Abstract:
A heat dissipation module for removing heat from a heat-generating electronic component includes a base ( 106 ) and a clip ( 40, 40   a ). The clip includes a connecting arm ( 42, 42   a ) and a securing arm ( 44, 44   a ) for locking the base to the heat-generating electronic component. The connecting arm engages with the base. The securing arm extends from the contacting arm and is curve-shaped with a free end thereof being for being depressed whereby the securing arm exerts a downward force on the base so that the base and the electronic component can have an intimate contact with each other.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to a heat dissipation module, and in particular to a heat dissipation module incorporating a clip for mounting the heat dissipation module on a circuit board to effectively dissipate heat generated by an electronic device on the circuit board. The clip has such a configuration that a steady pressure generated by the clip on the electronic device can be easily obtained. 
       DESCRIPTION OF RELATED ART 
       [0002]    With the advance of large scale integrated circuit technology, high speed processors have become faster and faster, which causes the processors to generate more redundant heat. Redundant heat if not quickly removed will have tremendous influence on the system stability and performance. Usually, people install a heat sink on the central processor to assist its heat dissipation, whilst a clip is required for mounting the heat sink to the processor. 
         [0003]      FIG. 5  shows a clip in accordance with related art for mounting a heat sink (not shown) to a processor (not shown) in accordance with related art. The clip is T-shaped, including a locking portion  42   c  and a securing portion  44   c.  The securing portion  44   c  is elongated and with two ends. The locking portion  42   c  extends transversely from a middle of the securing portion  44   c.  The locking portion  42   c  defines two locking holes  421   c  therein. Screws (not shown) extend through the locking holes  421   c  to lock the clip to the heat sink. The securing portion  44   c  defines two securing holes  441   c  in the two ends thereof. When the heat sink with the clip fixed thereon is mounted to a circuit board (not shown) on which the processor is arranged, rivets or screws extend through the securing holes  441   c  into corresponding holes defined in the circuit board to lock the heat sink to the circuit board. Thus the heat sink with the clip is fixedly mounted on the circuit board by riveting or screwing. The pressure exerted on the processor is generated by the downward deflection of the clip. However, for the requirement of compactness of the electronic device, the size of the clip is limited. A distance between each securing hole  441   c  of the securing portion  44   c  and the locking portion  42   c  is limited. Such a limitation causes that when the deflection of the clip has a little variation, the pressure exerted by the clip on the processor changes enormously, which results in that the pressure exerted on the processor can not be easily controlled. 
         [0004]    What is needed, therefore, is a heat dissipation module incorporating a clip for mounting the heat dissipation module to a circuit board, wherein the clip is so configured that the clip can exert a steady pressure to the processor even when the deflection of the clip has a large variation. 
       SUMMARY OF THE INVENTION 
       [0005]    According to a preferred embodiment of the present invention, a heat dissipation module includes a base and a clip for securing the base to a heat-generating electronic component. The clip includes a connecting arm engaging with the base and at least one securing arm for securing the base to the heat-generating electronic component. The at least one securing arm bends curvedly from the connecting arm and has an end remote from the connecting arm. The remote end is securely fixed to a circuit board on which the heat-generating electronic component is mounted. 
         [0006]    Other advantages and novel features of the present invention will be drawn from the following detailed description of the preferred embodiment of the present invention with attached drawings, in which: 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present heat dissipation module 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 heat dissipation module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views: 
           [0008]      FIG. 1  is an exploded, isometric view of a heat dissipation module in accordance with a preferred embodiment of the present invention; 
           [0009]      FIG. 2  is an assembled, isometric view of the heat dissipation module of  FIG. 1 ; 
           [0010]      FIG. 3  is a top view of a clip of the heat dissipation module of  FIG. 1 ; 
           [0011]      FIG. 4  is a top view of a clip in accordance with a second embodiment of the present invention; and 
           [0012]      FIG. 5  is a top view of the clip in accordance with related art. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Referring to  FIGS. 1-2 , a heat dissipation module includes a fan  10 , a base  106  extending from the fan  10 , a heat sink (not labeled) attached to the base  106 , and a pair of clips  40  for securing the base  106  to a printed circuit board  100  on which a heat-generating electronic device, such as a CPU  200 , is mounted. 
         [0014]    The fan  10  includes a housing  11  defining a space (not labeled) therein, and a motor  50  received in the space of the housing  11 . A plurality of fan blades  52  extends radially and outwardly from an outer-periphery of the motor  50  for generating forced airflow during rotation of the motor  50 . The housing  11  defines an air inlet  54  in a top wall  12  thereof. An air outlet  60  perpendicular to the air inlet  54  is defined in a sidewall  14  of the housing  11 . 
         [0015]    The base  106  is integrally formed with the housing  11  and extends from an outer periphery of the top wall  12  of the housing  11 . The base  106  is located at a side of the fan  10  opposite the air outlet  60  of the housing  11 . A pair of flanges  107  extends outwardly from two opposite sides of a distal end  104  of the base  106 , respectively. Three pins  109  extend upwardly from each of the flanges  107 . The pins  109  of the flanges  107  are arranged symmetric to each other. A through hole  108  is defined in the distal end  104  of the base  106 . 
