Abstract:
A heat sink includes a base having first and second regions, a first fin of a first type disposed on the first region of the base, and a second fin of a second type disposed on the second region of the base. The first and second regions of the base may be integral with or attached to one another. Such a heat sink can dissipate heat from multiple electronic components with the respective fin type that is most cost effective for each respective component. Using such a heat sink often reduces manufacturing time and costs as compared to using a separate heat sink for each component. In addition, such a heat sink can dissipate heat from multiple regions of a single electronic component with the respective fin type that is most cost effective for each region.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    It is well known that electronic components generate heat as a result of the electronic functions that the electronic components are designed to accomplish. As the generated heat increases above respective critical temperatures, failures can occur in the operation of these electronic components and, therefore, the excess heat must be dissipated to insure continued operation of these electronic components.  
           [0002]    In the past, heat has been dissipated by a respective heat sink attached directly to each electronic component. Typically, a heat sink is made of a substance optimal for conducting heat and maintaining the temperature of the electronic component at a safe level by dissipating the heat generated by the component into an ambient environment such as air.  
           [0003]    Generally, the respective heat sink that can provide the required heat dissipation at the lowest cost is used for each electronic component. As heat sinks have become a common means of maintaining safe operating temperatures in electronic components, different configurations of heat sinks have been developed that have different costs and heat-dissipation capabilities. In essence, by increasing the surface region exposed to the ambient environment, a heat sink can dissipate heat at a faster rate. Larger-area heat-sink configurations, however, have often proved to be more costly to manufacture because of more intricate shapes and designs. Generally speaking, as the rate of heat dissipation increases for a given heat sink, the cost of manufacturing the heat sink increases as well.  
           [0004]    Unfortunately, as circuit boards become more densely populated with electronic components, the cost and difficulty of installing individual heat sinks for each electronic component becomes increasingly troublesome and costly.  
           [0005]    Moreover, using a single heat sink for a large electronic component having regions with different heat-dissipation requirements can be costly because the heat sink typically includes the type of fin required by the highest heat-generating region.  
         SUMMARY OF THE INVENTION  
         [0006]    According to an embodiment of the invention, a heat sink includes a base having first and second regions, a first fin of a first type disposed on the first region of the base, and a second fin of a second type disposed on the second region of the base. The first and second regions of the base may be integral with or attached to one another.  
           [0007]    Such a heat sink can dissipate heat from multiple electronic components with the respective fin type that is most cost effective for each respective component. Using such a heat sink often reduces manufacturing time and costs as compared to using a separate heat sink for each component.  
           [0008]    In addition, such a heat sink can dissipate heat from multiple regions of a single electronic component with the respective fin type that is most cost effective for each region. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0010]    [0010]FIG. 1 is a side view of a heat sink having multiple fin configurations in accordance with one embodiment of the invention;  
         [0011]    [0011]FIG. 2 is an isometric view of circuit-board assembly that includes the heat sink of FIG. 1 in accordance with one embodiment of the invention;  
         [0012]    [0012]FIG. 3 is a perspective view of a skived fin configuration that the heat sink of FIG. 1 can incorporate according to an embodiment of the invention; and  
         [0013]    [0013]FIG. 4 is a block diagram of an electronic system that incorporates the circuit-board assembly of FIG. 2 according to an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]    [0014]FIG. 1 shows a heat sink  10  according to an embodiment of the invention. The heat sink  10  has a common integral base  11 , although the base may not be integral, i.e. it may include two or more base pieces (not shown) attached together to form the base  11 . The base  11  is of any shape suitable to be attached to a heat generating device, such as for example, an electronic component mounted to a printed circuit board (FIG. 2). Where the base  11  is integral, it is formed as a continuous body of material that has a high propensity for conducting heat. For example, the base  11  can be formed from materials such as aluminum, copper, and/or other metal alloys, plastic and/or epoxy, or any other suitable heat conducting material. In one embodiment, the base  11  is formed from a continuous piece of aluminum alloy and its bottom is shaped to fit the contour of one or more electronic components (FIG. 2) a printed circuit board. In another embodiment where the base  12  is not integral, the base may be formed from two different materials, such as for example, aluminum in a first region and copper in a second region. The two base regions, regardless of whether they are formed from the same or different materials, are attached together by a conventional means such as bolting, harnessing, adhesive, or welding.  
         [0015]    The heat sink  10  also includes multiple configurations of fins that are attached to the base  11  and are intended increase the heat sink&#39;s  10  surface area in order to increase ambient air contact, and thus, heat dissipation. By increasing the ambient air contact, heat is dissipated from the electronic component through the heat sink  10  and to the ambient air at a faster rate.  
         [0016]    The heat sink  10  can include two or more of several different fin configurations such as those described below. FIG. 1 shows the heat sink  10  with two different fin configurations in two different regions of the heat sink  10 . The heat sink  10  is shown having a first region on the left with a first fin configuration  12 . The first fin configuration  12  is shown as an extruded fin configuration; however, the first fin configuration  12  can be any other fin configuration. The heat sink  10  has a second region on the right with a second fin configuration  13 . The second fin configuration  16  is shown as a folded fin configuration; however, again, any other fin configuration that is different than the first fin configuration  14  can be used. Extruded, folded, and other types of fin configurations are discussed in more detail below.  
