Abstract:
An embodiment of an electronic system includes a printed circuit board (PCB) including fluid flow channel extending through the PCB. In addition, the electronic system includes an electronic component including a bottom surface and positioned on the PCB over the fluid flow channel to thereby expose the bottom surface of the electronic component to fluid flow through the fluid flow channel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional patent application Ser. No. 61/914,243 filed Dec. 10, 2013, and entitled “Printed Circuit Board with Air Flow Channels,” which is hereby incorporated herein by reference in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       BACKGROUND 
       [0003]    The disclosure relates generally to electronic circuit boards and more particularly to the regulation of temperature of electronic components that are positioned on such electronic circuit boards. 
         [0004]    Cooling large numbers of electrical modules on a printed circuit board (PCB) is usually achieved by arranging one or more active components (e.g., electronic components) in close proximity to each other on a surface of the PCB in some fashion (e.g., a single or double stacked connector arrangement). Air then flows over the components from side to side and/or from front to back in an attempt to maintain a proper operating temperature. Components that are positioned at the outer edges of the arrangement tend to have more surface area exposed to the flow of air such that their temperature is more efficiently regulated than the components positioned near the middle of the arrangement. As a result, there is typically a high level of variability in the temperature of components disposed in such arrangements on a PCB. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which: 
           [0006]      FIG. 1  shows a schematic side cross-sectional view of a conventional electronic system; 
           [0007]      FIG. 2  shows a schematic side cross-sectional view of an electronic system in accordance with the principles disclosed herein; 
           [0008]      FIG. 3  shows a schematic top view of the system of  FIG. 2 ; 
           [0009]      FIG. 4  shows a schematic top view of an electronic system in accordance with the principles disclosed herein; 
           [0010]      FIG. 5  shows a schematic top view of an electronic system in accordance with the principles disclosed herein; 
           [0011]      FIG. 6  is a schematic side cross-sectional view of an electronic system in accordance with the principles disclosed herein; 
           [0012]      FIG. 7  is a schematic perspective view of one electromagnetic interference cage and electronic component of the system of  FIG. 6 ; and 
           [0013]      FIG. 8  is a schematic side cross-sectional view of an electronic system in accordance with the principles disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment. Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness. 
         [0015]    In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the central axis. For instance, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance means a distance measured perpendicular to the central axis. 
         [0016]    As previously described, electronic components are typically arranged on a surface of a PCB in close proximity to one another such that components disposed at the outer edges of the arrangement have a larger amount of surface area that is exposed to air flowing across the PCB than the components disposed within the interior of the arrangement. As a result, the operating temperatures for these more interior components tend to be relatively high during operations. For example, referring now to  FIG. 1 , wherein a conventional electronic system  10  is shown. Electronic system  10  includes a substrate  20  and a plurality of electronic modules or components  50  disposed on substrate  20 . In this embodiment, substrate  20  comprises a PCB and includes a first or upper surface  20   a,  and a second or lower surface  20   b  that is opposite the upper surface  20   a.    
         [0017]    Each of the electronic components  50  includes a first or top surface  50   a,  a second or bottom surface  50   b  opposite the top surface  50   a,  and a plurality of lateral surfaces  50   c  extending between the top surface  50   a  and the bottom surface  50   b.  In addition, each of the electronic components  50  are arranged in close proximity to one another along the upper surface  20   a  of substrate  20  such that the bottom surface  50   b  of each component  50  engages or abuts (at least partially) the upper surface  20   a  of substrate  20 . 
         [0018]    During operation, electrical components  50  generate thermal energy. To regulate the temperature of the components  50  during operation, a cooling fluid  30  is flowed or forced over the surface  20   a  and/or surface  20   b  of the substrate  20  to induce convective cooling of the components  50  through contact of the fluid  30  and the exposed surfaces (e.g., surfaces  50   a,    50   c ). However, due to the close proximity of the components  50  along the upper surface  20   a  of substrate  20 , the components  50  that are disposed toward the center of the arrangement (e.g., components  50 ′) have a significantly decreased amount of surface area exposed to the fluid  30  when compared to the components  50  disposed along the edges of the arrangement (e.g., components  50 ″). As a result, during operation of system  10 , the components  50 ′ tend to have a higher average temperature than the components  50 ″. In some circumstances, the components  50 ′ may have a shorter working life due to this elevated average operating temperature. In addition, this difference in temperature between the components  50 ′,  50 ″ may, in some instances, limit the total number of components  50  that may be installed on substrate  20 . 
         [0019]    The embodiments disclosed herein include electronic systems that address this problem by having substrates that include one or more fluid flow channels extending therethrough such that one or more electronic components (e.g., components  50 ) may be positioned over the fluid flow channels to allow a greater amount of surface area of the components to be exposed to fluid flowing across the substrate during operations to thus improve the heat transfer properties of such components. 
         [0020]    Referring now to  FIGS. 2 and 3 , wherein an electronic system  100  in accordance with the principles disclosed herein is shown. System  100  includes a substrate  120  and a plurality of the electronic modules or components  50 . Electronic components  50  may include any suitable electronic component for use with an electronic device or system. For example, electronic components  50  may comprise capacitors, resistors, sensors, switches, optical components, or some combination thereof. In particular, in this embodiment, components  50  each comprise optical modules. 