         [0016]    The heat sink includes a heat spreader  70 , a heat pipe  30  thermally attached to the heat spreader  70 , and a fin unit  20  thermally attached to the heat pipe  30 . The heat spreader  70  is made of material having relatively high heat conductivity, such as copper or aluminum. The heat spreader  70  has a shape and size the same as that of the through hole  108  and is received in the through hole  108  of the base  106 . 
         [0017]    The heat pipe  30  is arranged on the base  106 . The heat pipe  30  includes an evaporating section  302  and a condensing section  304  at two opposite ends thereof. The evaporating section  302  is arranged on the distal end  104  of the base  106  and attaches to an upper surface  72  of the heat spreader  70  directly. Alternatively, for improving heat conductivity between the heat spreader  70  and the heat pipe  30 , thermal interface material such as thermal grease can be filled between the upper surface  72  of the heat spreader  70  and the heat pipe  30 . The condensing section  304  of the heat pipe  30  extends from the evaporating section  302  and across the top wall  12  to of the housing  11 . 
         [0018]    The fin unit  20  is arranged at the air outlet  60  of the housing  11 , including a plurality of fins  22  stacked together. Each fin  22  has a main body  28  and a pair of hems  26  bent from top and bottom sides of the main body  28 . The hems  26  of each fin  22  abut the main body  28  of an adjacent fin  22 . Cooperatively the top hems  26  form a top surface  29  of the fin unit  20 . The condensing section  304  of the heat pipe  30  contacts with the top surface  29  of the fin unit  20  to dissipate heat to the fin unit  20 . A flow channel  24  is defined between the main bodies  28  of any two neighboring fins  22  for the airflow generated by the fan  10  to flow therethrough. 
         [0019]    Also referring to  FIG. 3 , the clips  40  are connected to the flanges  107  of the base  106 . Each clip  40  includes a connecting arm  42  at a middle portion thereof and two securing arms  44  at two opposite ends thereof. The connecting arm  42  is elongated and has a rectangular shape. Three locking holes  421  are defined in the connecting arm  42  of each clip  40  corresponding to the pins  109  of each flange  107 . Each securing arm  44  of the clip  40  bends reversely from a corresponding end of the connecting arm  42  and extends toward the other end of the connecting arm  42 . In other words, free ends (not labeled) of the securing arms  44  face to each other. A securing hole  441  is defined in the free end of each of the securing arms  44 . The two securing holes  441  of the clip  40  have shapes different from each other. One of the two securing holes  441  is circular, whilst the other securing hole  441  is oblong. Alternatively, the two securing holes  441  can have the same shape with each other. 
         [0020]    When the heat dissipation module is assembled, the fin unit  20  is received in the air outlet  60  of the housing  11 . The condensing section  304  of the heat pipe  30  attaches to the top surface  29  of the fin unit  20 , and the evaporating section  302  is arranged on the base  106 . The heat spreader  70  is received in the through hole  108  of the base  106  with an upper surface  72  thermally connected with the evaporating section  302  of the heat pipe  30 . The clips  40  are connected to the flanges  107  of the base  106 . The two clips  40  are arranged opposite to each other. The connecting arms  42  of the two clips  40  are mounted on the flanges  107 , whilst the securing arms  44  of the two clips  40  are located beyond the base  106 . The connecting arms  42  are located closer to each other than the securing arms  44  of the two clips  40 . The pins  109  of the flanges  107  of the base  106  extend through the locking holes  421  of the connecting arms  42  of the clips  40  to lock the clips  40  to the heat dissipation module. The pins  109  of the flanges  107  can be fixedly engaged with the locking holes  421  of the clips  40  by riveting or interference fit. The four securing holes  441  of the securing arms  44  of the clips  40  are located around four corners (not labeled) of the base  106 . When the heat dissipation module is mounted to the CPU  200 , a lower surface (not shown) of the heat spreader  70  opposite to the upper surface  72  is thermally attached to the CPU  200 . Screws (not shown) extend through the securing holes  441  of the clips  40  into corresponding mounting holes (not labeled) of the circuit board  100  to secure the heat dissipation module to the circuit board  100 , whereby the heat spreader  70  can have an intimate contact with the CPU  200  mounted on the printed circuit board  100 . 
         [0021]    When the clips  40  engage with the flanges  107 , each securing arm  44  of the clips  40  acts as a cantilever which has one end fixed and the other end free. A portion of the connecting arm  42  corresponding to the locking holes  421  acts as the fixed end of the cantilever, whilst a portion of each securing arm  44  corresponding to the securing hole  441  act as the free end of the cantilever. Each screw provides a downward load P to a corresponding securing arm  44 . The securing arms  44  of the clips  40  under the downward load P deflect. When the securing arms  44  of the clips  40  undergo a deflection which is in the linearly elastic range, the following equation can be applied to the securing arms  44  of the clips  40 : P=E*Y*W*T3/(4*L3), wherein E is the elastic modulus of the cantilever; Y is the displacement of the free end of the cantilever under the load P; W is the width of the cantilever; T is the thickness of the cantilever; and L is the length of the cantilever. 
