Abstract:
A heat sink extends beyond the outer boundaries of a component cooled by the heat sink. In one embodiment, the heat sink may have a cutout shaped and located so that a protruding portion of a clip can extend through the cutout from one surface of the heat sink and mechanically fasten the component to another surface of the heat sink. There may be more than one cutout. Heat transfer values can be optimized by adjusting the number and the location of the cutouts and the size of the heat sink relative to the component and the fastening mechanism (e.g., a clip). In another embodiment, the clip that extends through the cutout holds the heat sink against a motherboard, pressing against a component located between the heat sink and the motherboard.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is related to, and incorporates by reference herein in its entirety, U.S. patent application Ser. No. 10/072,598, attorney docket No. entitled “A Fiber Guide Connected To A Heatsink Fastener”, filed concurrently herewith by Matthew K. Meeker. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     This invention relates generally to chip packaging and particularly to chip packaging including a heat sink. 
     2. Related Art 
     An electronic component (e.g., a Central Processing Unit) may generate a significant amount of heat when operating. If not dissipated in time, this heat can degrade performance of the component. To dissipate some of the generated heat, a heat sink device is commonly placed in contact with the component. The heat sink device usually includes a plate and several protrusions from the plate that increase the heat transfer surface area. Sometimes, a fan is used in addition to the heat sink device to assist in heat dissipation. 
     Currently, a number of methods are used to fasten the heat sink device to the component. FIG. 1 depicts an exemplary clip  10  disclosed in U.S. Pat. No. 6,153,932, which is incorporated by reference herein. Clip  10  includes a rectangular frame  12  with a hole  14 . Rectangular frame  12  has protruding portions that are designed to extend through a hole, such as side plates  16  and protruding rods  20 . Side plates  16  include a first side plate  16   a  connected to one part of rectangular frame  12  and a second side plate  16   b  connected to a different part of rectangular frame  12 . Each of side plates  16   a  and  16   b  may have fastening hooks  18   a  and  18   b , respectively. Side plates  16   a  and  16   b  press against two outer edges of a heat sink and a component, and fastening hooks  18   a  and  18   b  snap onto the bottom edges of the component. Protruding rods  20  may include a first protruding rod  20   a  and a second protruding rod  20   b  connected to the sides of frame  10  that do not have a side plate. Clip  10  may also have elastic rods  22  protruding from the inner side walls of frame  10  into hole  14  to provide extra stability and attachment to a heat sink. A person of ordinary skill in the art would understand that other structures for clip  10  are possible. For example, frame  12  and hole  14  may be of any other polygonal shape or even a circular shape. Furthermore, clip  10  may include any fastening device, such as a screw or a snap feature, that can be used to hold a heat sink in a fixed position relative to a component. 
     However, the currently used methods usually impose at least one limitation on the design of the motherboard or the heat sink. For example, while a screw allows flexibility in the dimensions of the heat sink, it requires that the motherboard have holes. A clip of the sort shown in FIG. 1 does not require that a motherboard have holes, but requires that heat sink and the component have a width substantially equal to the width of the clip. Such limitations compromise design optimization of heat sink devices. 
     A heat sink device that provides flexibility in terms of both the size of the heat sink and the motherboard circuitry design is needed. 
     SUMMARY 
     In accordance with the present invention, a heat sink extends beyond all outer boundaries of a component cooled by the heat sink. Such an oversized heat sink allows better optimization of heat transfer values than a conventional heat sink, which usually has at least one dimension (e.g. width as noted above) the same as or substantially equal to the corresponding dimension of the component to be cooled. An oversized heat sink attached by a clip to an electronic component not only allows better optimization of heat transfer values but also provides greater flexibility for motherboard circuitry design than a conventional heat sink. 
     In one embodiment, the heat sink has at least one cutout (or hole) shaped and located so that a portion (hereinafter “protruding portion”) of a clip can extend from one surface of the heat sink and mechanically fasten the electronic component to another (eg., the opposite) surface of the heat sink. The cutout (or hole) may be shaped to fit around the protruding portion. For example, if the protruding portion is a flat plate, the cutout (or hole) through which the protruding portion is inserted may be a rectangular slit. If the protruding portion is a rod, the cutout (or hole) may be circular-shaped. The clip may fasten the heat sink to the component by the protruding portion snapping onto one or more edges of the component. When the clip fastens the heat sink to the component, no hole is needed in the motherboard. In an alternative embodiment, the clip may fasten a component to a heat sink by two or more protruding portions attaching to a motherboard and sandwiching the component between the heat sink and the motherboard. In this alternative embodiment, protruding portions of the clip extend not only through a cutout in the heat sink but also through a cutout in the motherboard, and each snaps onto an edge of the hole in the motherboard. 
