Abstract:
A clip assembly includes a bolt, a sleeve, and a resilient component held between the bolt and the sleeve. The bolt includes a head formed at an end thereof, an engaging portion formed at an opposite end thereof, and an engaging structure located between the head and the engaging portion. The sleeve includes a hollow body having an engaging structure. When the bolt is inserted into the body of the sleeve along a first direction, the engaging structure of the bolt engages with the engaging structure of the sleeve to block the bolt from escaping from the sleeve along a second direction opposite to the first direction. The resilient component is adapted to exert a force on the bolt to cause the bolt to have a tendency to move along the second direction.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a clip assembly, and more particularly to a clip assembly for attaching a heat sink to an electronic package. 
       DESCRIPTION OF RELATED ART 
       [0002]    A heat sink is usually placed in thermal contact with an electronic package, such as a central processing unit (CPU), to transfer heat through conduction away from the electronic package thus preventing over-heating of the electronic package. One apparatus for attaching the heat sink on the CPU includes four through holes defined in four corners of the heat sink, four thread holes defined in a motherboard, four screws, and four springs. The screws are extended through the springs and the through holes of the heat sink in order to engage in the thread holes of the motherboard, thereby attaching the heat sink onto the CPU. 
         [0003]    However, the screws and the springs are discrete components prior to attachment of the heat sink onto the motherboard. Particularly in mass-production facilities, the assembly process can be time-consuming and inconvenient. 
         [0004]    Therefore, an improved apparatus for securing a heat sink, which overcomes the above-mentioned problem is desired. 
       SUMMARY OF THE INVENTION 
       [0005]    A clip assembly comprises a bolt, a sleeve, and a resilient component exerting a force on both the bolt and the sleeve. The bolt comprises a head formed at an end thereof, an engaging portion formed at an opposite end thereof, and an engaging structure located between the head and the engaging portion. The sleeve comprises a hollow body having an engaging structure. When the bolt is inserted into the body of the sleeve along a first direction, the engaging structure of the bolt engages with the engaging structure of the sleeve to stop the bolt from escaping from the sleeve along a second direction opposite to the first direction. The resilient component exerts a force on the bolt to cause the bolt to have a tendency to move along the second direction. 
         [0006]    Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is an exploded view of a clip assembly in accordance with a preferred embodiment of the present invention, together with a heat sink, a printed circuit board and an electronic package mounted on the printed circuited board; 
           [0009]      FIG. 2  is an enlarged exploded view of the clip assembly in  FIG. 1 ; 
           [0010]      FIG. 3  is a schematic cutaway view showing the heat sink placed onto the electronic package in position for its subsequent mounting on the printed circuited board by the clip assembly; 
           [0011]      FIG. 4  is a schematic cutaway view showing that the heat sink mounted to the printed circuited board by the clip assembly; and 
           [0012]      FIG. 5  is an assembled view of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Referring to  FIGS. 1 -5 , a clip assembly  10  in accordance with a preferred embodiment of the present invention is illustrated. The clip assembly  10  is used to secure a heat sink  20  to an electronic package such as a CPU  32  mounted on a printed circuit board  30 , which has four through holes  34  defined around the CPU  32 . In this embodiment, a back plate  40  is provided for engaging with the clip assembly  10  so as to secure the heat sink  20  to the printed circuit board  30 . 
         [0014]    The heat sink  20  comprises a cylindrical core  22  and a plurality of fins  24  radially and outwardly extending from a periphery of the core  22 . Four ears  222  symmetrically and outwardly extend from a bottom portion of the core  22 . Each ear  222  has a through hole  224  defined in a free end portion thereof corresponding to the through holes  34  of the printed circuit board  30 . An annular step  2242  is inwardly disposed in a lower end of the through hole  224  of each ear  222  of the heat sink  20 . An upper end of each through hole  224  has a hexagonal cross-section. The lower end of each through hole  224  has an inner diameter smaller than a diameter of the upper end of the through hole  224 , and has a cylindrical cross-section. 