         [0017]    Other embodiments of the heat sink  10  are contemplated. For example, the heat sink  10  may include more than two regions and more than two fin configurations. These regions may include their own base pieces or the heat sink  10  may include an integral base. Also, the heat sink  10  may be used with a single electronic component having regions with different heat-dissipation characteristics. In such an embodiment, the regions of the heat sink  10  would typically be disposed over the respective regions of the component.  
         [0018]    Still referring to FIG. 1, there are several different fin configurations that can be used in accordance with the present invention. The extruded fin configuration  12  on the left of the heat sink  10  is a common fin configuration that is inexpensive and often used when the rate of heat dissipation is not as vital. The extruded fin configuration is characterized by several fins  14  emanating from the base  11 . The region of the base  11  beneath the extruded fin configuration  12  is in thermal contact with an electronic component, or region thereof, from which heat is to be dissipated. Extruded fins are typically formed in one of two ways. The first way is to mold the fins and the base together using a molten substance, such as for example, molten aluminum, such that when the molten substance hardens, the fins and base are formed integral to one another. The second common way of forming extruded fins is to begin with a solid block of a particular substance and then use a machining tool to cut out the fins.  
         [0019]    The folded-fin configuration  14  one the right side of the heat sink  10  is typically more expensive than the extruded fin configuration  12  but provides a higher rate of heat dissipation. One typically forms folded-fin protrusions  15  by folding a piece of sheet metal in accordion-like fashion. The protrusions  15  have sides  16 , which are typically called the “fins,” although the protrusions themselves may be called the “fins.” The bottoms of the protrusions  15  are attached to the base  11  in a conventional manner that allows heat to conduct from the base to the protrusions. Because the protrusions  14  are formed separately from and then attached to the base  11 , folded fins are typically more expensive than extruded fins. But because the sides  16  are thinner than the extruded fins  14 , folded fins typically provide more heat dissipation per unit volume than extruded fins provide.  
         [0020]    [0020]FIG. 2 is a perspective view of a circuit-board assembly  18  that incorporates the heat sink  10  of FIG. 1 according to an embodiment of the invention. The heat sink  10  is attached to a printed circuit board  20  that contains electronic components that generate heat. Specifically, the printed circuit board  20  has a first electronic component  21  and a second electronic component  22  mounted thereto. The first component  21  runs cool enough such that an extruded-fin configuration provides adequate cooling, but the component  22  runs hotter such that a folded-fin configuration is needed for adequate cooling. Therefore, the base  11  of the heat sink  10  is formed to fit the contour of the printed circuit board  20  and the first and second electronic components  21  and  22  such that the first component is in direct contact with the first region of the heat sink  10  having the first fin configuration  12  and the second component is in direct contact with the second region of the heat sink having the second fin configuration  13 .  
         [0021]    By forming extruded- and folded-fin configurations in the first and second regions of the heat sink  10 , the heat sink need not have the more expensive folded-fin configuration in regions where the cheaper extruded-fin configuration will suffice. Therefore, the overall cost of a heat sink  10  is typically reduced because the more expensive fin configurations are only used in the regions of the heat sink  10  where they are needed.  
         [0022]    Still referring to FIG. 2, although described as having one fin configuration per electronic component, the heat sink  10  may include multiple fin configurations for a single component. For example, both the fin configurations  12  and  13  may be disposed over a single electronic component that generates different amounts of heat in different regions. Alternatively, there may be multiple electronic components beneath one fin configuration.  
         [0023]    [0023]FIG. 3 is a perspective view of a heat sink  10  having a skived fin configuration, which is another fin configuration that the multi-fin-configuration heat sink  10  of FIGS. 1 and 2 may incorporate. The skived-fin configuration is characterized by several fins  31  emanating from a base  30 . The base  30  is in thermal contact with the region of an electronic component that heat is to be dissipated from when used as a heat sink. A skived-fin configuration is similar to an extruded-fin configuration but differs in the way in which the fins are created. Generally, the skived fins are created by planning the base  30  in a controlled manner such that each planed shaving becomes one of the fins  31 . The skived-fin and extruded-fin configurations typically have similar heat-dissipation properties, but the skived-fin configuration is often cheaper to manufacture.  
         [0024]    Other fin configurations such as a swaged-fin configuration (not shown) and variations of these fin configurations and those described herein can also be used in accordance with other embodiments of the invention.  
         [0025]    [0025]FIG. 4 is a block diagram of a computer system  50  that incorporates one or more circuit-board assemblies  18  of FIG. 2 according to an embodiment of the invention. The system  50  includes computer circuitry  45 , which is typically composed of one or more circuit-board assemblies  18  that are mounted within an enclosure  47 . One or more of the assemblies  18  typically include a processor unit  40  and a memory  41 . Coupled to the circuitry  45  are one or more data-storage devices  43  such as a disk drive, one or more input devices  44  such as a keyboard, and one or more output devices  43  such as a display. Typically, a heat sink  48  is attached to circuitry  45 , the processor unit  40  and the memory  41  such that heat is dissipated more efficiently than heat sinks for each of these components.  
         [0026]    While embodiments of the invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.