         [0022]    As shown in the above equation, the load P is directly proportional to the displacement Y, whilst is inversely proportional to the cube of the length L. Thus, when the length L between the locking holes  421  and each securing hole  441  of the clips  40  is increased, the load P is approximately constant (i.e., having a small variation) even if the displacement Y of the securing arm  44  has a variation. As the securing arms  44  bend backward from the connecting arm  42 , the length L is thus increased. Thus, when the deflection of each of the clips  40  has a variation, the pressure exerted by the clips  40  on the CPU  200  is approximately constant. Therefore, the heat dissipation module is mounted on the CPU  200  with steady pressure. The heat dissipation module can be more reliably attached to the CPU  200 , and the heat generated by the CPU  200  can be more reliably absorbed by the heat sink of the heat dissipation module. During operation of the heat dissipation module, the heat generated by the CPU  200  is transferred firstly to the heat spreader  70 . Working fluid received in the evaporating section  302  of the heat pipe  30 , which thermally attaches the upper surface  72  of the heat spreader  70  absorbs the heat therefrom and evaporates into vapor. The vapor moves from the evaporating section  302  to the condensing section  304  which thermally attaches to the fin unit  20  to dissipate the heat, whereby the vapor cools and condenses at the condensing section  304 . The condensed working fluid returns to the evaporating section  302  and evaporates again to thereby repeat the heat transfer from the evaporating section  302  to the condensing section  304 . By this way, the heat generated by the CPU  200  is transferred from the heat pipe  30  to the fin unit  20  almost immediately. When the forced airflow generated by the fan  10  flows through the flow channels  24  of the fin unit  20 , the heat can be efficiently carried away by the airflow. Therefore, the heat of the CPU  200  can be dissipated immediately. 
         [0023]      FIG. 4  shows a top view of a clip  40   a  in accordance with a second embodiment of the present invention. Also the clip  40   a  has a connecting arm  42   a  to lock with the heat dissipation module, and a pair of securing arms  44   a  extending from two opposite ends of the connecting arm  42   a.  The connecting arm  42   a  is T-shaped, and includes a first portion  43   a  and a second portion  45   a  extending transversely from a middle of the first section  43   a . The connecting arm  42   a  defines two locking holes  421   a  therein. The locking holes  421   a  are respectively located in the first and second portions  43   a,    45   a.  To lock the clip  40   a  to the heat dissipation module, the positions and sizes of the pins  109  of the heat dissipation module can be changed according to the locking holes  421   a  of the clip  40   a.  The two securing arms  44   a  bent from opposite ends of the first portion  43   a  of the connecting arm  42   a,  respectively. Each securing arm  44   a  is U-shaped. Also each securing arm  44   a  defines a securing hole  441   a  in a free end (not labeled) thereof, wherein the free ends face a same lateral side of the clip  40   a.  The two securing holes  441   a  and the locking hole  421   a  in the first portion  43   a  of the connecting arm  42   a  are aligned with each other. As the securing arms  44   a  are curve-shaped, the length between each securing hole  441   a  and the locking holes  421   a  is increased in comparison with the related art. Thus when a deflection of each of the clips  40   a  has a variation during mounting of the heat dissipation module to the printed circuit board  100 , the pressure exerted by the clips  40   a  on the CPU  200  remains approximately constant. Accordingly, the heat dissipation module can be reliably mounted on the CPU  200  to have an intimate contact therewith. In both embodiments as shown in  FIGS. 3 and 4 , the securing arms  44 ,  44   a  are in a same horizontal plane with the connecting arms  42 ,  42   a  before the free ends of the securing arms  44 ,  44   a  are depressed. 
         [0024]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to accommodate various modifications and equivalent arrangements. The clips  40 ,  40   a  in accordance with the preferred embodiments of the present invention comprise a connecting arm  42 ,  42   a  and a pair of securing arms  44 ,  44   a  extending from the connecting arm  42 ,  42   a.  It is can be understood that the size, and the shape of the connecting arm  42 ,  42   a  and the securing arms  44 ,  44   a  can change according to the heat dissipation module or the space in which the heat dissipation module is mounted. As the securing arms  44 ,  44   a  bending from the locking portion  42 ,  42   a,  the clips  40 ,  40   a  are curve-shaped. The length between the locking holes  421 ,  421   a  and the securing holes  441 ,  441   a  is thus increased. The influence of variation of the deflection of the clips  40 ,  40   a  to the pressure exerted on the CPU  200  by the clips  40 ,  40   a  is lessened. Thus, the heat dissipation module can be easily and reliably mounted on the CPU  200 .