Abstract:
A heat dissipation device assembly is mounted on a printed circuit board ( 80 ). First and second electronic components ( 82, 84 ) are mounted on the printed circuit board. The heat dissipation device assembly includes a first heat sink ( 10 ) in thermal contact with the first electronic component, and a second heat sink ( 20 ) in thermal contact with the second electronic component. A spring tab ( 24 ) is sandwiched between the first and second heat sinks for providing spring force between the first and second heat sinks thus securely mounting the second heat sink on the second electronic component.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a heat dissipation device assembly having first and second heat sinks for dissipating heat from main and auxiliary heat-generating electronic components mounted on a printed circuit board. 
         [0003]    2. Description of related art 
         [0004]    The central processing unit (CPU) mounted on the motherboard in a computer is the center of operations of the computer. During the operation of the computer, the CPU produces heat. The heat must be quickly carried away from the CPU during the operation of the computer. Excessively high temperature causes the CPU to work abnormally. In addition to the CPU, MOSFETs (metal oxide semiconductor field effect transistors) near to the CPU are also sources of heat that need to be cooled. The MOSFETs on the motherboard regulate and provide the power for the CPU. The MOSFET delivers the heat to the motherboard and causes the motherboard temperature to increase quickly, thus shortening the life span of the motherboard. 
         [0005]    Typically, a related heat sink is mounted on the CPU to remove heat therefrom. However, the related heat sink can only dissipate heat generated by the CPU, and cannot dissipate the heat generated by other heat-generating electronic components, such as MOSFETs next to the CPU. 
         [0006]    Furthermore, with less room in the computer, it is needed to solve heat dissipation problem to the CPU and other heat-generating electronic components at the same time in a limited space environment such as a computer enclosure. 
         [0007]    Thus, it is desirable to devise a heat dissipation device which can not only dissipate the heat generated by the CPU but also dissipate the heat by other electronic components beside the CPU in a limited space environment. 
       SUMMARY OF THE INVENTION 
       [0008]    According to a preferred embodiment of the present invention, a heat dissipation device assembly is mounted on a printed circuit board. First and second electronic components are mounted on the printed circuit board. The heat dissipation device assembly includes a first heat sink in thermal contact with the first electronic component, and a second heat sink in thermal contact with the second electronic component. A spring tab is sandwiched between the first and second heat sinks for providing spring force between the first and second heat sinks whereby the second heat sink is securely mounted on the second electronic component. 
         [0009]    Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Many aspects of the present device 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 device. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0011]      FIG. 1  is a partly exploded isometric view of a heat dissipation device assembly in accordance with a preferred embodiment of the present invention; 
           [0012]      FIG. 2  is an exploded isometric view of a main heat sink of the heat dissipation device assembly of  FIG. 1 ; 
           [0013]      FIG. 3  is an assembled view of a second heat sink of the heat dissipation device assembly of  FIG. 1 , wherein the second heat sink is mounted on a printed circuit board; 
           [0014]      FIG. 4  is an assembled view of  FIG. 1 ; and 
           [0015]      FIG. 5  is a side view of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Reference will now be made to the drawings to describe a heat dissipation device having a fan duct in accordance with a preferred embodiment of the present invention in detail. 
         [0017]      FIG. 1  shows a heat dissipation device assembly mounted on a printed circuit board  80 . The heat dissipation device comprises a main heat sink  10  and a second heat sink  20 . A CPU  82  is mounted on a center of the printed circuit board  80 . The main heat sink  10  is mounted on the CPU  82  for dissipating heat generated by the CPU  82 . A pair of MOSFETs  84  are mounted on the printed circuit board  80  near to the CPU  82 . The second heat sink  20  is mounted on the MOSFETs  84  for dissipating heat generated by the MOSFETs  84 . 
         [0018]    Also referring to  FIG. 2 , the main heat sink  10  comprises a base  12 , a plurality of fins  14  attached to the base  12  and two heat pipes  16  connecting the base  12  and the fins  14 . A pair of locking members  18  is used for engaging with the base  12  and securing the main heat sink  10  to the printed circuit board  80 . 
         [0019]    The base  12  is a metal plate having a high heat conductivity, and has a rectangular configuration for contacting with the CPU  82 . The base  12  defines two parallel straight grooves  120  in a top portion thereof for receiving the heat pipes  16 . The grooves  120  are located in a central area of the base  12 . The base  12  defines two undercuts (not labeled) in opposite sides of a bottom portion thereof to form two locking portions  122  for engaging with the locking members  18 . The undercuts are aligned parallel to the grooves  120 . Each locking portion  122  defines two threaded holes  1220  therein at opposite ends thereof. 
