Abstract:
A cooling mechanism to dissipate thermal energy generated by the heat generating components of a graphics card assembly. An apparatus includes a circuit board having at least one heat generating component affixed thereto. The apparatus also includes a fan and carrier therefor including a heat sink plate having a portion thermally coupled to the heat generating component. The heat sink plate includes a means for forming at least one slot proximate the portion. The fan is adapted to direct airflow cross the portion. The thermal energy generated by the heat generating component is transferred to the fan carrier and ultimately removed from the fan carrier by the airflow. The airflow inducts a secondary airflow drawn through the slot during operation thereby to enhance transfer of the thermal energy from the heat generating component.

Description:
BACKGROUND OF THE INVENTION 
   The present invention generally relates to circuit board apparatus and, more particularly, to an improved circuit board assembly having a mechanism to generate induced air flow for heat dissipation. 
   In order to enable desktop and other computers to rapidly process graphics and game technology, add-on units generally referred to as “graphics cards” or “VGA” cards” are often installed in computer devices. Such cards include a separate processor, called a GPU, one or more memory chips, and other required circuitry, all mounted to a circuit board including an edge connector that is adapted to plug into an available slot in the associated computer device. 
   Such cards often have extremely large computing power and, as a consequence, generate substantial heat that if not dissipated will adversely affect operation of the graphics card. Heretofore, various approaches have been tried to dissipate or otherwise remove heat from the thermal energy generating components and normally include some type of fan for blowing air across the heat generating components, and perhaps some type of thermal mass capable of sinking the heat generated. The thermal energy generated by the GPU and memory chips for more sophisticated graphics and games, such as 3-D graphics, may approach the maximum capacity of the existing heat dissipation mechanisms. Thus, there is a need for an improved heat extraction or dissipation mechanism, which can be added to a standard graphics card to efficiently remove thermal energy generated thereby. 
   SUMMARY OF THE INVENTION 
   In one aspect of the present invention, an apparatus with improved heat dissipation includes a circuit board having at least one heat generating component affixed thereto. The apparatus also includes a fan and carrier therefor including a heat sink plate having a portion thermally coupled to the heat generating component. The heat sink plate includes a means for forming at least one slot proximate the portion. The fan is adapted to direct airflow cross the portion. The thermal energy generated by the heat generating component is transferred to the fan carrier and ultimately removed from the fan carrier by the airflow. The airflow inducts a secondary airflow drawn through the slot during operation thereby to enhance transfer of the thermal energy from the heat generating component. 
   In another aspect of the present invention, an assembly includes a printed circuit board with at least one heat generating component affixed thereto, and a heat dissipating mechanism also affixed to the printed circuit board for removing thermal energy from the heat generating component. An improved heat dissipating mechanism includes a fan and carrier therefor including a heat sink plate having a portion thermally coupled to the heat generating component. The heat sink plate includes a means for forming at least one slot proximate the portion. The fan is adapted to direct airflow cross the portion. The thermal energy generated by said heat generating component is transferred to the fan carrier and ultimately removed from the fan carrier by the airflow. The airflow inducts a secondary airflow drawn through the slot during operation thereby to enhance transfer of the thermal energy from the heat generating component. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing a presently preferred embodiment of a graphics card assembly including a heat dissipating subassembly in accordance with the present invention; 
       FIG. 2  is an exploded perspective view showing the several components of the assembly illustrated in  FIG. 1 ; 
       FIG. 3  is a partial cut away perspective view of a fan carrier of  FIG. 2 , showing the thermal block included therein; 
       FIG. 4  is a top perspective view of the thermal block of  FIG. 3 ; 
       FIG. 5  is a broken bottom perspective view showing the lower plate of  FIG. 2  and the thermal block affixed thereto; 
       FIG. 6  is a schematic cross sectional view of the assembly of  FIG. 1 , taken along the direction  6 - 6  in  FIG. 4 ; 
       FIG. 7  is a schematic cross sectional view of another embodiment of a graphics card assembly, taken along the direction  7 - 7  of  FIG. 4  in accordance with the present invention; 
       FIG. 8  is a schematic cross sectional view of yet another embodiment of a graphics card assembly, taken along the direction  7 - 7  in accordance with the present invention; and 
       FIG. 9  is a schematic cross sectional view of still another embodiment of a graphics card assembly, taken along the direction  7 - 7  in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following detailed description is of currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
   Referring to  FIG. 1  of the drawing, a graphics card assembly in accordance with the present invention is illustrated at  10  and includes a printed circuit board  12  having an edge connector  14 . For the purpose of illustration, the printed circuit board  12  is described as a graphics card in the present application. However, it should be apparent to those of ordinary skill that the printed circuit board  12  can be other types of circuit board, such as motherboard, having one or more heat generating components, such as CPU and chipset. Various cabling connectors  16 ,  18 , and  20  are secured to the printed circuit board  12  and used to communicate electrical signals into and out of the assembly. Affixed to the printed circuit board  12  is a fan carrier  40  secured to a top cover  22  by means of screws or other suitable fasteners  51   a.  The near right side portion of the top cover  22 , as depicted, can be formed by bending a portion of the top cover  22  that is preferably formed of, but not limited to, metal, along the substantially entire length of the assembly  10 . The top cover  22  includes a circular aperture  23  and slots  26 ,  28  through which airflow can pass. Positioned within the aperture  23  and affixed to and carried by the carrier  40  is a fan unit  24 . Note that the upper surface of the top cover  22  is substantially flat and ideally suited for decorative graphics, manufactures or marketers trademarks, etc. 