     The clip may include a polygonal (e.g., rectangular) frame with a hole in the middle and a protruding portion on each side of the polygonal frame. Since cutouts (or holes) can be located anywhere on the heat sink, such cutouts (or holes) provide flexibility in terms of the size of the heat sink that can be used with a standard sized clip, and the location on the heat sink where the component is fastened. For example, locating cutouts away from the edges of the heat sink results in a component being fastened near the center of a heat sink. In some embodiments the heat sink extends beyond all outer boundaries of the component, although this is not required in other embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a clip of the prior art. 
     FIG. 2 illustrates a plan view of a heat sink in one embodiment of the present invention. 
     FIG. 3 illustrates a plan view of another heat sink that may be used in an alternative embodiment of the present invention. 
     FIG. 4 illustrates a perspective view of another heat sink that may be used in another alternative embodiment of the present invention. 
     FIG. 5 illustrates a perspective view of an assembly of over-sized heat sink with an electronic component using a clip in accordance with an embodiment of the present invention. 
     FIG. 6A illustrates a side view of a heat sink device, in accordance with one embodiment of the present invention. 
     FIG. 6B illustrates in an enlarged side view a fastening mechanism for a heat sink device, in accordance with one embodiment of the present invention. 
     FIG. 7A illustrates a cross-sectional side view of a heat sink device mounted on a motherboard with a hole, in accordance with one embodiment of the present invention. 
     FIG. 7B illustrates in an enlarged side view a fastening mechanism for a heat sink device including a motherboard with a hole, in accordance with one embodiment of the present invention. 
     FIG. 8 illustrates a plan view of a heat sink device including a clip, in accordance with one embodiment of the present invention. 
     FIG. 9 illustrates a side view of a heat sink device including at least one metal clip, in accordance with one embodiment of the present invention. 
     FIG. 10 illustrates a plan view of a heat sink device including at least one metal clip, in accordance with one embodiment of the present invention. 
     FIG. 11 illustrates a side view of a heat sink device including at least one wire spring, in accordance with one embodiment of the present invention. 
     FIG. 12 illustrates a plan view of a heat sink device including at least one wire spring, in accordance with one embodiment of the present invention. 
     FIG. 13 illustrates a side view of a heat sink device including at least one screw, in accordance with one embodiment of the present invention. 
     FIG. 14 illustrates a plan view of a heat sink device including a at least one screw, in accordance with one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 2 depicts a view of a heat sink  30  in accordance with one embodiment of the present invention. Heat sink  30  includes a plate  32  that is larger in area than the area covered by an electronic component that is to be cooled by heat sink  30 . In the embodiment illustrated in FIG. 2, the electronic component as well as plate  32  are rectangular in shape (e.g. square shape) although other shapes may be used in other embodiments (e.g. both could be circular or one circular and the other square). Plate  32  (FIG. 2) is large enough for peripheral portions of plate  32  to extend beyond and overhang the electronic component on all four sides. Overhanging the electronic component on all sides ensures a substantially even heat distribution from the electronic component into the heat sink. Therefore, the electronic component is cooled more uniformly by heat sink  30  (in all directions) and also to a greater amount (due to larger area) than a heat sink of the prior art, e.g. U.S. Pat. No. 6,153,932. The amount of overhand depends on the specific application needs, and can be chosen to be any amount depending on the available space and the heat generated by the electronic component. In one example, the width of a peripheral portion of plate  32  is 25% of the width of the electronic component, although overhang as great as 50% may be used in other examples, and as little as 10% may be used in still other examples. 
     Heat sink  30 , which is designed to be combined with clip  10  (FIG.  1 ), has four cutouts  35   a ,  35   b ,  35   c , and  35   d  on plate  32  through which side plates  16   a  and  16   b  (FIG. 1) and protruding rods  20   a  and  20   b  can be extended. Note that the word “cutout” is used synonymously with the word “hole” when describing the embodiment of FIG. 2, although in some embodiments (e.g. see FIG. 3) the cutouts can be made open (with the periphery of the heat sink). 