         [0020]    The fins  14  has an L-shaped configuration. The fins  14  are oriented perpendicular to the base  12  and parallel to each other. The fins  14  comprise a first portion  140  and a second portion  142  connecting with one side of the first portion  140 , and the second portion  142  is higher than the first portion  140 . The first portion  140  defines two adjoining slots  144  at a bottom thereof. The second portion  142  of the fins  14  defines a pair of separate through holes  146  therein. 
         [0021]    The heat pipes  16  are U-shaped. The heat pipes  16  comprise horizontal evaporating portions  160 , condensing portions  162  parallel to the evaporating portions  160  and adiabatic portions  163  connecting the evaporating portions  160  and the condensing portions  162 . The evaporating portions  160  are received in channels (not labeled) formed by the slots  144  of the fins  14  incorporating the grooves  120  of the base  12  and the condensing portions  162  are received in the through holes  146  of the second portion  142  of the fins  14 , when the fins  14  are stacked together and mounted onto the base  12 . 
         [0022]    Each locking member  18  has an elongated configuration, engaging with the corresponding locking portion  122  of the base  12 . The locking member  18  defines a pair of mounting holes (not labeled) at opposite ends thereof. A pair of locating holes  182  are defined in the locking member  18  and located between the two mounting holes, corresponding to the threaded holes  1220  of the base  12 . Screws  19  are extended through the locating holes  182  and threadedly engaged in the threaded holes  1220  of the base  12 , thereby securing the locking members  18  to the base  12 . A pair of fasteners  50  are extended through the mounting holes of the locking members  18  to engage with a retainer (not shown) below the printed circuit board  80 . 
         [0023]    Referring to  FIGS. 1 and 3 , the second heat sink  20  mounted on the MOSFETs  84  near to the CPU  82  comprises a heat spreader  22  and a spring tab  24  mounted on the heat spreader  22 . The heat spreader  22  has a square base portion  220  and a leg  221  extending horizontally and outwardly from a corner of the base portion  220 . A central hole  2201  is defined in the base portion  220  of the heat spreader  22 . A through hole  2210  is defined in the leg  221  in alignment with one of four mounting holes  86  of the printed circuit board  80 . A cutout  222  is defined in the base portion  220  at another corner opposite to the leg  221  for preventing the heat spreader  22  from interfering with the CPU  82 . The spring tab  24  has a substantially V-shaped configuration. The spring tab  24  comprises an engaging portion  240  for engaging with a top surface of the base portion  220  of the heat spreader  22 . A through hole  2401  is defined in the engaging portion  240 , corresponding to the central hole  2201  of the base portion  220  of the heat spreader  22 . A pair of supporting arms  242  extend obliquely upwardly and outwardly from two opposite ends of the engaging portion  240 . A pair of arced pressing shoulders  244  are curved downwardly from free ends of the supporting arms  242 . A screw  21  is extended through the through hole  2401  of the engaging portion  240  of the spring tab  24  and threadedly engaged in the central hole  2201  of the heat spreader  22  of the second heat sink  20 , so that the spring tab  24  and the heat spreader  22  are assembled together and attached to the MOSFETs  84 . 
         [0024]    Also referring to  FIGS. 4 and 5 , in assembly the fasteners  50  are extended through the mounting holes of the locking members  1   8  of the main heat sink  10 , the through hole  2210  of the heat spreader  22  of the second heat sink  20  and the four mounting holes  86  of the printed circuit board  80  in series in a manner such that the fasteners  50  are threadedly engaged with the retainer (not shown) below the printed circuit board  80 . The pressing shoulders  244  of the spring tab  24  of the second heat sink  20  are pressed downwardly by the corresponding bottom portion of the fins  14 . The supporting arms  242  of the spring tab  24  can adjust spring force between the main heat sink  10  and the second heat sink  20 . 
         [0025]    In the present invention, the second heat sink  20  having the spring tab  24  is provided on the MOSFETs  84  near to the CPU  82  whereby heat generated by the MOSFETs  84  can be adequately dissipated and the second heat sink  20  can be secured on the MOSFETs  84  via the spring tab  24 . 
         [0026]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.