   In use, the graphics card assembly  10  is oriented so as to have the near right side of the assembly, as depicted, facing a slot on a computer motherboard and mounted thereto by slipping the edge connector  14  into the slot so that the assembly communicates with devices on the motherboard via the edge connector  14 . As describe in more detail below, heat generated by the electronic components of the assembly is transferred to the fan carrier  40  that is cooled by the airflow created by the fan unit  24 , as will also be further elucidated below. 
   In  FIG. 2 , the top cover  22 , fan unit  24 , and fan carrier  40  are shown exploded away from the printed circuit board  12 . The board  12  includes various types of electronic components  32 . Active heat generating components (or, shortly active component) will be positioned at  30  and can generate heat energy during operation. The active heat generating components, such as memory, are not shown in  FIG. 2  for brevity. As will be further explained below, the lower plate  41  of the fan carrier  40  may have protrusions that intimately engage the top surfaces of the active components and transfer heat energy therefrom. 
   The foremost side of the top cover  22 , as depicted in  FIG. 2 , overlaps the front side of the fan carrier  40  along the length of the fan carrier  40 . The fan carrier  40  includes threaded openings  50  for receiving the screws or other suitable fasteners  51   a  that secure the top cover  22  to the fan carrier  40 . The top cover  22  also includes a tap  25  with a hole or opening through which the screw  51   b  for mounting the top cover  22  to the fan carrier  40  pass. The top cover  22  further includes one or more holes or openings (not shown in  FIG. 2 ) formed on the rearmost right side, as depicted in  FIG. 2 , through which one or more the screws  51   c  for mounting the top cover  22  to the fan carrier  40  pass. The screws  51   a ,  51   b , and  51   c  engage threaded openings formed in the fan carrier  40 . 
   As depicted, a GPU PCB  34  is mounted on the board  12  by means of Ball Grid Array (BGA) solder bumps  38 , and a GPU  36  is mounted on the GPU PCB  34 . The GPU  36  may generate substantial amount of heat energy during operation, which will be transferred to and dissipated by the fan carrier  40 . As will be further explained below, the fan carrier  40  includes a thermal block positioned above and being in physical contact with the GPU  36  to transfer heat energy therefrom. As discussed above, the assembly  10  can be used to remove thermal energy from other types of heat generating components, such as CPU and chipset, affixed to a motherboard (not shown in  FIG. 2 ). 
   The fan carrier  40  includes heat conducting components: a lower plate (or, equivalently a heat sink plate)  41 , an upper plate  44 , and elongated vanes  42  disposed between the lower and upper plates. The heat conducting components may be formed of aluminum, copper, steel, or other suitable material capable of serving as heat sink. The fan unit  24  will be installed inside a space  46  in the fan carrier  40 . In  FIG. 2 , for the purpose of illustration, a portion of the upper plate  44  is broken away, revealing the vanes  42  and the lower plate  41  thereunder. The fan carrier  40  with fan unit  24  installed thereto is aligned with the aperture or opening  23  so that the fan unit  24  can draw cooling air therethrough during operation. The air drawn in by the fan unit  24  passes through the air passageways defined by the upper plate  44 , lower plate  41  and vanes  42 , extracting thermal energy from the fan carrier before it is discharged through the slots  26  and the openings in the rearmost left side of the top cover  22 , as depicted in  FIG. 2 . The fan carrier  40  further includes radiator fins  48  standing up from the lower plate  41  and configured to radiate heat energy to the surrounding air. The top cover  22  includes slots  28  and  54  for ventilating the radiator fins  48 . 
   The lower plate  41  of the fan carrier  40  is secured to the printed circuit board  12  by multiple screws or other suitable fasteners  52 , providing a firm contact between the top surface of the GPU  36  and the lower plate  41 , more specifically, the thermal block (now shown in  FIG. 2 ) affixed to the lower plate  41 . 