     Cutouts  35   a - 35   d  and flat portion  36 , which together accommodate frame  12  (FIG.  1 ), separate protrusions  34  into peripheral protrusions  34   a  and inside protrusions  34   b . Cutouts  35   a  and  35   b  are shown as slits having a generally rectangular shape configured to fit side plates  16   a  and  16   b  (FIG.  1 ), and cutouts  35   c  and  35   d  are shown as holes having a generally oval shape configured to fit protruding rods  20   a  and  20   b . Cutouts  35   a - 35   d  are illustrative and non-limiting. For example, heat sink  30  may have a different number of cutouts on different parts of heat sink  30 , possibly on more than one surface of plate  32 . Plate  32  has protrusions  34  on at least one surface in one embodiment. Protrusions  34  may be, for example, cooling pins or cooling fins. 
     As depicted in FIG. 3, a cutout may be located along the periphery of a heat sink surface. FIG. 3 depicts an exemplary heat sink  40  having cutout  45   a  and cutout  45   b  located along the outer boundaries of plate  42 , thereby allowing cutout  35   a  and cutout  35   b  (FIG. 2) to be eliminated. Depending on the design, a heat sink may include any combination of peripheral cutouts  45   a ,  45   b  of FIG. 3, and/or inner cutouts  35   a ,  35   b  (also called “holes” or simply “cutouts”) of FIG.  2 . For example, heat sink  40  includes peripheral cutouts  45   a  and  45   b  and inner cutouts  45   c  and  45   d.    
     FIG. 4 depicts a perspective view of a heat sink  50  in accordance with another embodiment of the present invention. Heat sink  50  includes a plate  52 , protrusions  54 , and cutouts  55   a - 55   d . Heat sink  50  is substantially similar to heat sink  30 , one of the differences being the arrangement of the protrusions. Although protrusions  54  are arranged differently from protrusions  34 , protrusions  54 , like protrusions  34 , are divided into peripheral protrusions  54   a  and inside protrusions  54   b  by cutouts  55   a - 55   d  and flat portion  56 . In some systems, protrusions  54  may aid heat dissipation by increasing the surface area of heat sink  50  and thereby increase heat transfer efficiency. In an alternative embodiment, protrusions that are uniformly arranged may be spaced far enough apart that clip  10  fits in the space between adjacent protrusions without the need to omit protrusions as in flat portion  56 . 
     FIG. 5 depicts assembling a heat sink device by using clip  10  to combine heat sink  50  with component  60 , in accordance with an embodiment of the present invention. Inside protrusions  54   b  are inserted upwards through hole  14  of clip  10  until flat portion  56  on plate  52  comes in contact with clip  10 . Clip  10  and heat sink  30  are designed so that insertion of inside protrusions  54   b  through hole  14  automatically results in downward extensions of side plates  16   a  and  16   b  and protruding rods  20   a  and  20   b  through cutouts  55   a ,  55   b ,  55   c , and  55   d , respectively. Component  60  is moved toward plate  52  (upward in FIG. 5) in a way that outer edges  64   a  and  64   b  of component  60  are aligned with cutouts  55   a  and  55   b . Fastening hooks  18   a  and  18   b  on side plates  16   a  and  16   b  extend through cutouts  55   a  and  55   b , press against outer edges  64   a  and  64   b  of component  60 , and fasten component  60  to heat sink  50  by applying a pressure on the surface of metallic plate  63  (FIG. 6 shows the fastening mechanism). Metallic plate  63  may be part of a component on silicon  66 . Silicon  66  may be attached to motherboard  62  by ball grid array (not shown). If clip  10  includes elastic rods  22 , elastic rods  22  would be in contact with and pushing down on plate  52 . When dissembling the heat sink device, clip  10  can be pulled to the side and/or upward so that it releases component  60  from the grip of fastening hooks  18   a  and  18   b.    
