Abstract:
A heat sink assembly includes a primary heat sink and a subordinate heat sink. The primary heat sink comprises a base with a main surface; the subordinate heat sink is attached to the primary heat sink and movable relative to the primary heat sink in a direction perpendicular to the main surface of the primary heat sink; the subordinate heat sink comprises a base with a main surface parallel to the main surface of the primary heat sink. The main surfaces of the primary heat sink and the subordinate heat sink face in a similar direction.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to a heat sink assembly, and more particularly to a heat sink assembly adapted for removing heat from multiple electronic heat-generating components of differing heights. 
       DESCRIPTION OF RELATED ART 
       [0002]    Electronic component includes numerous circuits operating at high speed and generating substantial heat. In many applications, it is desirable to employ a heat sink to remove heat from electronic heat-generating components, such as central processing units (CPUs) etc., to assure that the components function properly and reliably. A typical heat sink comprises a base for contacting with the heat-generating component to absorb the heat originated from the heat-generating component and a plurality of parallel planar fins attached to the base by soldering or adhering. Alternatively, the fins can be integrally formed with the base by metal extrusion, such as aluminum extrusion. The fins are used for dissipating the heat to ambient air. 
         [0003]    With the development of various types of electronic modules, an array of many discrete components may be mounted to a surface of a single circuit board. In some circumstances, more than one of the components must be cooled. Since the components are generally of different heights and their top surfaces are thus at different levels, conventional heat sinks can not meet the requirement to intimately contact with the top surfaces of the components simultaneously to remove the heat from all the components. Thus, more than one of individual heat sinks need to be employed to remove heat from each component. Accordingly, a large amount of space is required to install the heat sinks, thus restricting space for other components; furthermore, it is both expensive and time-consuming to attach individual heat sinks to each component. 
         [0004]    What is needed is a heat sink assembly with an improved structure able to cool an array of components with different heights. 
       SUMMARY OF THE INVENTION 
       [0005]    A heat sink assembly includes a primary heat sink and a subordinate heat sink. The primary heat sink comprises a base with a main surface; the subordinate heat sink is attached to the primary heat sink and movable relative to the primary heat sink in a direction perpendicular to the main surface of the primary heat sink. The subordinate heat sink comprises a base with a main surface parallel to the main surface of the primary heat sink. The main surfaces of the primary heat sink and the subordinate heat sink face in a similar 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 embodiment. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is an assembled isometric view of a heat sink assembly in accordance with a preferred embodiment of the present invention; 
           [0009]      FIG. 2  is similar to  FIG. 1 , but viewed from another aspect and having screws thereof separate from a base thereof; and 
           [0010]      FIG. 3  is an exploded, isometric view of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    Referring to  FIG. 1 , a heat sink assembly in accordance with a preferred embodiment of the invention comprises a primary heat sink  10 , a subordinate heat sink  20  and two fixtures  27  movably connecting the primary heat sink  10  and subordinate heat sink  20  together. Characteristics of the heat sink assembly are illustrated in more detail in  FIGS. 2 and 3 . 
         [0012]    The primary heat sink  10  is made of a thermally conductive metal such as aluminum, and comprises a base  11 , a plurality of parallel fins  13  integrally extending from the base  11  and a cutout  17  recessed from a lateral side of base  11 . 
         [0013]    The base  11  is board-shaped. The base  11  comprises a bottom surface  12  for contacting a heat-generating electronic component (not shown) and a top surface (not labeled). The base  11  in each corner thereof defines a blind hole  112  with inner thread extending from the bottom surface  12  of the base  11  in a direction perpendicular to the bottom surface  12  of the base  11 . Each blind hole  112  engages with a screw  19  to mount the heat assembly to a circuit board (not shown) on which the heat-generating electronic component is mounted. The fins  13  are formed integrally from the top surface of the base  11  and are spaced from each other. The cutout  17  of the primary heat sink  10  can be in various shapes corresponding to the shape of the subordinate heat sink  20 . In the preferred embodiment of the present invention, the cutout  17  is rectangular-shaped so as be capable of receiving the subordinate heat sink  20 . A pair of supports  15  are formed on the base  11  at opposite lateral sides of the cutout  17 , for supporting the subordinate heat sink  20  thereon. A mounting hole  152  extending from the top surface to the bottom surface  12  of the base  11 , is defined on each support  15  for receiving one of the fixtures  27  to mount the subordinate heat sink  20  onto the primary heat sink  10 . A pair of annular rings  154  are provided on the base  11 , and are disposed in the mounting holes  152 . The annular rings  154  are located near the bottom surface  12  of the primary heat sink  10 . 