   It is noted that two or more of the components of the fan carrier  40  may be formed as an integral body. For instance, the radiator fins  48  and the lower plate  41  may be formed as an integral body by means of molding. It is also noted that the top flat portion of the top cover  22  may be spaced apart from the upper plate  44  or in direct contact with the upper plate  44  so that a portion of the heat energy contained in the upper plate  44  can be transferred to the top cover  22  and dissipated by the top cover  22 . 
     FIG. 3  is a partial cut away perspective view of the fan carrier  40  revealing the upper surface of the thermal block  60  included therein as well as the flow direction vanes  42  which cross thereover, the vanes  42  being broken away and shown in phantom dashed lines for clarity.  FIG. 4  is a perspective view showing the top surface of the thermal block  60  removed from an opening  63  in the plate  41  (depicted in  FIG. 3 ) together with some of the vanes  42  (shown in phantom dashed lines for clarity). As depicted, the thermal block  60  has a generally rectangular shape with tabs  70  formed at the four corners thereof. Each tab  70  has a hole  73  through which a fastener  72  for securing the thermal block  60  to the lower plate  41  passes. As a variation, the tabs  70  may be soldered or brazed to the lower plate  41 . The thermal block  60  is installed in the rectangular opening  63  formed in the lower plate  41  and includes recessed portions  64  formed on two opposite side edges thereof. The thermal block  60  also includes two elongated recessed portions  62  formed in the opposite ends thereof. When installed in the opening  63 , the recessed portions  62 ,  64  form slots through which airflow can pass. Hereinafter, the terms recessed portion and slot are used interchangeably. The size, shape and number of recessed portions  62 ,  64  may be varied without deviating from the spirit and scope of the present invention. The thermal block  60  may be formed of aluminum, steel, copper, or other suitable material capable of serving as a heat sink. 
   As will be further explained below in conjunction with  FIG. 6 , the thermal block  60  is flush-mounted relative to the upper surface of lower plate  41  so that the top surface of the thermal block  60  and the top surface of the lower plate  41  are on the same plane. In  FIG. 3 , only three vanes are shown to extend across the thermal block  60 . However, it should be apparent to those of ordinary skill that the lateral intervals between vanes  42  can be varied so as to change the number of vanes crossing the thermal block  60 . 
   As the cooling air drawn in by the fan unit  24  through the aperture  23  ( FIG. 2 ) is caused to pass through the air passageways  65  formed by the vanes  42 , the air extracts heat energy from the fan carrier  40 . Due to the airflow across the passageways  65 , the pressure in the passageways  65  is lower than the ambient atmospheric pressure, generating a pressure difference between the top and bottom surfaces of the lower plate  41 . This pressure difference in turn induces secondary air flow  67  through the slots  62  and  64 , i.e., the pressure difference inducts additional airflow for cooling the thermal block  60  into the air passageways  65 . An experiment performed by the present inventor shows that the secondary flow  67  reduces the temperature of the thermal block  60  by at least one degree Celsius. 
     FIG. 5  is a broken perspective view showing the bottom surfaces of thermal block  60  and a portion of the lower plate  41 .  FIG. 6  is a schematic cross sectional view of a portion of the assembly  10 , taken along the line  6 - 6  in  FIG. 4 . As depicted, the thermal block  60  is aligned with the GPU  36  in the horizontal direction so that the bottom surface of the thermal block  60  physically engages the top surface of the GPU  36 . Alternatively, the thermal block  60  may be secured to the GPU  36  by applying heat conducting adhesive therebetween. As discussed above, the secondary air flow  67  passes through the slots  62 ,  64 , further cooling the thermal block  60  during operation. 
   Formed on the bottom surface of the lower plate  41  are multiple rectangular pads or protrusions  33  intended to physically engage the top surfaces of active components to be positioned at  30  (shown in  FIG. 2 ) and to transfer thermal energy therefrom to plate  41 . The lower plate  41  may also include spacing legs or risers  35  ( FIG. 5 ) having threaded holes that receive the fasteners  52  (shown in  FIG. 2 ) for securing the lower plate  41  to the printed circuit board  12 . The thermal energy generated by the CPU  36  and active components will be respectively transferred to the thermal block  60  and the protrusions  33 , and thence to the lower plate  41 . 
