Patent Publication Number: US-2011073283-A1

Title: Heat dissipation device

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to heat dissipation devices, and particularly to a heat dissipation device for use in an electronic device such as a computer. 
     2. Description of Related Art 
     With continuing development of electronic technology, heat-generating electronic components such as central processing units (CPUs) in enclosures of computers are generating more and more heat which requires immediate dissipation. Heat dissipation devices are commonly used to cool the CPUs. 
     A conventional heat dissipation device includes a substrate for contacting with a CPU installed in an enclosure of a computer, a plurality of fins extending upwardly from the substrate, and a cooling fan mounted on the fins. The fins are spaced from each other with an air passage defined between every two neighboring fins. The cooling fan provides cooling airflow through the air passages to accelerate heat convection between the fins and the ambient air. However, the cooling fan usually vibrates and makes noise during operation, which may irritate and distract users. Furthermore, the cooling fan occupies a large space of the enclosure, contrary to a desire for compactness in computers. 
     Therefore, an improved heat dissipation device is desired to overcome the above described shortcomings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded, isometric view of a heat dissipation device in accordance with an exemplary embodiment. 
         FIG. 2  is an assembled, isometric view of the heat dissipation device of  FIG. 1 . 
         FIG. 3  is a front view of the heat dissipation device of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-3 , a heat dissipation device  10  in accordance with an exemplary embodiment of the present disclosure is shown. The heat dissipation device  10  includes a substrate  12  for receiving heat from heat-generating components (not shown), a fin assembly  14  located above the substrate  12 , and four L-shaped heat pipes  16  connecting the fin assembly  14  with the substrate  12 . 
     The substrate  12  is made of metal with high heat conductivity coefficient and has a rectangular shape. The substrate  12  includes a planar bottom surface  120  and an opposite top surface  122  facing the fin assembly  14 . The substrate  12  defines four elongated parallel grooves  124  in the top surface  122  thereof. The grooves  124  extend from one edge to an opposite edge of the substrate  12 . The grooves  124  each are semicircular in cross section. The heat pipes  16  each include an elongated evaporating section  160  and an elongated condensing section  162  substantially perpendicular to the evaporating section  160 . The heat pipes  16  engage with the grooves  124  of the substrate  12  with the evaporating sections  160  respectively received in the grooves  124  of the substrate  12 , while the condensing sections  162  are perpendicular to the substrate  12 . 
     The fin assembly  14  includes a plurality of parallel fins  140  stacked one above another with a gap  142  defined between every two neighboring fins  140 . Each of the fins  140  has a flat, rectangular shape. The fins  140  have the same width but different lengths. The lengths of the fins  140  of the fin assembly  14  decreases gradually along a direction from bottom to top, and centers of the fins  140  are aligned with each other, thereby the fin assembly  14  forms an inverted frustum profile. A size of the bottommost fin  140  is greater than that of the substrate  12 . 
     Each of the fins  140  defines four through holes  144 . The through holes  144  of each fin  140  are aligned with the holes of the other fins  140  to form four passages for extension of the four condensing sections  162  of the heat pipes  16  therethrough, respectively. Each of the fins  140  defines a large number of ventilating holes  146  therein. The ventilating holes  146  of each fin  140  are substantially evenly distributed, and a density of the ventilating holes  146  of each fin  140  is the same as that of the other fins. Since the size of the fins  140  increases from bottom to top, a number of the ventilating holes  146  of the fins increases from bottom to top. Each of the ventilating holes  146  of each of the fins  140  is aligned with corresponding ventilating holes  146  of the other fins  140  to form a vertical air channel  148  in the fin assembly  14 . An extension direction of the air channels  148  is perpendicular to the substrate  12 . The air channels  148  communicate air below the fin assembly  14  with the air above the fin assembly  14 . Depth of the air channels  148  located at a center portion of the fin assembly  14  which is on the bottommost fin  140  are the same, and depth of other air channels  148  at lateral sides of the bottommost fin  140  decreases outwardly and gradually from the center portion to lateral sides of the topmost fin  140  since the size of the fins  140  decreases gradually from top to bottom. 
     In assembly, the evaporating sections  160  of the heat pipes  16  are received and welded in the grooves  124  of the substrate  12 , respectively, with the condensing sections  162  of the heat pipes  16  alternately located at two opposite sides of the substrate  12 . The fin assembly  14  is located above the substrate  12  with the fins  140  parallel with the substrate  12 . The bottommost fin  140  of the fin assembly  14  is spaced from the substrate  12  by a distance. The condensing sections  162  of the heat pipes  16  extend through the through holes  144  of the fins  140  from bottom to top, to thereby connect the substrate  12  and the fin assembly  14  together. 
     In operation, a minority of the heat generated by the heat-generating component is transferred to the substrate and then dissipated to outside directly by the substrate, while a majority of the heat is transferred to the evaporating sections  160  of the heat pipes  16 , then to each fin  140  of the fin assembly  14  via the condensing sections  162  of the heat pipes  16 . Finally the heat is dissipated to outside between the fins  140 . Accordingly, the air between the fins  140  of the fin assembly  14  is heated and has a tendency to flow upwardly. Since the air channels  148  of the present heat dissipation device extend through the fin assembly  14  from bottom to top and thus communicate air below the fin assembly  14  with the air above the fin assembly  14 , the heated air flows upwardly via the air channels  148  and finally escapes to outside. Further, since the bottommost fin  140  of the fin assembly  14  is spaced from the substrate  12  a distance, a space is defined between the fin assembly  14  and the substrate  12  for cooling air from outside to enter and pass through the air channels  148  enhancing heat exchange. Moreover, the sizes of the fins  140  of the fin assembly  14  increase from bottom to top, a few air channels  148  are at lateral sides of the bottommost fin  14 , thus airflow easily enters the air channels  148 , which can further enhance the heat exchange between the fin assembly  14  and the ambient air. 
     As described above, since the present heat dissipation device has a large number of air channels  148  defined therein for heat exchange, a heat dissipation capability of the present heat dissipation device is relatively greater. Thus a cooling fan of conventional heat dissipation device can be omitted. Accordingly, noise of the cooling fan is avoided, and a space occupied by the present heat dissipation device  10  without cooling fan is small. 
     It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the embodiments, 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.