         [0015]    The back plate  40  is located under the printed circuit board  30  opposite the CPU  32 . The back plate  40  comprises a rectangular base  42  abutting against a bottom side of the printed circuit board  30 , and four arms  44  symmetrically and outwardly extending from corners of the base  42 . Each arm  44  defines an aperture  442  in a free end thereof for an extending socket  46  to extend therethrough. A center of each extending socket  46  defines a thread hole  48  therein for receiving and threadly engaging with the clip assembly  10 . 
         [0016]    The clip assembly  10  comprises a bolt  16 , a sleeve  18 , and a resilient component, such as a coil spring  15  held between the sleeve  18  and the bolt  16 . 
         [0017]    Particularly referring to  FIG. 2 , the bolt  16  is a multistage body with different diameters, comprises a rounded head  162 , a first section  164  extending downwards from the head  162 , and a second section  166  depending from a bottom portion of the first section  164 . The second section  166  has a diameter smaller than a diameter of the first section  164 . 
         [0018]    The head  162  is formed at a top end of the bolt  16 , and has a cross-shaped groove (not labeled) defined in a top side thereof for engaging with tools, which can screw the bolt  16  downwardly. The head  162  has a diameter larger than a diameter of the adjacent first section  164  so as to form a flange. 
         [0019]    The first section  164  has an outer diameter substantially identical to an inner diameter of the coil spring  15 ; thus, the coil spring  15  can be coaxially positioned on the first section  164  of the bolt  16 . The first section  164  further has a cone portion  167  (see  FIG. 3-4 ) formed at the joint portion of the first section  164  and the second section  166  so as to reduce the stress concentrating thereat. 
         [0020]    The second section  166  has an engaging portion  169  formed at a free end thereof. The engaging portions  169  can extend downwards through the through holes  224  of the heat sink  20  and the through holes  34  of the printed circuit board  30  to engage with the extending sockets  46 . In this embodiment, the engaging portions  169  each form a thread portion for engaging in the thread holes  48  of the extending sockets  46 . A ring shaped projection  168  is formed at the second section  166  above and adjacent to the engaging portion  169 . In this embodiment, the projection  168  has a cone shaped outer surface (see  FIG. 3-4 ), which facilitates mounting the bolt  16  into the sleeve  18 . 
         [0021]    The sleeve  18  comprises an elongated hollow body  182  and a hexagonally shaped flange  186  formed at a top edge of the body  182 . A hole  184  is defined extending through the entire sleeve  18  coaxial with an axis of the body  182 . The hole  184  of the sleeve  18  has a diameter larger than an outer diameter of the projection  168  of the bolt  16 . Moreover, the diameter of the hole  184  of the sleeve  18  is slightly larger than an outer diameter of the extending socket  46  so that the extending socket  46  can move upwardly into the hole  184 ; thus, the extending socket  46  can be guided to engage with the engaging portion  169  of the bolt  16 . A pair of opposite engaging structures, such as two rectangular barbs  188 , are stamped inwardly from the body  182  of the sleeve  18 , and are slanted downward so as to guide the projection  168  moving downwards. 
         [0022]    The flange  186  is snuggly retained on the annular step  2242  of the through holes  224  of the heat sink  20 . The outer diameter of the flange  186  of the sleeve  18  is larger than an inner diameter of the coil spring  15  so that the coil spring  15  can be supported on the flange  186  of the sleeve  18 . 
         [0023]    When assembled, the bolt  16  is first pushed to extend through the coil spring  15 , then is inserted downwards into the hole  184  of the sleeve  18 . The projection  168  of the bolt  16  contacts the barbs  188  of the sleeves  18 , forces the bars  188  to move outwards so as to slide past the barbs  188 . Subsequently, the barbs  188  return to their previous forms, and block the projection  168  of the bolt  16  from moving upwardly. At the same time, opposite top and bottom sides of the coil spring  15  are rested respectively on the head  162  of the bolt  16  and the flange  186  of the sleeve  18 . The coil spring  15  is compressed, and exerts a force on the head  162  of the bolt  16  to upwardly push the bolt  16  away from the sleeve  18 . Therefore, the bolt  16 , the coil spring  15  and the sleeve  18  are assembled together to form the clip assembly  10 . In this state, the engaging portion  169  of the bolt  16  is shielded by the sleeve  18  so as to not scrape and damage the surrounding electronic components. 