   In an alternative embodiment, one or more flow directing fences  68  (shown in dashed lines in  FIGS. 5 and 6 ) may be disposed beneath the bottom surface of the lower plate  41 . The fences  68  may have a substantially bar shape and extend in a direction substantially parallel to the elongated slots  62 , defining opposite sides of a space that surrounds the bottom surface of the thermal block  60  (and the GPU  36 ). The fences  68  impede airflow thereacross so that most of the air flowing in the secondary flow  67  into and through the openings  62  and  64  comes from the space surrounding block  60  to thereby enhance the flow motion around and beneath the perimeter of the thermal block  60 . As a variation, the fences  68  and the lower plate  41  may be formed as an integral body. 
     FIG. 7  is a schematic cross sectional view of another embodiment of a graphics card assembly  100 , taken along a line similar to the direction  7 - 7  shown in the embodiment of  FIG. 4 . As depicted, a plurality of vanes  104  may be affixed to the top surfaces of the lower plate  102  and the thermal block  112  by means of soldering, brazing, or heat conduction adhesive to form flow passageways  106  directed normal to the plane of the drawing. Each vane  104  has a generally c-shaped cross section, i.e., each vane is formed by an elongated c-shaped channel member having upper and lower flanges. The flanges of each vane member contact an adjacent vane member to form an air passageway  106 . For those vane members passing directly over openings  108  in the perimeter of the thermal block  112 , a corresponding opening  107  is formed in the lower flange thereof so as not to block the openings  108 . As in the previously described embodiment, a secondary flow induced by the pressure difference between the top and bottom surfaces of the lower plate  102  passes through the slots  108  and openings  107 . In this embodiment, the top flanges of the vanes  104  collectively form a substantially flat plate having segmented sections, where the plate is substantially equivalent to and thereby replaces the upper plate  44  in the embodiment of  FIG. 3 . It is noted that the assembly  100  may have flow directing fences (not shown in  FIG. 7 ) beneath the lower plate  102  as an option. 
     FIG. 8  is a schematic cross sectional view of yet another embodiment of a graphics card assembly  120 , taken along the direction  6 - 6  in accordance with the present invention. As depicted, the components of the assembly  120  are similar to those of the assembly  10 , with the principal difference being that the upper plate  122  includes a varying surface curvature relative to the lower plate  126 . More specifically, the upper plate  122  has a portion A that is convex relative to the lower plate  126 , and the slots  124  are located within the portion A. The pressure in an air duct or passageway decreases as the cross sectional area of the passageway decreases. Thus, in air passageways defined by the upper plate  122 , lower plate  126 , and vanes  128 , the air pressure within the portion A will be lower than that outside the portion A. Given that the static pressure at the bottom surface of the lower plate  126  is the same as the pressure at the bottom surface of the lower plate  41  in  FIG. 3 , the pressure difference between the top and bottom surfaces of the lower plate  126  will be larger than that between the top and bottom surfaces of the lower plate  41 . As the flow rate of secondary flow  130  increases as the pressure difference increases, the configuration of the upper plate  122  will enhance the secondary flow rate and thereby enhance the efficiency in cooling the thermal block  132  during operation. As a variation, flow directing fences  134  may be disposed beneath the lower plate  126 . 
   It is noted that the fan  24  could be reversed to draw cooling air from the slots  26  and opening sides of the top cover  22  and exhausted out through the opening  23  in the top cover  22 . Flow in this direction would likewise induct the secondary flow through the slots  62 ,  64 , enhancing the efficiency in cooling the thermal block during operation. 
   In  FIGS. 3 and 4 , the thermal block  60  and the lower plate  41  are shown as two components secured to each other. However, it should be apparent to those of ordinary skill that they can be molded as an integral body with the slots  62  and  64  formed therein.  FIG. 9  is a schematic cross sectional view of yet another embodiment of a graphics card assembly  140 , taken along the direction  6 - 6  in accordance with the present invention. In this embodiment, the thermal block and lower plate form an integral body  142 . As a variation, flow directing fences  144  may be disposed beneath the plate  142 . 
   As discussed above, the exemplary embodiments of the assembly in  FIGS. 1-9  are described as means for removing thermal energy from GPUs and active electronic components, such as memories. However, it should be apparent to those of ordinary skill that the assembly can be used to remove heat energy from other types of heat generating components, such as CPUs and chipsets. For instance, the thermal bock may be in contact with a CPU and/or a chipset affixed to a motherboard and transfer thermal energy from the CPU and/or a chipset. As a variation, the protrusion  33  can be arranged to physically engage the top surfaces of CPUs and/or chipsets and transfer thermal energy therefrom. 
   Notwithstanding that the present invention has been described above in terms of several alternative embodiments, it is anticipated that still other alterations and modifications will become apparent to those of ordinary skilled in the art after having read this disclosure. It is therefore intended that such disclosure be considered illustrative and not limiting, and that the appended claims be interpreted to include all such alterations, modifications and embodiments as fall within the true spirit and scope of the invention.