material, such as copper or aluminum, selected to efficiently and reliably dissipate heat from the electronic component  14 . The heat sink  12  may also include a fin structure  22  in thermal communication with the base member  20  to aid in dissipating the heat transferred through the base member  20 . The fin structure  22  includes a plurality of fins  24  having a large surface area that effectively dissipates the heat transferred through the base member  20  to the fin structure  22 . Optionally, the fins  24  extend radially outward from a central core  26 . In one embodiment, the core  26  may be fabricated from a material having a first thermal transfer rate, and the fins  24  may be fabricated from a material having a second thermal transfer rate, which is lower than the thermal transfer rate of the core  26 .  
         [0015]     In one embodiment, the heat sink assembly  10  also includes a fan  28  positioned proximate the fin structure  22  to aide in cooling the heat sink  12 . The fan  28  generates airflow past the heat sink  12  to aide in cooling the heat sink  12 . As a result, the heat sink  12  may transfer heat from the electronic component  14  more efficiently.  
         [0016]     The heat sink assembly  10  includes a retention member or fastening clip  30  for securing the heat sink  12  in thermal communication with the electronic component  14 . Additionally, as better shown in  FIG. 2 , the heat sink assembly  10  includes a locking mechanism  31  for securing the heat sink  12  to the retention member  30 . In one embodiment, the retention member  30  is a spring clip, however other types of retention members  30  may be used, such as a screw or bolt. The heat sink  12  is capable of being secured, fastened or otherwise coupled to the retention member  30 , and the retention member  30  is capable of being secured, fastened, or otherwise coupled to the electronic component  14 . As a result, the heat sink  12  is held in thermal contact with the heat generating surface  18  of the electronic component  14  by the retention member  30 . Optionally, the retention member  30  provides an engagement force onto the heat sink  12  such that the heat sink  12  maintains proper engagement with the electronic component  14 . For example, the retention member  30  may be placed in tension when the heat sink  12  is coupled to the retention member  30 , or the retention member  30  may be placed in tension when the retention member  30  is coupled to the electronic component  14 . Optionally, the tension force may be adjustable by adjusting the position of the heat sink  12  with respect to the retention member  30  to provide an appropriate amount of force between the heat sink  12  and the electronic component  14 .  
         [0017]     In one embodiment, the retention member  30  includes a central body or member  32  and at least one securing member  34  integrally formed therewith. The central member  32  is substantially planar and is oriented substantially parallel to the upper side  16  of the electronic component  14 . The central member  32  provides a base for the heat sink  12  to rest on. The central member  32  includes an opening  36  extending therethrough for receiving the heat sink  12 , and more particularly the base member  20  of the heat sink  12 . Optionally, the opening  36  may be threaded to facilitate coupling the heat sink  12  to the retention member  30 . When assembled, the opening  36  is substantially aligned with the heat generating surface  18  of the electronic component  14  such that, after assembly, the heat sink  12  may engage the heat generating surface  18 .  
         [0018]     Each securing member  34  extends substantially perpendicular to the central member  32  and is coupled to the electronic component  14 . Optionally, the retention member  30  includes two opposed securing members  34  extending downward from opposite ends of the central member  32 . The securing members  34  include posts or legs  38  extending therefrom. The posts  38  extend into corresponding holes in the electronic component  14  such that the retention member  30  may be mounted to the electronic component  14 . Optionally, the posts  38  may include barbs  40  extending outward therefrom for engaging the body of the electronic component  14  to resist removal of the retention member  30  from the electronic component  14 .  
         [0019]      FIG. 2  is a bottom perspective view of the heat sink assembly  10  in an assembled state illustrating the heat sink  12  coupled to the retention member  30  using the locking mechanism  31 . In one embodiment, the locking mechanism  31  includes a ramp member, such as ramp member  52 , and a ramp engaging member, such as protrusion  60 , both of which are described in more detail below. When assembled, the base member  20  of the heat sink  12  is received within the opening  36  of the retention member  30 . As illustrated in  FIG. 2 , in one embodiment, the base member  20  and the opening  36  are circular. As such, the base member  20  may be rotated within the opening  36 , as will be described in detail below.  
         [0020]     The retention member  30  includes at least one receiving slot  50  in the central member  32  positioned proximate the opening  36 , such as along the perimeter of opening  36  and extending radially outward therefrom. Optionally, the retention member  30  includes two receiving slots  50  aligned approximately 180 degrees from one another along opening  36 . In one embodiment, the slots  50  extend outward from the opening  36  toward the securing members  34 .  
         [0021]     The retention member  30  also includes at least one ramp member  52  extending downward from the central member  32  and along the perimeter of opening  36 . Each ramp member  52  extends between a first end  54  and a second end  56 . Optionally, the first end  54  and the second end  56  are each positioned adjacent the slots  50  such that the ramp member  52  extends circumferentially from one slot  50  to the next slot  50  along the perimeter of the opening  36 . The ramp member  52  generally extends obliquely with respect to the central member  32  between the first and second ends  54  and  56 . For example, at the first end  54 , the ramp member  52  has a minimum height, H min  such as approximately zero. At the second end  56 , the ramp member  52  has a non-zero maximum height H max  which is greater than a height H at any other point along ramp member  52 . Additionally, the ramp member  52  includes a positive stop  58 . In one embodiment, the positive stop  58  is a detent, or area of reduced height, along the ramp member  52 . Optionally, the detent  58  is radiused to provide a transition along the ramp member  52 . In one embodiment, the detent  58  is positioned approximately equidistant between the first and second ends  54  and  56  of the ramp member  52 . Alternatively, the detent  58  is positioned closer to one of the first and second ends  54  and  56 .  