     FIG. 6A depicts a side view of a heat sink device, in accordance with one embodiment of the present invention. This heat sink device includes heat sink  80  fastened to component  60  by clip  10 , wherein component  60  is attached to motherboard  68 . Heat sink  80  includes plate  82 , protrusions  84  protruding from plate  82 , and cutouts  85  on plate  82 . In one embodiment, component  60  is attached to motherboard  68  by Ball Grid Array  65 . Ball Grid Array  65  attaches component  60  to motherboard  68  while creating a space between component  60  and motherboard  68 . The space allows fastening hooks  18   a  and  18   b  to snap around bottom edges  64   a  and  64   b  of component  60  without straining component  60  or motherboard  68 . A person of ordinary skill in the art would know of other ways to create the space between component  60  and the motherboard in order to allow fastening hooks  18   a  and  18   b  to snap on to a component, such as component  60 . 
     FIG. 6B depicts a fastening mechanism for a heat sink device, in accordance with one embodiment of the present invention. Heat sink  80  is fastened to component  60  by fastening hook  18   b  of clip  10  (shaded for clarity). A protruding portion of clip  10 , such as side plate  16   b , extends through a hole in heat sink  80 . Fastening hook  18   b  wraps around edge  64  of component  60 . Since component  60  is attached to motherboard  68  by Ball Grid Array  65 , clip  10  does not need to fasten component  60  to motherboard  68 . Motherboard  68  may or may not have a hole. 
     FIG. 7A depicts a side view of a heat sink device including a motherboard  70  with a hole, in accordance with another embodiment of the present invention. Like the embodiment of FIG. 6A, heat sink  80  is fastened to component  60  by a clip  90 , which has side plates  96   a  and  96   b  connected to fastening hooks  98   a  and  98   b , respectively. Clip  90  is similar to clip  10  (FIG.  1 ), except that side plates  96   a  and  96   b  are designed to extend through both cutouts  85  in a heat sink and cutouts  72  in motherboard  70 . Unlike in the embodiment of FIG. 6A, motherboard  70  also contains cutouts so that side plates  96   a  and  96   b  extend through motherboard  70 . Fastening hooks  98   a  and  98   b  at the ends of side plates  96   a  and  96   b  snap on to edges of cutouts  72  in motherboard  70 . Component  60  is located between plate  82  of heat sink  80  and motherboard  70 , and between side plate  86   a  and side plate  86   b . The same heat sink  80  can be used for the embodiments in both FIG.  6 A and FIG.  7 A. Therefore, heat sink  80  can be used with a motherboard that does not have cutouts or a motherboard that has cutouts. 
     FIG. 7B depicts a fastening mechanism for a heat sink device including a motherboard with a hole, in accordance with one embodiment of the present invention. Heat sink  80  is fastened to component  60  by fastening hook  98   b  of clip  90  (shaded for clarity). Fastening hook  98   b  at an end of side plate  96   b  wraps around edge of a cutout in motherboard  70 . A portion of clip  10 , such as side plate  96   b , extends through a cutout in heat sink  80  and a cutout in motherboard  70 . Fastening hook  98   b  at an end of side plate  96   b  wraps around edge of a cutout in motherboard  70 . 
     FIG. 8 depicts a plane view of a heat sink device assembled with a clip  110 , in accordance with one embodiment of the present invention. Clip  110  attaches heat sink  120  to a component, which is not shown. Heat sink  120  includes a plate  122 , protrusions  124  protruding from plate  122 , and cutouts  125   a  and  125   b . Clip  110  rests on a part of plate  122  that is free of protrusions. Protrusions  124  of heat sink  120  are substantially similar to protrusions  54  of FIG. 4, and may be cooling fins or cooling rods designed to increase the heat dissipation surface area. For simplicity, FIG. 8 shows protrusions  124  as protrusion clusters, indicated by shaded areas. Each protrusion cluster includes one or more protrusions  124 . Clip  110  rests on plate  122  in such a way that protruding portions (not shown) of clip  110  extend through cutouts  125   a  and  125   b  and fasten a component against a surface of plate  122  that is not shown. 