         [0021]    In addition, the substrate  120  may comprise any substrate suitable for mounting an electronic component thereto. In some embodiments, substrate  120  comprises a PCB. In particular, substrate  120  includes a first or upper surface  120   a,  a second or lower surface  120   b  opposite the upper surface  120   a,  and a lateral edge  120   c  extending between the surfaces  120   a,    120   b  along the entire periphery of substrate  120 . 
         [0022]    Referring still to  FIGS. 2 and 3 , substrate  120  also includes a plurality of channels or apertures  140  extending between the surfaces  120   a,    120   b.  As will be described in more detail below, during operation channels  140  allow fluid (e.g., fluid  30 ) to flow therethrough in order to enhance the heat transfer properties of electronic components (e.g., components  50 ) disposed on substrate  120 , and thus, may be referred to herein as “fluid flow channels”  140 . As is best shown in  FIG. 3 , in this embodiment, the channels  140  are arranged substantially parallel to one another along the substrate  120 ; however, it should be appreciated that in other embodiments, one or more of the channels  140  may not be parallel to one another along the substrate  120  while still complying with the principles disclosed herein. 
         [0023]    In addition, as is best shown in  FIG. 3 , in this embodiment, fluid flow channels  140  are generally rectangular in shape when viewed in cross-section in a direction normal to one of the surfaces  120   a,    120   b;  however, it should be appreciated that the channels  140  may comprise any number of suitable shapes while still complying with the principles disclosed herein. For example, in some embodiments, channels  140  may be square, circular, polygonal, hexagonal, octagonal, triangular, zigzag, or some combination thereof. Referring briefly to  FIG. 4 , one particular embodiment of an electronic system  100 ′ in accordance with the principles disclosed herein includes channels  140 ′ within substrate  120  that are generally the same as the channels  140  of system  100  except that channels  140 ′ are formed as elongate ovals. As will be described in more detail below, in some embodiments, the size and shape of the channels  140  (or channels  140 ′) are chosen to correspond to the bottom surface  50   b  of a corresponding electronic component  50 . 
         [0024]    Referring again to  FIG. 3 , in this embodiment, channels  140  are substantially disposed within the inner periphery of substrate  120  such that each channel  140  is substantially separate or distal from lateral edge  120   c.  However, it should be appreciated that in other embodiments, one or more of the channels  140  may be disposed substantially along the lateral edge  120   c  of substrate  120 . For example, referring briefly to the embodiment of  FIG. 5 , a system  100 ″ is generally the same as the system  100  of  FIGS. 2 and 3  except that each of the channels  140  is disposed along the lateral edge  120   c  of substrate  120  such that channels  140  form a portion of the lateral edge  120   c.    
         [0025]    Referring again to  FIGS. 2 and 3 , each of the electronic components  50  are mounted to the upper surface  120   a  of substrate  120  such that the bottom surface  50   b  of each is disposed over one of the fluid flow channels  140 . In addition, in this embodiment, each of the components  50  are electrically coupled to the substrate  120  (or electrical conductors disposed within substrate  120 ) through electrical connectors  60 . However, it should be appreciated that components  50  may be electrically connected to substrate  120  and/or another electronic component (not shown) through any suitable connection such as, for example, a wireless, wired, and/or optical connection. In some embodiments, the size and shape of the channels  140  are chosen such that substantially all or most of the bottom surface  50   b  of the electronic components are exposed along the lower surface  120   b  of substrate through the channels  140 . For example, in some embodiments, at least 50% of the bottom surface  50   b  of each electronic component  50  is exposed through the corresponding channel  140 , while in other embodiments at least 80% of the bottom surface  50   b  of each component  50  is exposed through a corresponding channel  140 . However, in some embodiments, the size and shape of channels  140  are chosen such that only a relatively small portion of the bottom surface  50   b  of each the electronic components  50  is exposed along the lower surface  120   b  of substrate  120  while still complying with the principles disclosed herein. Moreover, in some embodiments, the shape of the fluid flow channels  140  is substantially matches or is substantially similar to the shape of the bottom surface  50   b  of the corresponding components  50 . 
         [0026]    During operations, components  50  receive and/or emit electronic signals through the connectors  60  (or through any suitable connection as previously described), and thus, generate excess thermal energy. As a result, fluid  30  is flowed or forced over the lower surface  120   b  and upper surface  120   a  of substrate  120  in order to induce convective cooling of components  50  to maintain acceptable operating temperatures thereof. In this embodiment fluid  30  is air; however, any suitable fluid (e.g., liquid or gas) may be used while still complying with the principles disclosed herein. Due to the presence of channels  140 , fluid  30  directed along the lower surface  120   b  flows through channels  140  and is therefore free to access and flow along the bottom surface  50   b  of the components  50 . As a result, components  50  have a higher or increased amount of surface area exposed to cooling fluid than is typically the case for a conventional system (e.g., see system  10  shown in  FIG. 1 ), and therefore experience enhanced cooling during such operations. 
