Abstract:
A heat sink is built including a three dimensional array of cylindrical openings for air to flow through instead of fins. By having a larger surface area than heat sinks with fins, this high surface area heat sink results in increased heat transfer to the surrounding air than a similarly sized heat sink with fins. Heat sinks including an array of cylindrical openings may be manufactured through extrusion, stamping, and other common techniques.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to the field of heat sinks, and more particularly to the field of high efficiency heat sinks. 
   BACKGROUND OF THE INVENTION 
   As modern electronics evolve, they continue to shrink in size, yet increase in power density, and in the amount of heat they generate during operation. In order for these electronic devices to perform properly, their temperature must be strictly controlled within a given temperature range. Often, designers will attach heat sinks to the electronic devices to dissipate this excess heat. Typically heat sinks include fins or pins to increase the surface area of the heat sink within a constrained space and thus correspondingly increase the heat transfer capacity of the heat sink. 
   SUMMARY OF THE INVENTION 
   A heat sink is built including a three dimensional array of cylindrical openings for air to flow through instead of fins. By having a larger surface area than heat sinks with fins, this high surface area heat sink results in increased heat transfer to the surrounding air than a similarly sized heat sink with fins. Heat sinks including an array of cylindrical openings may be manufactured through extrusion, stamping, and other common techniques. 
   Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a typical prior art heat sink. 
       FIG. 2  is a side view of a high surface area heat sink according to the present invention. 
       FIG. 3  is a side view of a high surface area heat sink according to the present invention. 
       FIG. 4  is a side view of a high surface area heat sink according to the present invention. 
       FIG. 5A  is a side view of a sheet of thermally conductive material for use in manufacturing a high surface area heat sink according to the present invention. 
       FIG. 5B  is a side view of a pair of molds for use in manufacturing a high surface area heat sink according to the present invention. 
       FIG. 5C  is a side view of the pair of molds from  FIG. 5B  and the thermally conductive material from  FIG. 5A , during manufacturing of a high surface area heat sink according to the present invention. 
       FIG. 6  is a side view of a high surface area heat sink manufactured by the process illustrated in  FIGS. 5A to 5C  according to the present invention. 
       FIG. 7  is a side view of a high surface area heat sink according to the present invention. 
       FIG. 8  is a flow chart of a method of constructing a high surface area heat sink according to the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a side view of a typical prior art heat sink. In this example of a prior art heat sink, the heat sink includes a heat sink body  100 , a heat sink base  102  that is configured to thermally couple with a heat generating electronic device, along with a plurality of heat sink fins  104 . These fins  104  are used to increase the surface area of the heat sink since the heat transfer capability of the heat sink is proportional to surface area. Often fans are used to flow air through the fins  104 , also increasing heat transfer. When fans are used, the heat sink must be aligned with the flow of air, to allow the air to flow between the fins  104  instead of being blocked by the outer fins  104 . 
     FIG. 2  is a side view of a high surface area heat sink according to the present invention. In this example embodiment of the present invention, a heat sink is constructed including a heat sink body  200  a heat sink base  202  and an array of cylindrical openings  204  within the heat sink body  200 . Note, that not all cylinders have circular cross-sections, and that those shown in this example embodiment of the present invention have square cross-sections. Other embodiments of the present invention may use cylindrical openings  204  with other shapes of cross-sections, all within the scope of the present invention. By eliminating heat sink fins and instead constructing a heat sink including an array of cylindrical openings  204 , the surface area of the heat sink is increased, resulting in improved heat transfer from the heat sink to the atmosphere. Those of skill in the art will recognize that these heat sinks may be manufactured in a wide variety of methods such as extrusion, milling, or other fabrication techniques within the scope of the present invention. While this example embodiment of the present invention includes an array of cylindrical openings  204 , those of skill in the art will recognize that there is no need for these openings to form an array. In fact, any plurality of openings in any configuration may suffice to increase the surface area of the heat sink. 