         [0024]    During operation, a downward force is exerted on the head  162  of the bolt  16  to overcome the resilient force of the coil spring  15  so as to cause the bolt  16  to move downwardly relative to the sleeve  18 . Simultaneously, the engaging portion  169  of the bolt  16  engages with a corresponding component such as the thread hole  48  of the extending socket  46 . In this process, the resilient force of the coil spring  15  is gradually increased in proportion to the distance that the bolt  16  moves. When the downward force is disappeared, the bolt  16  returns back to its previous position caused by the resilient force of the coil spring  15 , where the projection  168  of the bolt  16  is blocked by the barbs  188  of the sleeve  18 . 
         [0025]    As described above, the bolt  16 , the coil spring  15  and the sleeve  18  of the clip assembly  10  are pre-assembled to form a module. This makes the clip assembly more easy to store, transport and use. Furthermore, the sleeve  18  of the clip assembly  10  serves as a shield preventing the engaging portion  169  of bolt  16  from contacting with nearby electronic components. Additionally, the sleeve  18  also serves as a guide for guiding the engaging portion  169  of the bolt  16  into the thread holes  48  of the extending socket  46  of the back plate  40  in a process of securing the heat sink  20  to the CPU  32  by the clip assembly  10 . This process will be described in following text in more detail. 
         [0026]    In the process of securing the heat sink  20  to the CPU  32  by the clip assembly  10 , the pre-assembled clip assemblies  10  are first extended through the associated through holes  224  of the heat sink  20  with the flanges  186  of the sleeves  18  supported on the inserting steps  2242  of the associated through holes  224  of the heat sink  20 . Then, the extending sockets  46  of the back plate  40  are pushed upwardly to extend through the corresponding through holes  34  of the printed circuit board  30 , and are guided into the corresponding holes  184  of the sleeves  18 . Therefore, the engaging portions  169  of the bolts  16  are aimed at the corresponding thread holes  48  of the extending sockets  46 . Subsequently, the thread portions of the bolts  16  are screwed downwards to engage in the thread holes  48  of the extending sockets  46 . Therefore, the heat sink  20  is mounted on the printed circuit board  30 , and the coil springs  15  exert a certain resilient force onto the heat sink  20  via the flanges  186  of the sleeves  18  to evenly contact the heat sink  20  with the CPU  32 . 
         [0027]    As shown in  FIGS. 3-4 , the bolt  16  is at a same position during the whole assembly process. However, in another embodiment, if adjusting the length of the thread portion of the bolt  16 , the length of the extending socket  46  or other parameters, the bolt  16  may move downwards relative to the sleeve  18  to cause the coil springs  15  to be further compressed between the heads  162  of the bolt  16  and the flange  186  of the sleeves  18 . 
         [0028]    When disassembled, the heat sink  20 , the clip assembly  10  and the printed circuit board  30  can be separated from each other so long as the thread portions of the bolts  16  are unscrewed from the thread holes  48  of the extending sockets  266 . Then, the clip assembly  10  can easily be used in other heat sinks, or other types of heat sink in a quite similar manner, so long as the other heat sink has a hole defined therein for the clip assembly  10  to extend through. Therefore, the clip assembly  10  has high versatility of use. 
         [0029]    In this embodiment, the sleeve  18  can guide the engaging portion  169  of the bolt  16  into the thread hole  48  of the extending socket  46 . This facilitates engagement of the bolt  16  in the extending socket  46 . The engaging portion  169  of the bolt  16  is hidden in the sleeve  18  before engaging with the extending socket  46 . This can prevent the engaging portion  169  of the bolt  16  from scraping the nearby electronic components. 
         [0030]    Furthermore, the clip assembly  10  is pre-assembled to form a module. Installation or removal of the clip assembly  10  is thus both quick and simple. Additionally, the coil springs  15  serve to lessen vibrations; therefore, the heat sink  20  can be securely fastened in the desired position on the printed circuit board  30  and is not overly subjected to the vibrations. 
         [0031]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.