         [0014]    The subordinate heat sink  20  is made of a thermally conductive metal such as aluminum, and comprises a rectangular base  21 , a plurality of parallel fins  23  and two shoulders  25 . The base  21  has a bottom surface  22  for contacting another heat-generating electronic component (not shown) and a top surface (not labeled). The fins  23  integrally extend from the top surface of the base  21 . Each fin  21  is oriented parallel to and spaced with a predetermined distance from the adjacent fins  21 . The shoulders  25  are horizontally and outwardly extended from opposite edges of the base  21 . The shoulders  25  are mounted on the supports  15  of the primary heat sink  10 . A mounting hole  252  is defined on each shoulder  25 , for cooperating with one mounting hole  152  of the primary heat sink  10  to receive one fixture  17 . 
         [0015]    Each fixture  27  includes a pin formed from a molded plastic material and a spring  277 . The pin has a head  271  at one end thereof, an elongated shaft  273  extending axially from the head  271  and a barb  275  at an opposite end thereof. The spring  277  closely encircles the shaft  273  and is held between the head  271  and the barb  275 . 
         [0016]    In order to assemble the heat sink assembly, the base  21  of the subordinate heat sink  20  should be properly accommodated in the cutout  17  of the primary heat sink  10 . The shoulders  25  of the subordinate heat sink  20  are then rested on the supports  15  of the primary heat sink  10 . The mounting holes  252  of the shoulders  25  are aligned with the mounting holes  152  of the supports  15 . The shafts  273  of the fixtures  27  can then be subsequently extended into their respective mounting holes  252 ,  152 , during which the barbs  275  are deformed. After the barbs  275  slide over the annular rings  154 , the barbs  275  rebound and are blocked by the annular rings  154  disposed in the mounting holes  152  of the primary heat sink  10 . Thus, the fixtures  27  lock the subordinate heat sink  20  to the primary heat sink  10 . Each spring  277  is slightly compressed between the head  271  and the shoulder  25  to urge the subordinate heat sink  20  toward the primary heat sink  10  and to make the shoulders  25  of the subordinate heat sink  20  contact with the supports  15  of the primary heat sink  10 . In order to protect the electronic components from being interfered with by the fixtures  27 , the fixtures  27  terminate in the mounting holes  152  and do not stretch out of the mounting holes  152 . 
         [0017]    In the heat sink assembly, the bottom surface  22  of the subordinate heat sink  20  is disposed at a level below the bottom surface  12  of the primary heat sink  10 , when the shoulders  25  of the subordinate heat sink  20  rest on the supports  15  of the primary heat sink  10 . The bottom surface  22  of the subordinate heat sink  20  can also be at a level coplanar with or higher than the bottom surface  12  of the primary heat sink  10 , in which case the shoulders  25  of the subordinate heat sink  20  can be separated from the supports  15  of the primary heat sink  10  by further compressing the springs  27 . In other words, the subordinate heat sink  20  is vertically movable relative to the primary heat sink  10  in a direction perpendicular to the bottom surface  12  of the primary heat sink  10  by changing compression of the springs  27 . Therefore, the heat sink assembly can be used to cool two electronic components having top surfaces at identical or different levels. The springs  277  provide a downwardly pressing force on the subordinate heat sink  20  so it can intimately contact with the corresponding electronic component. 
         [0018]    In other embodiment of the present invention, the heat sink assembly can be provided with more than one cutout and an amount of subordinate heat sinks according to the number of electronic components to be cooled. 
         [0019]    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.