     FIG. 3  is a side view of a high surface area heat sink according to the present invention. The example embodiment shown in  FIG. 3  is similar to that of  FIG. 2  with the exception that the cross-section of the cylindrical columns  304  within the heat sink body  300  is now hexagonal instead of square. This example embodiment of the present invention is a heat sink including a heat sink body  300 , a heat sink base  302  configured to thermally couple to a heat generating electronic device, along with an array of cylindrical openings  304  within the heat sink body  300 . Once again these cylindrical openings  304  act to increase the surface area of the heat sink and thus increase its heat transfer capacity. 
     FIG. 4  is a side view of a high surface area heat sink according to the present invention. This example embodiment of the present invention is similar to that of  FIG. 4  with the exception, that some of the heat sink material on the top and sides of the heat sink body  400  have been removed to reduce weight and slightly increase surface area of the heat sink. This example embodiment of the present invention may be more easily manufactured by extrusion than the example shown in  FIG. 3 . This example embodiment of the present invention is a heat sink including a heat sink body  400 ,a heat sink base  402  configured to thermally couple to a heat generating electronic device, along with an array of cylindrical openings  404 . Similar honeycomb material suitable for use as a heat sink body  400  may be found in material used in electromagnetic interference (EMI) applications. This material may then be mechanically and thermally coupled to a heat sink base  402  to create a high surface area heat sink. 
     FIG. 5A  is a side view of a sheet of thermally conductive material for use in manufacturing a high surface area heat sink according to the present invention.  FIGS. 5A through 5C  demonstrate one possible method of manufacturing a high surface area heat sink according to the present invention.  FIG. 5A  shows a side view of a sheet of thermally conductive material  500  for use in manufacturing a high surface area heat sink. This thermally conductive material  500  may be any of a variety of materials such as aluminum or copper within the scope of the present invention. 
     FIG. 5B  is a side view of a pair of molds for use in manufacturing a high surface area heat sink according to the present invention. A top mold  502  and a bottom mold  504  are configured to stamp material into a shape configured to create cylindrical openings when sheets of stamped material are mechanically and thermally coupled together to form a heat sink body. 
     FIG. 5C  is a side view of the pair of molds from  FIG. 5B  and the thermally conductive material from  FIG. 5A , during manufacturing of a high surface area heat sink according to the present invention. In this example embodiment of the present invention the top mold  502  and the bottom mold  504  have been brought together to stamp the thermally conductive material  500  into a sheet of stamped material  506 . This stamped material  506  may then be assembled with other sheets of stamped material  506  to form a high surface area heat sink similar to that of  FIG. 6 . 
     FIG. 6  is a side view of a high surface area heat sink manufactured by the process illustrated in  FIGS. 5A to 5C  according to the present invention. In this example embodiment of the present invention, a plurality of stamped sheets of thermally conductive material has been assembled into a high surface area heat sink. Those of skill in the art will recognize that the sheets of stamped material  506  may be mechanically and thermally coupled using a variety of methods such as soldering or welding. This finished heat sink includes a heat sink body  600 , a heat sink base  602  configured to thermally couple with a heat generating electronic device and includes an array of cylindrical openings  604  in the heat sink  600  resulting in a high surface area heat sink. 
     FIG. 7  is a side view of a high surface area heat sink according to the present invention. This example embodiment of the present invention is a heat sink including a heat sink body  700 , a heat sink base  702  configured to thermally couple with a heat generating electronic device and includes an array of cylindrical openings  704  lo resulting in a high surface area heat sink. Also, each of the cylindrical openings  704  includes a slight chamfer  706  on one or both ends of the cylinders. This chamfer helps to funnel the air into the cylindrical openings  704  and reduces turbulence in the air flow at the leading face of the heat sink body  700 . This example embodiment is a simple example of the present invention such as may be used as a prototype constructed by milling a block of thermally conductive material such as aluminum or copper. While this example embodiment of the present invention does have a high surface area, it contains more material than other examples and thus may weigh more, and also be more expensive. However, its construction is quite simple compared to the other example embodiments shown previously, and may be used in situations where ease of construction is critical. 
     FIG. 8  is a flow chart of a method of constructing a high surface area heat sink according to the present invention. In a step  800 , a heat sink base is provided. In a step  802 , a heat sink body is provided. In a step  804 , a plurality of cylindrical openings is created in the heat sink body. In a step  806 , the heat sink body is thermally and mechanically coupled to the heat sink base. 
   The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.