     FIG. 9 depicts a side view of a heat sink device assembled with at least one metal clip  130 , in accordance with one embodiment of the present invention. Metal clip  130  may be, for example, any appropriate metal clip that is currently available in the market. Heat sink  140  may be substantially similar to heat sink  50  (FIG.  4 ), one of the differences being the arrangement of the surface protrusions  144 . Like clip  10  of FIG. 6A, metal clip  130  rests on a part of plate  142  where there are no protrusions. Protruding portions  136   a  and  136   b  of metal clip  130  extend through cutouts  145   a  and  145   b  and snap around edges  64   a  and  64   b  of component  60 , fastening component  60  against heat sink  140 . In another embodiment including a motherboard with cutouts, protruding portions  136   a  and  136   b  of clip  130  may extend through the motherboard and snap around the edges of the cutouts in the motherboard, fastening heat sink  140  to the motherboard. 
     FIG. 10 depicts a plane view of a heat sink device assembled with at least one metal clip  150 , in accordance with one embodiment of the present invention. Metal clip  150  fastens heat sink  160  to a component (not shown) or a motherboard (not shown). Heat sink  160  includes a plate  162  and protrusions  164  protruding from plate  162 . The embodiment in FIG. 10 includes two metal clips, metal clip  150   a  and metal clip  150   b , resting on a part of plate  162  free of protrusions  164 . Protruding portions of metal clip  150   a  and metal clip  150   b  extend through cutouts  155   a ,  155   b ,  155   c , and  155   d  on plate  152 . For simplicity, protrusions  154  are shown as protrusion clusters indicated by shaded areas. Each protrusion cluster includes one or more protrusions  154 , which maybe cooling fins or cooling rods. 
     FIG. 11 depicts a side view of a heat sink device assembled with at least one wire spring  170  and a motherboard  180  with cutouts  182 , in accordance with another embodiment of the present invention. Wire spring  170  may be any appropriate wire spring currently available in the market Wire spring  170  fastens heat sink  190  to motherboard  180 , pressing component  60  between heat sink  190  and motherboard  180 . Heat sink  190  includes a plate  192 , protrusions  194 , and cutouts  195 . Wire spring  170  rests on surface  192  of heat sink  190  and extend protruding portions  176  through cutouts  195 . Protruding portions  176  extend through cutouts  182  in motherboard  180  and snaps around edges of cutouts  182  to fasten heat sink  190  to motherboard  180 . Wire spring  170  does not have to contact component  60 . 
     FIG. 12 depicts a plane view of a heat sink device assembled with at least one wire spring  200 , in accordance with one embodiment of the present invention. The embodiment in FIG. 12 includes wire spring  200   a , wire spring  200   b , and heat sink  210  including a plate  212 , protrusions  214  substantially similar to protrusions  54  of FIG. 4, and cutouts  215   a ,  215   b ,  215   c , and  215   d  on plate  212 . Wire spring  200   a  and wire spring  200   b  rest on parts of plate  212  free of protrusions  214  and extend through cutouts  215   a ,  215   b ,  215   c , and  215   d  of heat sink  210 . For simplicity, FIG. 12 shows protrusions  214  as shaded areas of protrusion clusters, each of which includes one or more protrusions such as cooling fins or cooling rods. 
     FIG. 13 depicts a side view of a heat sink device including at least one screw  220  and a motherboard  230  that has holes, in accordance with one embodiment of the present invention. Screw  220  attaches a heat sink  240  to motherboard  230 , sandwiching component  60  between heat sink  240  and motherboard  230 . Screw  220  may be, for example, an appropriate screw currently available in the market. Heat sink  240  includes a plate  242 , protrusions  244  that are substantially similar to protrusions  54  (FIG.  4 ), and cutouts  245 . Screw  220  may be inserted into a threaded standoff  250  between heat sink  240  and motherboard  230 . A longer screw  220  may also be inserted through the holes in the motherboard and the heatsink. Optionally, a nut may be used. There may be threads in heat sink  240 . In some embodiments, the threads may be in the motherboard. 
     FIG. 14 depicts a plane view of a heat sink device assembled with a screw  260 , in accordance with one embodiment of the present invention. For example, the embodiment in FIG. 14 could be a view from the top of the embodiment depicted in FIG.  13 . The embodiment in FIG. 14 includes two screws, screw  260   a  and screw  260   b , resting on a flat portion of heat sink  270  that is free of the protrusions  274 . For simplicity, protrusions  274  are shown as shaded areas. Protrusions include cooling fins or cooling rods. 
     While particular examples of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as fall within the true spirit and scope of this invention.