         [0027]    While embodiments disclosed above have shown only a single row of electronic components  50  disposed along an upper surface  120   a  of the substrate  120 , in other embodiments, multiple rows of components  50  may be disposed along one of the surfaces  120   a,    120   b  of the substrate  120 . For example, referring now to  FIG. 6 , wherein an electronic system  200  is shown. Electronic system  200  is the same as the electronic system  100 , previously described, except that the electronic components are arranged in a pair of stacked rows along the upper surface  120   a  of substrate  120 . In particular, system  200  includes a first or lower row  52  of electronic components  50  mounted to the upper surface  120   a  and a second or upper row  54  of components  50  generally mounted on top of or above the lower row  52 . 
         [0028]    In addition, in this embodiment, an electromagnetic interference (EMI) cage  70 , which is some embodiments may comprise a metallic material, surrounds each of the components  50  in rows  52 ,  54  to at least partially insulate the components  50  from EMI produced during operation. Referring briefly now to  FIG. 7 , wherein one EMI cage  70  and electronic component  50  of the lower row  52  (see  FIG. 6 ) are shown, it being understood that each EMI cage  70  and component  50  of the lower row  52  are configured in the same manner. For clarity, in the embodiment of  FIG. 7 , the component  50  is shown uninstalled and separated from both substrate  120  and cage  70 . 
         [0029]    Cage  70  includes an inner region  72  that is sized and shaped to receive a component  50  therein. In addition, cage  70  is mounted to the upper surface  120   a  of substrate  120  such that cage  70  is substantially centered over one of the fluid flow channels  140 . Further, in this embodiment cage  70  is electrically grounded to substrate  120  through soldering  75 . 
         [0030]    Component  50  is installed within the inner region  72  by inserting component  50  within region  72  along direction A such that component  50  is disposed over the fluid flow channel  140 . In some embodiments, component  50  is electrically coupled to cage  70  through connectors (not shown) that are disposed within the inner region  72 ; however, it should be appreciated that any suitable method or device for electrically coupling component  50  to other electrical components or systems may be used while still complying with the principles disclosed herein. It should also be appreciated that each of the cages  70  and components  50  of the upper row  54  (see  FIG. 6 ) are configured essentially the same as the cages  70  and components  50  of the lower row  52  except that cages  70  are mounted to one of the cages  70  disposed within the lower row  52  rather than to the upper surface  120   a  of substrate  120 , and components  50  disposed therein are not directly exposed to one of the fluid flow channels  140 . 
         [0031]    Referring again to  FIG. 6 , during operation, fluid  30  is flowed along the upper surface  120   a  and the lower surface  120   b  of substrate  120  such that each electronic component  50  experiences convective cooling. Typically, components  50  disposed along the lower row  52  receive less fluid flow (e.g., fluid  30 ) because they have less exposed surface area. However, because substrate  120  includes fluid flow channels  140  as shown, as fluid  30  is flowed across the lower surface  120   b,  the bottom surfaces  50   b  of each of the components  50  disposed along the lower row  52  are exposed to the fluid  30  through the fluid flow channels  140  in the same manner described above with regard to system  100 . As a result, electronic components  50  disposed within the lower row  52  present a greater amount of exposed surface area and are more efficiently cooled than similarly situated components  50  in a conventional system (e.g., system  10 ). 
         [0032]    While the cages  70  of the electronic system  200  have been described and shown as including open lower ends such that components  50  disposed along lower row  52  are directly exposed to fluid flow channels  140 , it should be appreciated that in other embodiments, one or more of the cages  70  may include a bottom or lower surface such that fluid  30  is not directly exposed to the bottom surfaces  50   b  of the corresponding components  50 . For example, referring briefly to  FIG. 8 , where an electronic system  200 ′ is shown. System  200 ′ is substantially the same as the system  200  previously described except that each of the cages  70  further include a lower or bottom surface  70 A. Thus, during operation, as fluid  30  is flowed along the lower surface  120   b  of substrate  120 , the bottom surface  70 A of each cage  70  along the lower row  52  (rather than the bottom surface  50   b  of each component  50  in row  52 ) is exposed to the fluid  30  through the fluid flow channels  140 . Without being limited to this or any other theory, in this embodiment, cooling of each of the components  50  along the lower row  52  is at least partially accomplished through conductive heat transfer from the component  50  to the cage  70  and subsequent convective heat transfer from cage  70  to fluid  30  through contact of the fluid  30  and the lower surfaces  70 A of cages  70  within the channels  140 . 
         [0033]    In the manner described, through use of a substrate (e.g., substrate  120 ) having one or more channels (e.g., channels  140 ) extending therethrough, more effective cooling of electronic components (e.g., components  50 ) may be achieved. Thus, through use of an electronic system (e.g., systems  100 ,  100 ′,  200 , and  200 ′) in accordance with the principles disclosed herein, one may potentially extend the working life of electrical components included therein. In addition, through use of an electronic system (e.g., systems  100 ,  100 ′,  200 , and  200 ′) in accordance with the principles disclosed herein, a greater number of electronic components (e.g., components  50 ) may be installed on the surface of a substrate (e.g., substrate  120 ).