         [0022]     The base member  20  of the heat sink  12  includes at least one projection or pin  60  extending radially outward from a side wall  62  of the base member  20 . Optionally, the projection  60  has a cylindrical shape such that the projection  60  has a curved outer surface. In one embodiment, the heat sink  12  includes two projections  60  generally opposed from one another. The projections  60  extend outward from the side wall  62  for a distance such that a width of the base member  20  and the outer portion of each projection  60  is greater than the diameter of the opening  36  of the central member  32 . As a result, the base member  20  may not be inserted into the opening  36  unless the projections  60  are aligned with the slots  50  in the central member  32 . As such, the slots  50  in the central member  32  must be sized to accommodate the projections  60  during assembly of the heat sink assembly  10 .  
         [0023]     As illustrated in  FIG. 2 , the locking mechanism  31  includes the ramp member  52  and the protrusion  60 . In an alternative embodiment, the base member  20  may include a structure similar to ramp member  52 , and the retention member  30  may include a structure similar to protrusion  60 . The assembly of the base member  20  and the retention member  30  would be substantially similar to the assembly of the structure illustrated in  FIG. 2 , and described below.  
         [0024]     During assembly, the projections  60  are aligned with the slots  50  and the base member  20  is received in the opening  36  until the projections  60  are positioned below the central member  32  of the retention member  30 . The heat sink  12  is then rotated in the direction of arrow A, such as in a direction generally toward the first end  54  of the ramp member  52 . As the heat sink  12  is rotated, the projections  60  ride up the ramp member  52  and draw the heat sink  12  into engagement with the electronic component  14  (shown in  FIG. 1 ). Additionally, when the second end  56  of the ramp member  52  is positioned adjacent the slot  50 , the second end  56  operates as a stop for rotation of the heat sink  12  in the wrong direction. As such, the heat sink  12  may only be rotated in the direction of arrow A when the projections  60  are within the slots  50 . The heat sink  12  is rotated until the projections  60  engage the detents  58 . As such, the detents  58  facilitate providing a mechanical indication to an operator that the heat sink  12  is loaded onto retention member  30 . Optionally, the heat sink  12  is fully loaded onto the retention member  30  when the projections  60  engage the detents  58 . In one embodiment, the detents  58  operate to limit further rotation of the heat sink  12 . Alternatively, the detents  58  are sized and shaped such that further pressure or torque to the heat sink  12  will facilitate further tightening of the heat sink  12 .  
         [0025]      FIG. 3  is a side perspective view of the heat sink assembly  10  and fastening clip  30  illustrating the heat sink  12  in thermal engagement with the electronic component  14 . More particularly, the base member  20  is positioned within the opening  36  and the heat sink  12  has been rotated to a loaded position such that the projections  60  have engaged the detents  58 .  
         [0026]     In one embodiment, the central member  32  of the retention member  30  is pre-flexed or pre-bowed in a downward direction (e.g. toward from the electronic component  14  when assembled). The pre-flexing allows the central member  32  to become substantially planar as the projections  60  are moved along the ramp members  52 . Specifically, the amount of flexing in the central member  32  is reduced as the heat sink  12  is rotated, and simultaneously, the retention member  30  imparts a greater tension force on the heat sink  12 . The greater tension force between the heat sink  12  and the retention member  30  corresponds to a greater engagement force between the heat sink  12  and the electronic component  14 . The detents  58  are positioned along the ramp members  52  to provide an appropriate amount of engagement force between the heat sink  12  and the electronic component  14 . Additionally, because the central member  32  is allowed to flex, the risk of over-tightening the heat sink  12  with respect to the retention member  30  is substantially reduced, if not eliminated.  
         [0027]      FIG. 4  is a side view of the heat sink assembly  10  and an alternative fastening clip  70 . The fastening clip  70  is similar to the fastening clip  70 , and as such, like components are numbered with like reference numerals. The heat sink  12  is illustrated as being loaded and engaged with the fastening clip  70  and thermally engaging the electronic component  14 . More particularly, the base member  20  is positioned within the opening  36  of the fastening clip  70  and the heat sink  12  has been rotated such that the projections  60  have engaged the detents  58 .  
         [0028]     As further illustrated in  FIG. 4 , the central member  32  of the retention member  70  has been bowed or flexed upwardly (e.g. away from the electronic component  14 ) from an unflexed and substantially planar orientation. The flexing is caused by the positioning of the projections  60  along the ramp members  52 . Specifically, as the heat sink  12  is rotated, the central member  32  becomes more flexed, thus imparting a greater tension force between the heat sink  12  and the retention member  70 . The greater tension force between the heat sink  12  and the retention member  70  corresponds to a greater engagement force between the heat sink  12  and the electronic component  14 . The detents  58  are positioned along the ramp members  52  to provide an appropriate amount of engagement force between the heat sink  12  and the electronic component  14 . Additionally, because the central member  32  is allowed to flex, the risk of over-tightening the heat sink  12  with respect to the retention member  70  is substantially reduced, if not eliminated.  
         [0029]     The design and structure of the retention member  30  facilitate assembling the heat sink assembly  10  without the need for a tool such as a torque wrench. Rather, an operator rotates the heat sink  12  until the projections  60  mechanically engage the detents  58 . Removal of the heat sink  12  is accomplished by rotating the heat sink  12  in the opposite direction either by hand or with the use of a tool such as a wrench. However, by positioning the ramp member  52  as a stop, the heat sink  12  cannot be over-tightened in the opposite direction. As a result, a cost effective and reliable means is provided for assembling the heat sink assembly  10 . The assembly time is reduced as compared to heat sink assemblies which are assembled using a torque wrench, and the risk of over-tightening or under-tightening the heat sink  12  with respect to the retention member  30  is substantially reduced, if not eliminated. Thus the risk of operator error is reduced with the use of the heat sink assembly  10 .  
         [0030]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.